10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

(Mark One)

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2023

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ___________________ to ___________________

Commission File Number: 001-38433

Homology Medicines, Inc.

(Exact Name of Registrant as Specified in its Charter)

Delaware	47-3468154
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)
One Patriots Park Bedford, MA	01730
(Address of principal executive offices)	(Zip Code)

(781) 301-7277

(Registrant’s telephone number, including area code)

N/A

(Former name, former address, and former fiscal year, if changed since last report)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, $0.0001 par value per share	FIXX	Nasdaq Global Select Market

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer	☐	Accelerated filer	☐
Non-accelerated filer	☒	Smaller reporting company	☒
Emerging growth company	☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

As of November 7, 2023, the registrant had 57,934,332 shares of common stock, $0.0001 par value per share, outstanding.

FORWARD-LOOKING STATEMENTS

This Quarterly Report on Form 10-Q contains forward-looking statements. We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. All statements other than statements of historical fact contained in this Quarterly Report on Form 10-Q, including, without limitation, statements regarding the timing and anticipated benefits of and costs associated with our recent reduction in force, strategic initiatives and related corporate restructuring efforts, our future results of operations and financial position, the anticipated impact of COVID-19 and the current economic environment on our business, the anticipated use of cash and business strategy, the potential, safety, efficacy, and regulatory and clinical progress of our former product candidates, prospective products, product approvals, research and development costs, the anticipated timing and likelihood of success of clinical trials, the expected timing of the release of clinical trial data, the timing and expectations surrounding regulatory communications, our relationship with third-parties, our intent to engage in future strategic partnerships, and the plans and objectives of management for future operations and future results of anticipated products, are forward-looking statements. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential," or “continue” or the negative of these terms or other similar expressions, though not all forward-looking statements use these words or expressions. The forward-looking statements in this Quarterly Report on Form 10-Q are only predictions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this Quarterly Report on Form 10-Q and are subject to a number of important factors that could cause actual results to differ materially from those in the forward-looking statements, including the factors described under “Summary Risk Factors” below and in the sections in this Quarterly Report on Form 10-Q titled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties.

You should read this Quarterly Report on Form 10-Q and the documents that we reference in this Quarterly Report on Form 10-Q completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of our forward-looking statements by these cautionary statements. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise. Unless the context requires otherwise, we use the terms “Homology,” “the Company,” “we,” “us,” “our” and similar designations in this Quarterly Report on Form 10-Q to refer to Homology Medicines, Inc. and its wholly-owned subsidiary.

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SUMMARY RISK FACTORS

Our business is subject to numerous risks and uncertainties, including those described in Part II, Item 1A. “Risk Factors” in this Quarterly Report on Form 10-Q. You should carefully consider these risks and uncertainties when investing in our common stock. The principal risks and uncertainties affecting our business include the following:

•We have incurred significant losses since inception and anticipate that we will incur continued losses for the foreseeable future. If we are unable to achieve and sustain profitability, the market value of our common stock will likely decline. We may never achieve or maintain profitability.

•We will require additional capital to fund our operations, and if we fail to obtain necessary financing, we may not be able to complete the development and commercialization of our product candidates.

•Any financial or strategic option we pursue may not be successful. Moreover, our decision to discontinue further program development efforts may not result in the anticipated savings for the Company and may adversely affect our business.

•We have a limited operating history and no history of commercializing genetic medicine products, which may make it difficult to evaluate the prospects for our future viability.

•Should we resume development of our product candidates, we would be heavily dependent on the success of our product candidates, and if none of our candidates receives regulatory approval or is not successfully commercialized, our business may be harmed.

•Should we resume development of our product candidates, we intend to identify and develop product candidates based on our novel genetic medicines platform, which makes it difficult to predict the time and cost of product candidate development. No products that utilize gene editing technology have been approved in the United States or in Europe, and there have only been a limited number of human clinical trials involving a gene editing product candidate. Moreover, none of those trials has involved our nuclease-free gene editing technology, prior to our initiated Phase 1 pheEDIT clinical trial. In addition, there have been a limited number of gene therapy products approved in the United States or in Europe and none of these products have utilized our AAVHSC platform.

•The regulatory approval processes of the FDA and comparable foreign authorities are lengthy, time consuming and inherently unpredictable.

•Our product candidates have caused and may in the future cause serious adverse events or undesirable side effects or have other properties which may delay or prevent their regulatory approval, limit the commercial profile of an approved label or result in significant negative consequences following marketing approval, if any.

•Adverse public perception of genetic medicine, and gene editing in particular, may negatively impact the length of time required to advance our product candidates through clinical trials, should we resume development of our product candidates, including the pace at which we advance patient enrollment, and potential regulatory approval of, or demand for, our potential products.

•We have historically contracted with third parties, including Oxford Biomedica Solutions LLC, for the manufacture of certain materials for our research programs, preclinical and clinical studies. This reliance on third parties increases the risk that we will not have sufficient quantities of such materials, product candidates, or any medicines that we may develop and commercialize, or that such supply will not be available to us at an acceptable cost or in compliance with regulatory requirements, which could delay, prevent, or impair our development or commercialization efforts.

•Our contract manufacturers, including Oxford Biomedica Solutions LLC, are subject to significant regulation with respect to manufacturing our former product candidates. The manufacturing facilities on which we historically and may in the future rely may not meet or continue to meet regulatory requirements, as applicable and as imposed to date, and have limited capacity.

•Even if we obtain FDA approval for our product candidates in the United States in the future, we may never obtain approval for or commercialize them in any other jurisdiction, which would limit our ability to realize their full market potential.

•We may collaborate with third parties for the development and commercialization of our product candidates in the future, but there are no assurances that we will succeed in establishing and maintaining such collaborative relationships, which may significantly limit our ability to develop and commercialize our product candidates successfully, if at all.

•If we are unable to obtain and maintain patent protection for our technology and products or if the scope of the patent protection obtained is not sufficiently broad, we may not be able to compete effectively in our markets.

•Our recent reduction in force undertaken to significantly reduce our ongoing operating expenses may not result in our intended outcomes and may yield unintended consequences and additional costs.

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Table of Contents

		Page
PART I.	FINANCIAL INFORMATION	5
Item 1.	Condensed Consolidated Financial Statements (Unaudited)	5
	Condensed Consolidated Balance Sheets as of September 30, 2023 and December 31, 2022 (Unaudited)	5
	Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2023 and 2022 (Unaudited)	6
	Condensed Consolidated Statements of Comprehensive Loss for the three and nine months ended September 30, 2023 and 2022 (Unaudited)	7
	Condensed Consolidated Statements of Stockholders’ Equity for the three and nine months ended September 30, 2023 and 2022 (Unaudited)	8
	Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2023 and 2022 (Unaudited)	10
	Notes to Condensed Consolidated Financial Statements (Unaudited)	11
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	29
Item 3.	Quantitative and Qualitative Disclosures About Market Risk	41
Item 4.	Controls and Procedures	42
PART II.	OTHER INFORMATION	43
Item 1.	Legal Proceedings	43
Item 1A.	Risk Factors	43
Item 2.	Unregistered Sales of Equity Securities, Use of Proceeds, and Issuer Purchases of Equity Securities	92
Item 3.	Defaults Upon Senior Securities	92
Item 4.	Mine Safety Disclosures	92
Item 5.	Other Information	92
Item 6.	Exhibits	94
Signatures		94

4

PART I—FINANCIAL INFORMATION

Item 1. Financial Statements.

HOMOLOGY MEDICINES, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(in thousands, except share and per share amounts)

(UNAUDITED)

	As of
	September 30, 2023			December 31, 2022
Assets
Current assets:
Cash and cash equivalents	$	29,111		$	33,986
Short-term investments		74,187			141,040
Assets held for sale		314			—
Prepaid expenses and other current assets		3,023			5,989
Total current assets		106,635			181,015
Equity method investment		13,957			25,814
Property and equipment, net		—			1,078
Right-of-use assets		19,471			20,563
Total assets	$	140,063		$	228,470
Liabilities and stockholders' equity
Current liabilities:
Accounts payable	$	7,803		$	1,144
Accrued expenses and other liabilities		15,711			18,715
Operating lease liabilities		1,778			1,561
Deferred revenue		—			1,156
Total current liabilities		25,292			22,576
Non-current liabilities:
Operating lease liabilities, net of current portion		26,560			27,916
Total liabilities		51,852			50,492
Commitments and contingencies (Note 9)					—
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized;    no shares issued and outstanding at September 30, 2023 and    December 31, 2022		—			—
Common stock, $0.0001 par value; 200,000,000 shares authorized;    57,902,210 and 57,483,910 shares issued and outstanding as of    September 30, 2023 and December 31, 2022, respectively		6			6
Additional paid-in capital		614,220			607,513
Accumulated other comprehensive loss		(36	)		(404	)
Accumulated deficit		(525,979	)		(429,137	)
Total stockholders’ equity		88,211			177,978
Total liabilities and stockholders' equity	$	140,063		$	228,470

See notes to condensed consolidated financial statements.

5

HOMOLOGY MEDICINES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(in thousands, except share and per share amounts)

(UNAUDITED)

	Three months ended September 30,						Nine months ended September 30,
	2023			2022			2023			2022
Collaboration revenue	$	—		$	802		$	1,156		$	2,406
Operating expenses:
Research and development		17,519			25,854			60,489			71,202
General and administrative		6,842			7,810			23,355			29,991
Restructuring and other charges		6,640			—			6,640			—
Total operating expenses		31,001			33,664			90,484			101,193
Loss from operations		(31,001	)		(32,862	)		(89,328	)		(98,787	)
Other income:
Gain on sale of business		—			—			—			131,249
Interest income		1,423			1,269			4,403			1,775
Total other income		1,423			1,269			4,403			133,024
Income (loss) before income taxes		(29,578	)		(31,593	)		(84,925	)		34,237
Benefit from (provision for) income taxes		—			46			—			(816	)
Loss from equity method investment		(3,376	)		(2,179	)		(11,917	)		(4,131	)
Net income (loss)	$	(32,954	)	$	(33,726	)	$	(96,842	)	$	29,290
Net income (loss) per share-basic	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51
Net income (loss) per share-diluted	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51
Weighted-average common shares outstanding-basic		57,853,132			57,447,192			57,788,755			57,372,399
Weighted-average common shares outstanding-diluted		57,853,132			57,447,192			57,788,755			57,901,298

See notes to condensed consolidated financial statements.

6

HOMOLOGY MEDICINES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)

(in thousands)

(UNAUDITED)

	Three months ended September 30,						Nine months ended September 30,
	2023			2022			2023			2022
Net income (loss)	$	(32,954	)	$	(33,726	)	$	(96,842	)	$	29,290
Other comprehensive gain (loss):
Change in unrealized gain (loss) on available for   sale securities, net		52			(416	)		368			(450	)
Total other comprehensive gain (loss)		52			(416	)		368			(450	)
Comprehensive income (loss)	$	(32,902	)	$	(34,142	)	$	(96,474	)	$	28,840

See notes to condensed consolidated financial statements.

7

HOMOLOGY MEDICINES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

(in thousands, except share and per share amounts)

(UNAUDITED)

	Common Stock $0.0001 Par Value				Additional Paid-in		Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital		Gain (Loss)			Deficit			Equity
Balance at January 1, 2022		57,150,274	$	6	$	593,784	$	(7	)	$	(424,132	)	$	169,651
Issuance of common stock from    RSU vesting		87,140		—		—		—			—			—
Issuance of common stock from    option exercises		293		—		1		—			—			1
Issuance of common stock pursuant to    employee stock purchase plan		147,871		—		439		—			—			439
Stock-based compensation		—		—		4,051		—			—			4,051
Other comprehensive gain		—		—		—		7			—			7
Net income		—		—		—		—			92,105			92,105
Balance at March 31, 2022		57,385,578	$	6	$	598,275	$	—		$	(332,027	)	$	266,254
Stock-based compensation		—		—		3,143		—			—			3,143
Stock-based compensation for equity method    investee		—		—		21		—			—			21
Other comprehensive loss		—		—		—		(41	)		—			(41	)
Net loss		—		—		—		—			(29,089	)		(29,089	)
Balance at June 30, 2022		57,385,578	$	6	$	601,439	$	(41	)	$	(361,116	)	$	240,288
Issuance of common stock from    RSU vesting		16,450		—		—		—			—			—
Issuance of common stock pursuant to    employee stock purchase plan		78,582		—		124		—			—			124
Stock-based compensation		—		—		2,771		—			—			2,771
Stock-based compensation for equity method    investee		—		—		20		—			—			20
Other comprehensive loss		—		—		—		(416	)		—			(416	)
Net loss		—		—		—		—			(33,726	)		(33,726	)
Balance at September 30, 2022		57,480,610	$	6	$	604,354	$	(457	)	$	(394,842	)	$	209,061

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	Common Stock $0.0001 Par Value				Additional Paid-in		Accumulated Other Comprehensive			Accumulated			Total Stockholders’
	Shares		Amount		Capital		Gain (Loss)			Deficit			Equity
Balance at January 1, 2023		57,483,910	$	6	$	607,513	$	(404	)	$	(429,137	)	$	177,978
Issuance of common stock from    RSU vesting		194,525		—		—		—			—			—
Issuance of common stock pursuant to    employee stock purchase plan		116,332		—		150		—			—			150
Stock-based compensation		—		—		2,369		—			—			2,369
Stock-based compensation for equity method    investee		—		—		24		—			—			24
Other comprehensive gain		—		—		—		222			—			222
Net loss		—		—		—		—			(28,844	)		(28,844	)
Balance at March 31, 2023		57,794,767	$	6	$	610,056	$	(182	)	$	(457,981	)	$	151,899
Issuance of common stock from    option exercises		3,366		—		2		—			—			2
Stock-based compensation		—		—		2,402		—			—			2,402
Stock-based compensation for equity method    investee		—		—		22		—			—			22
Other comprehensive gain		—		—		—		94			—			94
Net loss		—		—		—		—			(35,044	)		(35,044	)
Balance at June 30, 2023		57,798,133	$	6	$	612,482	$	(88	)	$	(493,025	)	$	119,375
Issuance of common stock from    RSU vesting		86,592		—		—		—			—			—
Issuance of common stock pursuant to    employee stock purchase plan		17,485		—		18		—			—			18
Stock-based compensation		—		—		1,706		—			—			1,706
Stock-based compensation for equity method    investee		—		—		14		—			—			14
Other comprehensive gain		—		—		—		52			—			52
Net loss		—		—		—		—			(32,954	)		(32,954	)
Balance at September 30, 2023		57,902,210	$	6	$	614,220	$	(36	)	$	(525,979	)	$	88,211

See notes to condensed consolidated financial statements.

9

HOMOLOGY MEDICINES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands)

(UNAUDITED)

	Nine months ended September 30,
	2023			2022
Cash flows from operating activities:
Net income (loss)	$	(96,842	)	$	29,290
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation		578			997
Noncash lease expense		1,091			969
Loss from equity method investment		11,917			4,131
Stock-based compensation expense		6,477			9,965
Accretion of discount on short-term investments		(2,279	)		(872	)
Loss on disposal of property and equipment		68			—
Gain on sale of business		—			(131,249	)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		2,966			(5,301	)
Accounts payable		6,659			2,711
Accrued expenses and other liabilities		(2,996	)		5,672
Deferred revenue		(1,156	)		(2,406	)
Operating lease liabilities		(1,138	)		(369	)
Net cash used in operating activities		(74,655	)		(86,462	)
Cash flows from investing activities:
Purchases of short-term investments		(73,240	)		(157,460	)
Maturities of short-term investments		142,740			47,461
Proceeds from sale of business		—			130,000
Proceeds from sale of property and equipment		338			—
Purchases of property and equipment		(228	)		(1,276	)
Net cash provided by investing activities		69,610			18,725
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to employee    stock purchase plan		168			563
Proceeds from issuance of common stock from option exercises		2			1
Net cash provided by financing activities		170			564
Net change in cash, cash equivalents and restricted cash		(4,875	)		(67,173	)
Cash, cash equivalents and restricted cash, beginning of period		33,986			110,335
Cash, cash equivalents and restricted cash, end of period	$	29,111		$	43,162
Supplemental disclosures of noncash investing and financing activities:
Property and equipment additions included in accrued expenses and other liabilities	$	—		$	8
Unrealized gain (loss) on available for sale securities, net	$	368		$	(450	)

See notes to condensed consolidated financial statements.

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HOMOLOGY MEDICINES, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(in thousands, except share and per share amounts)

(UNAUDITED)

1. NATURE OF BUSINESS AND BASIS OF PRESENTATION

Nature of Business—Homology Medicines, Inc. (the “Company” or "Homology") is a clinical-stage genetic medicines company historically focused on transforming the lives of patients suffering from rare diseases by addressing the underlying cause of the disease with one-time gene therapy and gene editing treatments. The Company was founded in March 2015 as a Delaware corporation. Its principal offices are in Bedford, Massachusetts.

On July 27, 2023, the Company announced that it had completed a review of its business and the Company's Board of Directors had approved a plan to explore, review and evaluate a range of potential strategic options available to the Company, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the current financing environment and the Company's anticipated clinical development timeline for its lead program, HMI-103, the Company also announced that it was stopping further development of its programs and reduced its workforce by 86% in an effort to significantly reduce its ongoing operating costs as it evaluates strategic alternatives. The workforce reduction was substantially completed in the third quarter of 2023 (see Note 8).

On March 9, 2023, the Company filed a Registration Statement on Form S-3 (File No. 333-270414) (the “Shelf”) with the SEC in relation to the registration of up to an aggregate of $250.0 million of its common stock, preferred stock, debt securities, warrants and/or units of any combination thereof for a period up to three years from the date of the filing. The Shelf became effective on March 17, 2023. The Company also simultaneously entered into a sales agreement with Cowen and Company, LLC (“Cowen”), as sales agent, providing for the offering, issuance and sale by the Company of up to an aggregate of $75.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf (the “ATM”). The Company did not sell any shares of common stock under the ATM during the nine months ended September 30, 2023. As of September 30, 2023, there remained $75.0 million of common stock available for sale under the ATM.

On March 10, 2022, the Company closed a transaction with Oxford Biomedica plc ("Oxford"), to establish a new adeno-associated virus ("AAV") vector manufacturing company, Oxford Biomedica Solutions ("OXB Solutions") that provides AAV vector process development and manufacturing services to biotechnology companies. Under the terms of the agreement, the Company contributed its manufacturing team of 125 employees, manufacturing facility and equipment, manufacturing-related intellectual property and know-how and certain other assets. Oxford paid the Company $130.0 million of upfront cash and invested $50.0 million of cash to fund OXB Solutions in exchange for an 80 percent ownership interest, while Homology retained a 20 percent ownership interest in the new company and received a put option on this ownership position (see Note 5).

Since its inception and until recently, the Company devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates through discovery, preclinical and clinical trials, developing and implementing manufacturing processes, building out manufacturing and research and development space, and maintaining and building its intellectual property portfolio. The Company is subject to a number of risks similar to those of other companies conducting high-risk, early-stage research and development of product candidates. Principal among these risks are dependency on key individuals and intellectual property, competition from other products and companies, and the technical and regulatory risks associated with the successful research, development and manufacturing of its product candidates.

To date, the Company has not generated any revenue from product sales and does not expect to generate any revenue from the sale of product in the foreseeable future. Through September 30, 2023, the Company has financed its operations primarily through public offerings of its common stock, the issuance of convertible preferred stock, and with proceeds from its transaction with Oxford (see Note 5), its collaboration and license agreement with a former collaboration partner and its private placement with Pfizer (see Note 12). During the nine months ended September 30, 2023, the Company incurred a loss from operations of $96.8 million and as of September 30, 2023, the Company had $526.0 million in accumulated deficit.

The Company has incurred and expects to continue to incur costs and expenditures in connection with the process of evaluating strategic alternatives. There can be no assurance, however, that the Company will be able to successfully consummate any particular strategic transaction. The process of evaluating strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges.

11

Based on current projections, management believes that the Company's existing cash and cash equivalents and short-term investments as of September 30, 2023 will enable the Company to continue its operations for at least one year from the date of this filing. However, due to the consideration of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as the Company's workforce reduction of all but a few custodial employees, management has concluded there is substantial doubt regarding the Company's ability to continue as a going concern for more than twelve months from the date that the unaudited condensed consolidated financial statements included in this Quarterly Report on Form 10-Q have been issued. These financial statements do not include any adjustments that might result from the outcome of this uncertainty. Should the Company resume the development of product candidates, it would need to obtain substantial additional funding in connection with continuing operations, particularly as the Company resumes its preclinical activities and clinical trials for its product candidates. There can be no assurance that the Company will be able to obtain sufficient capital to cover its costs on acceptable terms, if at all.

Basis of Presentation— The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2022, included in the Company's Annual Report on Form 10-K on file with the SEC.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position as of September 30, 2023, and consolidated results of operations for the three and nine months ended September 30, 2023 and 2022, and cash flows for the nine months ended September 30, 2023 and 2022. Such adjustments are of a normal and recurring nature. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023.

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation—The Company’s condensed consolidated financial statements include the accounts of the Company and its subsidiary, Homology Medicines Securities Corporation, a wholly owned Massachusetts corporation, for the sole purpose of buying, selling, and holding securities on the Company’s behalf. All intercompany balances and transactions have been eliminated in the condensed consolidated financial statements.

Use of Estimates—The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, accrued research and development expenses and the valuation of the Company's equity method investment. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Comprehensive Income (Loss)—Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company’s only element of other comprehensive income (loss) is unrealized gains and losses on available-for-sale investments.

Cash and Cash Equivalents and Restricted Cash—Cash and cash equivalents consist of standard checking accounts, money market accounts and certain investments. The Company considers all highly liquid investments with original or remaining maturities at the time of purchase of 90 days or less to be cash equivalents. The Company did not have any restricted cash at September 30, 2023 or December 31, 2022.

Short-Term Investments—Short-term investments represent holdings of available-for-sale marketable securities in accordance with the Company’s investment policy and cash management strategy. Short-term investments have maturities of greater than 90 days at the time of purchase and mature within one year from the balance sheet date. Investments in marketable securities are recorded at fair value, with any unrealized gains and losses reported within accumulated other comprehensive income as a separate component of stockholders’ equity until realized or until a determination is made that an other-than-temporary decline in market value has occurred. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the

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underlying security. Such amortization and accretion, together with interest on securities, are included in interest income in the Company’s condensed consolidated statements of operations. The cost of marketable securities sold is determined based on the specific identification method and any realized gains or losses on the sale of investments are reflected as a component of other income.

Assets Held for Sale—The Company classifies assets as held for sale when the following conditions are met: (1) management has committed to a plan to sell, (2) the assets are available for immediate sale in their present condition, (3) the Company has initiated an active program to identify a buyer, (4) it is probable that a sale will occur within one year, (5) the assets are actively marketed for sale at a reasonable price in relation to their current fair value, and (6) there is a low likelihood of significant changes to the plan or that the plan will be withdrawn. If all of the aforementioned criteria are met as of the balance sheet date, the assets are presented separately in the consolidated balance sheet as held for sale at the lower of the carrying amount or fair value less costs to sell. The assets are then no longer depreciated or amortized while classified as held for sale.

Equity Method Investment—The Company uses the equity method of accounting to account for an investment in an entity that it does not control, but in which it has the ability to exercise significant influence over operating and financial policies. The Company's proportionate share of the net income or loss of the entity is included in consolidated net loss. Judgments regarding the level of influence over the equity method investment include consideration of key factors such as the Company's ownership interest, representation on the board of directors or other management body and participation in policy-making decisions.

Under the equity method of accounting, the Company’s investment is initially recorded at fair value on the condensed consolidated balance sheets. Upon initial investment, the Company evaluates whether there are basis differences between the carrying value and fair value of the Company’s proportionate share of the investee’s underlying net assets. Typically, the Company amortizes basis differences identified on a straight-line basis over the underlying assets’ estimated useful lives when calculating the attributable earnings or losses, excluding the basis differences attributable to in-process research and development that has no alternative future use. If the Company is unable to attribute all of the basis differences to specific assets or liabilities of the investee, the residual excess of the cost of the investment over the proportional fair value of the investee’s assets and liabilities is considered to be equity method goodwill and is recognized within the equity investment balance, which is tracked separately within the Company’s memo accounts. The Company subsequently records in the condensed consolidated statements of operations its share of income or loss of the other entity within other income/expense, which results in an increase or decrease to the carrying value of the investment. If the share of losses exceeds the carrying value of the Company’s investment, the Company will suspend recognizing additional losses and will continue to do so unless it commits to providing additional funding; however, if there are intra-entity profits this can cause the investment balance to go negative.

The Company evaluates its equity method investments for impairment whenever events or changes in circumstances indicate that a decline in value has occurred that is other than temporary. Evidence considered in this evaluation includes, but would not necessarily be limited to, the financial condition and near-term prospects of the investee, recent operating trends and forecasted performance of the investee, market conditions in the geographic area or industry in which the investee operates and the Company’s strategic plans for holding the investment in relation to the period of time expected for an anticipated recovery of its carrying value. If the investment is determined to have a decline in value deemed to be other than temporary it is written down to estimated fair value.

At September 30, 2023, the Company accounted for its investment in OXB Solutions using the equity method of accounting (see Note 5).

Offering Costs—The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with equity financings as other current assets until the transactions are completed. After equity financings are complete, these costs are recorded in stockholders’ equity as a reduction of additional paid-in capital generated as a result of the offering.

Leases—The Company determines if an arrangement is a lease at contract inception. The Company’s contracts are determined to contain a lease when all of the following criteria based on the specific circumstances of the arrangement are met: (1) there is an identified asset for which there are no substantive substitution rights; (2) the Company has the right to obtain substantially all of the economic benefits from the identified asset; and (3) the Company has the right to direct the use of the identified asset.

At the commencement date, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of future lease payments over the expected lease term. The Company’s lease agreements do not provide an implicit rate. As a result, the Company utilizes an estimated incremental borrowing rate to discount lease payments, which is based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or lease incentives received. Operating lease cost is recognized over the expected term on a straight-line basis. The expected lease term includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as

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periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option. Variable lease cost is recognized as incurred. Right-of-use assets are periodically evaluated for impairment.

The Company acts as sublessor related to a sublease of a substantial portion of the Company's headquarters that is now occupied by OXB Solutions. Fixed sublease payments received are recorded as a reduction to lease cost. Although Homology assigned all of its right, title and interest in, to and under this lease to OXB Solutions, the Company remained jointly and severally liable for the payment of rent under this lease as of and for the three and nine months ended September 30, 2023. Therefore, the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s condensed consolidated balance sheets as of September 30, 2023. The Company was released from being the primary obligor under such lease effective October 1, 2023 (see Note 14).

Research and Development Costs—Research and development costs are charged to expense as incurred. Research and development expense consists of expenses incurred in performing research and development activities, including salaries and benefits, materials and supplies, preclinical and clinical expenses, stock-based compensation expense, depreciation of equipment, contract services, and other outside expenses.

Costs for certain development activities are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense.

Income Taxes—The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s condensed consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. Since inception, the Company has provided a valuation allowance for the full amount of the net deferred tax assets as the realization of the net deferred tax assets has not been determined to be more likely than not.

The Company recorded an income tax benefit of less than $0.1 million and an income tax provision of $0.8 million for the three and nine months ended September 30, 2022, respectively. The year-to-date tax provision predominately resulted from the gain associated with the sale of the Company's manufacturing business due to the transaction with Oxford (see Note 5), offset by available federal and state net operating loss carryforwards and research and development tax credits which are subject to certain limitations as to their utilization. The Company did not record an income tax provision (benefit) for the three and nine months ended September 30, 2023.

Revenue Recognition—Revenue is recognized in accordance with FASB Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”).

Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer.

The promised goods or services in the Company’s arrangements would likely consist of a license, rights to the Company’s intellectual property or research, development and manufacturing services. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers

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factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration and variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of consideration to which the Company expects to be entitled to. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

The Company’s contracts may include development and regulatory milestone payments that are assessed under the most likely amount method and constrained until it is probable that a significant revenue reversal would not occur. Milestone payments that are not within the Company’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and regulatory milestones and any related constraint, and if necessary, adjust its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from the Company’s collaboration arrangement.

The Company allocates the transaction price based on the estimated standalone selling price of each performance obligation. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress for its over-time arrangements at each reporting period and, if necessary, updates the measure of progress and revenue recognized.

Net Income (Loss) per Share—Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding during the period. Diluted net income (loss) per share is computed using the weighted-average number of common shares outstanding during the period and, if dilutive, the weighted-average number of potential shares of common stock. The weighted-average number of common shares included in the computation of diluted net income (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, restricted stock units and unvested shares of common stock.

Common stock equivalent shares are excluded from the computation of diluted net income (loss) per share if their effect is antidilutive. In periods in which the Company reports a net (loss) attributable to common stockholders, diluted net (loss) per share attributable to common stockholders is generally the same as basic net (loss) per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.

Recent Accounting Pronouncements—The Jumpstart Our Business Startups Act of 2012 permits an emerging growth company to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. As an emerging growth company, the Company has elected to take advantage of this extended transition period.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) to improve financial reporting by requiring more timely recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. ASU 2016-13 requires the measurement

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of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. ASU 2016-13 also requires enhanced disclosures to help investors and other financial statement users better understand significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. The Company adopted ASU 2016-13 on January 1, 2023. The adoption of ASU 2016-13 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

3. SHORT-TERM INVESTMENTS

The Company may invest its excess cash in fixed income instruments denominated and payable in U.S. dollars, including U.S. treasury securities, commercial paper, corporate debt securities and asset-backed securities in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital.

The following table summarizes the Company’s short-term investments as of September 30, 2023 and December 31, 2022:

As of September 30, 2023	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Commercial paper	$	3,965	$	—	$	(2	)	$	3,963
US Treasury securities		55,268		6		(7	)		55,267
Corporate debt securities		14,990		—		(33	)		14,957
Total	$	74,223	$	6	$	(42	)	$	74,187
As of December 31, 2022	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Commercial paper	$	57,138	$	—	$	—		$	57,138
US Treasury securities		65,160		—		(335	)		64,825
Corporate debt securities		19,146		—		(69	)		19,077
Total	$	141,444	$	—	$	(404	)	$	141,040

The Company utilizes the specific identification method in computing realized gains and losses. The Company had no realized gains and losses on its available-for-sale securities for the three and nine months ended September 30, 2023 and 2022. The contractual maturity dates of all of the Company’s investments are less than one year.

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4. FAIR VALUE MEASUREMENTS

The Company’s financial instruments consist of cash and cash equivalents, short-term investments, restricted cash and accounts payable. The carrying amount of cash, restricted cash and accounts payable are each considered a reasonable estimate of fair value due to the short-term maturity.

Assets measured at fair value on a recurring basis were as follows:

Description	September 30, 2023		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	28,375	$	28,375	$	—	$	—
Total cash equivalents	$	28,375	$	28,375	$	—	$	—
Short-term investments:
Commercial paper	$	3,963	$	—	$	3,963	$	—
US Treasury securities		55,267		—		55,267		—
Corporate debt securities		14,957		—		14,957		—
Total short-term investments	$	74,187	$	—	$	74,187	$	—
Total financial assets	$	102,562	$	28,375	$	74,187	$	—
Description	December 31, 2022		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	33,967	$	33,967	$	—	$	—
Total cash equivalents	$	33,967	$	33,967	$	—	$	—
Short-term investments:
Commercial paper	$	57,138	$	—	$	57,138	$	—
US Treasury securities		64,825		—		64,825		—
Corporate debt securities		19,077		—		19,077		—
Total short-term investments	$	141,040	$	—	$	141,040	$	—
Total financial assets	$	175,007	$	33,967	$	141,040	$	—

Short-term securities are valued using models or other valuation methodologies that use Level 2 inputs. These models are primarily industry-standard models that consider various assumptions, including time value, yield curve, volatility factors, default rates, current market and contractual prices for the underlying financial instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace.

There were no transfers between fair value measurement levels during the three and nine months ended September 30, 2023 and 2022.

5. EQUITY METHOD INVESTMENT

Summary of Transaction

On March 10, 2022, the Company closed a transaction with OXB Solutions, Oxford Biomedica (US), Inc., ("OXB"), and Oxford, pursuant to the Equity Securities Purchase Agreement (the "Purchase Agreement"), dated as of January 28, 2022, by and among Homology, OXB Solutions and Oxford, whereby, among other things, Homology and Oxford agreed to collaborate to operate OXB Solutions, which provides AAV vector process development and manufacturing services to pharmaceutical and biotechnology companies (the "OXB Solutions Transaction").

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Pursuant to the terms of the Purchase Agreement and a contribution agreement (the "Contribution Agreement") entered into between Homology and OXB Solutions prior to the closing of the OXB Solutions Transaction (the "Closing"), Homology contributed its manufacturing team of 125 employees and assigned and transferred to OXB Solutions all of its assets that are primarily used in the manufacturing of AAV vectors for use in gene therapy and gene editing products, including its manufacturing facility and equipment and manufacturing-related intellectual property and know-how, but excluding certain assets related to manufacturing or testing of Homology's proprietary AAV vectors (collectively, the "Transferred Assets"), in exchange for 175,000 common equity units in OXB Solutions ("Units"), representing 100 percent (100%) of the ownership interest of OXB Solutions, and OXB Solutions assumed from the Company, and agreed to pay, perform and discharge when due, all of the Company's duties, obligations, liabilities, interests and commitments of any kind under, arising out of or relating to the Transferred Assets.

Effective as of the Closing, Homology sold to OXB, and OXB purchased from Homology, 130,000 Units, (the "Transferred Units") in exchange for $130.0 million of cash consideration. In connection with the Closing, OXB contributed $50.0 million in cash to OXB Solutions in exchange for an additional, newly issued 50,000 Units. Immediately following the Closing, (i) OXB owned 180,000 Units, representing 80 percent (80%) of the fully diluted equity interests in OXB Solutions, and (ii) Homology owned 45,000 Units, representing 20 percent (20%) of the fully diluted equity interests in OXB Solutions.

Pursuant to the Amended and Restated Limited Liability Company Agreement of OXB Solutions (the "OXB Solutions Operating Agreement") which was executed in connection with the Closing, at any time following the three-year anniversary of the Closing, (i) OXB will have an option to cause Homology to sell and transfer to OXB, and (ii) Homology will have an option to cause OXB to purchase from Homology, in each case all of Homology's equity ownership interest in OXB Solutions at a price equal to 5.5 times the revenue for the immediately preceding 12-month period (together, the "Options"), subject to a maximum amount of $74.1 million. Pursuant to the terms of the OXB Solutions Operating Agreement, Homology is entitled to designate one director to the board of directors of OXB Solutions, currently Albert Seymour, Homology's Chief Executive Officer.

Pursuant to the OXB Solutions Transaction, the Company also assigned all of its right, title and interest in, to and under its facility lease to OXB Solutions. However, as the Company remained jointly and severally liable for the payment of rent under the facility lease, the Company had not been released from being the primary obligor under such lease as of September 30, 2023 and therefore the related right-of-use asset and lease liability were not derecognized and remained on the Company’s balance sheet. The Company determined that the expected disposal of the fixed assets did not qualify for reporting as a discontinued operation since it did not represent a strategic shift that has or will have a major effect on the Company's operations and financial results. Subsequently, the Company was released from being the primary obligor under such lease effective as of October 1, 2023 (see Note 14).

Equity Method of Accounting

The Company has significant influence over, but does not control, OXB Solutions through its noncontrolling representation on OXB’s board of directors and the Company’s equity interest in OXB Solutions. In addition, the Company and OXB Solutions have intra-entity transactions through a series of agreements entered into in conjunction with the OXB Solutions Transaction, OXB Solutions granted certain licenses to the Company, and the Company has representation on the joint steering committee which oversees the activities governed by the Supply Agreement. Accordingly, the Company does not consolidate the financial statements of OXB Solutions and accounts for its investment using the equity method of accounting.

The Company recorded its equity method investment in OXB Solutions at fair value upon deconsolidation of OXB Solutions as of the Closing. The fair value of the equity method investment was determined based on the market approach. This approach estimated the fair value of OXB Solutions based on the implied value for the entity using the consideration paid, including the Options, for a controlling interest in OXB Solutions at the entity’s formation. As part of its fair value analysis, the Company determined that the Options are embedded in the common equity units because the Options are not legally detachable or separately exercisable. Accordingly, the equity method investment and the Options represent one unit of account and the fair value recorded reflects the value of the equity interest and the Options. The valuation included certain subjective assumptions including discounts for lack of control and marketability given the consideration paid for OXB Solutions was for a controlling interest in the entity and the Company owns a noncontrolling interest. As of March 10, 2022, the Closing, the fair value of the Company’s investment in OXB Solutions was $31.2 million and the Company recorded a gain of $131.2 million on the sale of its manufacturing business in other income in the Company's condensed consolidated statements of operations. The gain was computed as follows:

(in thousands)	March 10, 2022
Cash received	$	130,000
Plus: Fair value of equity method investment		31,223
Less: Carrying value of transferred assets		(29,974	)
Gain on sale of business	$	131,249

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During the nine months ended September 30, 2023, the Company determined that the fair value of its investment in OXB Solutions was negatively impacted due to a change in OXB Solutions' forecasted performance relative to expected performance when the Company initially invested in OXB Solutions. The Company determined that the decline in value was deemed to be other than temporary and recorded an impairment charge of $3.8 million to reduce its equity method investment to fair value. The impairment charge is included in the loss on equity method investment in the Company's condensed consolidated statements of operations.

In addition, the Company records its share of income or losses from OXB Solutions on a quarterly basis. For the nine months ended September 30, 2023, the Company recorded $8.1 million representing its share of OXB Solution's net loss for the period. As of September 30, 2023, the carrying value of the equity method investment was $14.0 million.

6. PROPERTY AND EQUIPMENT, NET

Property and equipment, net consists of the following:

	As of
	September 30, 2023		December 31, 2022
	(in thousands)
Laboratory equipment	$	—	$	6,025
Computers and purchased software		—		644
Furniture and fixtures		—		645
Property and equipment, at cost		—		7,314
Less: accumulated depreciation and amortization		—		(6,236	)
Property and equipment, net	$	—	$	1,078

In August 2023, consistent with its decision to stop further development of its programs and explore, review and evaluate a range of potential strategic options available to the Company, the Company committed to a plan to sell its remaining property and equipment and therefore has classified the amount as assets held for sale on the consolidated balance sheet as of September 30, 2023. The assets held for sale were reported at the lower of the carrying amount or fair value with no depreciation expense taken after August 2023.

Depreciation expense for the three and nine months ended September 30, 2023 was approximately $0.1 million and $0.6 million, respectively, compared to $0.3 million and $1.0 million, respectively for the three and nine months ended September 30, 2022. The Company had approximately $0.4 million of disposals of property and equipment during the three and nine months ended September 30, 2023. The Company had no disposals of property and equipment during the three and nine months ended September 30, 2022.

7. ACCRUED EXPENSES AND OTHER LIABILITIES

Accrued expenses and other liabilities consist of the following:

	As of
	September 30, 2023		December 31, 2022
	(in thousands)
Accrued research and development expenses	$	8,198	$	9,447
Accrued compensation and benefits		6,660		5,953
Accrued professional fees		648		1,052
Accrued other		205		2,263
Total accrued expenses and other liabilities	$	15,711	$	18,715

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8. RESTRUCTURING AND OTHER CHARGES

On July 25, 2023, the Company's Board of Directors approved a process to explore, review and evaluate a range of potential strategic options available to the Company, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Therefore, based on cost-reduction initiatives intended to reduce the Company’s ongoing operating expenses and maximize shareholder value as the Company plans to pursue strategic options, the Company's Board of Directors also approved a reduction in the Company’s workforce by approximately 80 employees, or 86% of the Company's workforce as of July 2023. In connection with this corporate restructuring, the Company recorded a restructuring charge for severance and related costs of $6.9 million in the Company's condensed consolidated statements of operations during the three months ended September 30, 2023.

The Company’s restructuring liability, which was included in accrued compensation and benefits, consisted of the following:

(in thousands)	Employee-Related Costs
Accrued restructuring balance at January 1, 2023	$	-
Expenses incurred		6,895
Payments		(2,154	)
Accrued restructuring balance at September 30, 2023	$	4,741

The Company had previously granted certain of the terminated employees restricted stock units (“RSUs”) that vest in annual installments based on continued service to the Company, as well as options to purchase shares of the Company’s common stock that typically vest over a period of four years. In connection with the reduction in workforce, the Company agreed to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates, and also modify the stock options for terminated employees such that subject to the satisfaction of severance conditions, the terminated employees’ vested options will remain outstanding and exercisable until the first anniversary of each employee’s termination date. These equity modifications, described in detail in Note 10, resulted in a net reduction to stock based compensation expense of $0.3 million reflected within restructuring and other charges in the Company's condensed consolidated statements of operations during the three months ended September 30, 2023.

9. COMMITMENTS AND CONTINGENCIES

Operating Leases—In December 2017, the Company entered into a noncancelable operating lease for approximately 67,000 square feet of research and development, manufacturing and general office space in Bedford, Massachusetts. Prior to a subsequent amendment described below, the lease was set to expire in February 2027 with an option for an additional five-year term. Rent became due under the lease in two phases; rent on the first 46,000 square feet started in September 2018 and rent on the remaining 21,000 square feet started in March 2019. The initial annual base rent was $39.50 per square foot and increases by three percent annually. The Company is obligated to pay, on a pro-rata basis, real estate taxes and operating costs related to the premises. The lease agreement allowed for a tenant improvement allowance not to exceed $10.9 million, which the Company received in full, to be applied to the total cost of tenant improvements to the leased premises. The unamortized balance of the tenant improvement allowance was included in deferred rent incentives and recorded as a reduction to operating right-of-use asset upon adoption of the new leasing standards.

In November 2021, the Company entered into an amendment of its December 2017 lease agreement (the “Lease Amendment”) for its corporate headquarters in Bedford, Massachusetts. The Lease Amendment increases the space under lease by approximately 23,011 square feet (the "Expansion Premises") and extended the expiration date of the existing premises under the lease from February 2027 to June 2030. The payment term with respect to the Expansion Premises commenced on May 1, 2022 and continues for a period of ten years and five months. The term of the Expansion Premises and the existing premises are not coterminous. Annual base rent for the existing premise under the Lease Amendment is approximately $4.7 million beginning on March 1, 2027, and increases by three percent annually; annual base rent for the Expansion Premises is approximately $1.4 million per year and increases by three percent annually. The Lease Amendment allows for tenant improvement allowances not to exceed $6.3 million in the aggregate. The Lease Amendment was accounted for as a lease modification and the right-of-use asset and operating lease liability for the existing premises were remeasured at the modification date, which resulted in an increase of $10.9 million to both the right-of-use asset and operating lease liabilities. In February 2022, the Company revised its assumption for when it expects to utilize the tenant improvement allowances. This change in assumption was accounted for as a lease modification and the right-of-use asset and operating lease liability for the existing premises were remeasured at the modification date, which resulted in an increase of $0.2 million to both the right-of-use asset and operating lease liabilities.

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In March 2022, in accordance with its transaction with OXB Solutions, the Company assigned all of its right, title and interest in, to and under its corporate headquarters lease to OXB Solutions and entered into a sublease agreement whereby OXB Solutions subleased certain premises in its facility to Homology. The Company was not released from being the primary obligor under such lease as of September 30, 2023 and therefore the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s balance sheet and the Company acted as sublessor to OXB Solutions for accounting purposes. See Note 5 for details. During the nine months ended September 30, 2023, the Company received $2.3 million in sublease payments from OXB Solutions, which is recorded as a reduction to lease cost. In October 2023, the Company was released from being primary obligor under the lease (see Note 14).

In September 2022, the Company concluded that 100% of the tenant improvement allowances would be utilized by OXB Solutions. This change in assumption was accounted for as a lease modification and the right-of-use asset and operating lease liability for the existing premises were remeasured at the modification date, which resulted in an increase of $6.1 million to both the right-of-use asset and operating lease liabilities.

The following table summarizes operating lease costs and variable lease costs, as well as sublease income:

	Nine months ended September 30,
	2023			2022
	(in thousands)
Operating lease costs	$	3,263		$	2,826
Variable lease costs		1,551			1,698
Sublease income		(2,312	)		(1,210	)
Net lease cost	$	2,502		$	3,314

The maturities of the Company's operating lease liabilities and minimum lease payments as of September 30, 2023 were as follows:

For the Years Ending December 31,	Amount (in thousands)
2023		1,134
2024		4,578
2025		4,715
2026		4,857
Thereafter		26,265
Total undiscounted lease payments	$	41,549
Less: imputed interest		(13,211	)
Present value of operating lease liabilities	$	28,338

The following table summarizes the lease term and discount rate as of September 30, 2023:

	September 30, 2023
Weighted-average remaining lease term (years)
Operating leases		7.5
Weighted-average discount rate
Operating leases		10.6	%

The following table summarizes the supplemental cash flow information related to the Company's operating lease:

	Nine months ended September 30,
	2023		2022
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities	$	3,310	$	2,226
Increase in lease liabilities and right-of-use assets due to lease remeasurements	$	—	$	6,262

Legal Proceedings—On March 25, 2022, the Company and certain of its executives were named as defendants in a putative securities class action lawsuit filed in the United States District Court for the Central District of California; Pizzuto v. Homology Medicines, Inc., No. 2:22–CV–01968 (C.D. Cal 2022). The complaint alleges that the Company failed to disclose certain information regarding efficacy and safety in connection with a Phase I/II HMI-102 clinical trial, and seeks damages in an unspecified amount. The

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case is in its early stages. The Company believes the claims alleged lack merit and filed a motion to transfer venue (filed September 2, 2022) and a motion to dismiss (filed October 17, 2022). On April 18, 2023, the court granted the motion to transfer, finding that venue was not proper in the Central District of California and transferring the case to the District of Massachusetts. Following the transfer, the case number changed to 1:23-cv-10858-AK (D. Mass.). On May 9, 2023, the Massachusetts court issued an order permitting the parties to submit updated briefs in connection with the motion to dismiss, which were submitted on June 8, 2023, July 13, 2023, and August 3, 2023. The motion to dismiss remains pending. As the outcome is not presently determinable, any loss is neither probable nor reasonably estimable.

10. STOCK INCENTIVE PLANS

2015 Stock Incentive Plan

In December 2015, the Company’s Board of Directors adopted the 2015 Stock Incentive Plan (the “2015 Plan”), which provided for the grant of incentive stock options, nonqualified stock options and restricted stock awards to the Company’s employees, officers, directors, advisors, and outside consultants. Stock options granted under the 2015 Plan generally vest over a four-year period and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the 2015 Plan. At September 30, 2023, there were no additional shares available for future grant under the 2015 Plan.

2018 Incentive Award Plan

In March 2018, the Company’s Board of Directors adopted and the Company’s stockholders approved the Homology Medicines, Inc. 2018 Incentive Award Plan (the “2018 Plan” and, together with the 2015 Plan, the “Plans”), which became effective on the day prior to the first public trading date of the Company’s common stock. Upon effectiveness of the 2018 Plan, the Company ceased granting new awards under the 2015 Plan.

The 2018 Plan provides for the grant of incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock or cash-based awards to employees and consultants of the Company and certain affiliates and directors of the Company. The number of shares of common stock initially available for issuance under the 2018 Plan was 3,186,205 shares of common stock plus the number of shares subject to awards outstanding under the 2015 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company on or after the effective date of the 2018 Plan. In addition, the number of shares of common stock available for issuance under the 2018 Plan is subject to an annual increase on the first day of each calendar year beginning on January 1, 2019, and ending on and including January 1, 2028, equal to the lesser of (i) 4% of the Company’s outstanding shares of common stock on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as determined by the Company’s Board of Directors, provided that not more than 20,887,347 shares of common stock may be issued under the 2018 Plan upon the exercise of incentive stock options. Therefore, on January 1, 2023, an additional 2,299,356 shares were added to the 2018 Plan, representing 4% of total common shares outstanding at December 31, 2022. As of September 30, 2023, there were 1,978,793 shares available for future grant under the 2018 Plan.

2018 Employee Stock Purchase Plan

In March 2018, the Company’s Board of Directors adopted and the Company’s stockholders approved the Homology Medicines, Inc. 2018 Employee Stock Purchase Plan (the “2018 ESPP”). The 2018 ESPP allows employees to buy Company stock through after-tax payroll deductions at a discount from market value. The 2018 ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. The number of shares of common stock initially available for issuance under the 2018 ESPP was 353,980 shares of common stock plus an annual increase on the first day of each calendar year, beginning on January 1, 2019, and ending on and including January 1, 2028 equal to the lesser of (i) 1% of the Company’s outstanding shares of common stock on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as determined by the Company’s Board of Directors, provided that not more than 4,778,738 shares of common stock may be issued under the 2018 ESPP. Therefore, on January 1, 2023, an additional 574,839 shares were added to the 2018 ESPP, representing 1% of total common shares outstanding at December 31, 2022. As of September 30, 2023, there were 2,693,911 shares available for future issuance under the 2018 ESPP.

Under the 2018 ESPP, employees may purchase common stock through after-tax payroll deductions at a price equal to 85% of the lower of the fair market value on the first trading day of an offering period or the last trading day of an offering period. The 2018 ESPP generally provides for offering periods of six months in duration that end on the final trading day of each February and August. In accordance with the Internal Revenue Code, no employee will be permitted to accrue the right to purchase stock under the 2018

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ESPP at a rate in excess of $25,000 worth of shares during any calendar year during which such a purchase right is outstanding (based on the fair market value per share of the Company’s common stock as of the first day of the offering period).

During the nine months ended September 30, 2023, 133,817 shares were issued under the 2018 ESPP for aggregate proceeds to the Company of approximately $0.2 million. During the nine months ended September 30, 2022, 226,453 shares were issued under the 2018 ESPP for aggregate proceeds to the Company of approximately $0.6 million. Pursuant to the 2018 ESPP, the Company recorded stock-based compensation of less than $0.1 million during the three and nine months ended September 30, 2023 and 2022, respectively.

Stock Options

The fair value of each option award is estimated on the date of grant using the Black-Scholes option pricing model, with the assumptions noted in the table below. Expected volatility for the Company’s common stock was determined based on an average of the historical volatility of a peer group of publicly traded companies that are similar to the Company. The expected term of options was calculated using the simplified method, which represents the average of the contractual term of the option and the weighted-average vesting period of the option. The Company uses the simplified method because it does not have sufficient historical option exercise data to provide a reasonable basis upon which to estimate expected term. The assumed dividend yield is based upon the Company’s expectation of not paying dividends in the foreseeable future. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods commensurate with the expected term of the award. The Company recognizes forfeitures as they occur.

The assumptions used in the Black-Scholes option pricing model are as follows (note that there were no options granted during the three months ended September 30, 2023):

	Three months ended	Nine months ended September 30,
	September 30, 2022	2023	2022
Expected volatility	70.1%	69.2% - 69.7%	68.7% - 70.1%
Weighted-average risk-free interest rate	3.20% - 3.66%	3.45% - 4.22%	1.46% - 3.66%
Expected dividend yield	— %	— %	— %
Expected term (in years)	6.25	5.5 - 6.25	5.5 - 6.25
Underlying common stock fair value	$1.82-$2.82	$0.92-$1.60	$1.78-$4.17

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2023:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
								(in thousands)
Outstanding at January 1, 2023		9,865,734		$	10.96		7.2	$	493
Granted		3,188,150		$	1.53
Exercised		(3,366	)	$	0.47
Cancelled/Forfeited		(623,776	)	$	11.11
Outstanding at September 30, 2023		12,426,742		$	8.55		4.9	$	488
Vested and expected to vest at    September 30, 2023		12,426,742		$	8.55		4.9	$	488
Exercisable at September 30, 2023		7,566,304		$	11.80		4.5	$	421

The total intrinsic value of options exercised during the nine months ended September 30, 2023 and 2022 was insignificant for each period. The weighted-average grant date fair value per share of options granted during the nine months ended September 30, 2023 and 2022 was $1.01 and $1.72, respectively.

Stock Awards Modifications - Corporate Restructuring

In connection with the Company's corporate restructuring (see Note 8), the Company terminated approximately 80 employees and modified approximately 3.3 million existing stock options and approximately 0.4 million existing restricted stock units ("RSUs") granted to these terminated employees in prior periods. The modification of the vested stock options to permit terminated employees

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up to one year following their termination date to exercise their options, rather than the 90-day window for terminated employees, is accounted for as a modification under FASB ASC Topic 718, Compensation—Stock Compensation ("ASC 718"). Accordingly, the Company recognized incremental compensation cost on the modification date in an amount equal to the difference between the fair value of the awards before and after the modification. The fair value of the awards immediately before assumes an expected term equal to 90 days from the termination date, whereas the fair value immediately after assumes an expected term equal to one year from the termination date. Total incremental compensation cost recognized in the three months ended September 30, 2023 related to awards that were vested as of the modification date was less than $0.1 million. All unvested stock options were forfeited upon termination and the Company reversed all compensation cost previously recorded on the forfeited awards. Total compensation cost reversed in the three months ended September 30, 2023 was less than $0.1 million.

The terminated employees' RSUs were modified to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates. The accelerated vesting of certain RSUs is accounted for as a Type III (improbable to probable) modification under ASC 718. Accordingly, the Company reversed all compensation cost previously recorded on the awards that are not expected to vest under the original terms. Total compensation cost reversed in the three months ended September 30, 2023 was approximately $0.2 million. Total compensation cost of less than $0.1 million, equal to the modification date fair value, was recognized over the remaining service period, beginning on the modification date and ending on each employee’s termination date.

Stock Awards Modifications - OXB Solutions Transaction

As part of the transaction with OXB Solutions (see Note 5), the Company transferred employees to OXB Solutions and modified approximately 1.6 million existing stock options and approximately 0.1 million existing restricted stock units granted to these transferred employees in prior periods in order to permit such individuals to continue vesting in their awards and exercise their vested options as long as they are employed by and provide services to OXB Solutions. The modification of the unvested stock awards to continue vesting was accounted for as a Type III (improbable to probable) modification under ASC 718. Accordingly, the Company reversed all compensation cost previously recorded on the awards that were not expected to vest under the original terms. Total compensation cost reversed in the three months ended March 31, 2022 was less than $0.1 million. Total compensation cost of $0.8 million, equal to the modification date fair value, will be recognized over the remaining service period. A portion of this total compensation cost will be included as a component of the loss from equity method investment.

The modification of the vested stock awards to permit transferred employees to exercise their options over the remaining life of the award, rather than the 90-day window for terminated employees, was accounted for as a modification under ASC 718. Accordingly, the Company recognized incremental compensation cost on the modification date in an amount equal to the difference between the fair value of the awards before and after modification. The fair value of the awards immediately before modification assumed a 90-day expected term, whereas the fair value immediately after assumed an expected term equal to the remaining life of the modified options. Total incremental compensation cost recognized in the year ended December 31, 2022 related to awards that were vested as of the modification date was $0.4 million.

Restricted Stock Units

The fair value of RSUs is based on the fair market value of the Company's common stock on the date of grant. Each RSU represents a contingent right to receive one share of the Company's common stock upon vesting. In general, RSUs vest annually in two or three equal installments on January 1st of each year after the grant date. The following table summarizes the Company's RSU activity for the nine months ended September 30, 2023:

	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2023		543,179		$	6.12
Granted		483,850		$	1.60
Vested		(281,117	)	$	5.31
Forfeited		(258,184	)	$	2.54
Outstanding at September 30, 2023		487,728		$	3.04

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Stock-based Compensation Expense

The Company recognizes compensation expense for awards to employees based on the grant date fair value of stock-based awards on a straight-line basis over the period during which an award holder provides service in exchange for the award, which is generally the vesting period. The Company recorded stock-based compensation expense related to stock options, shares purchased under the 2018 ESPP, restricted stock units and stock award modifications as follows:

	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
	(in thousands)
Research and development	$	230	$	889	$	1,507	$	4,143
General and administrative		1,477		1,882		4,970		5,822
	$	1,707	$	2,771	$	6,477	$	9,965

As of September 30, 2023, there was $10.5 million of unrecognized compensation expense related to unvested employee and non-employee share-based compensation arrangements granted under the Plans. The unrecognized compensation expense is estimated to be recognized over a period of 2.2 years at September 30, 2023.

11. NET INCOME (LOSS) PER SHARE

Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding during the applicable period. Diluted net income (loss) per share incorporates the additional shares issuable upon assumed exercise of stock options and the vesting of restricted stock units, except in such case when their inclusion would be anti-dilutive.

	Three months ended September 30,						Nine months ended September 30,
(in thousands, except per share amounts)	2023			2022			2023			2022
Numerator:
Net income (loss)	$	(32,954	)	$	(33,726	)	$	(96,842	)	$	29,290
Denominator:
Weighted-average common shares outstanding-basic		57,853,132			57,447,192			57,788,755			57,372,399
Dilutive securities		—			—			—			528,899
Weighted-average common shares outstanding-diluted		57,853,132			57,447,192			57,788,755			57,901,298
Net income (loss) per share-basic	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51
Net income (loss) per share-diluted	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51

For the three and nine months ended September 30, 2023, as well as for the three months end September 30, 2022, the effect of dilutive securities including stock options, restricted stock units and unvested common stock from early exercise of options, was excluded from the denominator for the calculation of diluted net loss per share because the Company recognized a net loss for the periods and their inclusion would be anti-dilutive. Anti-dilutive securities excluded for the three months ended September 30, 2023 and 2022 were 12,993,266 and 9,933,508, respectively, and for the nine months ended September 30, 2023 and 2022 were 12,507,026 and 9,048,927, respectively.

12. PFIZER STOCK PURCHASE AGREEMENT

On November 9, 2020, the Company entered into a common stock purchase agreement (the “Stock Purchase Agreement”) with Pfizer Inc. (“Pfizer”), pursuant to which the Company agreed to issue and sell to Pfizer 5,000,000 shares of the Company’s common stock through a private placement transaction (the “Private Placement”) at a purchase price of $12.00 per share, for an aggregate purchase price of $60.0 million. The shares of common stock sold to Pfizer were subject to a one-year lock-up from closing, during which time Pfizer was prohibited from selling or otherwise disposing of such shares.

Under the Stock Purchase Agreement, Pfizer was granted an exclusive right of first refusal (the “ROFR”) for a 30-month period (the “ROFR Period”) beginning on the date of the closing of the Private Placement (collectively, the “ROFR Provision”), to negotiate a potential collaboration on the development and commercialization of HMI-102 and HMI-103. The ROFR Period expired on May 9, 2023. In addition to the ROFR, the Stock Purchase Agreement provided for an information sharing committee (the “Information Committee”), comprised of representatives of each company, which served as a forum for sharing information regarding the development of HMI-102 and HMI-103 during the ROFR Period.

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The Company recorded the issuance of common stock at its estimated fair value of $52.0 million, which reflected a discount for the lack of marketability of the shares. The remaining $8.0 million of aggregate purchase price was allocated to the other elements of the Stock Purchase Agreement, which represented a contract with a customer. The Company concluded that the Information Committee represented the only performance obligation under the contract. The ROFR did not provide Pfizer with a material right and was therefore not a performance obligation. As such, the Company allocated the $8.0 million to the Information Committee obligation.

The Company recognizes revenue over time as the measure of progress, which it believes best depicts the transfer of control to Pfizer. The Information Committee met regularly over the ROFR Period to share information which resulted in recognition of the transaction price over the 30-month ROFR Period.

During the nine months ended September 30, 2023, the Company recognized collaboration revenue of $1.2 million, compared to $0.8 million and $2.4 million, respectively for the three and nine months ended September 30, 2022. As the ROFR Period expired in May 2023, there was no revenue recognized during the three months ended September 30, 2023. There was no deferred revenue related to the Company’s obligation to Pfizer as of September 30, 2023. As of December 31, 2022, there was approximately $1.2 million of deferred revenue related to the Company’s obligation to Pfizer.

13. RELATED PARTY TRANSACTIONS

Oxford Biomedica Solutions LLC

As described in Note 5, the Company has significant influence over, but does not control, OXB Solutions through its noncontrolling representation on OXB Solution’s board of directors and the Company’s equity interest in OXB Solutions. In March 2022, concurrently with the closing of the transaction with OXB Solutions, the Company entered into certain ancillary agreements with OXB Solutions including a supply agreement, a lease assignment and assumption agreement, a sublease agreement and a transitional services agreement.

Supply Agreement

Pursuant to the terms of the Manufacturing and Supply Agreement with OXB Solutions entered into in March 2022 (the "Supply Agreement"), the Company agreed to purchase from OXB Solutions at least 50% of its clinical supply requirements of AAV-based products during the initial term of the supply agreement. The Supply Agreement provides for an initial term of three years, which may be extended for an additional one-year term. Under the Supply Agreement, the Company is committed to purchase a minimum number of batches of drug substance and drug product, as well as process development services, totaling approximately $29.7 million by the fiscal year ending December 31, 2023. As of September 30, 2023, the Company had approximately $1.4 million in remaining purchase obligations to OXB Solutions pursuant to the Supply Agreement. There are no minimum purchase commitments in 2024 (year three) of the Supply Agreement. After the initial term, the Company will have the right to terminate the Supply Agreement for convenience or other reasons specified in the Supply Agreement upon prior written notice. Either party may terminate the Supply Agreement upon an uncured material breach by the other party or upon the bankruptcy or insolvency of the other party.

During the three and nine months ended September 30, 2023, the Company recorded purchases of drug substance from OXB Solutions related to the Supply Agreement of $8.4 million and $21.7 million, respectively, as well as purchases of process development services of approximately $3.1 million and $5.8 million, respectively, and stability services and other support services of approximately $0.4 million and $1.2 million, respectively. During the three and nine months ended September 30, 2022, the Company recorded purchases of drug substance from OXB Solutions related to the Supply Agreement of $6.0 million and $7.5 million, respectively, as well as purchases of process development services of approximately $2.2 million and $10.2 million, respectively. These amounts are included within research and development expenses on the Company's condensed consolidated statements of operations. The amounts due to OXB Solutions under the Supply Agreement were $12.6 million and $5.2 million as of September 30, 2023 and December 31, 2022, respectively, and were included in accounts payable and accrued expenses and other liabilities on the Company's condensed consolidated balance sheets.

Lease Assignment and Sublease Agreement

As described in Note 9, the Company leases space for research and development, manufacturing and general office space in Bedford, Massachusetts. In March 2022, the Company and OXB Solutions entered into a lease assignment and assumption agreement pursuant to which Homology assigned all of its right, title and interest in, to and under this lease to OXB Solutions and a sublease agreement whereby OXB Solutions subleased certain premises in its facility to Homology. However, as of and for the three and nine

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months ended September 30, 2023, the Company remained jointly and severally liable for the payment of rent under this lease and had not been released from being the primary obligor under such lease and therefore the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s condensed consolidated balance sheets. Therefore, the Company is recording sublease income from OXB Solutions as if it were subleasing the space to OXB Solutions. On October 1, 2023, the Company was released from being the primary obligor under the lease (see Note 14).

During the three and nine months ended September 30, 2023, the Company recorded sublease income of $0.8 million and $2.3 million, respectively, related to the sublease agreement with OXB Solutions. During the three and nine months ended September 30, 2022, the Company recorded sublease income of $0.5 million and $1.2 million, respectively, related to the sublease agreement with OXB Solutions. This amount was recognized as a reduction to lease expense in the Company's condensed consolidated statements of operations.

During 2023, OXB Solutions assumed responsibility for paying the landlord for invoices related to the leased property and, as such, the Company began making direct payments to OXB Solutions for amounts due to OXB Solutions under the sublease. Therefore, as of September 30, 2023, the amount of sublease income payable to OXB Solutions was $0.1 million and was included in accrued expenses on the Company's condensed consolidated balance sheets. As of December 31, 2022, the amount of sublease income receivable from OXB Solutions was $0.5 million and was included in prepaid expenses and other current assets on the Company's condensed consolidated balance sheets.

Transitional Services Agreement

Under the transitional services agreement with OXB Solutions (the “Services Agreement”), the Company is performing certain services for the benefit of OXB Solutions and OXB Solutions is performing certain services for the benefit of the Company. The term of the Services Agreement will not exceed eighteen months and lasts until the earlier of termination for convenience, termination for cause in the event of an uncured material breach, termination as a result of bankruptcy of either party, and expiration or termination of the only remaining outstanding service as set forth in the Services Agreement. Each company is fully reimbursing the other for these services. The Services Agreement was substantially complete as of September 30, 2023.

Expenses incurred by the Company for services provided by OXB Solutions recognized under the Services Agreement totaled $0.3 million for the nine months ended September 30, 2023, and $0.2 million and $0.5 million for the three and nine months ended September 30, 2022, respectively, and are presented within research and development expenses in the condensed consolidated statements of operations as the services related to facilities support within the Company's research and development labs. As of September 30, 2023 and December 31, 2022, the amount due to OXB Solutions under the Services Agreement was $0.1 million at each balance sheet date, and was included in accrued expenses and other liabilities on the Company's condensed consolidated balance sheets.

The Company provided finance, human resources, IT and legal services to OXB Solutions under the Services Agreement and recognized $0.5 million for the nine months ended September 30, 2023, and $0.8 million and $1.7 million for the three and nine months ended September 30, 2022, respectively, for amounts reimbursed by OXB Solutions as a reduction to general and administrative expense in the Company's condensed consolidated statements of operations. The Company did not provide reimbursable services to OXB Solutions under the Services Agreement during the three months ended September 30, 2023. As of December 31, 2022, the Company had a receivable balance of $0.3 million from OXB Solutions which was recorded as a component of prepaid expenses and other current assets in the Company's condensed consolidated balance sheets. Pursuant to the Services Agreement, the Company has been paying vendors on OXB Solutions' behalf; this process will be fully transitioned to OXB Solutions in 2023. As of December 31, 2022, the amount receivable from OXB Solutions for amounts paid to vendors on their behalf was $1.1 million and was included in prepaid expenses and other current assets on the Company's condensed consolidated balance sheets.

14. SUBSEQUENT EVENTS

On September 25, 2023, the Company signed and executed a release letter with its lessor related to its headquarters in Bedford, MA. The lessor agreed to release the Company of all obligations under the lease effective October 1, 2023 (the “Release Date”) in exchange for a $0.1 million cash payment. For accounting purposes, the release letter is not considered a modification of the lease until the Release Date as the Company is not released from its obligations under the lease until such date. As of September 30, 2023, the lease had a remaining right-of-use asset balance of $19.5 million and an operating lease liability balance of $28.3 million. On October 1, 2023, the Company will write off the right-of-use asset and operating lease liability and record the difference as a gain of $8.8 million within other income on the condensed consolidated statements of operations. Because the Company’s sublease agreement with OXB Solutions remains in effect after termination of the head lease, the Company will recognize a new right-of-use asset and an operating lease liability of $1.6 million, which equals the present value of the future sublease payments owed to OXB Solutions for

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the remaining term of the sublease. The Company is actively searching for a subtenant to take over its sublease with OXB Solutions and is evaluating whether there is any impairment of the related right-of-use asset.

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Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our condensed consolidated financial statements and related notes appearing elsewhere in this Quarterly Report on Form 10-Q. Some of the information contained in this discussion and analysis or set forth elsewhere in this Quarterly Report on Form 10-Q, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. As a result of many important factors, including those set forth in the "Risk Factors" section of this Quarterly Report on Form 10-Q, our actual results could differ materially from the results described in, or implied, by these forward-looking statements.

Overview

We are a clinical-stage genetic medicines company historically focused on transforming the lives of patients suffering from rare genetic diseases with significant unmet medical needs by addressing the underlying cause of the disease. Our proprietary platform is designed to utilize our human hematopoietic stem cell-derived adeno-associated virus vectors, or AAVHSCs, to precisely and efficiently deliver single administration genetic medicines in vivo through a nuclease-free gene editing modality, gene therapy, or gene therapy to express antibodies platform, or GTx-mAb, which is designed to produce antibodies throughout the body.

In July 2023, we completed a review of our business and our Board of Directors approved a plan to explore, review and evaluate a range of potential strategic options available to us, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the current financing environment and our anticipated clinical development timeline for our lead program, HMI-103, we stopped further development of our programs and reduced our workforce by 86% to significantly reduce our ongoing operating costs as we evaluate strategic alternatives. We have retained TD Cowen as our strategic financial advisor. There can be no assurance that a transaction will result from this process and we do not intend to disclose additional details unless and until we have entered into a specific transaction or otherwise determined that further disclosure is appropriate.

Our former clinical programs include: HMI-103, an investigational gene editing candidate for the treatment of patients with phenylketonuria, or PKU, HMI-203, an investigational gene therapy candidate for the treatment of patients with mucopolysaccharidosis type II (MPS II), or Hunter syndrome and HMI-102, an investigational gene therapy candidate for the treatment of adult patients with PKU. Our preclinical programs include: HMI-104, a GTx-mAb gene therapy candidate for the treatment of patients with paroxysmal nocturnal hemoglobinuria, or PNH, and HMI-204, a gene therapy candidate for metachromatic leukodystrophy, or MLD.

HMI-103: Gene Editing Candidate for the Treatment of Patients with PKU

In October 2023, we reported clinical data from the first dose cohort in the pheEDIT Phase 1, dose-escalation trial evaluating HMI-103 in adults with classical PKU. As of the data cut-off date of September 14, 2023, HMI-103 has been generally well-tolerated in all three participants. Participant 1 experienced a reduction in plasma phenylalanine, or Phe, levels to below the U.S. American College of Medical Genetics and Genomics PKU treatment guideline threshold of <360 μmol/L, and the majority of Phe levels have been below 360 μmol/L through 39 weeks post-dose, including after the initiation of dietary protein supplementation. Participant 2 experienced a meaningful plasma Phe reduction of 50% at 23 weeks post-dose. Participant 3 experienced a meaningful plasma Phe reduction of 60% at 14 weeks post-dose. In accordance with our decision to stop developing our programs, we terminated the pheEDIT trial in October 2023.

HMI-103 was administered to participants via a one-time I.V. infusion at a dose of 6E13 vg/kg. As of the data cut-off date of September 14, 2023, HMI-103 has been generally well-tolerated by all three participants with no serious adverse events, and the majority of treatment-related adverse events have been mild and transient. All liver function tests have remained in the normal range during the prophylactic immunosuppression regimen incorporating the T-cell inhibitor tacrolimus in combination with corticosteroid. In July 2023, we received approval from the Independent Data Monitoring Committee to escalate to the next dose cohort in the trial.

The pheEDIT clinical trial was an open-label, dose-escalation study evaluating the safety and efficacy of a single I.V. administration of HMI-103 in patients ages 18-55 years old who have been diagnosed with classical PKU due to phenylalanine hydroxylase, or PAH, deficiency. In addition to safety endpoints, the trial measured serum Phe changes. The trial incorporated an immunosuppressive regimen that included a T-cell inhibitor used in combination with a steroid-sparing regimen. Prior to dosing, participants completed an up to 82-day screening/run-in period to help us account for and more closely understand day-to-day Phe fluctuations.

We received Fast Track Designation for HMI-103 from the U.S. Food and Drug Administration, or FDA, for the treatment of neurocognitive and neuropsychiatric manifestations of PKU secondary to PAH deficiency.

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We have presented preclinical data on the mechanism of action of our optimized HMI-103 gene editing candidate, which is designed to harness the body's natural DNA repair process of HR to replace the disease-causing PAH gene with a functional PAH gene and liver-specific promoter and to maximize PAH expression in all transduced liver cells through episomal expression. We observed significant Phe reduction following a single I.V. administration of the murine surrogate of HMI-103 in the PKU disease model out to 43 weeks (end of study). In this preclinical PKU model, the murine surrogate of HMI-103 was ten times more potent than non-integrating gene therapy vector HMI-102. Additionally, we observed on-target integration and no off-target integration following a single I.V. administration of HMI-103 in a humanized liver model, as determined by a genome-wide integration assay. Using quantitative molecular methods, we also demonstrated achievement of gene integration efficiencies in the humanized murine liver model that corresponded with Phe correction in the PKU murine model.

In 2023, we presented new preclinical data supporting the immunosuppression regimen incorporated in our clinical trials at WORLDSymposium™. In non-human primates, or NHPs, our data demonstrated that modulating T-cell activity using tacrolimus together with dexamethasone is important in reducing B- and T-cell activity, neutralizing antibody, or nAb, formation, and maintaining transgene expression following rAAV administration in NHPs.

HMI-104: GTx-mAb Gene Therapy Candidate for the Treatment of Patients with PNH

HMI-104 is a clinical development candidate for PNH from our GTx-mAb platform. This platform represents an additional way that we can leverage our AAVHSCs in an effort to deliver one-time in vivo gene therapy to express and secrete antibodies from the liver, which we believe may allow us to target diseases with larger patient populations. In support of this program, we generated and presented preclinical data targeting complement protein 5, demonstrating preclinical proof-of-concept in PNH. A single I.V. dose of an AAVHSC GTx-mAb showed expression of full-length antibodies from the liver consistent with levels associated with anti-C5 therapeutics, sustained and robust Immunoglobulin G, or IgG, expression in vivo in a humanized murine liver model and a murine NOD-SCID model, and in vivo vector-expressed C5 mAb had potent functional activity as shown by an ex vivo hemolysis assay. Additionally, we observed sustained expression of C5 mAb in the presence of murine and human neonatal fragment crystallizable (Fc) receptor, or FcRn. We have completed IND-enabling studies with HMI-104.

Oxford Biomedica Solutions Transaction

On March 10, 2022, we closed a transaction with Oxford Biomedica Solutions LLC (f/k/a Roadrunner Solutions LLC), or OXB Solutions, Oxford Biomedica (US), Inc., or OXB, and Oxford Biomedica plc, or OXB Parent, and collectively with OXB, Oxford, pursuant to the Equity Securities Purchase Agreement, or the Purchase Agreement, dated as of January 28, 2022, by and among Homology, OXB Solutions and Oxford, whereby, among other things, we and Oxford agreed to collaborate to operate OXB Solutions, which provides AAV vector process development and manufacturing services to biotechnology companies, which we refer to as the Oxford Biomedica Solutions Transaction, or the OXB Solutions Transaction. OXB Solutions incorporates our proven 'plug and play' process development and manufacturing platform, as well as our experienced team and high-quality GMP vector production capabilities that we built and operated since 2019.

Pursuant to the terms of the Purchase Agreement and a contribution agreement, or the Contribution Agreement, entered into between us and OXB Solutions prior to the closing of the OXB Solutions Transaction, or the Closing, we agreed to assign and transfer to OXB Solutions all of our assets that are primarily used in the manufacturing of AAV vectors for use in gene therapy or gene editing products, but excluding certain assets related to manufacturing or testing of our proprietary AAV vectors, or collectively, the Transferred Assets, in exchange for 175,000 common equity units in OXB Solutions, or Units, and OXB Solutions assumed from us, and agreed to pay, perform and discharge when due, all of our duties, obligations, liabilities, interests and commitments of any kind under, arising out of or relating to the Transferred Assets.

Effective as of the Closing, we sold to OXB, and OXB purchased from us, 130,000 Units, or the Transferred Units, in exchange for $130.0 million. In connection with the Closing, OXB contributed $50.0 million in cash to OXB Solutions in exchange for an additional 50,000 Units. Immediately following the Closing, (i) OXB owned 180,000 Units, representing 80 percent (80%) of the fully diluted equity interests in OXB Solutions, and (ii) we owned 45,000 Units, representing 20 percent (20%) of the fully diluted equity interests in OXB Solutions.

Pursuant to the Amended and Restated Limited Liability Company Agreement of OXB Solutions, or the OXB Solutions Operating Agreement, which was executed in connection with the Closing, at any time following the three-year anniversary of the Closing, (i) OXB will have an option to cause us to sell and transfer to OXB, and (ii) we will have an option to cause OXB to purchase from us, in each case all of our equity ownership interest in OXB Solutions at a price equal to 5.5 times the revenue for the immediately preceding 12-month period, subject to a maximum amount of $74.1 million. Pursuant to the terms of the OXB Solutions Operating Agreement, we are entitled to designate one director on the board of directors of OXB Solutions, currently Albert Seymour, our President and Chief Executive Officer.

Concurrently with the Closing, we entered into certain ancillary agreements with OXB Solutions including a license and patent management agreement whereby OXB Solutions granted certain licenses to us, a supply agreement, or the Supply Agreement, for a

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term of three years which includes certain annual minimum purchase commitments, a lease assignment pursuant to which we assigned all of our right, title and interest in, to and under our facility lease to OXB Solutions, a sublease agreement whereby OXB Solutions subleased certain premises in its facility to us, as well as several additional ancillary agreements.

Corporate Headquarters Lease

In November 2021, we entered into an amendment of our December 2017 lease agreement, or the Lease Amendment, for our corporate headquarters in Bedford, Massachusetts. The Lease Amendment increases the space under lease by approximately 23,011 square feet, or the Expansion Premises, and extends the expiration date of the existing premises under the lease from February 2027 to June 2030. The term with respect to the Expansion Premises commenced on May 1, 2022 and continues for a period of ten years and five months. The term of the Expansion Premises and the existing premises are not coterminous. Annual base rent for the existing premise under the Lease Amendment is approximately $4.7 million beginning on March 1, 2027, and increases by three percent annually; annual base rent for the Expansion Premises is approximately $1.4 million per year and increases by three percent annually. The Lease Amendment allows for tenant improvement allowances not to exceed $6.3 million in the aggregate. Under the terms of the agreement with Oxford, our lease for our corporate headquarters, including the Expansion Premises, has been assigned to OXB Solutions with Homology subleasing a portion of lab and office space back from the newly created company. We remained jointly and severally liable for the payment of rent under this lease as of September 30, 2023. However as of October 1, 2023, we were released from being primary obligor under the lease. See Notes 9 and 13 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding our lease agreement.

License Agreements

In April 2016, we entered into an exclusive license agreement with City of Hope, or COH, pursuant to which COH granted us an exclusive, sublicensable, worldwide license, or the COH License, to certain AAV vector-related patents and know-how owned by COH to develop, manufacture, use and commercialize products and services covered by such patents and know-how in any and all fields. On August 6, 2021, we received notice from COH that we did not accomplish at least one of the partnering milestones by the applicable deadline, as set forth in the COH License. This notice does not affect our exclusive license in the field of mammalian therapeutics, including all human therapeutics, associated diagnostics, and target validation, or the Mammalian Therapeutic Field, where we retain exclusive rights. Instead, the notice served as written notice that the exclusive license granted pursuant to the COH License in all fields except the Mammalian Therapeutic Field converted from exclusive to non-exclusive effective as of September 20, 2021, which was forty-five days from the receipt of notice. In connection with the conversion, any royalty obligations and sublicensee fees relating to fields outside of the Mammalian Therapeutic Field shall be reduced by a certain percentage. This change to our exclusive worldwide license with COH does not impact any of our current therapeutic product development candidates, including HMI-103, HMI-203, HMI-102, HMI-204 and HMI-104, nor will it impact any potential future therapeutic product development candidates.

Financial Overview

Since our inception in 2015 through September 30, 2023, we have raised approximately $721 million in aggregate net proceeds through our initial public offering, or IPO, in April 2018, follow-on public offerings of common stock in April 2019 and April 2021, proceeds from the sale of common stock under an “at-the-market” sales agreement, equity investments from pharmaceutical companies, preferred stock financings and our agreement with Oxford. Included in our net proceeds is a $130.0 million up-front cash payment from our agreement with Oxford, $50.0 million from a former collaboration partner, comprised of an up-front payment of $35.0 million and a $15.0 million equity investment, and a $60.0 million equity investment from Pfizer Inc., or Pfizer, through a private placement transaction.

We were incorporated and commenced operations in 2015. Since our incorporation and until recently, we devoted substantially all of our resources to organizing and staffing our Company, business planning, raising capital, developing our technology platform, advancing HMI-102, HMI-103 and HMI-203 through IND-enabling studies and into clinical trials, advancing HMI-202 and HMI-104 into IND-enabling studies, researching and identifying additional product candidates, developing and implementing manufacturing processes and manufacturing capabilities, building out our manufacturing and research and development space, enhancing our intellectual property portfolio and providing general and administrative support for these operations. To date, we have financed our operations primarily through the sale of common stock, through the sale of preferred stock, through funding from our collaboration partner and through proceeds received as a result of our transaction with OXB Solutions.

To date, we have not generated any revenue from product sales and do not expect to generate any revenue from the sale of products in the foreseeable future, if at all. We recognized $1.2 million in collaboration revenue for the nine months ended September 30, 2023, and $0.8 million and $2.4 million for the three and nine months ended September 30, 2022, respectively. We did not recognize any collaboration revenue for the three months ended September 30, 2023.

Since inception, we have incurred significant operating losses. Our net loss was $33.0 million and $96.8 million for the three and nine months ended September 30, 2023, respectively. For the three months ended September 30, 2022, our net loss was $33.7

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million and for the nine months ended September 30, 2022, our net income was $29.3 million as a result of our transaction with OXB Solutions, as we recorded a gain of $131.2 million on the sale of our manufacturing business (see Note 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding the OXB Solutions Transaction). As of September 30, 2023 and December 31, 2022, we had an accumulated deficit of $526.0 million and $429.1 million, respectively.

Our total operating expenses were $31.0 million and $90.5 million for the three and nine months ended September 30, 2023, respectively, and $33.7 million and $101.2 million for the three and nine months ended September 30, 2022, respectively. We expect operating expenses to continue to decrease over the prior year as we recently reduced our workforce by 86% and have stopped all further program development efforts. We expect to continue to incur costs and expenditures in connection with our ongoing evaluation of strategic alternatives and we will continue to incur costs associated with operating as a public company. There can be no assurance, however, that we will be able to successfully consummate any particular strategic transaction. The process of evaluating strategic transactions has been and may continue to be costly, time-consuming and complex, and we may incur significant costs related to these processes, such as legal, accounting and advisory fees and expenses and other related charges. A considerable portion of these costs will be incurred regardless of whether any particular course of action is implemented or transaction is completed. Any such expenses will decrease the remaining cash available for use in our business. In addition, any strategic business combination or other transactions that we may consummate in the future, could have a variety of negative consequences and we may implement a course of action or consummate a transaction that yields unexpected results that adversely affects our business and decreases the remaining cash available for use in our business or the execution of our strategic plan. There can be no assurances that any particular course of action, business arrangement, transaction, or series of transactions, will be pursued, successfully consummated, lead to increased stockholder value or achieve the anticipated results. Any failure of such potential transaction to achieve the anticipated results could significantly impair our ability to enter into any future strategic transactions and may significantly diminish or delay any future distributions to our stockholders.

Should we resume development of product candidates, our ability to generate product revenue sufficient to achieve profitability would depend heavily on the successful development and eventual commercialization of one or more product candidates. Our future operating requirements will depend on many factors, including:

•the costs, timing, and results of research and development efforts for any product candidates, including clinical trials;

•the costs and timing of process development scale-up activities, and the adequacy of supply of any product candidates for preclinical studies and clinical trials through CMOs, including OXB Solutions;

•the costs and timing of preparing, filing, and prosecuting patent applications, maintaining and enforcing our intellectual property rights and defending any intellectual property-related claims, including any claims by third parties that we are infringing upon their intellectual property rights;

•the effect of competitors and market developments; and

•our ability to establish and maintain strategic collaborations, licensing or other agreements and the financial terms of such agreements for our product candidates.

As of September 30, 2023, we had cash, cash equivalents, and short-term investments of $103.3 million. Based on our current projections, including our recent reduction in force and stopping further program development efforts, we believe that our existing cash, cash equivalents, and short-term investments will enable us to continue our operations for at least one year from the date of this filing. However, due to the discontinuation of all of our clinical trials and research activities, as well as our recent reduction in force of all but a few custodial employees, management has concluded that there is a substantial doubt regarding our ability to continue as a going concern for more than twelve months after the date the unaudited condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q have been issued. See “Liquidity and Capital Resources.”

Components of Our Results of Operations

Revenue

To date, we have not generated any revenue from product sales and do not expect to generate any revenue from the sale of products in the foreseeable future. We recorded $1.2 million and $2.4 million in collaboration revenue for the nine months ended September 30, 2023 and 2022, respectively, related to the Stock Purchase Agreement with Pfizer (see Note 12 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding revenue recognition discussions).

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Operating Expenses

Our operating expenses since inception have consisted solely of research and development costs and general and administrative costs.

Research and Development Expenses

Research and development expenses consist primarily of costs incurred for research activities, including discovery efforts, and the development of our product candidates, and include:

•salaries, benefits and other related costs, including stock-based compensation expense, for personnel engaged in research and development functions;

•expenses incurred under agreements with third parties, including contract research organizations, or CROs, and other third parties that conduct research, preclinical activities and clinical trials on our behalf as well as CMOs, including OXB Solutions, that manufacture our product candidates for use in preclinical testing and clinical trials;

•costs of outside consultants, including their fees and related travel expenses;

•costs of laboratory supplies and acquiring, developing and manufacturing preclinical study and clinical trial materials; and

•allocated expenses for rent and other operating costs.

We expense research and development costs as incurred.

Research and development activities have historically been central to our business model. We expect our research and development expenses to continue to decrease significantly given the discontinuation of all of our clinical trials and research activities. Should we resume development of product candidates, we would expect research and development costs to increase significantly for the foreseeable future as the product candidate development programs progress.

Should we resume development of product candidates, the duration, costs and timing of development activities including clinical trials would depend on a variety of factors, including:

•the scope, rate of progress, expense and results of clinical trials and other research and development activities that we may conduct;

•uncertainties in clinical trial design and patient enrollment rates;

•the actual probability of success for our product candidates, including the safety and efficacy results, early clinical data, competition, manufacturing capability and commercial viability;

•significant and changing government regulation and regulatory guidance;

•the timing and receipt of any marketing approvals; and

•the expense of filing, prosecuting, defending and enforcing any patent claims and other intellectual property rights.

Should we resume development of product candidates, a change in the outcome of any of these variables with respect to the development of a product candidate could mean a significant change in the costs and timing associated with the development of that product candidate. For example, if the FDA or another regulatory authority were to require us to conduct clinical trials beyond those that we anticipate will be required for the completion of clinical development of a product candidate, or if we experience significant delays in our clinical trials due to patient enrollment or other reasons, we would be required to expend significant additional financial resources and time on the completion of clinical development.

General and Administrative Expenses

General and administrative expenses consist primarily of salaries and other related costs, including stock-based compensation, for personnel in our executive, finance, human resources, legal, business development and administrative functions. General and administrative expenses also include legal fees relating to intellectual property and corporate matters; professional fees for accounting, auditing, tax and consulting services; insurance costs; travel expenses; and facility-related expenses, which include direct depreciation costs, rent expense, maintenance of facilities and other operating costs including expenses associated with being a public company.

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We expect our general and administrative expenses to decrease in the near future due to our recent workforce reductions. We have incurred and expect to continue to incur significant costs, however, related to our exploration of strategic alternatives, including legal, accounting and advisory expenses and other related charges.

Other Income

Other income consists of a gain on the sale of our manufacturing business and interest income earned on our cash, cash equivalents, and short-term investments. Our interest income has increased due to significantly higher yields on invested funds during the three and six months ended September 30, 2023 as compared to the prior year.

Critical Accounting Estimates

Our management’s discussion and analysis of financial condition and results of operations is based on our condensed consolidated financial statements, which have been prepared in accordance with generally accepted accounting principles in the United States. The preparation of our condensed consolidated financial statements and related disclosures requires us to make estimates, assumptions and judgments that affect the reported amount of assets, liabilities, revenue, costs and expenses, and related disclosures. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

Our critical accounting policies are described under the heading “Management’s Discussion and Analysis of Financial Condition and Results of Operations— Critical Accounting Policies and Use of Estimates” in our Annual Report on Form 10-K for the year ended December 31, 2022 and in the notes to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q. There were no material changes to our critical accounting policies during the three months ended September 30, 2023 from those discussed in our Annual Report on Form 10-K for the year ended December 31, 2022.

Results of Operations

Comparison of Three Months Ended September 30, 2023 and 2022

The following table summarizes our results of operations for the three months ended September 30, 2023 and 2022:

	Three months ended September 30,
(in thousands)	2023			2022			Change
Collaboration revenue	$	—		$	802		$	(802	)
Operating expenses:
Research and development		17,519			25,854			(8,335	)
General and administrative		6,842			7,810			(968	)
Restructuring and other charges		6,640			—			6,640
Total operating expenses		31,001			33,664			(2,663	)
Loss from operations		(31,001	)		(32,862	)		1,861
Other income:
Interest income		1,423			1,269			154
Total other income		1,423			1,269			154
Loss before income taxes		(29,578	)		(31,593	)		2,015
Benefit from income taxes		—			46			(46	)
Loss from equity method investment		(3,376	)		(2,179	)		(1,197	)
Net loss	$	(32,954	)	$	(33,726	)	$	772

Collaboration Revenue

Collaboration revenue for the three months ended September 30, 2022 was $0.8 million and was due to the recognition of deferred revenue related to the Stock Purchase Agreement with Pfizer. We previously recognized deferred revenue from Pfizer over Pfizer's right of first refusal, or ROFR, period of 30 months during which Pfizer could have negotiated a potential collaboration on the development and commercialization of HMI-102 and HMI-103. The ROFR period expired in May 2023.

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Research and Development Expenses

	Three months ended September 30,
(in thousands)	2023			2022		Change
External development costs for clinical programs:
HMI-102	$	3,046		$	3,866	$	(820	)
HMI-103		7,258			5,459		1,799
HMI-203		(366	)		5,984		(6,350	)
Other development-stage programs' external    development costs		5,221			2,498		2,723
Employee-related costs		1,193			5,684		(4,491	)
Other research and development costs		1,167			2,363		(1,196	)
Total research and development expenses	$	17,519		$	25,854	$	(8,335	)

Research and development expenses for the three months ended September 30, 2023 were $17.5 million, compared to $25.9 million for the three months ended September 30, 2022. The decrease of $8.3 million was primarily associated with our decision to stop further development of our programs and reduce our workforce by 86% in July 2023 in an effort to decrease our ongoing operating costs. External costs for our three clinical programs for the three months ended September 30, 2023 reflect the results of reconciliations performed at our CRO and other vendors associated with our clinical trials, as well as the recognition of expense for contractual obligations owed under our Supply Agreement with OXB Solutions. In addition, employee-related costs decreased over the prior quarter primarily due to our workforce reduction, which we instituted during the three months ended September 30, 2023.

General and Administrative Expenses

General and administrative expenses for the three months ended September 30, 2023 were $6.8 million, compared to $7.8 million for the three months ended September 30, 2022. The decrease of $1.0 million was primarily due to lower consulting, market research costs and facility-related costs.

Restructuring and Other Charges

In connection with the corporate restructuring that reduced our current workforce by approximately 80 employees, or 86%, we recorded a restructuring charge for severance and related costs of $6.9 million during the three months ended September 30, 2023. We also modified certain stock options and restricted stock units granted to the terminated employees in a prior period. These equity modifications resulted in a net reduction to stock based compensation expense of $0.3 million reflected within restructuring and other charges during the three months ended September 30, 2023. See Notes 8 and 10 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding our corporate restructuring and other charges. We did not record restructuring and other charges for the three months ended September 30, 2022.

Interest Income

Interest income for the three months ended September 30, 2023 was $1.4 million, compared to $1.3 million for the three months ended September 30, 2022. The increase of $0.1 million was primarily the result of interest income generated at higher yields on invested funds for the three months ended September 30, 2023, compared to the three months ended September 30, 2022.

Income Tax Benefit

We recorded an income tax benefit of less than $0.1 million for the three months ended September 30, 2022. We did not record an income tax provision (benefit) for the three months ended September 30, 2023.

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Loss from Equity Method Investment

We record our share of gains or losses from OXB Solutions on a quarterly basis. For the three months ended September 30, 2023 and 2022, we recorded a loss from equity method investment of $3.4 million and $2.2 million, respectively, representing our share of OXB Solutions' net loss. See Notes 2 and 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for more information regarding the equity method of accounting.

Net Loss

Net loss for the three months ended September 30, 2023 was $33.0 million, compared to $33.7 million for the three months ended September 30, 2022. The decrease in net loss was primarily due to the decrease in operating expenses discussed above.

Comparison of Nine Months Ended September 30, 2023 and 2022

The following table summarizes our results of operations for the nine months ended September 30, 2023 and 2022:

	Nine months ended September 30,
(in thousands)	2023			2022			Change
Collaboration revenue	$	1,156		$	2,406		$	(1,250	)
Operating expenses:
Research and development		60,489			71,202			(10,713	)
General and administrative		23,355			29,991			(6,636	)
Restructuring and other charges		6,640			—			6,640
Total operating expenses		90,484			101,193			(10,709	)
Loss from operations		(89,328	)		(98,787	)		9,459
Other income:
Gain on sale of business		—			131,249			(131,249	)
Interest income		4,403			1,775			2,628
Total other income		4,403			133,024			(128,621	)
Income (loss) before income taxes		(84,925	)		34,237			(119,162	)
Provision for income taxes		—			(816	)		816
Loss from equity method investment		(11,917	)		(4,131	)		(7,786	)
Net income (loss)	$	(96,842	)	$	29,290		$	(126,132	)

Collaboration Revenue

Collaboration revenue for the nine months ended September 30, 2023 was $1.2 million, compared to $2.4 million for the nine months ended September 30, 2022, and was due to the recognition of deferred revenue related to the Stock Purchase Agreement with Pfizer in both periods.

Research and Development Expenses

	Nine months ended September 30,
(in thousands)	2023		2022		Change
External development costs for clinical programs:
HMI-102	$	5,822	$	13,643	$	(7,821	)
HMI-103		16,371		10,767		5,604
HMI-203		8,942		11,095		(2,153	)
Other development-stage programs' external    development costs		13,685		6,330		7,355
Employee-related costs		11,631		24,025		(12,394	)
Other research and development costs		4,038		5,342		(1,304	)
Total research and development expenses	$	60,489	$	71,202	$	(10,713	)

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Research and development expenses for the nine months ended September 30, 2023 were $60.5 million, compared to $71.2 million for the nine months ended September 30, 2022. The decrease of $10.7 million was primarily due to lower employee-related costs as a result of the reduction in workforce we instituted during the three months ended September 30, 2023, in addition to transferring employees to OXB Solutions upon the sale of our manufacturing business to Oxford in March 2022. In addition, external development costs related to HMI-102, including costs incurred with our CRO to conduct and manage our pheNIX clinical trial, decreased as the trial was placed on clinical hold in February 2022 and enrollment was paused in August 2022. Partially offsetting these decreases were increased external development costs in the first half of 2023 related to our development-stage programs, including higher spending on HMI-104, our GTx-mAb product candidate for PNH. In addition, external development costs for the HMI-103 clinical program increased over the nine months ended September 30, 2022.

General and Administrative Expenses

General and administrative expenses for the nine months ended September 30, 2023 were $23.4 million, compared to $30.0 million for the nine months ended September 30, 2022. The decrease of $6.6 million was primarily due to a $3.3 million decrease in consulting expense as the prior year included a fee of $2.5 million paid to a strategic advisory firm that assisted us with the OXB Solutions transaction. Employee-related costs decreased $1.5 million as a result of the reduction in workforce we instituted in the three months ended September 30, 2023. In addition, professional fees decreased $0.8 million as we incurred higher legal fees in the prior year related to the OXB Solutions Transaction, and depreciation expense and overall facilities costs decreased $0.7 million as compared to the prior year period.

Restructuring and Other Charges

In connection with the corporate restructuring that reduced our workforce by approximately 80 employees, or 86%, we recorded a restructuring charge for severance and related costs of $6.9 million during the nine months ended September 30, 2023. We also modified certain stock options and restricted stock units granted to the terminated employees in a prior period. These equity modifications resulted in a net reduction to stock based compensation expense of $0.3 million reflected within restructuring and other charges during the nine months ended September 30, 2023. See Notes 8 and 10 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding restructuring and other charges. We did not record restructuring and other charges for the nine months ended September 30, 2022.

Gain on Sale of Business

Gain on sale of business for the nine months ended September 30, 2022 was $131.2 million. On March 10, 2022, we closed our transaction with Oxford and recorded a gain of $131.2 million on the sale of our manufacturing business. See Note 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for details surrounding the sale.

Interest Income

Interest income for the nine months ended September 30, 2023 was $4.4 million, compared to $1.8 million for the nine months ended September 30, 2022. The increase of $2.6 million was primarily the result of interest income generated at higher yields on invested funds for the nine months ended September 30, 2023 compared to the nine months ended September 30, 2022.

Provision for Income Taxes

We recorded an income tax provision of $0.8 million for the nine months ended September 30, 2022. The tax provision predominately resulted from the gain associated with the sale of the Company's manufacturing business due to the transaction with Oxford. Though we had substantial pre-tax income for the nine months ended September 30, 2022, we had federal and state net operating loss carryforwards and research and development tax credits available to offset most of that taxable income for the period. We did not record an income tax provision (benefit) for the nine months ended September 30, 2023.

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Loss from Equity Method Investment

We record our share of gains or losses from OXB Solutions on a quarterly basis. For the nine months ended September 30, 2023 and 2022, we recorded a loss from equity method investment of $11.9 million and $4.1 million, respectively, representing our share of OXB Solutions' net loss. The loss from equity method investment for the nine months ended September 30, 2023 includes an other-than-temporary impairment charge of approximately $3.8 million we recorded because it was determined that the fair value of our equity method investment in OXB Solutions was less than its carrying value. See Notes 2 and 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for more information regarding the equity method of accounting.

Net Income (Loss)

Net loss for the nine months ended September 30, 2023 was $96.8 million, compared to net income of $29.3 million for the nine months ended September 30, 2022. Net income for the nine months ended September 30, 2022 was primarily due to a gain of $131.2 million on the sale of our manufacturing business, offset by our operating expenses of $101.2 million as described above.

Liquidity and Capital Resources

Since our inception, we have incurred significant operating losses. We do not have any approved products and have never generated any revenue from product sales. To date, we have financed our operations primarily through the sale of common stock, the sale of preferred stock, through an up-front payment and funding of research candidates from a collaboration partner and through the gross proceeds from our transaction with OXB Solutions. Since our inception in 2015, we have raised approximately $721 million in aggregate net proceeds through our IPO in April 2018, follow-on public offerings of common stock in April 2019 and April 2021, proceeds from the sale of common stock under an “at-the-market” sales agreement, equity investments from pharmaceutical companies, preferred stock financings and our agreement with Oxford. Included in our net proceeds is a $130.0 million up-front cash payment from our agreement with Oxford, $50.0 million from a former collaboration partner, comprised of an up-front payment of $35.0 million and a $15.0 million equity investment, and a $60.0 million equity investment from Pfizer through a private placement transaction.

ATM Program

On March 9, 2023, we filed a Registration Statement on Form S-3 (File No. 333-270414) (the “Shelf”) with the SEC in relation to the registration of up to an aggregate of $250.0 million of our common stock, preferred stock, debt securities, warrants and/or units of any combination thereof for a period up to three years from the date of the filing. The Shelf became effective on March 17, 2023. We also simultaneously entered into a sales agreement with Cowen and Company, LLC (“Cowen”), as sales agent, providing for the offering, issuance and sale by the Company of up to an aggregate of $75.0 million of our common stock from time to time in “at-the-market” offerings under the Shelf (the “ATM”). We did not sell any shares of common stock under the ATM during the nine months ended September 30, 2023. As of September 30, 2023, there remained $75.0 million of common stock available for sale under the ATM.

Oxford Biomedica Solutions Transaction

On March 10, 2022, we closed a transaction with Oxford pursuant to the Purchase Agreement, dated as of January 28, 2022, by and among Homology, OXB Solutions and Oxford, whereby, among other things, we and Oxford agreed to collaborate to operate OXB Solutions, which will provide AAV vector process development services and manufacturing services to pharmaceutical and biotechnology companies. Pursuant to the terms of the agreements entered into as part of the OXB Solutions Transaction, we have assigned and transferred to OXB Solutions all of our assets that are primarily used in the manufacturing of AAV vectors for use in gene therapy and gene editing products. Oxford paid us $130.0 million upfront and invested $50.0 million to fund the new company in exchange for an 80 percent ownership stake, while we own 20 percent of the new company. Also, at any time following the three-year anniversary of the closing of the transaction, Oxford has an option to cause us to sell and transfer to Oxford and we have an option to cause Oxford to purchase from us, in each case all of our equity ownership interest in OXB Solutions at a price equal to 5.5 times the revenue for the immediately preceding 12-month period, subject to a maximum amount of $74.1 million. See Note 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding the Oxford transaction.

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Strategic Collaborations and Investments

On November 9, 2020, we entered into the Stock Purchase Agreement with Pfizer, pursuant to which Pfizer purchased 5,000,000 shares of our common stock through a private placement transaction at a purchase price of $12.00 per share, for an aggregate purchase price of $60.0 million. Under the Stock Purchase Agreement, Pfizer was granted an exclusive right of first refusal, or ROFR, for a 30-month period to negotiate a potential collaboration on the development and commercialization of HMI-102 and HMI-103. The 30-month ROFR period expired on May 9, 2023. In addition to the ROFR, the Stock Purchase Agreement provided for an information sharing committee comprised of representatives of each company which served as a forum for sharing information regarding the development of HMI-102 and HMI-103 during the ROFR period. Additionally, Pfizer designated a member to join our Scientific Advisory Board to participate in matters related to the development of these programs.

Strategic Review and Reduction in Force

On July 25, 2023, our Board of Directors approved a process to explore, review and evaluate a range of potential strategic options available to us, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Therefore, based on cost-reduction initiatives intended to reduce our ongoing operating expenses and maximize shareholder value as we evaluate strategic options, our Board of Directors also approved a reduction in our current workforce by approximately 80 employees. In connection with this corporate restructuring, we recorded a restructuring charge for severance and related costs of $6.9 million in our condensed consolidated statements of operations during the three months ended September 30, 2023.

Cash Flows

Our cash, cash equivalents, and short-term investments totaled $103.3 million and $175.0 million as of September 30, 2023 and December 31, 2022, respectively. We had no indebtedness as of September 30, 2023 and December 31, 2022.

The following table summarizes our sources and uses of cash for each of the periods presented:

	Nine months ended September 30,
(in thousands)	2023			2022
Net cash used in operating activities	$	(74,655	)	$	(86,462	)
Net cash provided by investing activities		69,610			18,725
Net cash provided by financing activities		170			564
Net change in cash, cash equivalents and restricted cash	$	(4,875	)	$	(67,173	)

Operating Activities

Net cash used in operating activities for the nine months ended September 30, 2023 was $74.7 million, which was primarily utilized for the funding of our operating expenses of $90.5 million, as we incurred expenses associated with research and development activities including clinical trial activities associated with our HMI-103 and HMI-203 programs, preclinical development activities including IND-enabling studies for HMI-104 and research activities on other applications for our technology, adjusted for non-cash expenses of $17.9 million. Non-cash expenses includes an $11.9 million loss from our equity method investment in OXB Solutions, $6.5 million of stock-based compensation expense and noncash lease expense of $1.1 million, partially offset by accretion on short-term investments of $2.3 million. The change in operating assets and liabilities of $4.3 million was driven by increased accounts payable of $6.7 million and decreased prepaid expenses and other current assets of $3.0 million, partially offset by decreased accrued expenses and other liabilities of $3.0 million and decreased deferred revenue of $1.2 million.

Net cash used in operating activities for the nine months ended September 30, 2022 was $86.5 million, primarily due to our net income of $29.3 million offset by the $131.2 million gain recognized on the sale of our manufacturing business to Oxford. Further offsetting our net income was an increase in prepaid expenses and other current assets of $5.3 million primarily due to the receivable from OXB Solutions, as well as a decrease in deferred revenue of $2.4 million. Conversely, we had net non-cash expenses of $15.2 million, which included $10.0 million of stock-based compensation expense and a $4.1 million loss from our equity method investment in OXB Solutions, $5.7 million of increased accrued expenses and other liabilities and $2.7 million of increased accounts payable, all of which reduced our net cash used in operating activities for the nine months ended September 30, 2022.

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Investing Activities

Net cash provided by investing activities for the nine months ended September 30, 2023 was $69.6 million, primarily due to proceeds from maturities of short-term investments of $142.7 million, offset by purchases of short-term investments of $73.2 million.

Net cash provided by investing activities for the nine months ended September 30, 2022 was $18.7 million, primarily due to $130.0 million of cash received from Oxford pursuant to the OXB Solutions Transaction (see Note 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q). We also had proceeds from maturities of short-term investments of $47.5 million, offset by purchases of short-term investments of $157.5 million and purchases of property and equipment of $1.3 million.

Financing Activities

Net cash provided by financing activities for the nine months ended September 30, 2023 was $0.2 million, due to proceeds from the issuance of common stock pursuant to our employee stock purchase plan.

Net cash provided by financing activities for the nine months ended September 30, 2022 was $0.6 million, due to proceeds from the issuance of common stock pursuant to our employee stock purchase plan.

Funding Requirements

Operating expenses decreased during the nine months ended September 30, 2023 as compared to the nine months ended September 30, 2022. We currently expect our expenses to continue to decrease in 2023 compared to 2022 due to our decision to stop all further development of our product candidates and the recent implementation of an 86% workforce reduction. We will continue to incur costs associated with operating as a public company. If we decide to resume the development of our product candidates, however, we expect our expenses to increase in order to advance preclinical activities and clinical trials for product candidates in development.

As of September 30, 2023, we had cash, cash equivalents, and short-term investments of $103.3 million. Based on our current projections, we believe that our existing cash, cash equivalents, and short-term investments as of September 30, 2023 will enable us to continue our operations for at least one year from the date of this filing. However, in light of the discontinuation of all of our clinical trials and research activities, as well as our recent reduction in force of all but a few custodial employees, we have concluded that there is a substantial doubt regarding our ability to continue as a going concern for more than twelve months after the date the unaudited condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q have been issued.

We have based these estimates on assumptions that may prove to be imprecise, and we may use our available capital resources sooner than we currently expect. In addition, our resource requirements could materially change depending on the outcome of our ongoing strategic alternative review process. Because our resource requirements could materially change depending on the outcome of our ongoing strategic alternative review process, we are unable to estimate the exact amount of our working capital requirements. Should we resume development of our product candidates in the future, our future funding requirements would depend on and could increase significantly as a result of many factors, including:

•the costs, timing, and results of research and development efforts, including clinical trials;

•the costs and timing of process development scale-up activities, and the adequacy of supply of product candidates for preclinical studies and clinical trials through CMOs, including OXB Solutions;

•the costs and timing of preparing, filing, and prosecuting patent applications, maintaining and enforcing our intellectual property rights and defending any intellectual property-related claims, including any claims by third parties that we are infringing upon their intellectual property rights;

•the effect of competitors and market developments; and

•our ability to establish and maintain strategic collaborations, licensing or other agreements and the financial terms of such agreements for our product candidates.

We maintain the majority of our cash and cash equivalents in accounts with major highly rated multi-national and local financial institutions, and our deposits at these institutions exceed insured limits. Market conditions can impact the viability of these institutions, and any inability to access or delay in accessing these funds could adversely affect our business and financial position. In the event of failure of any of the financial institutions where we maintain our cash and cash equivalents, there can be no assurance that we will be able to access uninsured funds in a timely manner or at all.

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Further, the global economy, including credit and financial markets, has recently experienced extreme volatility and disruptions, including severely diminished liquidity and credit availability, rising interest and inflation rates, declines in consumer confidence, declines in economic growth, increases in unemployment rates, uncertainty about economic stability, and COVID-19. All of these factors could impact our liquidity and future funding requirements, including but not limited to our ability to raise additional capital when needed on acceptable terms, if at all. The duration of this economic slowdown is uncertain and the impact on our business is difficult to predict. See “Risk Factors— Unstable global political or economic conditions may have serious adverse consequences on our business, financial condition and share price” and “Risk Factors— COVID-19 has and could continue to adversely impact our business, including our preclinical studies and clinical trials.” in Part II, Item 1A of this Quarterly Report on Form 10-Q.

Until such time, if ever, that we can generate product revenue, and subject to our pursuit of a potential strategic transaction and the consummation of such potential transaction, we expect to finance our cash needs through a combination of equity offerings, debt financings, collaboration agreements, other third-party funding, strategic alliances, licensing arrangements and marketing and distribution arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interests of our stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our stockholders as common stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise additional funds through other third-party funding, collaboration agreements, strategic alliances, licensing arrangements or marketing and distribution arrangements, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. If we resume the development of our product candidates and are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts, or grant rights to develop and market products or product candidates that we would otherwise prefer to develop and market ourselves.

Contractual Obligations

There have been no material changes to our contractual obligations during the nine months ended September 30, 2023 from those previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2022.

Item 3. Quantitative and Qualitative Disclosures About Market Risk.

We are exposed to market risks in the ordinary course of our business. These risks primarily include interest rate sensitivities.

Interest Rate Risk

Our interest-earning assets consist of cash and cash equivalents and short-term investments of $103.3 million, or 73.8% of our total assets at September 30, 2023, and $175.0 million, or 76.6% of our total assets at December 31, 2022. Interest income earned on these assets was approximately $4.4 million and $1.8 million for the nine months ended September 30, 2023 and 2022, respectively. Our interest income is sensitive to changes in the general level of interest rates, primarily U.S. interest rates. If a 10% change in interest rates were to have immediately occurred on September 30, 2023, this change would not have had a material effect on the fair value of our investment portfolio as of that date. At September 30, 2023, our cash equivalents consisted of bank deposits and money market funds. Such interest-earning instruments carry a degree of interest rate risk; however, historical fluctuations in interest income have not been significant for us. We had no debt outstanding as of September 30, 2023 and December 31, 2022.

Inflation Rate Risk

As of September 30, 2023, we do not believe that inflation has had a material effect on our business, financial condition or results of operations. To the extent inflation results in rising interest rates and has other adverse effects on the market, it may adversely affect our business, financial condition and results of operations.

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Item 4. Controls and Procedures.

Limitations on Effectiveness of Controls and Procedures

In designing and evaluating our disclosure controls and procedures, management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving the desired control objectives. In addition, the design of disclosure controls and procedures must reflect the fact that there are resource constraints and that management is required to apply judgment in evaluating the benefits of possible controls and procedures relative to their costs.

Evaluation of Disclosure Controls and Procedures

Our management, with the participation of our Chief Executive Officer and Chief Financial Officer, has evaluated, as of the end of the period covered by this Quarterly Report on Form 10-Q, the effectiveness of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act). Based on such evaluation, our Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures were effective at the reasonable assurance level as of September 30, 2023.

Changes in Internal Control Over Financial Reporting

There were no changes in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) during the three months ended September 30, 2023 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

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PART II—OTHER INFORMATION

Item 1. Legal Proceedings.

On March 25, 2022, a stockholder of the Company, Michael C. Pizzuto, filed a putative class action complaint alleging violations of Sections 10(b) and 20(a) of the Securities and Exchange Act of 1934, as amended, against the Company and certain of its executives. Pizzuto v. Homology Medicines, Inc., No. 2:22– CV – 01968 (C.D. Cal 2022). The complaint alleges that the Company failed to disclose certain information regarding efficacy and safety in connection with a Phase I/II HMI-102 clinical trial, and seeks damages in an unspecified amount. The case is in its early stages. The Company believes the claims alleged lack merit and filed a motion to transfer venue (filed September 2, 2022) and a motion to dismiss (filed October 17, 2022). On April 18, 2023, the court granted the motion to transfer, finding that venue was not proper in the Central District of California and transferring the case to the District of Massachusetts. Following the transfer, the case number changed to 1:23-cv-10858-AK (D. Mass.). On May 9, 2023, the Massachusetts court issued an order permitting the parties to submit updated briefs in connection with the motion to dismiss, which were submitted on June 8, 2023, July 13, 2023, and August 3, 2023. The motion to dismiss remains pending. As the outcome is not presently determinable, any loss is neither probable nor reasonably estimable.

Item 1A. Risk Factors.

Investing in our common stock involves a high degree of risk. You should consider carefully the risks described below, together with the other information included in this Quarterly Report on Form 10-Q. If any of the following risks occur, our business, financial condition, results of operations and future growth prospects could be materially and adversely affected. In these circumstances, the market price of our common stock could decline. Other events that we do not currently anticipate or that we currently deem immaterial may also affect our business, prospects, financial condition and results of operations.

Risks Related to Our Financial Position and Need for Additional Capital

We have incurred significant losses since inception and anticipate that we will incur continued losses for the foreseeable future. If we are unable to achieve and sustain profitability, the market value of our common stock will likely decline. We may never achieve or maintain profitability.

We are a clinical-stage genetic medicines company with a limited operating history. Since inception, we have incurred significant operating losses. Our net loss for the nine months ended September 30, 2023 was $96.8 million. As of September 30, 2023, we had an accumulated deficit of approximately $526.0 million. On March 10, 2022, we closed our transaction with OXB Solutions and recorded a gain of $131.2 million on the sale of our manufacturing business which resulted in net income of $29.3 million for the nine months ended September 30, 2022 (see Note 5 to our condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for additional information regarding the OXB Solutions Transaction). In addition, we have not commercialized any products and have never generated any revenue from product sales. We have historically devoted most of our financial resources to research and development, including our preclinical development activities.

In July 2023, we completed a review of our business and our Board of Directors approved a plan to explore, review and evaluate a range of potential strategic options available to us, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the current financing environment and our anticipated clinical development timeline, we stopped further development of our programs and reduced our workforce by 86% to significantly reduce our ongoing operating costs as we evaluate strategic alternatives.

We have incurred and expect to continue to incur costs and expenditures in connection with our process of evaluating our strategic alternatives and we will continue to incur costs associated with operating as a public company. The process of continuing to evaluate strategic transactions may be costly, time-consuming and complex, and we may incur significant costs related to these processes, such as legal, accounting and advisory fees and expenses and other related charges. A considerable portion of these costs will be incurred regardless of whether any particular course of action is implemented or transaction is completed. Any such expenses will decrease the remaining cash available for use in our business.

Should we resume development of our product candidates, we would expect to continue to incur significant additional operating losses for the foreseeable future as we seek to advance product candidates through preclinical and clinical development, expand our research and development activities, develop new product candidates, complete clinical trials, seek regulatory approval and, if we receive FDA or foreign regulatory authorities approval, commercialize our products. Furthermore, the costs of advancing product candidates into each succeeding clinical phase tend to increase substantially over time. The total costs to advance any of our product candidates to marketing approval in even a single jurisdiction would be substantial. Because of the numerous risks and uncertainties

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associated with genetic medicines product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to begin generating revenue from the commercialization of products or achieve or maintain profitability. Our expenses will also increase substantially if we:

•continue our current research programs and our preclinical development of product candidates from our current research programs;

•seek to identify, assess, acquire and/or develop additional research programs and additional product candidates;

•initiate preclinical testing and clinical trials for any product candidates we identify and develop;

•establish a sales, marketing and distribution infrastructure to commercialize any product candidates for which we may obtain marketing approval;

•maintain, expand and protect our intellectual property portfolio;

•further develop our genetic medicines platform;

•hire additional clinical, scientific and commercial personnel;

•add operational, financial and management information systems and personnel, including personnel to support our product development and planned future commercialization efforts, as well as to support our operations as a public reporting company;

•acquire or in-license other commercial products, product candidates and technologies;

•make royalty, milestone or other payments under current and any future in-license agreements; and

•further expand our Good Manufacturing Practices, or GMP, manufacturing capacity.

Furthermore, should we resume development of our product candidates, our ability to successfully develop, commercialize and license our products and generate product revenue would be subject to substantial additional risks and uncertainties. Each of our programs and product candidates would require additional preclinical and clinical development, potential regulatory approval in multiple jurisdictions, securing manufacturing supply, capacity and expertise, building of a commercial organization, substantial investment and significant marketing efforts before we generate any revenue from product sales. These risks are further described under “—Risks Related to Discovery, Development, Clinical Testing, Manufacturing and Regulatory Approval” and “—Risks Related to Commercialization.”

As a result, we expect to continue to incur net losses and negative cash flows for the foreseeable future. These net losses and negative cash flows have had, and will continue to have, an adverse effect on our stockholders’ equity and working capital. The amount of our future net losses will depend, in part, on the rate of future growth of our expenses and our ability to generate revenues. If we are unable to develop and commercialize one or more of our product candidates either alone or with collaborators, or if revenues from any product candidate that receives marketing approval are insufficient, we will not achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability. If we are unable to achieve and then maintain profitability, the value of our equity securities will be materially and adversely affected.

Any financial or strategic option we pursue may not be successful.

In July 2023, our Board of Directors approved a process to explore, review and evaluate a range of potential strategic options available to us, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. The process of continuing to evaluate these strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges. There can be no assurance of completion of any particular course of action or a defined timeline for completion, and we can provide no assurance that any strategic alternative we pursue will have a positive impact on our results of operations or financial condition.

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Raising additional capital may cause dilution to our stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

Until such time, if ever, as we can generate substantial revenue, we may finance our cash needs through a combination of equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements. As of September 30, 2023, we do not have any committed external source of funds. In addition, we may seek additional capital due to favorable market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans.

To the extent that we raise additional capital through the sale of equity or convertible debt securities, including under our effective Registration Statement on Form S-3, the ownership interests of our stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may be required to relinquish valuable rights to our technologies, future revenue streams or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts, should we resume development of our product candidates, or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

Our decision to discontinue further program development efforts may not result in the anticipated savings for the Company and may adversely affect our business.

In connection with our decision to pursue strategic alternatives and reduce our ongoing operating expenses, in July 2023 we decided to stop further program developments. Based on the anticipated clinical development timeline of HMI-103 and the current financing environment, we believe this decision to discontinue further program development efforts will significantly reduce our ongoing operating costs. We may not realize, in full or in part, the anticipated benefits and savings in operating expenses from this decision due to unforeseen difficulties, delays or other unexpected costs. For instance, this decision to stop further program developments may include higher than expected costs associated with winding down our clinical programs. Moreover, if we are unable to realize the expected cost savings, our financial condition could be adversely affected, and it may be more difficult to complete a potential strategic transaction.

We will require additional capital to fund our operations, and if we fail to obtain necessary financing, we may not be able to complete the development and commercialization of our product candidates.

We will require additional capital, which we may raise through equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements or other sources to enable us to complete the development and potential commercialization of our product candidates and any future product candidates should we resume such activities. In addition, we may not be able to enter into any collaborations that will generate significant cash. Adequate additional financing may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative effect on our financial condition and our ability to pursue our business strategy. In addition, attempting to secure additional financing may divert the time and attention of our management from day-to-day activities.

Based on our current projections, we believe that our existing cash, cash equivalents, and short-term investments will enable us to continue to fund our operations for at least one year from the date of this filing. However, due to considerations of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as our significant reduction in force of all but a few custodial employees, management has concluded that there is substantial doubt regarding our ability to continue as a going concern for more than twelve months after the date the unaudited condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q have been issued. Beyond that, we will need to raise additional capital in order to fund operating expenses and capital expenditure requirements. This estimate is based on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect. In addition, our resource requirements could materially change depending on the outcome of our ongoing strategic alternative review process. As a result, we are unable to estimate the exact amount of our working capital requirements. Changing circumstances could cause us to consume capital significantly faster than we currently anticipate, and we may need to spend more than currently expected because of circumstances beyond our control. Should we

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resume development of our product candidates, our future funding requirements, both near and long-term, would depend on many factors, including, but not limited to:

•the initiation, progress, timing, costs and results of our planned clinical trials for our product candidates;

•the outcome, timing and cost of meeting regulatory requirements established by the FDA and other comparable foreign regulatory authorities;

•the cost of filing, prosecuting, defending and enforcing our patent claims and other intellectual property rights;

•the cost of defending potential intellectual property disputes, including patent infringement actions brought by third parties against us or our product candidates;

•the effect of competing technological and market developments;

•the cost and timing of completion of commercial-scale manufacturing activities;

•the costs of operating as a public company;

•the extent to which we in-license or acquire other products and technologies;

•the cost of establishing sales, marketing and distribution capabilities for our product candidates in regions where we choose to commercialize our products; and

•the initiation, progress, timing and results of our commercialization of our product candidates, if approved for commercial sale.

We maintain the majority of our cash and cash equivalents in accounts with major U.S. and multi-national financial institutions, and our deposits at these institutions exceed insured limits. Market conditions can impact the viability of these institutions. In the event of failure of any of the financial institutions where we maintain our cash and cash equivalents, there can be no assurance that we would be able to access uninsured funds in a timely manner or at all. Any inability to access or delay in accessing these funds could adversely affect our business and financial position.

We cannot be certain that additional funding will be available on acceptable terms, or at all. For example, the trading prices for our and other biopharmaceutical companies’ stock have been highly volatile as a result of macroeconomic conditions, developments in our industry and COVID-19. As a result, we may face difficulties raising capital through sales of our common stock and any such sales may be on unfavorable terms. If we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we may have to significantly delay, scale back or discontinue the development or commercialization of or product candidates or potentially discontinue operations.

We have a limited operating history and no history of commercializing genetic medicine products, which may make it difficult to evaluate the prospects for our future viability.

We were established and began operations in 2015. Our operations to date have been limited to financing and staffing our company, developing our technology and identifying and developing our product candidates. We have not yet demonstrated an ability to successfully complete any clinical trials, including large-scale, pivotal clinical trials, obtain marketing approval, manufacture a commercial scale product, or arrange for a third party to do so on our behalf, or conduct sales and marketing activities necessary for successful product commercialization. Typically, it takes about six to ten years to develop a new drug from the time it enters Phase 1 clinical trials to when it is approved for treating patients, but in many cases, it may take longer. Consequently, should we resume development of our product candidates, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing and commercializing genetic medicine products.

In addition, as a business with a limited operating history, we may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown factors. We will eventually need to transition from a company with a research focus to a company capable of supporting commercial activities. We may not be successful in such a transition.

We expect our financial condition and operating results may fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, you should not rely upon the results of any particular quarterly or annual period as indications of future operating performance.

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Should we resume development of our product candidates, we would be heavily dependent on the success of our product candidates, and if none of our candidates receives regulatory approval or is not successfully commercialized, our business may be harmed.

We have historically invested a significant portion of our efforts and financial resources in the development of our product candidates. Our future success and ability to generate product revenue is substantially dependent on our ability to successfully develop, obtain regulatory approval for and successfully commercialize our product candidates. We have no products that are approved for commercial sale and may never be able to develop marketable products, and we have stopped development activities. Should we resume development of our product candidates, we expect that a substantial portion of our efforts and expenditures over the next few years would be devoted to development of these candidates, which would require additional clinical development, management of clinical and manufacturing activities, regulatory approval in multiple jurisdictions, securing manufacturing supply, building of a commercial organization, substantial investment and significant marketing efforts before we can generate any revenues from any commercial sales. Accordingly, our business has historically depended heavily on the successful development, regulatory approval and commercialization of our product candidates, which may never occur. Therefore, we cannot be certain that any of our product candidates would be successful in future clinical trials, receive regulatory approval or be successfully commercialized even if we receive regulatory approval.

Even if we receive approval to market any product candidate from the FDA or other regulatory authorities, we cannot be certain that our product candidates will be successfully commercialized, widely accepted in the marketplace or more effective than other commercially available alternatives. Additionally, the research, testing, manufacturing, labeling, approval, sale, marketing and distribution of genetic medicine products are and will remain subject to extensive regulation by the FDA and other regulatory authorities in the United States and other countries that each have differing regulations. We are not permitted to market any product candidate in the United States until it receives approval of a Biologics License Application, or BLA from the FDA, or in any foreign countries until it receives the requisite approval from such countries.

We have not submitted a BLA to the FDA or comparable applications to other regulatory authorities and do not expect to be in a position to do so for the foreseeable future.

If any of our product candidates shows unexpected adverse events or a lack of efficacy in the indications we intend to treat, or if we experience other regulatory or developmental issues, our development plans and business could be significantly harmed. Further, competitors may be developing products with similar technology and may experience problems with their products that could identify problems that would potentially harm our business.

We may not be successful in our efforts to identify additional product candidates.

Historically, part of our strategy has involved, and to the extent such activities are resumed in the future may involve, identifying novel product candidates. The process by which we identify product candidates may fail to yield product candidates for clinical development for a number of reasons, including those discussed in these risk factors and also:

•we may not be able to assemble sufficient resources to acquire or discover additional product candidates;

•competitors may develop alternatives that render our potential product candidates obsolete or less attractive;

•potential product candidates we develop may nevertheless be covered by third parties’ patents or other exclusive rights;

•potential product candidates may, on further study, be shown to have harmful side effects, toxicities or other characteristics that indicate that they are unlikely to be products that will receive marketing approval and achieve market acceptance;

•potential product candidates may not be effective in treating their targeted diseases;

•the market for a potential product candidate may change so that the continued development of that product candidate is no longer reasonable;

•a potential product candidate may not be capable of being produced in commercial quantities at an acceptable cost, or at all; or

•the regulatory pathway for a potential product candidate may be complex and difficult to navigate successfully or economically.

In addition, should we resume development of our product candidates, we may choose to focus our efforts and resources on a potential product candidate that ultimately proves to be unsuccessful. As a result, we may fail to capitalize on viable commercial

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products or profitable market opportunities, be required to forego or delay pursuit of opportunities with other product candidates or other diseases that may later prove to have greater commercial potential, or relinquish valuable rights to such product candidates through collaboration, licensing or other royalty arrangements in cases in which it would have been advantageous for us to retain sole development and commercialization rights. If we are unable to identify additional suitable product candidates for clinical development, this would adversely impact our business strategy and our financial position and share price and could potentially cause us to cease operations.

We may be required to make significant payments in connection with our license agreement with the City of Hope.

Under our license agreement with COH, we are subject to significant obligations, including payment obligations upon achievement of specified milestones and royalties on product sales, as well as other material obligations, including potential payments if we were to sublicense the COH technology to additional strategic collaborators. If these payments become due, we may not have sufficient funds available to meet our obligations or we may have to direct funds from other development efforts, and as a result, our development efforts may be materially harmed.

Risks Related to Discovery, Development, Clinical Testing, Manufacturing and Regulatory Approval

Should we resume development our of product candidates, we intend to identify and develop product candidates based on our novel genetic medicines platform, which makes it difficult to predict the time and cost of product candidate development. No products that utilize gene editing technology have been approved in the United States or in Europe, and there have only been a limited number of human clinical trials involving a gene editing product candidate. Moreover, none of those trials has involved our nuclease-free gene editing technology, prior to our initiated Phase 1 pheEDIT clinical trial. In addition, there have been a limited number of gene therapy products approved in the United States or in Europe and none of these products have utilized our AAVHSC platform.

We have historically concentrated our research and development efforts on our genetic medicines platform, which uses both nuclease-free gene editing and gene therapy technologies. Our future success depends on the successful development of this novel therapeutic approach. To date, no product that utilizes gene editing has been approved in the United States or Europe. There have been a limited number of clinical trials of gene editing technologies, however no product candidates have been approved, and, prior to our initiated Phase 1 pheEDIT clinical trial, none of these clinical trials involved product candidates that utilize our novel gene correction editing technology. Moreover, there have been a limited number of gene therapy products approved in the United States or in Europe and none of these products have utilized our AAVHSC platform. In addition, because our programs are all in the research, preclinical or early-clinical stage, we have not yet been able to fully assess safety in humans, and there may be long-term effects from treatment with any of our future product candidates that we cannot predict at this time. Any gene correction editing product candidates we may develop will act at the level of DNA, and, because animal DNA differs from human DNA, it will be difficult for us to test our future product candidates in animal models for either safety or efficacy. Also, animal models may not exist for some of the diseases we expect to pursue. Our genetic medicines platform is based on a family of 15 proprietary AAVHSCs which we can deploy through a nuclease-free gene editing modality, gene therapy, or GTx-mAb, which is designed to produce antibodies throughout the body. All applications rely on the unique ability of our AAVHSCs to efficiently target multiple tissues in the body. The mechanism of action by which these vectors target particular tissues is still not completely understood. Therefore, it is difficult for us to determine that our vectors will be able to properly integrate corrective DNA in or deliver gene transfer constructs to enough tissue cells to reach therapeutic levels. Should we resume development our of product candidates, we cannot be certain that our AAVHSCs will be able to meet safety and efficacy levels needed to be therapeutic in humans or that they will not cause significant adverse events or toxicities. Furthermore, studies conducted by a third party in non-human primates suggest that intravenous delivery of certain AAV vectors at very high doses may result in severe toxicity of the dorsal root ganglion, or DRG. To date, we have not observed the severe DRG toxicities described in these publications after intravenous administration in non-human primates with our naturally occurring AAVHSC vectors, and we have not seen these toxicities in our product candidates. However, we cannot be certain that we will be able to avoid triggering toxicities in our future preclinical or clinical studies. Any such results could impact our ability to develop a product candidate. As a result of these factors, it is more difficult for us to predict the time and cost of product candidate development, and we cannot predict whether the application of our genetic medicines platform, or any similar or competitive gene therapy or gene editing platforms, will result in the identification, development, and regulatory approval of any medicines, or that other genetic medicine technologies will not be considered better or more attractive for the development of medicines. There can be no assurance that any development problems we experience in the future related to our genetic medicines platform or any of our research programs will not cause significant delays or unanticipated costs, or that such development problems can be solved. We may also experience delays in developing a sustainable, reproducible, and scalable manufacturing process or transferring that process to commercial partners. Any of these factors may prevent us from completing our preclinical studies or any clinical trials that we may initiate or commercializing any product candidates we may develop on a timely or profitable basis, if at all.

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Because gene therapy and gene editing are novel and the regulatory landscape that governs any product candidates we may develop is uncertain and continues to change, we cannot predict the time and cost of obtaining regulatory approval, if we receive it at all, for any product candidates we may develop to the extent we resume such activities.

Regulatory requirements governing products created with genome editing technology or involving gene therapy treatment have changed frequently and will likely continue to change in the future. Approvals by one regulatory authority may not be indicative of what any other regulatory authority may require for approval, and there is substantial, and sometimes uncoordinated, overlap in those responsible for regulation of gene therapy products, cell therapy products and other products created with genome editing technology. For example, the FDA maintains the Office of Therapeutic Products within its Center for Biologics Evaluation and Research, or CBER, with responsibility for the review of gene therapy and related products, and the Cellular, Tissue and Gene Therapies Advisory Committee to advise CBER on its review. Should we resume development of our product candidates, these and other regulatory review agencies, committees and advisory groups and any requirements and guidelines they promulgate may lengthen the regulatory review process, require us to perform additional preclinical studies or clinical trials, increase our development costs, lead to changes in regulatory positions and interpretations, delay or prevent approval and commercialization of these treatment candidates or lead to significant post-approval limitations or restrictions.

Additionally, under NIH Guidelines supervision of human gene transfer trials includes evaluation and assessment by an institutional biosafety committee, or IBC, a local institutional committee that reviews and oversees research utilizing recombinant or synthetic nucleic acid molecules at that institution. The IBC assesses the safety of the research and identifies any potential risk to public health or the environment, and such review may result in some delay before initiation of a clinical trial. While the NIH Guidelines are not mandatory unless the research in question is being conducted at or sponsored by institutions receiving NIH funding of recombinant or synthetic nucleic acid molecule research, many companies and other institutions not otherwise subject to the NIH Guidelines voluntarily follow them.

In the European Union, or EU, the European Medicines Agency, or EMA, has a Committee for Advanced Therapies, or CAT, that, in conjunction with the Committee for Human Medicinal Products, or CHMP, is responsible for assessing the quality, safety and efficacy of advanced therapy medicinal products, or ATMPs. ATMPs include gene therapy medicines, somatic-cell therapy medicines and tissue-engineered medicines. The role of the CAT is to prepare a draft opinion on an application for marketing authorization for a gene therapy medicinal candidate that is submitted to the EMA. The CAT’s opinion is considered by the CHMP when giving its final recommendation regarding the authorization of a product in view of the balance of benefits and risks identified. Although the CAT’s draft opinion is submitted to the CHMP for final approval, the CHMP may depart from the draft opinion, if it provides detailed scientific justification. In the EU, the development and evaluation of a gene therapy medicinal product must be considered in the context of the relevant EU guidelines. The CHMP and CAT are also responsible for providing guidelines on ATMPs and have published numerous guidelines, including specific guidelines on gene therapies and cell therapies. These guidelines provide additional guidance on the factors that the EMA will consider in relation to the development and evaluation of ATMPs and include, among other things, the preclinical studies required to characterize ATMPs; the manufacturing and control information that should be submitted in a marketing authorization application; and post-approval measures required to monitor patients and evaluate the long term efficacy and potential adverse reactions of ATMPs. Although these guidelines are not legally binding, we believe that our compliance with them is likely necessary to gain and maintain approval for any of our product candidates. In addition, the EMA may issue new guidelines concerning the development and marketing authorization for gene therapy medicinal products and require that we comply with these new guidelines. Similarly complex regulatory environments exist in other jurisdictions in which we might consider seeking regulatory approvals for our product candidates, further complicating the regulatory landscape. As a result, the procedures and standards applied to gene therapy products and cell therapy products may be applied to any of our gene therapy or genome editing product candidates, but that remains uncertain at this point.

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The clinical trial requirements of the FDA, the EMA and other regulatory authorities and the criteria these regulators use to evaluate the safety and efficacy of a product candidate vary substantially according to the type, complexity, novelty and intended use and market of the potential products. The regulatory approval process for product candidates created with novel genome editing technology such as ours can be more lengthy, rigorous and expensive than the process for other better known or more extensively studied product candidates and technologies. Since we are developing novel treatments for diseases in which there is little clinical experience with new endpoints and methodologies, there is heightened risk that the FDA, the EMA or comparable regulatory authorities may not consider the clinical trial endpoints to provide clinically meaningful results, and the resulting clinical data and results may be more difficult to analyze. This may be a particularly significant risk for many of the genetically defined diseases for which we may develop product candidates alone or with collaborators due to small patient populations for those diseases, and designing and executing a rigorous clinical trial with appropriate statistical power is more difficult than with diseases that have larger patient populations. Regulatory authorities administering existing or future regulations or legislation may not allow production and marketing of products utilizing genome editing technology in a timely manner or under technically or commercially feasible conditions. Even if our product candidates obtain required regulatory approvals, such approvals may later be withdrawn as a result of changes in statute or regulations or the interpretation of new available data by applicable regulatory agencies.

Changes in applicable regulatory guidelines may lengthen the regulatory review process for our product candidates, require additional studies or trials, increase development costs, lead to changes in regulatory positions and interpretations, delay or prevent approval and commercialization of such product candidates, or lead to significant post-approval limitations or restrictions. Additionally, adverse developments in clinical trials conducted by others of gene therapy products or products created using genome editing technology, or adverse public perception of the field of genome editing, may cause the FDA and other regulatory authorities to revise the requirements for approval of any product candidates we may develop or limit the use of products utilizing genome editing technologies, either of which could materially harm our business. Furthermore, regulatory action or private litigation could result in expenses, delays or other impediments to our research programs or the development or commercialization of current or future product candidates.

Should we resume development of our product candidates, we would be required to consult with these regulatory and advisory groups and comply with all applicable guidelines, rules and regulations. If we fail to do so, we may be required to delay or terminate development of such product candidates. Delay or failure to obtain, or unexpected costs in obtaining, the regulatory approval necessary to bring a product candidate to market could decrease our ability to generate sufficient product revenue to maintain our business.

Clinical trials are expensive, time-consuming, difficult to design and implement, and involve an uncertain outcome.

Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain. Failure can occur at any time during the clinical trial process. Should we resume development of our product candidates, the results of preclinical studies and early clinical trials of our product candidates may not be predictive of the results of later-stage clinical trials. Product candidates in later stages of clinical trials may fail to show the desired safety and efficacy traits despite having progressed through preclinical studies and initial clinical trials. A number of companies in the biotechnology and genetic medicines industries have suffered significant setbacks in advanced clinical trials due to lack of efficacy or adverse safety profiles, notwithstanding promising results in earlier trials. Even if our current and future clinical trials are completed as planned, we cannot be certain that their results will establish the safety, purity, potency and/or effectiveness of any of our product candidates to the satisfaction of the FDA or other regulatory authorities, even if we believe that such trials were successful.

To date, we have not completed any clinical trials for our product candidates. Should we resume development of our product candidates, we may experience delays in conducting any clinical trials and we do not know whether planned clinical trials will begin on time, need to be redesigned, recruit and enroll patients on time or be completed on schedule, or at all. Clinical trials can be delayed or terminated for a variety of reasons, including delays or failures related to:

•the FDA or comparable foreign regulatory authorities disagreeing as to the design or implementation of our clinical studies;

•obtaining regulatory approval to commence a trial;

•reaching an agreement on acceptable terms with prospective contract research organizations, or CROs, and clinical trial sites, the terms of which can be subject to extensive negotiation and may vary significantly among different CROs and trial sites;

•obtaining institutional review board, or IRB, and ethics committee approval or positive opinion at each site;

•recruiting suitable patients to participate in a trial;

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•developing and validating the companion diagnostic to be used in a clinical trial, if applicable;

•having patients complete a trial or return for post-treatment follow-up;

•clinical sites deviating from trial protocol or dropping out of a trial;

•addressing patient safety concerns that arise during the course of a trial;

•adding a sufficient number of clinical trial sites; or

•manufacturing sufficient quantities of product candidate for use in clinical trials.

Should we resume development of our product candidates, we may experience numerous unforeseen events during, or as a result of, clinical trials that could delay or prevent our ability to receive marketing approval or commercialize our product candidates or significantly increase the cost of such trials, including:

•we may receive feedback from regulatory authorities that requires us to modify the design of our clinical trials;

•clinical trials of our product candidates may produce negative safety and/or efficacy data or inconclusive results, and we may decide, or regulators may require us, to conduct additional clinical trials or abandon development programs;

•the number of patients required for clinical trials of our product candidates may be larger than we anticipate, enrollment in these clinical trials may be slower than we anticipate or participants may drop out of these clinical trials at a higher rate than we anticipate;

•our third-party contractors may fail to comply with regulatory requirements or meet their contractual obligations to us in a timely manner, or at all;

•we or our investigators might have to suspend or terminate clinical trials of our product candidates for various reasons, including non-compliance with regulatory requirements, a finding that our product candidates have undesirable side effects or other unexpected characteristics, or a finding that the participants are being exposed to unacceptable health risks;

•the cost of clinical trials of our product candidates may be greater than we anticipate and we may not have funds to cover the costs;

•the supply or quality of our product candidates or other materials necessary to conduct clinical trials of our product candidates may be insufficient or inadequate;

•regulators may revise the requirements for approving our product candidates, or such requirements may not be as we anticipate; and

•any future collaborators that conduct clinical trials may face any of the above issues, and may conduct clinical trials in ways they view as advantageous to them but that are suboptimal for us.

If we are required to conduct additional clinical trials or other testing of our product candidates beyond those that we contemplate, if we are unable to successfully complete clinical trials of our product candidates or other testing, if the results of these trials or tests are not positive or are only modestly positive or if there are safety concerns, we may:

•incur unplanned costs;

•be delayed in obtaining marketing approval for our product candidates or not obtain marketing approval at all;

•obtain marketing approval in some countries and not in others;

•obtain marketing approval for indications or patient populations that are not as broad as intended or desired;

•obtain marketing approval with labeling that includes significant use or distribution restrictions or safety warnings, including boxed warnings;

•be subject to additional post-marketing testing requirements; or

•have the product removed from the market after obtaining marketing approval.

We could encounter further delays if a clinical trial is suspended or terminated by us, by the IRBs of the institutions in which such trials are being conducted, by the Data Monitoring Committee, or DMC, for such trial or by the FDA or other regulatory authorities. Such authorities may impose such a suspension or termination due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site

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by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a drug, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial. Furthermore, we may rely on CROs and clinical trial sites to ensure the proper and timely conduct of clinical trials and while we would have agreements governing their committed activities, we would have limited influence over their actual performance, as described in “—Risks Related to Our Dependence on Third Parties.”

To the extent we resume such activities, all of our product candidates would require extensive clinical testing before we are prepared to submit a BLA or similar applications seeking regulatory approval. We cannot predict with any certainty if or when we might complete the development of any of our product candidate and submit a BLA or similar applications or whether any such BLA or similar applications will be approved by the FDA or comparable foreign authorities. We may seek feedback from the FDA or other regulatory authorities on our clinical development program, and the FDA or such regulatory authorities may not provide such feedback on a timely basis, or such feedback may not be favorable, which could further delay our development programs.

If we experience delays in the commencement or completion of our clinical trials, or if we terminate a clinical trial prior to completion, the commercial prospects of our product candidates could be harmed, and our ability to generate revenues from our product candidates may be delayed. In addition, any delays in our clinical trials could increase our costs, slow down the development and approval process and jeopardize our ability to commence product sales and generate revenues. Any of these occurrences may harm our business, financial condition and results of operations. In addition, many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our product candidates.

In addition, the FDA’s and other regulatory authorities’ policies with respect to clinical trials may change and additional government regulations may be enacted. For instance, the regulatory landscape related to clinical trials in EU recently evolved. The EU Clinical Trials Regulation, or CTR, which was adopted in April 2014 and repeals the EU Clinical Trials Directive, became applicable on January 31, 2022. While the Clinical Trials Directive required a separate clinical trial application, or CTA, to be submitted in each member state in which the clinical trial takes place, to both the competent national health authority and an independent ethics committee, the CTR introduces a centralized process and only requires the submission of a single application for multi-center trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed. The CTR foresees a three-year transition period. The extent to which ongoing and new clinical trials will be governed by the CTR varies. Clinical trials for which an application was submitted (i) prior to January 31, 2022 under the Clinical Trials Directive, or (ii) between January 31, 2022 and January 31, 2023 and for which the sponsor has opted for the application of the EU Clinical Trials Directive remain governed by said Directive until January 31, 2025. After this date, all clinical trials (including those which are ongoing) will become subject to the provisions of the CTR. Compliance with the CTR requirements by us and our third-party service providers, such as clinical research organizations, or CROs, may impact our developments plans.

It is currently unclear to what extent the United Kingdom, or UK, will seek to align its regulations with the EU. The UK regulatory framework in relation to clinical trials is derived from existing EU legislation (as implemented into UK law, through secondary legislation). On January 17, 2022, the UK Medicines and Healthcare Regulatory Agency, or MHRA, launched an eight-week consultation on reframing the UK legislation for clinical trials, with the aim to streamline clinical trials approvals, enable innovation, enhance clinical trials transparency, enable greater risk proportionality, and promote patient and public involvement in clinical trials. The UK Government published its response to the consultation on March 21, 2023 confirming that it would bring forward changes to the legislation. These resulting legislative amendments will be closely watched and will determine how closely the UK regulations are aligned with the CTR. Under the terms of the Protocol on Ireland/Northern Ireland, provisions of the CTR which relate to the manufacture and import of investigational medicinal products and auxiliary medicinal products apply in Northern Ireland. On February 27, 2023, the UK Government and the European Commission reached a political agreement on the “Windsor Framework” which will revise the Protocol on Ireland/Northern Ireland in order to address some of the perceived shortcomings in its operation. Once implemented, this may have further impact on the application of the CTR in Northern Ireland. A decision by the UK Government not to closely align any new legislation with the new approach adopted in the EU may have an effect on the cost of conducting clinical trials in the UK as opposed to other countries.

If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies governing clinical trials, our development plans may also be adversely impacted.

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Adverse public perception of genetic medicine, and gene editing in particular, may negatively impact the length of time required to advance our product candidates through clinical trials should we resume development of our product candidates, including the pace at which we advance patient enrollment, and potential regulatory approval of, or demand for, our potential products.

Some of our potential therapeutic products involve editing the human genome. If we resume the development of our product candidates in the future, the clinical and commercial success of our potential products will depend in part on public acceptance of the use of gene editing and gene therapy for the prevention or treatment of human diseases. Public attitudes may be influenced by claims that gene therapy and gene editing are unsafe, unethical, or immoral, and, consequently, our products may not gain the acceptance of the public or the medical community. Adverse public attitudes may adversely impact our ability to enroll clinical trials. Moreover, our success will depend upon physicians prescribing, and their patients being willing to receive, treatments that involve the use of product candidates we may develop in lieu of, or in addition to, existing treatments with which they are already familiar and for which greater clinical data may be available.

In addition, gene editing technology is subject to public debate and heightened regulatory scrutiny due to ethical concerns relating to the application of gene editing technology to human embryos or the human germline. For example, in April 2015, Chinese scientists reported on their attempts to edit the genome of human embryos to modify the gene for hemoglobin beta. This is the gene in which a mutation occurs in patients with the inherited blood disorder beta thalassemia. Although this research was purposefully conducted in embryos that were not viable, the work prompted calls for a moratorium or other types of restrictions on gene editing of human eggs, sperm, and embryos. The Alliance for Regenerative Medicine in Washington, D.C. has called for a voluntary moratorium on the use of gene editing technologies in research that involved altering human embryos or human germline cells. Similarly, the NIH has announced that it would not fund any use of gene editing technologies in human embryos, noting that there are multiple existing legislative and regulatory prohibitions against such work, including the Dickey-Wicker Amendment, which prohibits the use of appropriated funds for the creation of human embryos for research purposes or for research in which human embryos are destroyed. Laws in the UK prohibit genetically modified embryos from being implanted into women, but embryos can be altered in research labs under license from the Human Fertilisation and Embryology Authority. Research on embryos is more tightly controlled in many other European countries.

Although we do not use our technologies to edit human embryos or the human germline, should we resume development of our product candidates, such public debate about the use of gene editing technologies in human embryos and heightened regulatory scrutiny could prevent or delay our development of product candidates. More restrictive government regulations or negative public opinion would have a negative effect on our business or financial condition and may delay or impair our development and commercialization of product candidates or demand for any products we may develop. Adverse events in our preclinical studies or clinical trials or those of our competitors or of academic researchers utilizing gene therapy or gene editing technologies, even if not ultimately attributable to product candidates we may discover and develop, and the resulting publicity could result in increased governmental regulation, unfavorable public perception, potential regulatory delays in the testing or approval of potential product candidates we may identify and develop, stricter labeling requirements for those product candidates that are approved, a decrease in demand for any such product candidates and a suspension or withdrawal of approval by regulatory authorities of our product candidates.

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A Breakthrough Therapy Designation from the FDA, even if granted for any of our product candidates, may not lead to a faster development or regulatory review or approval process and it does not increase the likelihood that our product candidates will receive marketing approval.

We may seek a Breakthrough Therapy Designation for our product candidates if the clinical data support such a designation for one or more product candidates to the extent we resume development of our product candidates. A breakthrough therapy is defined as a drug or biologic that is intended, alone or in combination with one or more other drugs or biologics, to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the drug, or biologic in our case, may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. For product candidates that have been designated as breakthrough therapies, interaction and communication between the FDA and the sponsor of the trial can help to identify the most efficient path for clinical development while minimizing the number of patients placed in ineffective control regimens. Biologics designated as breakthrough therapies by the FDA may also be eligible for priority review and rolling review of a BLA, if the relevant criteria are met.

Designation as a breakthrough therapy is within the discretion of the FDA. Accordingly, even if we believe one of our product candidates meets the criteria for designation as a breakthrough therapy, the FDA may disagree and instead determine not to make such designation. In any event, the receipt of a Breakthrough Therapy Designation for a product candidate may not result in a faster development process, review or approval compared to drugs considered for approval under non-expedited FDA review procedures and does not assure ultimate approval by the FDA. In addition, even if one or more of our product candidates qualify as breakthrough therapies, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

A Fast Track Designation from the FDA, even if granted for any of our product candidates, may not lead to a faster development or regulatory review or approval process, and does not increase the likelihood that our product candidates will receive marketing approval.

On May 1, 2019, we received Fast Track Designation for HMI-102 for the prevention or treatment of neurocognitive defects due to phenylalanine hydroxylase deficiency through normalization of circulating phenylalanine levels, and on October 25, 2021, we received Fast Track Designation for HMI-103 for the treatment of neurocognitive and neuropsychiatric manifestations of PKU secondary to phenylalanine hydroxylase deficiency. We intend to seek such designation for some or all of our other product candidates. If a drug or biologic, in our case, is intended for the treatment of a serious or life-threatening condition and the biologic demonstrates the potential to address unmet medical needs for this condition, the biologic sponsor may apply for FDA Fast Track Designation. The sponsor of a Fast Track product candidate has opportunities for more frequent interactions with the applicable FDA review team during product development and, once a BLA is submitted, the product candidate may be eligible for priority review. A Fast Track product candidate may also be eligible for rolling review, where the FDA may consider for review sections of the BLA on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the BLA, the FDA agrees to accept sections of the BLA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the BLA. The FDA has broad discretion whether or not to grant this designation. Even if we believe a particular product candidate is eligible for this designation, we cannot assure you that the FDA would decide to grant it. Even if we do receive Fast Track Designation, we may not experience a faster development process, review or approval compared to conventional FDA procedures. The FDA may withdraw Fast Track Designation if it believes that the designation is no longer supported by data from our clinical development program. Many biologics that have received Fast Track Designation have failed to obtain approval.

In the future we may seek EMA PRIME designation or apply for other expedited regulatory pathways, designations, schemes or tools in the EU or UK for one or more of our product candidates, which we may not receive. Such designations may not lead to a faster development or regulatory review or approval process and do not increase the likelihood that our product candidates will receive marketing authorization.

In the future we may seek EMA PRIME (Priority Medicines) designation or other designations, schemes or tools for one or more of our product candidates. In the EU, innovative products that target an unmet medical need and are expected to be of major public health interest may be eligible for a number of expedited development and review programs, such as the PRIME scheme, which provides incentives similar to the Breakthrough Therapy and Fast-Track designation in the United States. PRIME is a voluntary scheme aimed at enhancing the EMA’s support for the development of medicines that target unmet medical needs. It is based on increased interaction and early dialogue with companies developing promising medicines, to optimize their product development plans and speed up their evaluation to help them reach patients earlier. The benefits of a PRIME designation include the appointment of a rapporteur before submission of a marketing authorization application, early dialogue and scientific advice at key development milestones, and the potential to qualify products for accelerated review earlier in the application process.

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Even if we believe one of our product candidates is eligible for PRIME, the EMA may disagree and instead determine not to make such designation. The EMA PRIME scheme or other schemes, designations, or tools, even if obtained or used for any of our product candidates may not lead to a faster development, regulatory review or approval process compared to therapies considered for approval under conventional procedures and do not assure ultimate approval. In addition, even if one or more of our product candidates is eligible to the PRIME scheme, the EMA may later decide that such product candidates no longer meet the conditions for qualification or decide that the time period for review or approval will not be shortened. Product developers that benefit from PRIME designation may be eligible for accelerated assessment (in 150 days instead of 210 days), which may be granted for medicinal products of major interest from a public health perspective or that target an unmet medical need, but this is not guaranteed.

We may equally pursue some of the post-Brexit MHRA procedures to prioritize access to new medicines that will benefit patients, such as a 150-day assessment, a rolling review procedure and an innovative licensing and access pathway, or ILAP. ILAP aims to accelerate the time to market and to facilitate patient access to medicines, including new chemical entities, biological medicines, new indications and repurposed medicines. To benefit from ILAP, we must first apply to the MHRA for an innovation passport. Product developers that benefit from ILAP will be provided with advice on clinical trial design to ensure optimal data generation for both regulatory approval and health technology appraisal.

The competent regulatory authorities in the EU and the UK have broad discretion whether to grant access to the aforementioned schemes and designations, and even if we were to be eligible for some of these procedures, we may not experience a faster development process, review or authorization compared to conventional procedures. Moreover, the removal or threat of removal of such designation may create uncertainty or delay in the clinical development of our product candidates and threaten the commercialization prospects of our product candidates, if approved. Such an occurrence could materially impact our business, financial condition and results of operations.

Should we resume development of our product candidates, we may attempt to secure approval from the FDA or comparable foreign regulatory authorities through the use of accelerated approval pathways or similar expedited approval pathways outside the United States. If we are unable to obtain such approval, we may be required to conduct additional clinical trials beyond those that we contemplate, which could increase the expense of obtaining, and delay the receipt of, necessary marketing approvals. Even if we receive accelerated approval from the FDA or similar expedited approval pathways by foreign regulatory authorities, if our confirmatory trials do not verify clinical benefit, or if we do not comply with rigorous post-marketing requirements, the FDA or foreign regulatory authorities may seek to withdraw accelerated approval or similar expedited approval.

To the extent we resume development of our product candidates, we may in the future seek an accelerated approval for one or more of our product candidates. Under the accelerated approval program, the FDA may grant accelerated approval to a product candidate designed to treat a serious or life-threatening condition that provides meaningful therapeutic benefit over available therapies upon a determination that the product candidate has an effect on a surrogate endpoint or intermediate clinical endpoint that is reasonably likely to predict clinical benefit. The FDA considers a clinical benefit to be a positive therapeutic effect that is clinically meaningful in the context of a given disease, such as irreversible morbidity or mortality. For the purposes of accelerated approval, a surrogate endpoint is a marker, such as a laboratory measurement, radiographic image, physical sign, or other measure that is thought to predict clinical benefit, but is not itself a measure of clinical benefit. An intermediate clinical endpoint is a clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit.

The accelerated approval pathway may be used in cases in which the advantage of a drug or biologic over available therapy may not be a direct therapeutic advantage, but is a clinically important improvement from a patient and public health perspective. If granted, accelerated approval is usually contingent on the sponsor’s agreement to conduct, in a diligent manner, confirmatory studies to verity and describe the drug or biologic’s predicted clinical benefit. If confirmatory studies fail to confirm such clinical benefit or if the sponsor fails to conduct such studies in a timely manner, the FDA may withdraw its approval of the drug on an expedited basis. In addition, in December 2022, President Biden signed an omnibus appropriations bill to fund the U.S. government through fiscal year 2023. Included in the omnibus bill is the Food and Drug Omnibus Reform Act of 2022, which among other things, introduced reforms intended to expand the FDA’s ability to regulate products receiving accelerated approval, including by increasing the FDA’s oversight over the conduct of confirmatory trials; however, the ultimate impact of these reforms remains unclear.

In the EU, a “conditional” marketing authorization may be granted in cases where all the required safety and efficacy data are not yet available. A conditional marketing authorization is subject to conditions to be fulfilled for generating missing data or ensuring increased safety measures. A conditional marketing authorization is valid for one year and has to be renewed annually until fulfillment of all relevant conditions. Once the applicable pending studies are provided, a conditional marketing authorization can become a “standard” marketing authorization. However, if the conditions are not fulfilled within the timeframe set by the EMA, the marketing authorization will cease to be renewed. Furthermore, marketing authorizations may also be granted “under exceptional circumstances” when the applicant can show that it is unable to provide comprehensive data on the efficacy and safety under normal conditions of use even after the product has been authorized and subject to the introduction of specific procedures. This may arise when the intended

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indications are very rare and, in the present state of scientific knowledge, it is not possible to provide comprehensive information, or when generating data may be contrary to generally accepted ethical principles. This type of marketing authorization is close to a conditional marketing authorization as it is reserved to medicinal products to be approved for severe diseases or unmet medical needs and the applicant does not hold the complete data set legally required for the grant of a marketing authorization. However, unlike a conditional marketing authorization, the applicant does not have to provide the missing data and will never have to. Although a marketing authorization “under exceptional circumstances” is granted definitively, the risk-benefit balance of the medicinal product is reviewed annually and the marketing authorization may be withdrawn where the risk-benefit ratio is no longer favorable.

Prior to seeking accelerated approval or similar expedited approval for any of our product candidates, we intend to seek feedback from the FDA or other comparable regulatory authorities and will otherwise evaluate our ability to seek and receive accelerated approval or similar expedited approval. Furthermore, if we decide to submit an application for accelerated approval or similar expedited approval, there can be no assurance that such submission or application will be accepted or that any expedited development, review or approval will be granted on a timely basis, or at all. The FDA or other comparable foreign regulatory authorities could also require us to conduct further studies prior to considering our application or granting approval of any type. A failure to obtain accelerated approval or any other form of expedited development, review or approval for our product candidate would result in a longer time period to commercialization of such product candidate, or make commercialization unfeasible, and could increase the cost of development of such product candidate and could harm our competitive position in the marketplace.

We have received orphan drug designation for HMI-103, and in the future we may intend to seek orphan drug designation for our other product candidates, but any orphan drug designations we receive may not confer marketing exclusivity or other expected benefits.

We have received orphan drug designation for HMI-103 in the United States and the EU for the use of AAVHSC15 expressing PAH for the treatment of PAH deficiency. In the United States, orphan drug designation entitles a party to financial incentives such as opportunities for grant funding towards clinical trial costs, tax advantages and user-fee waivers. In addition, if a product that has orphan drug designation subsequently receives the first FDA approval for the disease for which it has such designation, the product is entitled to orphan drug exclusivity. Orphan drug exclusivity in the United States provides that the FDA may not approve any other applications, including a full BLA, to market the same drug for the same disease or condition for seven years, except in limited circumstances. The applicable exclusivity period is ten years in the EU. The European exclusivity period can be reduced to six years if, at the end of the fifth year, a drug no longer meets the criteria for orphan drug designation or if the drug is sufficiently profitable so that market exclusivity is no longer justified.

In the future even if we, or any prospective collaborators, obtain orphan drug designation for a product candidate, we, or they, may not be able to obtain or maintain orphan drug exclusivity for that product candidate. We may not be the first to obtain marketing approval of any product candidate for which we have obtained orphan drug designation for the orphan-designated disease or condition due to the uncertainties associated with developing pharmaceutical products. In addition, exclusive marketing rights in the United States may be limited if we seek approval for a disease or condition broader than the orphan-designated disease or condition or may be lost if the FDA later determines that the request for designation was materially defective or if we are unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition. Further, even if we, or any future collaborators, obtain orphan drug exclusivity for a product, that exclusivity may not effectively protect the product from competition because different drugs with different active moieties may be approved for the same disease or condition. Even after an orphan drug is approved, the FDA can subsequently approve the same drug for the same disease or condition if the FDA concludes that the later drug is clinically superior in that it is shown to be safer, more effective or makes a major contribution to patient care or the manufacturer of the product with orphan exclusivity is unable to maintain sufficient product quantity. Orphan drug designation neither shortens the development time or regulatory review time of a drug nor gives the drug any advantage in the regulatory review or approval process, nor does it prevent competitors from obtaining approval of the same product candidate as ours for diseases or conditions other than those in which we have been granted orphan drug designation. The same principles are valid for the EU as well.

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A Regenerative Medicine Advanced Therapy designation from the FDA, or Advanced Therapy Medicinal Product classification by the EMA, even if granted for any of our product candidates, may not lead to a faster development or regulatory review or approval process and does not increase the likelihood that our product candidates will receive marketing approval.

Should we resume development of our product candidates, we may seek a Regenerative Medicine Advanced Therapy, or RMAT, designation for HMI-102 or our product candidates. In 2017, the FDA established the RMAT designation as part of its implementation of the 21st Century Cures Act. An investigational drug is eligible for RMAT designation if: (1) it meets the definition of a regenerative medicine therapy, which is defined as a cell therapy, therapeutic tissue engineering product, human cell and tissue product, or any combination product using such therapies or products, with limited exceptions; (2) it is intended to treat, modify, reverse, or cure a serious disease or condition; and (3) preliminary clinical evidence indicates that the investigational drug has the potential to address unmet medical needs for such disease or condition. In a February 2019 final guidance, the FDA also stated that certain gene therapies that lead to a sustained effect on cells or tissues may meet the definition of a regenerative medicine therapy. RMAT designation provides potential benefits that include more frequent meetings with FDA to discuss the development plan for the product candidate, and eligibility for rolling review of BLAs and priority review. Product candidates granted RMAT designation may also be eligible for accelerated approval on the basis of a surrogate or intermediate endpoint reasonably likely to predict long-term clinical benefit, or reliance upon data obtained from a meaningful number of sites, including through expansion to additional sites, as appropriate. RMAT-designated product candidates that receive accelerated approval may, as appropriate, fulfill their post-approval requirements through the submission of clinical evidence, clinical studies, patient registries, or other sources of real world evidence (such as electronic health records); through the collection of larger confirmatory data sets; or via post-approval monitoring of all patients treated with such therapy prior to approval of the therapy.

RMAT designation does not change the standards for product approval, and there is no assurance that such designation or eligibility for such designation will result in expedited review or approval or that the approved indication will not be narrower than the indication covered by the RMAT designation. Additionally, RMAT designation can be revoked if the criteria for eligibility cease to be met as clinical data emerges.

In the EU, a specific framework has been implemented for ATMPs to facilitate their access to the EU market. An ATMP can be classified into three main types of medicinal products: (i) gene therapy medicinal products containing genes that lead to a therapeutic, prophylactic or diagnostic effect, (ii) somatic-cell therapy medicinal products containing cells or tissues that have been manipulated to change their biological characteristics or cells or tissues not intended to be used for the same essential functions in the body which can be used to cure, diagnose or prevent diseases, and (iii) tissue-engineered products containing cells or tissues that have been modified so they can be used to repair, regenerate or replace human tissue. Companies developing product candidates may seek a scientific recommendation from the EMA’s CAT on ATMP classification. This optional procedure allows applicants to clarify whether a given product candidate based on genes, cells or tissues meets the scientific criteria which define ATMPs, in order to address, as early as possible, questions of borderline with other areas, which may arise as science develops. ATMP classification recommendation is adopted by the EMA’s CAT, after consultation with the EC. The EMA offers a range of advisory services and incentives to support the development of ATMPs such as contribution of the CAT’s members in the discussion of the scientific advice and fee waivers. Similarly to RMAT designation, ATMP classification in the EU does not change the standards for product approval, and there is no assurance that such classification will result in expedited review or approval.

Our contract manufacturers, including Oxford Biomedica Solutions LLC, are subject to significant regulation with respect to manufacturing our former product candidates. The manufacturing facilities which we have historically and may in the future rely may not meet or continue to meet regulatory requirements, as applicable and as imposed to date, and have limited capacity.

Historically we have had relationships with a limited number of suppliers for the manufacturing of our viral vectors and product candidates. In March 2022, we closed an agreement with Oxford to establish a new AAV vector manufacturing company, Oxford Biomedica Solutions LLC, that incorporates our proven 'plug and play' process development and manufacturing platform, as well as our experienced team and high-quality GMP vector production capabilities that we built and operated since 2019. The related transactions closed on March 10, 2022. Each supplier may require licenses to manufacture such components if such processes are not owned by the supplier or in the public domain and we may be unable to transfer or sublicense the intellectual property rights we may have with respect to such activities.

All entities involved in the preparation of therapeutics for clinical studies or commercial sale, including our existing contract manufacturers for our product candidates, are subject to extensive regulation. Components of a finished therapeutic product approved for commercial sale or used in late-stage clinical studies must be manufactured in accordance with cGMP or similar requirements outside the United States. These regulations govern manufacturing processes and procedures (including record keeping) and the implementation and operation of quality systems to control and assure the quality of investigational products and products approved for sale. Poor control of production processes can lead to the introduction of adventitious agents or other contaminants, or to

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inadvertent changes in the properties or stability of our product candidates that may not be detectable in final product testing. Our contract manufacturers must supply all necessary documentation in support of a BLA on a timely basis and must adhere to the FDA’s current good laboratory practices, or GLP, and GMP regulations enforced by the FDA through its facilities inspection program. Similar requirements apply in foreign jurisdictions. Some of our contract manufacturers have not produced a commercially-approved product and therefore have not obtained the requisite FDA and foreign regulatory approvals to do so. Our facilities and quality systems and the facilities and quality systems of some or all of our third-party contractors must pass a pre-approval inspection for compliance with the applicable regulations as a condition of regulatory approval of our product candidates or any of our other potential products. In addition, the regulatory authorities may, at any time, audit or inspect a manufacturing facility involved with the preparation of our product candidates or our other potential products or the associated quality systems for compliance with the regulations applicable to the activities being conducted. If these facilities do not pass a pre-approval plant inspection, FDA or foreign regulatory authorities approval of the products will not be granted.

The regulatory authorities also may, at any time following approval of a product for sale, audit our manufacturing facilities or those of our third-party contractors. If any such inspection or audit identifies a failure to comply with applicable regulations or if a violation of our product specifications or applicable regulations occurs independent of such an inspection or audit, we or the relevant regulatory authority may require remedial measures that may be costly and/or time-consuming for us or a third party to implement and that may include the temporary or permanent suspension of a clinical study or commercial sales or the temporary or permanent closure of a facility. Any such remedial measures imposed upon us or third parties with whom we contract could materially harm our business.

If our third-party manufacturers fail to maintain regulatory compliance, the FDA or other regulatory authorities can impose regulatory sanctions including, among other things, refusal to approve a pending application for a new drug product or biologic product, or revocation of a pre-existing approval. As a result, our business, financial condition and results of operations may be materially harmed.

Additionally, if supply from one approved manufacturer is interrupted, there could be a significant disruption in commercial supply. An alternative manufacturer would need to be qualified through a BLA supplement and/or marketing authorization application supplement which could result in further delay. The regulatory agencies may also require additional studies if a new manufacturer is relied upon for commercial production. Switching manufacturers may involve substantial costs and is likely to result in a delay in our desired clinical and commercial timelines.

These factors could cause the delay of clinical studies, regulatory submissions, required approvals or commercialization of our product candidates, cause us to incur higher costs and prevent us from commercializing our products successfully. Furthermore, if our suppliers fail to meet contractual requirements, and we are unable to secure one or more replacement suppliers capable of production at a substantially equivalent cost, our clinical studies may be delayed or we could lose potential revenue.

If we resume development of product candidates and encounter difficulties enrolling patients in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

Should we resume development of our product candidates, the timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the study until its conclusion. We may encounter delays in enrolling, or be unable to enroll, a sufficient number of patients to complete any of our clinical trials, and even once enrolled we may be unable to retain a sufficient number of patients to complete any of our trials. The enrollment of patients depends on many factors, including:

•the patient eligibility criteria defined in the protocol;

•the size of the patient population required for analysis of the trial’s primary endpoints;

•the proximity of patients to study sites;

•the design of the trial;

•our ability to recruit clinical trial investigators with the appropriate competencies and experience;

•clinicians’ and patients’ perceptions as to the potential advantages of the product candidate being studied in relation to other available therapies, including any new products that may be approved for the indications we are investigating;

•our ability to obtain and maintain patient consents; and

•the risk that patients enrolled in clinical trials will drop out of the trials before completion.

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In addition, should we resume development of our product candidates, our clinical trials would compete with other clinical trials for product candidates that are in the same therapeutic areas as our product candidates, and this competition would reduce the number and types of patients available to us, because some patients who might have opted to enroll in our trials may instead opt to enroll in a trial being conducted by one of our competitors. Since the number of qualified clinical investigators is limited, we would expect to conduct some of our clinical trials at the same clinical trial sites that some of our competitors use, which would reduce the number of patients who are available for our clinical trials in such clinical trial site.

Delays or failures in planned patient enrollment or retention may result in increased costs, program delays or both, which could have a harmful effect on our ability to develop our product candidates, or could render further development impossible.

Our product candidates have caused and may in the future cause serious adverse events or undesirable side effects or have other properties which may delay or prevent their regulatory approval, limit the commercial profile of an approved label or result in significant negative consequences following marketing approval, if any.

Serious adverse events or undesirable side effects caused by our product candidates have caused, and could in the future cause, us or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign authorities. Results of our clinical trials could reveal a high and unacceptable severity and prevalence of side effects, toxicities or unexpected characteristics, including death. A significant risk in any gene editing product is that the edit will be “off-target” (or “on-target,” but unwanted) and cause serious adverse events, undesirable side effects, toxicities or unexpected characteristics. For example, off-target cuts could lead to disruption of a gene or a genetic regulatory sequence at an unintended site in the DNA, or, in those instances where we also provide a segment of DNA to serve as a repair template, it is possible that following off-target cut events, DNA from such repair template could be integrated into the genome at an unintended site, potentially disrupting another important gene or genomic element. We cannot be certain that off-target editing will not occur in any of our planned or future clinical studies. There is also the potential risk of delayed adverse events following exposure to gene editing and/or gene therapy, due to the potential for persistent biological activity of the genetic material or other product components used to carry the genetic material.

If unacceptable side effects arise in the development of our product candidates, we, the FDA, the IRBs at the institutions in which our studies are conducted or DMC, could suspend or terminate our clinical trials or the FDA or comparable foreign regulatory authorities could order us to cease clinical trials or deny approval of our product candidates for any or all targeted indications. Treatment-related side effects could also affect patient recruitment or the ability of enrolled patients to complete the trial or result in potential product liability claims. In addition, these side effects may not be appropriately recognized or managed by the treating medical staff. We expect to have to train medical personnel using our product candidates to understand the side effect profiles for our clinical trials and upon any commercialization of any of our product candidates. Inadequate training in recognizing or managing the potential side effects of our product candidates could result in patient injury or death. Any of these occurrences may harm our business, financial condition and prospects significantly.

If we resume development of our product candidates and any of our product candidates receives marketing approval, and we or others later identify undesirable side effects caused by any such product, including during any long-term follow-up observation period recommended or required for patients who receive treatment using our products, a number of potentially significant negative consequences could result, including:

•regulatory authorities may withdraw approvals of such product;

•we may be required to recall a product or change the way such product is administered to patients;

•additional restrictions may be imposed on the marketing of the particular product or the manufacturing processes for the product;

•regulatory authorities may require additional warnings on the label, such as a “black box” warning or contraindication;

•we may be required to implement a Risk Evaluation and Mitigation Strategy, or REMS, or create a medication guide outlining the risks of such side effects for distribution to patients or implement similar risk management measures;

•the product could become less competitive;

•we could be sued and held liable for harm caused to patients; and

•our reputation may suffer.

Any of these events could prevent us from achieving or maintaining market acceptance of the particular product candidate, if approved, and could significantly harm our business, results of operations and prospects.

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The regulatory approval processes of the FDA and comparable foreign authorities are lengthy, time consuming and inherently unpredictable.

The time required to obtain approval by the FDA and comparable foreign authorities is unpredictable but typically takes many years following the commencement of clinical trials and depends upon numerous factors, including the substantial discretion of the regulatory authorities. In addition, approval policies, regulations, or the type and amount of clinical data necessary to gain approval may change during the course of a product candidate’s clinical development and may vary among jurisdictions. We have not obtained regulatory approval for any product candidate and it is possible that neither our current product candidates, nor any other product candidates we may seek to develop in the future will ever obtain regulatory approval. Neither we nor any future collaborator is permitted to market any of our product candidates in the United States until we receive regulatory approval of a BLA from the FDA. It is possible that the FDA may refuse to file for substantive review any BLAs, that we submit for our product candidates or may conclude after review of our data that our application is insufficient to obtain marketing approval of our product candidates. Similar risks exist in foreign jurisdictions.

Prior to obtaining approval to commercialize a product candidate in the United States or abroad, we or our collaborators must demonstrate with substantial evidence from well-controlled clinical trials, and to the satisfaction of the FDA or foreign regulatory authorities, that such product candidates are safe and effective, or in the case of biologics, safe, pure, and potent, for their intended uses. Results from nonclinical studies and clinical trials can be interpreted in different ways. Even if we believe the nonclinical or clinical data for our product candidates are promising, such data may not be sufficient to support approval by the FDA and other regulatory authorities. The FDA and other regulatory authorities may also require us to conduct additional preclinical studies or clinical trials for our product candidates either prior to or post-approval, or it may object to elements of our clinical development program. Depending on the extent of these or any other FDA- and other regulatory authorities- required studies, approval of any BLA or application that we submit may be delayed by several years, or may require us to expend significantly more resources than we have available.

Of the large number of potential products in development, only a small percentage successfully complete the FDA or foreign regulatory approval processes and are commercialized. The lengthy approval process as well as the unpredictability of future clinical trial results may result in our failing to obtain regulatory approval to market our product candidates, which would significantly harm our business, results of operations and prospects.

In addition, even if we were to obtain approval, regulatory authorities may approve any of our product candidates for fewer or more limited indications than we request, may not approve the price we intend to charge for our products, may grant approval contingent on the performance of costly post-marketing clinical trials, including Phase 4 clinical trials, and/or the implementation of a REMS or similar risk management measures, which may be required to ensure safe use of the drug after approval. The FDA or the applicable foreign regulatory agency also may approve a product candidate for a more limited indication or patient population than we originally requested, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. Any of the foregoing scenarios could materially harm the commercial prospects for our product candidates.

In addition, changes in marketing approval policies during the development period, changes in or the enactment of additional statutes or regulations, or changes in regulatory review for each submitted product application, may cause delays in the approval or rejection of an application. For instance, the EU pharmaceutical legislation is currently undergoing a complete review process, in the context of the Pharmaceutical Strategy for Europe initiative, launched by the EC in November 2020. The EC’s proposal for revision of several legislative instruments related to medicinal products (potentially revising the duration of regulatory exclusivity, eligibility for expedited pathways, etc.) was published on April 26, 2023. The proposed revisions remain to be agreed and adopted by the European Parliament and European Council (not expected before the end of 2024 or early 2025). The revisions may, however, have a significant impact on the pharmaceutical industry and our business in the long term.

Disruptions at the FDA and other government agencies caused by funding shortages or global health concerns could hinder their ability to hire, retain or deploy key leadership and other personnel, or otherwise prevent new or modified products from being developed, approved or commercialized in a timely manner or at all, which could negatively impact our business to the extent we resume such activities.

The ability of the FDA and foreign regulatory authorities to review and or approve new products can be affected by a variety of factors, including government budget and funding levels, statutory, regulatory, and policy changes, the FDA’s or and foreign regulatory authorities’ ability to hire and retain key personnel and accept the payment of user fees, and other events that may otherwise affect the FDA’s or foreign regulatory authorities’ ability to perform routine functions. Average review times at the agency and foreign regulatory authorities have fluctuated in recent years as a result. In addition, government funding of other government

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agencies that fund research and development activities is subject to the political process, which is inherently fluid and unpredictable. Disruptions at the FDA and other agencies, such as the EMA following its relocation to Amsterdam and related reorganization, may also slow the time necessary for new drugs and biologics to be reviewed and/or approved by necessary government agencies, which would adversely affect our business. For example, over the last several years, the U.S. government has shut down several times and certain regulatory agencies, such as the FDA, have had to furlough critical FDA employees and stop critical activities. Also, resource constraints resulting from COVID-19 have caused and could continue to cause the FDA and/or other agencies to be unable to provide requested feedback to companies navigating the regulatory review process on a timely basis.

Separately, in response to the COVID-19 pandemic, the FDA postponed most inspections of domestic and foreign manufacturing facilities at various points. Even though the FDA has since resumed standard inspection operations of domestic facilities where feasible, the FDA has continued to monitor and implement changes to its inspectional activities to ensure the safety of its employees and those of the firms it regulates, and any resurgence of the virus or emergence of new variants may lead to further inspectional delays. Regulatory authorities outside the United States have adopted similar restrictions or other policy measures in response to COVID-19. If a prolonged government shutdown occurs, or if global health concerns continue to prevent the FDA or other regulatory authorities from conducting their regular inspections, reviews, or other regulatory activities, it could significantly impact the ability of the FDA or other regulatory authorities to timely review and process our regulatory submissions, which could have a material adverse effect on our business.

Even if we obtain FDA approval for our product candidates in the United States in the future, we may never obtain approval for or commercialize them in any other jurisdiction, which would limit our ability to realize their full market potential.

In order to market any products in any particular jurisdiction, we must establish and comply with numerous and varying regulatory requirements on a country-by-country basis regarding safety and efficacy. Approval by the FDA in the United States does not ensure approval by regulatory authorities in other countries or jurisdictions. However, the failure to obtain approval in any one jurisdiction may negatively impact our ability to obtain approval elsewhere. In addition, clinical trials conducted in one country may not be accepted by regulatory authorities in other countries, and regulatory approval in one country does not guarantee regulatory approval in any other country.

Approval processes vary among countries and can involve additional product testing and validation and additional administrative review periods. Seeking foreign regulatory approval could result in difficulties and increased costs for us and require additional preclinical studies or clinical trials which could be costly and time consuming. Regulatory requirements can vary widely from country to country and could delay or prevent the introduction of our products in those countries. We do not have any product candidates approved for sale in any jurisdiction, including in international markets, and we do not have experience in obtaining regulatory approval in international markets. If we fail to comply with regulatory requirements in international markets or to obtain and maintain required approvals, or if regulatory approvals in international markets are delayed, our target market will be reduced and our ability to realize the full market potential of any product we develop will be unrealized.

Even if we receive regulatory approval of our product candidates, we will be subject to ongoing regulatory obligations and continued regulatory review, which may result in significant additional expense, and we may be subject to penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our product candidates.

Any product candidate for which we obtain marketing approval, along with the manufacturing processes, post-approval clinical data, labeling, packaging, distribution, adverse event reporting, storage, recordkeeping, export, import, advertising and promotional activities for such product, among other things, will be subject to extensive and ongoing requirements of and review by the FDA and other regulatory authorities. These requirements include submissions of safety and other post-marketing information and reports, establishment registration and drug listing requirements, continued compliance with GMP requirements relating to manufacturing, quality control, quality assurance and corresponding maintenance of records and documents, requirements regarding the distribution of samples to physicians and recordkeeping and GCP requirements for any clinical trials that we conduct post-approval. Manufacturers of drug products and their facilities are subject to continual review and periodic, unannounced inspections by the FDA and other regulatory authorities for compliance with cGMP or similar regulations and standards.

In addition, any marketing approvals that we may receive for our product candidates may contain significant limitations related to use restrictions for specified age groups, warnings, precautions or contraindications, and may include burdensome post-approval study or risk management requirements. For example, the FDA may require a REMS in order to approve our product candidates, which could entail requirements for a medication guide, physician training and communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools.

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In addition, later discovery of previously unknown adverse events or other problems with our products, manufacturers or manufacturing processes, including adverse events of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may yield various results, including:

•restrictions on manufacturing such products;

•restrictions on the labeling or marketing of a product;

•restrictions on product distribution or use;

•requirements to conduct post-marketing studies or clinical trials;

•warning letters or holds on clinical trials;

•withdrawal of the products from the market;

•refusal to approve pending applications or supplements to approved applications that we submit;

•recall of products;

•fines, restitution or disgorgement of profits or revenues;

•suspension or withdrawal of marketing approvals;

•refusal to permit the import or export of our products;

•product seizure or detention; or

•injunctions or the imposition of civil or criminal penalties.

The FDA’s and other regulatory authorities’ policies may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our product candidates.

We also cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may be subject to enforcement action and we may not achieve or sustain profitability.

The FDA and other regulatory authorities actively enforce the laws and regulations prohibiting the promotion of off-label uses.

If any of our product candidates are approved and we are found to have improperly promoted off-label uses of those products, we may become subject to significant liability. The FDA and other regulatory authorities strictly regulate the promotional claims that may be made about prescription products, such as our product candidates, if approved. In particular, a product may not be promoted for uses that are not approved by the FDA or such other regulatory agencies as reflected in the product’s approved labeling. If we receive marketing approval for a product candidate, physicians may nevertheless prescribe it to their patients in a manner that is inconsistent with the approved label. If we are found to have promoted such off-label uses, we may become subject to significant liability. The U.S. federal government has levied large civil and criminal fines against companies for alleged improper promotion of off-label use and has enjoined several companies from engaging in off-label promotion. The FDA has also requested that companies enter into consent decrees or permanent injunctions under which specified promotional conduct is changed or curtailed. If we cannot successfully manage the promotion of our product candidates, if approved, we could become subject to significant liability, which would materially adversely affect our business and financial condition.

Potential product liability lawsuits against us could cause us to incur substantial liabilities and limit commercialization of any products that we may develop.

The use of our product candidates in clinical trials and the sale of any products for which we obtain marketing approval exposes us to the risk of product liability claims. Product liability claims might be brought against us by consumers, healthcare providers, pharmaceutical companies or others selling or otherwise coming into contact with our products. On occasion, large judgments have been awarded in class action lawsuits based on products that had unanticipated adverse effects. If we cannot successfully defend

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against product liability claims, we could incur substantial liability and costs. In addition, regardless of merit or eventual outcome, product liability claims may result in:

•impairment of our business reputation and significant negative media attention;

•withdrawal of participants from our clinical trials;

•significant costs to defend the related litigation and related litigation;

•distraction of management’s attention from our primary business;

•substantial monetary awards to patients or other claimants;

•inability to commercialize our product candidates;

•product recalls, withdrawals or labeling, marketing or promotional restrictions;

•decreased demand for our product candidates, if approved for commercial sale; and

•loss of revenue.

Our insurance policies are expensive and protect us only from some business risks, which leaves us exposed to significant uninsured liabilities.

We do not carry insurance for all categories of risk that our business may encounter. Some of the policies we currently maintain include general liability, employment practices liability, property, auto, workers’ compensation, umbrella, and directors’ and officers’ insurance.

Any additional product liability insurance coverage we acquire in the future, may not be sufficient to reimburse us for any expenses or losses we may suffer. Moreover, insurance coverage is becoming increasingly expensive and in the future we may not be able to maintain insurance coverage at a reasonable cost or in sufficient amounts to protect us against losses due to liability. If we obtain marketing approval for any of our product candidates, we intend to acquire insurance coverage to include the sale of commercial products; however, we may be unable to obtain product liability insurance on commercially reasonable terms or in adequate amounts. A successful product liability claim or series of claims brought against us could cause our share price to decline and, if judgments exceed our insurance coverage, could adversely affect our results of operations and business, including preventing or limiting the commercialization of any product candidates we develop. We do not carry specific biological or hazardous waste insurance coverage, and our property, casualty and general liability insurance policies specifically exclude coverage for damages and fines arising from biological or hazardous waste exposure or contamination. Accordingly, in the event of contamination or injury, we could be held liable for damages or be penalized with fines in an amount exceeding our resources, and our clinical trials or regulatory approvals could be suspended.

We also expect that operating as a public company will continue to make it more expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage. As a result, it may be more difficult for us to attract and retain qualified people to serve on our board of directors, our board committees or as executive officers. We do not know if we will be able to maintain existing insurance with adequate levels of coverage. Any significant uninsured liability may require us to pay substantial amounts, which would adversely affect our cash position and results of operations.

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Our employees and independent contractors, including principal investigators, CROs, consultants, vendors, and any third parties we may engage in connection with development and commercialization, to the extent we resume such activities, may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements, which could have a material adverse effect on our business.

Misconduct by our employees and independent contractors, including principal investigators, CROs, consultants, vendors, and any third parties we may engage in connection with development and commercialization, could include intentional, reckless or negligent conduct or unauthorized activities that violate: (i) the laws and regulations of the FDA, foreign regulatory authorities rules and regulations and other similar regulatory requirements, including those laws that require the reporting of true, complete and accurate information to such authorities; (ii) manufacturing standards; or (iii) data privacy, security, fraud and abuse and other healthcare laws and regulations. Specifically, sales, marketing and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, misconduct, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. Activities subject to these laws could also involve the improper use or misrepresentation of information obtained in the course of clinical trials, creation of fraudulent data in preclinical studies or clinical trials or illegal misappropriation of drug product, which could result in regulatory sanctions and cause serious harm to our reputation. It is not always possible to identify and deter misconduct by employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with such laws or regulations. Additionally, we are subject to the risk that a person or government could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business and results of operations, including the imposition of significant civil, criminal and administrative penalties, damages, monetary fines, disgorgements, possible exclusion from participation in Medicare, Medicaid, other U.S. federal healthcare programs or healthcare programs in other jurisdictions, individual imprisonment, other sanctions, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations.

Our business and operations may suffer in the event of information technology system failures, cyberattacks or deficiencies in our cybersecurity.

In the ordinary course of our business, we collect and store sensitive data, including intellectual property, clinical trial data, proprietary business information, personal data and personally identifiable information of our clinical trial subjects and employees, in our data centers and on our networks. The secure processing, maintenance and transmission of this information is critical to our operations. Our information technology systems, as well as those of our CROs and other contractors and consultants, are vulnerable to failure or damage from computer viruses and malware (e.g. ransomware), unauthorized access or other cybersecurity attacks, natural disasters (including hurricanes), terrorism, and telecommunication and electrical failures. We and certain of our service providers are from time to time subject to cyberattacks and security incidents. While we do not believe that we have experienced any significant system failure, accident or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our product candidate development programs. For example, the loss of preclinical or clinical trial data from completed, ongoing or planned trials could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach were to result in a loss of or damage to our data or applications, or inappropriate disclosure of personal, confidential or proprietary information, we could incur liability and the further development of our product candidates could be delayed.

Despite our security measures, our information technology and infrastructure may be vulnerable to attacks by hackers or internal bad actors, or breached due to human error (e.g., social engineering, phishing), a technical vulnerability, malfeasance or other disruptions. Attacks upon information technology systems are increasing in their frequency, levels of persistence, sophistication and intensity, and are being conducted by sophisticated and organized groups and individuals with a wide range of motives and expertise.

We may also face increased cybersecurity risks due to our reliance on internet technology and the number of our employees who are working remotely, which may create additional opportunities for cybercriminals to exploit vulnerabilities. Even if identified, we may be unable to adequately investigate or remediate incidents or breaches due to attackers increasingly using tools and techniques (including artificial intelligence) that are designed to circumvent controls, to avoid detection, and to remove or obfuscate forensic evidence. Any significant security breach could compromise our networks and the information stored there could be accessed, publicly disclosed, lost or stolen. Any such access, disclosure or other loss of information could require significant resources to remediate or recover from the incident, result in legal claims or proceedings (including class actions), liability under laws that protect the privacy of personal information, significant regulatory penalties, and such an event could disrupt our operations, damage our reputation, and cause a loss of confidence in us and our ability to conduct clinical trials, which could adversely affect our reputation

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and delay our clinical development of our product candidates. Further, our insurance coverage may not be sufficient to cover the financial, legal, business or reputational losses that may result from an interruption or breach of our systems.

Should we resume development of our product candidates, initial, interim, “top-line” and preliminary data from our clinical trials that we announce or publish from time to time may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.

If we resume development of our product candidates we may publicly disclose initial, interim, top-line or preliminary data from our clinical trials, which is based on a preliminary analysis of then-available data, and the results and related findings and conclusions are subject to change following a more comprehensive review of the data related to the particular study or trial. We also make assumptions, estimations, calculations and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. As a result, the initial, top-line or preliminary results that we report may differ from future results of the same studies, or different conclusions or considerations may qualify such results, once additional data have been received and fully evaluated. Initial, top-line or preliminary data also remain subject to audit and verification procedures that may result in the final data being materially different from the initial, top-line or preliminary data we previously published. As a result, initial, top-line and preliminary data should be viewed with caution until the final data are available.

We may also disclose interim or initial data from our preclinical studies and clinical trials. Interim or initial data from clinical trials that we may complete are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available. Adverse differences between initial, interim, top-line or preliminary data and final data could significantly harm our business prospects. Further, disclosure of any such data by us or by our competitors could result in volatility in the price of our common stock.

Further, others, including regulatory agencies, may not accept or agree with our assumptions, estimates, calculations, conclusions or analyses or may interpret or weigh the importance of data differently, which could impact the value of the particular program, the approvability or commercialization of the particular product candidate or product and our Company in general. In addition, the information we choose to publicly disclose regarding a particular study or clinical trial is based on what is typically extensive information, and you or others may not agree with what we determine is material or otherwise appropriate information to include in our disclosure.

If the top-line or preliminary data that we report differ from actual results, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to obtain approval for, and commercialize, our product candidates may be harmed, which could harm our business, operating results, prospects or financial condition.

To the extent we resume development of our product candidates, we may expend our limited resources to pursue a particular product candidate or indication and fail to capitalize on product candidates or indications that may be more profitable or for which there is a greater likelihood of success.

Because we have limited financial and managerial resources, we focus on research programs and product candidates that we identify for specific indications. As a result, we may forego or delay pursuit of opportunities with other product candidates or for other indications that later prove to have greater commercial potential. Our resource allocation decisions may cause us to fail to timely capitalize on viable commercial products or profitable market opportunities. Our spending on current and future research and development programs and product candidates for specific indications may not yield any commercially viable products. If we do not accurately evaluate the commercial potential or target market for a particular product candidate, we may relinquish valuable rights to that product candidate through collaboration, licensing or other royalty arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights to such product candidate.

Risks Related to Healthcare Laws and Other Legal Compliance Matters

If we resume development of our product candidates, enacted and future healthcare legislation could increase the difficulty and cost for us to obtain marketing approval of and commercialize our product candidates and may affect the prices we may set.

In the United States, the EU and other jurisdictions, there have been, and we expect there will continue to be, a number of legislative and regulatory changes and proposed changes to the healthcare system that could affect our future results of operations. In particular, there have been and continue to be a number of initiatives at the U.S. federal and state levels that seek to reduce healthcare costs and improve the quality of healthcare. For example, in March 2010, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, or collectively the ACA, was enacted, which substantially changed the way

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healthcare is financed by both governmental and private insurers. Among the provisions of the ACA, those of greatest importance to the pharmaceutical and biotechnology industries include the following:

•an annual, non-deductible fee payable by any entity that manufactures or imports certain branded prescription drugs and biologic agents (other than those designated as orphan drugs), which is apportioned among these entities according to their market share in certain government healthcare programs;

•a new Medicare Part D coverage gap discount program, in which manufacturers must agree to offer point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D;

•an increase in the statutory minimum rebates a manufacturer must pay under the Medicaid Drug Rebate Program to 23.1% and 13.0% of the average manufacturer price for branded and generic drugs, respectively;

•a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected;

•extension of a manufacturer’s Medicaid rebate liability to covered drugs dispensed to individuals who are enrolled in Medicaid managed care organizations;

•expansion of eligibility criteria for Medicaid programs by, among other things, allowing states to offer Medicaid coverage to certain individuals with income at or below 133% of the federal poverty level, thereby potentially increasing a manufacturer’s Medicaid rebate liability;

•a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research; and

•establishment of a Center for Medicare and Medicaid Innovation at the Centers for Medicare & Medicaid Services, or CMS, to test innovative payment and service delivery models to lower Medicare and Medicaid spending, potentially including prescription drug spending.

Since its enactment, there have been judicial, executive, and Congressional challenges to certain aspects of the ACA. On June 17, 2021, the U.S. Supreme Court dismissed the most recent judicial challenge to the ACA brought by several states without specifically ruling on the constitutionality of the ACA.

In addition, other legislative changes have been proposed and adopted in the United States since the ACA was enacted. For example, the Budget Control Act of 2011 resulted in aggregate reductions of Medicare payments to providers, which went into effect in April 2013 and, due to subsequent legislative amendments to the statute, will remain in effect through 2032, unless additional action is taken by Congress. In January 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, further reduced Medicare payments to several types of providers, including hospitals, imaging centers and cancer treatment centers, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. These new laws or any other similar laws introduced in the future may result in additional reductions in Medicare and other healthcare funding, which could negatively affect our customers and accordingly, our financial operations.

Moreover, payment methodologies may be subject to changes in healthcare legislation and regulatory initiatives. For example, CMS may develop new payment and delivery models, such as bundled payment models. On March 11, 2021, the American Rescue Plan Act of 2021 was signed into law, which eliminates the statutory cap on the Medicaid drug rebate, currently set at 100% of a drug’s AMP, beginning January 1, 2024. In addition, recently there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products. On August 16, 2022, the Inflation Reduction Act of 2022, or IRA, was signed into law. Among other things, the IRA requires manufacturers of certain drugs to engage in price negotiations with Medicare (beginning in 2026), with prices that can be negotiated subject to a cap; imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation (first due in 2023); and replaces the Part D coverage gap discount program with a new discounting program (beginning in 2025). The IRA permits the Secretary of the Department of Health and Human Services (HHS) to implement many of these provisions through guidance, as opposed to regulation, for the initial years. The impact of the IRA on our business and the pharmaceutical industry cannot yet be fully determined, but it could have a significant impact. In particular, if a product becomes subject to the IRA negotiation provision and related price cap, that may significantly alter the economic rationale for developing and commercializing a biosimilar. We expect that additional U.S. federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that the U.S. federal government will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures.

Individual states in the United States have also become increasingly active in passing legislation and implementing regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts,

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restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. Legally-mandated price controls on payment amounts by third-party payors or other restrictions could harm our business, results of operations, financial condition and prospects. In addition, regional healthcare authorities and individual hospitals are increasingly using bidding procedures to determine what pharmaceutical products and which suppliers will be included in their prescription drug and other healthcare programs. This could reduce the ultimate demand for our product candidates or put pressure on our product pricing.

In the EU, similar political, economic and regulatory developments may affect our ability to profitably commercialize our product candidates, if approved. In addition to continuing pressure on prices and cost containment measures, legislative developments at the EU or member state level may result in significant additional requirements or obstacles that may increase our operating costs. The delivery of healthcare in the EU, including the establishment and operation of health services and the pricing and reimbursement of medicines, is almost exclusively a matter for national, rather than EU, law and policy. National governments and health service providers have different priorities and approaches to the delivery of healthcare and the pricing and reimbursement of products in that context. In general, however, the healthcare budgetary constraints in most EU member states have resulted in restrictions on the pricing and reimbursement of medicines by relevant health service providers. Coupled with ever-increasing EU and national regulatory burdens on those wishing to develop and market products, this could prevent or delay marketing approval of our product candidates, restrict or regulate post-approval activities and affect our ability to commercialize our product candidates, if approved.

In markets outside of the United States and EU, reimbursement and healthcare payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies.

On December 13, 2021, Regulation No 2021/2282 on Health Technology Assessment, or HTA amending Directive 2011/24/EU, was adopted. While the Regulation entered into force in January 2022, it will only begin to apply from January 2025 onwards, with preparatory and implementation-related steps to take place in the interim. Once the Regulation becomes applicable, it will have a phased implementation depending on the concerned products. This regulation intends to boost cooperation among EU member states in assessing health technologies, including new medicinal products, and providing the basis for cooperation at the EU level for joint clinical assessments in these areas. The regulation foresees a three-year transitional period and will permit EU member states to use common HTA tools, methodologies, and procedures across the EU, working together in four main areas, including joint clinical assessment of the innovative health technologies with the most potential impact for patients, joint scientific consultations whereby developers can seek advice from HTA authorities, identification of emerging health technologies to identify promising technologies early, and continuing voluntary cooperation in other areas. Individual EU member states will continue to be responsible for assessing non-clinical (e.g., economic, social, ethical) aspects of health technology, and making decisions on pricing and reimbursement.

We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action in the United States, the EU or any other jurisdiction. If we or any third parties we may engage are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we or such third parties are not able to maintain regulatory compliance, our product candidates may lose any regulatory approval that may have been obtained and we may not achieve or sustain profitability.

Our business operations and current and future relationships with investigators, healthcare professionals, consultants, third-party payors, patient organizations and customers will be subject to applicable healthcare regulatory laws, which could expose us to penalties.

Our business operations and current and future arrangements with investigators, healthcare professionals, consultants, third-party payors, patient organizations and customers, may expose us to broadly applicable fraud and abuse and other healthcare laws and regulations. These laws may constrain the business or financial arrangements and relationships through which we conduct our operations, including how we research, market, sell and distribute our product candidates, if approved. Such laws include:

•the U.S. federal Anti-Kickback Statute, which prohibits, among other things, persons or entities from knowingly and willfully soliciting, offering, receiving or providing any remuneration (including any kickback, bribe, or certain rebate), directly or indirectly, overtly or covertly, in cash or in kind, to induce or reward, or in return for, either the referral of an individual for, or the purchase, lease, order or recommendation of, any good, facility, item or service, for which payment may be made, in whole or in part, under U.S. federal and state healthcare programs such as Medicare and Medicaid. A person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation;

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•the U.S. federal false claims and civil monetary penalties laws, including the civil False Claims Act, which, among other things, impose criminal and civil penalties, including through civil whistleblower or qui tam actions, against individuals or entities for knowingly presenting, or causing to be presented, to the U.S. federal government, claims for payment or approval that are false or fraudulent, knowingly making, using or causing to be made or used, a false record or statement material to a false or fraudulent claim, or from knowingly making a false statement to avoid, decrease or conceal an obligation to pay money to the U.S. federal government. In addition, the government may assert that a claim including items and services resulting from a violation of the U.S. federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the False Claims Act;

•The Health Insurance Portability and Accountability Act of 1996, or HIPAA, which imposes criminal and civil liability for, among other things, knowingly and willfully executing, or attempting to execute, a scheme to defraud any healthcare benefit program, or knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false statement, in connection with the delivery of, or payment for, healthcare benefits, items or services; similar to the U.S. federal Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation;

•the FDCA, which prohibits, among other things, the adulteration or misbranding of drugs, biologics and medical devices;

•the U.S. Public Health Service Act, which prohibits, among other things, the introduction into interstate commerce of a biological product unless a biologics license is in effect for that product;

•the U.S. federal legislation commonly referred to as the Physician Payments Sunshine Act, enacted as part of the ACA, and its implementing regulations, which requires certain manufacturers of drugs, devices, biologics and medical supplies that are reimbursable under Medicare, Medicaid, or the Children’s Health Insurance Program to report annually to the government information related to certain payments and other transfers of value to physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors), certain non-physician practitioners (physician assistants, nurse practitioners, clinical nurse specialists, certified nurse anesthetists, anesthesiologist assistants and certified nurse midwives), and teaching hospitals, as well as ownership and investment interests held by the physicians described above and their immediate family members;

•analogous U.S. state laws and regulations, including: state anti-kickback and false claims laws, which may apply to our business practices, including but not limited to, research, distribution, sales and marketing arrangements and claims involving healthcare items or services reimbursed by any third-party payor, including private insurers; state laws that require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the U.S. federal government, or otherwise restrict payments that may be made to healthcare providers and other potential referral sources; and state laws and regulations that require drug manufacturers to file reports relating to pricing and marketing information, which requires tracking gifts and other remuneration and items of value provided to healthcare professionals; and

•similar healthcare laws and regulations in the EU and other jurisdictions, including reporting requirements detailing interactions with and payments to healthcare providers. For instance, in the EU, interactions between pharmaceutical companies and healthcare professionals and healthcare organizations are also governed by strict laws, regulations, industry self-regulation codes of conduct and physicians’ codes of professional conduct both at EU level and member states level. The provision of benefits or advantages to physicians to induce or encourage the prescription, recommendation, endorsement, purchase, supply, order or use of pharmaceutical products is prohibited in the EU. Relationships with healthcare professionals and associations are subject to stringent anti-gift statutes and anti-bribery laws, the scope of which differs across the EU. In addition, national “Sunshine Acts” may require pharmaceutical companies to report/publish transfers of value provided to healthcare professionals and associations on a regular (e.g., annual) basis.

Ensuring that our internal operations and future business arrangements with third parties comply with applicable healthcare laws and regulations will involve substantial costs. It is possible that governmental authorities will conclude that our business practices do not comply with current or future statutes, regulations, agency guidance or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of the laws described above or any other governmental laws and regulations that may apply to us, we may be subject to significant penalties, including civil, criminal and administrative penalties, damages, fines, exclusion from government-funded healthcare programs, such as Medicare and Medicaid or similar programs in other countries or jurisdictions, disgorgement, individual imprisonment, contractual damages, reputational harm, diminished profits and the curtailment or restructuring of our operations. If any of the physicians or other providers or entities with whom we expect to do business are found to not be in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs and imprisonment, which could affect

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our ability to operate our business. Further, defending against any such actions can be costly, time-consuming and may require significant personnel resources. Therefore, even if we are successful in defending against any such actions that may be brought against us, our business may be impaired.

Actual or perceived failures to comply with applicable data protection, privacy and security laws, regulations, standards and other requirements could adversely affect our business, results of operations, and financial condition.

The global data protection landscape is rapidly evolving, and we are or may become subject to numerous state, federal and foreign laws, requirements and regulations governing the collection, use, disclosure, retention, and security of personal information, such as information that we may collect in connection with clinical trials. In the United States, HIPAA as amended by the Health Information Technology for Economic and Clinical Health Act of 2009, and regulations promulgated thereunder, or collectively, HIPAA, imposes, among other things, certain standards relating to the privacy, security, transmission and breach reporting of individually identifiable health information. Certain states have also adopted comparable privacy and security laws and regulations, some of which may be more stringent than HIPAA. Such laws and regulations will be subject to interpretation by various courts and other governmental authorities, thus creating potentially complex compliance issues for us and our future customers and strategic partners. For example, California enacted the California Consumer Privacy Act, or CCPA, which went into effect January 1, 2020. The CCPA increases data privacy obligations for covered companies and provides individual privacy rights to California consumers, including the right to opt out of certain disclosures of their information. The CCPA also creates a private right of action with statutory damages for certain data breaches, thereby potentially increasing the likelihood of and risks associated with a data breach. Although the law includes limited exceptions, including for “protected health information” maintained by a covered entity or business associate, it may regulate or impact our processing of personal information depending on the context. Further, the California Privacy Rights Act, or CPRA, generally went into effect on January 1, 2023 and significantly amends the CCPA. It imposes additional data protection obligations on covered companies doing business in California, including additional consumer rights processes and opt outs for certain uses of sensitive data. It also creates a new California data protection agency specifically tasked to enforce the law, which will likely result in increased regulatory scrutiny of California businesses in the areas of data protection and security. The substantive requirements for businesses subject to the CPRA become enforceable on July 1, 2023. Similar laws have passed in other states and are continuing to be proposed at the state and federal level, reflecting a trend toward more stringent privacy legislation in the United States. The enactment of such laws could have potentially conflicting requirements that would make compliance challenging.

Furthermore, the Federal Trade Commission, or FTC, and many state Attorneys General continue to enforce federal and state consumer protection laws against companies for online collection, use, dissemination and security practices that appear to be unfair or deceptive. For example, according to the FTC, failing to take appropriate steps to keep consumers’ personal information secure can constitute unfair acts or practices in or affecting commerce in violation of Section 5(a) of the Federal Trade Commission Act. The FTC expects a company’s data security measures to be reasonable and appropriate in light of the sensitivity and volume of consumer information it holds, the size and complexity of its business, and the cost of available tools to improve security and reduce vulnerabilities.

Our operations abroad may also be subject to increased scrutiny or attention from data protection authorities. For example, in Europe, the GDPR imposes obligations and restrictions on the collection and use of personal data relating to individuals located in the European Economic Area, or EEA. Companies that must comply with the GDPR face increased compliance obligations and risk, including more robust regulatory enforcement of data protection requirements and potential fines for noncompliance of up to €20 million or 4% of the annual global revenues of the noncompliant company, whichever is greater. Among other requirements, the GDPR regulates transfers of personal data subject to the GDPR to third countries that have not been found to provide adequate protection to such personal data, including the United States. Case law from the Court of Justice of the European Union (“CJEU”) states that reliance on the standard contractual clauses - a standard form of contract approved by the European Commission as an adequate personal data transfer mechanism - alone may not necessarily be sufficient in all circumstances and that transfers must be assessed on a case-by-case basis. Following a period of legal complexity and uncertainty regarding international personal data transfers, particularly to the United States, we expect the regulatory guidance and enforcement landscape to continue to develop, in relation to transfers to the United States and elsewhere. As a result, we may have to make certain operational changes and we will have to implement revised standard contractual clauses and other relevant documentation for existing data transfers within required time frames.

Since the beginning of 2021, we have also been subject to the UK data protection regime, which imposes separate but similar obligations to those under the GDPR and comparable penalties, including fines of up to £17.5 million or 4% of a noncompliant company’s global annual revenue for the preceding financial year, whichever is greater. If we continue to expand into other foreign countries and jurisdictions, we may be subject to additional laws and regulations that may affect how we conduct business.

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Although we work to comply with applicable laws, regulations and standards, our contractual obligations and other legal obligations, these requirements are evolving and may be modified, interpreted and applied in an inconsistent manner from one jurisdiction to another, and may conflict with one another or other legal obligations with which we must comply. Any failure or perceived failure by us or our employees, representatives, contractors, consultants, collaborators, or other third parties to comply with such requirements or adequately address privacy and security concerns, even if unfounded, could result in additional cost and liability to us, damage our reputation, and adversely affect our business and results of operations.

We are subject to environmental, health and safety laws and regulations, and we may become exposed to liability and substantial expenses in connection with environmental compliance or remediation activities.

Our operations are subject to numerous environmental, health and safety laws and regulations. These laws and regulations govern, among other things, the controlled use, handling, release and disposal of and the maintenance of a registry for, hazardous materials and biological materials, such as chemical solvents, human cells, carcinogenic compounds, mutagenic compounds and compounds that have a toxic effect on reproduction, laboratory procedures and exposure to blood-borne pathogens. If we fail to comply with such laws and regulations, we could be subject to fines or other sanctions.

As with other companies engaged in activities similar to ours, we face a risk of environmental liability inherent in our historical activities, including liability relating to releases of or exposure to hazardous or biological materials. Environmental, health and safety laws and regulations are becoming more stringent. We may be required to incur substantial expenses in connection with future environmental compliance or remediation activities, in which case, the production efforts of our third-party manufacturers or our development efforts may be interrupted or delayed.

We are currently subject to securities class action litigation and may be subject to similar or other litigation in the future, which will require significant management time and attention, result in significant legal expenses and may result in unfavorable outcomes, which may have a material adverse effect on our business, operating results and financial condition, and negatively affect the price of our common stock.

We are, and may in the future become, subject to various legal proceedings and claims that arise in or outside the ordinary course of business. In the past, securities class action litigation has often been brought against a company following a decline in the market price of its securities. This risk is especially relevant for us because biopharmaceutical companies have experienced significant stock price volatility in recent years. For example, on March 25, 2022, a stockholder of the Company, Michael C. Pizzuto, filed a putative class action complaint alleging violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, against us and certain of our executives. Pizzuto v. Homology Medicines, Inc., No. 2:22– CV – 01968 (C.D. Cal 2022). The complaint alleges that we failed to disclose certain information regarding efficacy and safety in connection with a Phase 1/2 HMI-102 clinical trial, and seeks damages in an unspecified amount. The Company filed a motion to transfer the case to the United States District Court for the District of Massachusetts on September 2, 2022, and a motion to dismiss on October 17, 2022. On April 18, 2023, the court granted the motion to transfer, finding that venue was not proper in the Central District of California and transferring the case to the District of Massachusetts. Following the transfer, the case number changed to 1:23-cv-10858-AK (D. Mass.). On May 9, 2023, the Massachusetts court issued an order permitting the parties to submit updated briefs in connection with the motion to dismiss, which were submitted on June 8, 2023, July 13, 2023, and August 3, 2023. The motion to dismiss remains pending.

The results of the securities class action lawsuit and any future legal proceedings cannot be predicted with certainty. Also, our insurance coverage may be insufficient, our assets may be insufficient to cover any amounts that exceed our insurance coverage, and we may have to pay damage awards or otherwise may enter into settlement arrangements in connection with such claims. Any such payments or settlement arrangements in current or future litigation could have a material adverse effect on our business, operating results or financial condition. Even if the plaintiffs’ claims are not successful, current or future litigation could result in substantial costs and significantly and adversely impact our reputation and divert management’s attention and resources, which could have a material adverse effect on our business, operating results and financial condition, and negatively affect the price of our common stock. In addition, such lawsuits may make it more difficult to finance our operations.

Risks Related to Commercialization

Should we resume development of our product candidates, we face significant competition in an environment of rapid technological change, and there is a possibility that our competitors may achieve regulatory approval before us or develop

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therapies that are safer or more advanced or effective than ours, which may harm our financial condition and our ability to successfully market or commercialize any product candidates we may develop.

The development and commercialization of new genetic medicine products is highly competitive. Moreover, the gene editing field is characterized by rapidly changing technologies, significant competition, and a strong emphasis on intellectual property. Should we resume development of our product candidates, we will face competition with respect to any product candidates that we may seek to develop or commercialize from major pharmaceutical companies, specialty pharmaceutical companies, and biotechnology companies worldwide. Potential competitors also include academic institutions, government agencies, and other public and private research organizations that conduct research, seek patent protection, and establish collaborative arrangements for research, development, manufacturing, and commercialization.

There are a number of large pharmaceutical and biotechnology companies that currently market and sell products or are pursuing the development of products for the treatment of the disease indications for which we had research programs, including PKU, MLD, Hunter syndrome, hemoglobinopathies and ophthalmological diseases. Some of these competitive products and therapies are based on scientific approaches that are similar to our approach, and others are based on entirely different approaches.

Historically, our platform and product focus was the development of genetic medicines using our proprietary AAVHSCs in vivo through a nuclease-free gene editing modality, gene therapy, or GTx-mAb, which is designed to produce antibodies throughout the body. Should we resume development of such programs, if our programs are approved for the indications for which we are planning clinical trials, they may compete with other products under development, including gene editing and gene therapy products or other types of therapies, such as small molecule, antibody or protein therapies. If our PKU treatments are approved, they may compete with therapies from American Gene Technologies, BioMarin, Censa Pharmaceuticals, Generation Bio, Nestlé Health Science, Sangamo Therapeutics and Synlogic. However, we believe that only gene therapy or gene editing approaches have the potential to restore the normal Phe biochemical pathway with a single administration. If our Hunter syndrome treatment is approved, it may compete with therapies from Shire and/or GC Pharma. If our MLD treatment is approved, it may compete with therapies from Orchard Therapeutics, Passage Bio and/or Shire. In vivo gene therapy approaches provide potential advantages over ex vivo approaches. There are a number of companies developing nuclease-based gene editing technologies using CRISPR/Cas9, TALENs, meganucleases, Mega-TALs and ZFNs, including but not limited to Beam Therapeutics, bluebird bio, Caribou Biosciences, Cellectis, CRISPR Therapeutics, Editas Medicine, Intellia Therapeutics, Precision BioSciences, Prime Therapeutics and Sangamo Therapeutics and non-nuclease-based technology, including LogicBio Therapeutics.

Many of our current or potential competitors, either alone or with their collaboration partners, have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals, and marketing approved products than we do. Mergers and acquisitions in the pharmaceutical, biotechnology, and gene therapy industries may result in even more resources being concentrated among a smaller number of our competitors. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These competitors also compete with us in recruiting and retaining qualified scientific and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Our commercial opportunities could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient, or are less expensive than any products that we may develop or that would render any products that we may develop obsolete or non-competitive. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours, which could result in our competitors establishing a strong market position before we are able to enter the market. Additionally, technologies developed by our competitors may render our potential product candidates uneconomic or obsolete, and we may not be successful in marketing any product candidates we may develop against competitors.

In addition, as a result of the expiration or successful challenge of our patent rights, we could face more litigation with respect to the validity and/or scope of patents relating to our competitors’ products. The availability of our competitors’ products could limit the demand, and the price we are able to charge, for any products that we may develop and commercialize.

The successful commercialization of our product candidates will depend in part on the extent to which governmental authorities and health insurers establish adequate coverage, reimbursement levels and pricing policies. Failure to obtain or maintain coverage

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and adequate reimbursement for our product candidates, if approved, could limit our ability to market those products and decrease our ability to generate revenue.

The availability and adequacy of coverage and reimbursement by governmental healthcare programs such as Medicare and Medicaid, private health insurers and other third-party payors are essential for most patients to be able to afford prescription medications such as our product candidates, assuming FDA or foreign authorities approval. Our ability to achieve acceptable levels of coverage and reimbursement for products by governmental authorities, private health insurers and other organizations will have an effect on our ability to successfully commercialize our product candidates. Assuming we obtain coverage for our product candidates by a third-party payor, the resulting reimbursement payment rates may not be adequate or may require co-payments that patients find unacceptably high. Moreover, for drugs and biologics administered under the supervision of a physician, obtaining coverage and adequate reimbursement may be particularly difficult because of the higher prices often associated with such products. We cannot be sure that coverage and reimbursement in the United States, the EU or elsewhere will be available for our product candidates or any product that we may develop, and any reimbursement that may become available may be decreased or eliminated in the future.

Third-party payors increasingly are challenging prices charged for pharmaceutical products and services, and many third-party payors may refuse to provide coverage and reimbursement for particular drugs or biologics when an equivalent generic drug, biosimilar or a less expensive therapy is available. It is possible that a third-party payor may consider our product candidates as substitutable and only offer to reimburse patients for the less expensive product. Even if we show improved efficacy or improved convenience of administration with our product candidates, pricing of existing third-party therapeutics may limit the amount we will be able to charge for our product candidates. These third-party payors may deny or revoke the reimbursement status of a given product or establish prices for new or existing marketed products at levels that are too low to enable us to realize an appropriate return on our investment in our product candidates. For products administered under the supervision of a physician, obtaining coverage and adequate reimbursement may be particularly difficult because of the higher prices often associated with such drugs. Additionally, separate reimbursement for the product itself or the treatment or procedure in which the product is used may not be available, which may impact physician utilization. If reimbursement is not available or is available only at limited levels, we may not be able to successfully commercialize our product candidates, and may not be able to obtain a satisfactory financial return on our product candidates.

There is significant uncertainty related to the insurance coverage and reimbursement of newly-approved products. In the United States, third-party payors, including private and governmental payors, such as the Medicare and Medicaid programs, play an important role in determining the extent to which new drugs and biologics will be covered. The Medicare and Medicaid programs increasingly are used as models in the United States for how private payors and other governmental payors develop their coverage and reimbursement policies for drugs and biologics. Some third-party payors may require pre-approval of coverage for new or innovative devices or drug therapies before they will reimburse healthcare providers who use such therapies. We cannot predict at this time what third-party payors will decide with respect to the coverage and reimbursement for our product candidates.

No uniform policy for coverage and reimbursement for products exists among third-party payors in the United States. Therefore, coverage and reimbursement for products can differ significantly among third-party payors. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our product candidates to each third-party payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. Furthermore, rules and regulations regarding reimbursement change frequently, in some cases on short notice, and we believe that changes in these rules and regulations are likely.

Outside the United States, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in Europe and other countries have and will continue to put pressure on the pricing and usage of our product candidates. In many countries, the prices of medical products are subject to varying price control mechanisms as part of national health systems. Other countries allow companies to fix their own prices for medical products, but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our product candidates. Accordingly, in markets outside the United States, the reimbursement for our product candidates may be reduced compared with the United States and may be insufficient to generate commercially-reasonable revenue and profits.

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Even if a pharmaceutical product obtains a marketing authorization in the EU, there can be no assurance that reimbursement for such product will be secured on a timely basis or at all. Governments influence the price of medicinal products through their pricing and reimbursement rules and control of national healthcare systems that fund a large part of the cost of those products to consumers. Member states are free to restrict the range of pharmaceutical products for which their national health insurance systems provide reimbursement, and to control the prices and reimbursement levels of pharmaceutical products for human use. Some jurisdictions operate positive and negative list systems under which products may only be marketed once a reimbursement price has been agreed to by the government. Member states may approve a specific price or level of reimbursement for the pharmaceutical product, or alternatively adopt a system of direct or indirect controls on the profitability of the company responsible for placing the pharmaceutical product on the market, including volume-based arrangements, caps and reference pricing mechanisms. To obtain reimbursement or pricing approval, some of these countries may require the completion of clinical trials that compare the cost-effectiveness of a particular product candidate to currently available therapies. Other member states allow companies to fix their own prices for medicines but monitor and control company profits. The downward pressure on healthcare costs in general, particularly prescription medicines, has become very intense. As a result, increasingly high barriers are being erected to the entry of new products. In addition, in some countries, cross border imports from low-priced markets exert a commercial pressure on pricing within a country.

Moreover, increasing efforts by governmental and third-party payors in the United States and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our product candidates. We expect to experience pricing pressures in connection with the sale of our product candidates due to the trend toward managed healthcare, the increasing influence of health maintenance organizations and additional legislative changes.

Even if any of our product candidates receives marketing approval in the future, it may fail to achieve market acceptance by physicians, patients, third-party payors or others in the medical community necessary for commercial success.

If any of our product candidates receives marketing approval in the future, it may nonetheless fail to gain sufficient market acceptance by physicians, patients, third-party payors and others in the medical community. If it does not achieve an adequate level of acceptance, we may not generate significant product revenues or become profitable. The degree of market acceptance of our product candidates, if approved for commercial sale, will depend on a number of factors, including but not limited to:

•the safety, efficacy and potential advantages compared to alternative treatments;

•effectiveness of sales and marketing efforts;

•the cost of treatment in relation to alternative treatments, including any similar generic treatments;

•our ability to offer our products for sale at competitive prices;

•the convenience and ease of administration compared to alternative treatments;

•the willingness of the target patient population to try new therapies and of physicians to prescribe these therapies;

•the strength of marketing and distribution support;

•the timing of market introduction of competitive products;

•the availability of third-party coverage and adequate reimbursement;

•product labeling or product insert requirements of the FDA, EMA or other regulatory authorities, including any limitations or warnings contained in a product’s approved labeling;

•the prevalence and severity of any side effects; and

•any restrictions on the use of our product together with other medications.

Because we expect sales of our product candidates, if approved, to generate substantially all of our product revenues for a substantial period, the failure of this product to find market acceptance would harm our business and could require us to seek additional financing.

Should we resume development of our product candidates, if we are unable to establish sales, marketing and distribution capabilities either on our own or in collaboration with third parties, we may not be successful in commercializing our product

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candidates, if approved. Moreover, provisions in our agreements with Pfizer may inhibit our ability to enter into future collaborations with third parties.

We do not have any infrastructure for the sales, marketing or distribution of our products, and the cost of establishing and maintaining such an organization may exceed the cost-effectiveness of doing so.

Should we resume development of our product candidates, there are significant expenses and risks involved with establishing our own sales, marketing and distribution capabilities, including our ability to hire, retain and appropriately incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, and effectively manage a geographically dispersed sales and marketing team. Any failure or delay in the development of our internal sales, marketing and distribution capabilities could delay any product launch, which would adversely impact the commercialization of our product candidates. Additionally, if the commercial launch of any of our product candidates for which we recruit a sales force and establish marketing capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization expenses. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel.

We do not anticipate having the resources in the foreseeable future to allocate to the sales and marketing of our product candidates in certain markets overseas. Therefore, our future sales in these markets will largely depend on our ability to enter into and maintain collaborative relationships for such capabilities, the collaborator’s strategic interest in the product and such collaborator’s ability to successfully market and sell the product. We intend to pursue collaborative arrangements regarding the sale and marketing of our product candidates, if approved, for certain markets overseas; however, we cannot assure that we will be able to establish or maintain such collaborative arrangements, or if able to do so, that they will have effective sales forces.

If we are unable to build our own sales force or negotiate a collaborative relationship for the commercialization of our product candidates, we may be forced to delay the potential commercialization of our product candidates or reduce the scope of our sales or marketing activities for our product candidates. If we elect to increase our expenditures to fund commercialization activities ourselves, we will need to obtain additional capital, which may not be available to us on acceptable terms, or at all. We could enter into arrangements with collaborative partners at an earlier stage than otherwise would be ideal and we may be required to relinquish rights to our product candidates or otherwise agree to terms unfavorable to us, any of which may have an adverse effect on our business, operating results and prospects.

If we are unable to establish adequate sales, marketing and distribution capabilities, either on our own or in collaboration with third parties, we will not be successful in commercializing our product candidates, and may not become profitable and may incur significant additional losses. We will be competing with many companies that currently have extensive and well-funded marketing and sales operations. Without an internal team or the support of a third party to perform marketing and sales functions, we may be unable to compete successfully against these more established companies.

If we obtain approval to commercialize any products outside of the United States, a variety of risks associated with international operations could materially adversely affect our business.

If any of our product candidates are approved for commercialization, we may enter into agreements with third parties to market it in certain jurisdictions outside the United States. We expect that we will be subject to additional risks related to international pharmaceutical operations, including:

•different regulatory requirements for drug and biologic approvals and rules governing drug and biologic commercialization and country-specific regulations of gene therapies in foreign countries;

•complex and restrictive import/export regulations;

•reduced protection for intellectual property rights;

•foreign reimbursement, pricing and insurance regimes;

•potential noncompliance with the U.S. Foreign Corrupt Practices Act, the U.K. Bribery Act 2010 and similar anti-bribery and anticorruption laws in other jurisdictions;

•production shortages resulting from any events affecting raw material supply or manufacturing capabilities abroad;

•political and economic instability, including in light of the international terrorism and conflicts;

•fluctuations in currency exchange rates; and

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•higher costs of doing business internationally, including increased accounting, travel infrastructure and legal compliance costs.

We have no prior experience in these areas. In addition, there are complex regulatory, tax, labor and other legal requirements imposed by both the EU and many of the EU member states with which we will need to comply. Many U.S.-based biotechnology companies have found the process of marketing their own products in Europe to be very challenging.

In the future, any product candidates for which we may seek approval as biologic products may face competition sooner than anticipated.

The Patient Protection and Affordable Care Act, signed into law on March 23, 2010, includes a subtitle called the Biologics Price Competition and Innovation Act of 2009, or BPCIA, which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product. Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four years following the date that the reference product was first licensed by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first licensed. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves a full BLA for the competing product containing the sponsor’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of their product. The law is complex and is still being interpreted and implemented by the FDA. As a result, its ultimate impact, implementation, and meaning are subject to uncertainty.

There is a risk that any of our product candidates approved as a biological product under a BLA would not qualify for the 12-year period of exclusivity or that this exclusivity could be shortened due to congressional action or otherwise, or that the FDA will not consider our product candidates to be reference products for competing products, potentially creating the opportunity for generic competition sooner than anticipated. Jurisdictions in addition to the United States have established abbreviated pathways for regulatory approval of biological products that are biosimilar to earlier approved reference products. For example, the EU has had an established regulatory pathway for biosimilars since 2006. Moreover, the extent to which a biosimilar, once approved, will be substituted for any one of our reference products in a way that is similar to traditional generic substitution for non-biological products is not yet clear, and will depend on a number of marketplace and regulatory factors that are still developing.

Risks Related to Our Dependence on Third Parties

We have historically contracted with third parties, including Oxford Biomedica Solutions LLC, for the manufacture of certain materials for our research programs, preclinical and clinical studies. This reliance on third parties increases the risk that we will not have sufficient quantities of such materials, product candidates, or any medicines that we may develop and commercialize, or that such supply will not be available to us at an acceptable cost or in compliance with regulatory requirements, which could delay, prevent, or impair our development or commercialization efforts if we were to resume such activities.

We have historically relied on third-party manufacturers for the manufacture of materials for research programs, preclinical and clinical studies. We do not have long-term supply agreements with all of the third-party manufacturers, and we purchase our required supply on a purchase order basis. Furthermore, the raw materials for our product candidates are sourced, in some cases, from a single-source supplier. Should we resume development of our product candidates, if we were to experience an unexpected loss of supply of any of our product candidates or any of our future product candidates for any reason, whether as a result of manufacturing, supply or storage issues or otherwise, we could experience delays, disruptions, suspensions or terminations of, or be required to restart or repeat, any pending or ongoing clinical trials.

We may be unable to establish any agreements with third-party manufacturers or to do so on acceptable terms. Even if we are able to establish agreements with third-party manufacturers, reliance on third-party manufacturers entails additional risks, including:

•the possible breach of the manufacturing agreement by the third party;

•the possible termination or nonrenewal of the agreement by the third party at a time that is costly or inconvenient for us;

•reliance on the third party for regulatory compliance, quality assurance, safety, and pharmacovigilance and related reporting;

•inability to meet our drug specifications and quality requirements consistently;

•delay or inability to procure sufficient manufacturing capacity;

•issues related to scale-up of manufacturing;

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•costs and validation of new equipment and facilities required for scale-up;

•reliance on single sources for drug components;

•lack of qualified backup suppliers for those components that are purchased from a sole or single-source supplier;

•misappropriation of proprietary information, including our trade secrets and know-how;

•the mislabeling of clinical supplies, potentially resulting in the wrong dose amounts being supplied or study drug or placebo not being properly identified;

•clinical supplies not being delivered to clinical sites on time, leading to clinical trial interruptions, or of drug supplies not being distributed to commercial vendors in a timely manner, resulting in lost sales;

•operations of our third-party manufacturers or suppliers could be disrupted by conditions unrelated to our business or operations, including the bankruptcy of the manufacturer or supplier; and

•carrier disruptions or increased costs that are beyond our control.

We do not have complete control over all aspects of the manufacturing process of, and are dependent on, contract manufacturing partners for compliance with cGMP regulations for manufacturing both active drug substances and finished drug products. Third-party manufacturers may not be able to comply with GMP regulations or similar regulatory requirements outside the United States. The failure of third-party manufacturers, to comply with applicable regulations could result in sanctions being imposed on us, including fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, license revocations, seizures or recalls of product candidates or medicines, operating restrictions, and criminal prosecutions, any of which could significantly and adversely affect supplies of our medicines and harm our business, financial condition, results of operations, and prospects.

Assuming we were to resume the development of product candidates, any medicines that we may develop may compete with other product candidates and products for access to manufacturing facilities. There are a limited number of manufacturers that operate under GMP regulations and that might be capable of manufacturing for us. Any performance failure on the part of our existing or future manufacturers could delay clinical development or marketing approval.

Any future dependence upon others for the manufacture of any product candidates we may develop or medicines may adversely affect our future profit margins and our ability to commercialize any medicines that receive marketing approval on a timely and competitive basis.

Should we resume development of our product candidates, we would rely on third parties to conduct, supervise and monitor our clinical trials. If those third parties did not successfully carry out their contractual duties, or if they performed in an unsatisfactory manner, it may harm our business.

Should we resume development of our product candidates, we would rely on CROs and clinical trial sites to ensure the proper and timely conduct of our clinical trials, and we expect to have limited influence over their actual performance. We would rely upon CROs to monitor and manage data for our clinical programs, as well as the execution of future nonclinical studies. Our reliance on CROs for clinical development activities limits our control over these activities, but we would remain responsible for ensuring that each of our studies was conducted in accordance with the applicable protocol, legal, regulatory and scientific standards and our reliance on the CROs would not relieve us of our regulatory responsibilities.

We and our CROs will be required to comply with GLP and GCP, which are regulations and guidelines enforced by the FDA and are also required by the competent authorities in the EU and comparable foreign regulatory authorities in the form of International Conference on Harmonization guidelines for any of our product candidates that are in preclinical and clinical development. The Regulatory authorities enforce GCP through periodic inspections of trial sponsors, principal investigators and clinical trial sites. If we or our CROs fail to comply with GCP, the clinical data generated in our clinical trials may be deemed unreliable and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot assure you that upon inspection by a given regulatory authority, such regulatory authority will determine that any of our clinical trials comply with GCP requirements. In addition, our clinical trials must be conducted with product produced under GMP regulations. Accordingly, if our CROs fail to comply with these regulations or fail to recruit a sufficient number of subjects, we may be required to repeat clinical trials, which would delay the regulatory approval process.

Our CROs will not be our employees, and we will not control whether or not they devote sufficient time and resources to our future clinical and nonclinical programs. These CROs may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials, or other product development activities which could harm our competitive position. We face the risk of potential unauthorized disclosure or misappropriation of our intellectual property by CROs,

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which may reduce our trade secret protection and allow our potential competitors to access and exploit our proprietary technology. If our CROs do not successfully carry out their contractual duties or obligations or fail to meet expected deadlines, or if the quality or accuracy of the clinical data they obtain is compromised due to the failure to adhere to our clinical protocols or regulatory requirements or for any other reasons, our clinical trials may be extended, delayed or terminated, and we may not be able to obtain regulatory approval for, or successfully commercialize any product candidate that we develop. As a result, our financial results and the commercial prospects for any product candidate that we develop would be harmed, our costs could increase, and our ability to generate revenues could be delayed.

If our relationship with any CROs terminate, we may not be able to enter into arrangements with alternative CROs or do so on commercially reasonable terms. Switching or adding additional CROs involves substantial cost and requires management time and focus. In addition, there is a natural transition period when a new CRO commences work. As a result, delays occur, which can materially impact our ability to meet our desired clinical development timelines. Though we intend to carefully manage our relationships with our CROs, there can be no assurance that we will not encounter challenges or delays in the future or that these delays or challenges will not have an adverse impact on our business, financial condition and prospects.

We may collaborate with third parties for the development and commercialization of our product candidates in the future, but there are no assurances that we will succeed in establishing and maintaining such collaborative relationships, which may significantly limit our ability to develop and commercialize our product candidates successfully, if at all.

We may seek collaborative relationships for the development and commercialization of our product candidates in the future should we resume such activities. Failure to obtain a collaborative relationship for any of our product candidates may significantly impair the potential for the product candidate. We would also need to enter into collaborative relationships to provide funding to support our other research and development programs. The process of establishing and maintaining collaborative relationships is difficult, time-consuming and involves significant uncertainty, such as:

•a collaboration partner may shift its priorities and resources away from our product candidates due to a change in business strategies, or a merger, acquisition, sale or downsizing;

•a collaboration partner may seek to renegotiate or terminate their relationships with us due to unsatisfactory clinical results, manufacturing issues, a change in business strategy, a change of control or other reasons;

•a collaboration partner may cease development in therapeutic areas which are the subject of our strategic collaboration;

•a collaboration partner may not devote sufficient capital or resources towards our product candidates;

•a collaboration partner may change the success criteria for a product candidate thereby delaying or ceasing development of such candidate;

•a significant delay in initiation of certain development activities by a collaboration partner will also delay payment of milestones tied to such activities, thereby impacting our ability to fund our own activities;

•a collaboration partner could develop a product that competes, either directly or indirectly, with our product candidate;

•a collaboration partner with commercialization obligations may not commit sufficient financial or human resources to the marketing, distribution or sale of a product;

•a collaboration partner with manufacturing responsibilities may encounter regulatory, resource or quality issues and be unable to meet demand requirements;

•a collaboration partner may terminate a strategic alliance;

•a dispute may arise between us and a partner concerning the research, development or commercialization of a product candidate resulting in a delay in milestones, royalty payments or termination of an alliance and possibly resulting in costly litigation or arbitration which may divert management attention and resources; and

•a partner may use our products or technology in such a way as to invite litigation from a third party.

If any collaborator fails to fulfill its responsibilities in a timely manner, or at all, our research, clinical development, manufacturing or commercialization efforts related to that collaboration could be delayed or terminated, or it may be necessary for us to assume responsibility for expenses or activities that would otherwise have been the responsibility of our collaborator. If we are unable to establish and maintain collaborative relationships on acceptable terms or to successfully transition terminated collaborative agreements, we may have to delay or discontinue further development of one or more of our product candidates, undertake development and commercialization activities at our own expense or find alternative sources of capital. Moreover, any collaborative

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partners we enter into agreements with in the future may shift their priorities and resources away from our product candidates or seek to renegotiate or terminate their relationships with us.

If we fail to comply with our obligations in the agreements under which we in-license or acquire development or commercialization rights to products, technology or data from third parties, we could lose such rights that are important to our business.

We are a party to agreements with COH for certain AAV vector-related patents and know-how and we may enter into additional agreements, including license agreements, with other parties in the future that impose diligence, development and commercialization timelines, milestone payments, royalties, insurance and other obligations on us. If we fail to comply with our obligations under the COH license, or any of our other collaborators, our counterparties may have the right to terminate these agreements, in which event we might not be able to develop, manufacture or market any product candidate that is covered by these agreements, which could materially adversely affect the value of the product candidate being developed under any such agreement. Termination of these agreements or reduction or elimination of our rights under these agreements may result in our having to negotiate new or reinstated agreements with less favorable terms, or cause us to lose our rights under these agreements, including our rights to important intellectual property or technology.

Risks Related to Our Intellectual Property

If we are unable to obtain and maintain patent protection for our technology and products or if the scope of the patent protection obtained is not sufficiently broad, we may not be able to compete effectively in our markets.

We rely upon a combination of patents, trade secret protection and confidentiality agreements to protect the intellectual property related to our proprietary technologies, product candidate development programs and product candidates. Our success depends in large part on our ability to secure and maintain patent protection in the United States and other countries with respect to all current and future product candidates. We seek to protect our proprietary position by filing or collaborating with our licensors to file patent applications in the United States and abroad related to our proprietary technologies, development programs and product candidates. The patent prosecution process is expensive and time-consuming, and we may not be able to file and prosecute all necessary or desirable patent applications at a reasonable cost or in a timely manner.

It is also possible that we will fail to identify patentable aspects of our research and development output before it is too late to obtain patent protection. The patent applications that we own or in-license may fail to result in issued patents with claims that cover our proprietary products and technology, including our product candidates in the United States or in other foreign countries, in whole or in part. Alternately, our existing patents and any future patents we obtain may not be sufficiently broad to prevent others from using our technology or from developing competing products and technologies. There is no assurance that all potentially relevant prior art relating to our patents and patent applications has been found, which can prevent a patent from issuing from a pending patent application or later invalidate or narrow the scope of an issued patent. Even if patents do successfully issue and even if such patents cover our current product candidates or any future product candidate, third parties may challenge their validity, enforceability or scope thereof, which may result in such patents being narrowed, invalidated, or held unenforceable. Any successful challenge to these patents or any other patents owned by or licensed to us could deprive us of rights necessary for the successful commercialization of any product candidates or companion diagnostic that we may develop. Further, if we encounter delays in regulatory approvals, the period of time during which we could market a product candidate and companion diagnostic under patent protection could be reduced.

If the patent applications we hold or have in-licensed with respect to our development programs and product candidates fail to issue, if their validity, breadth or strength of protection is threatened, or if they fail to provide meaningful exclusivity for our current product candidates or any future product candidate, it could dissuade companies from collaborating with us to develop product candidates, encourage competitors to develop competing products or technologies and threaten our ability to commercialize future product candidates. Any such outcome could have a materially adverse effect on our business.

The patent position of biotechnology and pharmaceutical companies is highly uncertain, involves complex legal and factual questions, and is characterized by the existence of large numbers of patents and frequent litigation based on allegations of patent or other intellectual property infringement or violation. In addition, the laws of jurisdictions outside the United States may not protect our rights to the same extent as the laws of the United States. For example, European patent law restricts the patentability of methods of treatment of the human body more than United States law does. Changes in either the patent laws or interpretation of the patent laws in the United States and other countries may diminish the value of our patents or narrow the scope of our patent protection. Since patent applications in the United States and other jurisdictions are confidential for a period of time after filing, we cannot be certain that we were the first to file for patents covering our inventions. As a result, the issuance, scope, validity, enforceability and commercial value of our patent rights are highly uncertain. Our pending and future patent applications may not result in the issuance

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of patents, or may result in the issuance of patents which fail to protect our technology or products, in whole or in part, or which fail to effectively prevent others from commercializing competitive technologies and products.

The issuance of a patent is not conclusive as to its inventorship, scope, validity or enforceability, and our owned and licensed patents may be challenged in the courts or patent offices in the United States and abroad. Such challenges may result in loss of exclusivity or freedom to operate or in patent claims being narrowed, invalidated or held unenforceable, in whole or in part, which could limit our ability to stop others from using or commercializing similar or identical technology and products, or limit the duration of the patent protection of our technology and products. Thus, even if our patent applications issue as patents, they may not issue in a form that will provide us with meaningful protection, prevent competitors from competing with us or otherwise provide us with any competitive advantage. Moreover, patents have a limited lifespan. In the United States, the natural expiration of a patent is generally 20 years after it is filed. Various extensions may be available; however, the life of a patent, and the protection it affords, is limited. Without patent protection for our current or future product candidates, we may be open to competition from generic versions of such products. Given the amount of time required for the development, testing and regulatory review of new product candidates, patents protecting such candidates might expire before or shortly after such candidates are commercialized. As a result, our owned and licensed patent portfolio may not provide us with sufficient rights to exclude others from commercializing products similar or identical to ours.

Third parties may assert claims against us alleging infringement of their patents and proprietary rights, or we may need to become involved in lawsuits to defend or enforce our patents, either of which could result in substantial costs or loss of productivity, delay or prevent the development and commercialization of our product candidates, prohibit our use of proprietary technology or sale of products or put our patents and other proprietary rights at risk.

Our commercial success depends, in part, upon our ability to develop, manufacture, market and sell our product candidates without alleged or actual infringement, misappropriation or other violation of the patents and proprietary rights of third parties. Litigation relating to infringement or misappropriation of patent and other intellectual property rights in the pharmaceutical and biotechnology industries is common, including patent infringement lawsuits, interferences, oppositions and reexamination proceedings before the U.S. Patent and Trademark Office, or USPTO, and corresponding foreign patent offices. The various markets in which we plan to operate are subject to frequent and extensive litigation regarding patents and other intellectual property rights. In addition, many companies in intellectual property-dependent industries, including the biotechnology and pharmaceutical industries, have employed intellectual property litigation as a means to gain an advantage over their competitors. Numerous United States, EU and foreign issued patents and pending patent applications, which are owned by third parties, exist in the fields in which we are developing product candidates, and as the biotechnology and pharmaceutical industries expand and more patents are issued, the risk increases that our product candidates may be subject to claims of infringement of the intellectual property rights of third parties. Some claimants may have substantially greater resources than we do and may be able to sustain the costs of complex intellectual property litigation to a greater degree and for longer periods of time than we could. In addition, patent holding companies that focus solely on extracting royalties and settlements by enforcing patent rights may target us.

We may be subject to third-party claims including infringement, interference or derivation proceedings, post-grant review and inter partes review before the USPTO or similar adversarial proceedings or litigation in other jurisdictions. Even if such claims are without merit, a court of competent jurisdiction could hold that these third-party patents are valid, enforceable and infringed, and the holders of any such patents may be able to block our ability to commercialize the applicable product candidate unless we obtained a license under the applicable patents, or until such patents expire or are finally determined to be invalid or unenforceable. Similarly, if any third-party patents were held by a court of competent jurisdiction to cover aspects of our compositions, formulations, or methods of treatment, prevention or use, the holders of any such patents may be able to prohibit our use of those compositions, formulations, methods of treatment, prevention or use or other technologies, effectively blocking our ability to develop and commercialize the applicable product candidate until such patent expires or is finally determined to be invalid or unenforceable or unless we obtained a license.

In addition, defending such claims would cause us to incur substantial expenses and, if successful, could cause us to pay substantial damages if we are found to be infringing a third party’s patent rights. These damages potentially include increased damages and attorneys’ fees if we are found to have infringed such rights willfully. Further, if a patent infringement suit is brought against us or our third-party service providers, our development, manufacturing or sales activities relating to the product or product candidate that is the subject of the suit may be delayed or terminated. As a result of patent infringement claims, or in order to avoid potential infringement claims, we may choose to seek, or be required to seek, a license from the third party, which may require payment of substantial royalties or fees, or require us to grant a cross-license under our intellectual property rights. These licenses may not be available on reasonable terms or at all. Even if a license can be obtained on reasonable terms, the rights may be nonexclusive, which would give our competitors access to the same intellectual property rights. If we are unable to enter into a license on acceptable terms, we could be prevented from commercializing one or more of our product candidates, or forced to modify such product

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candidates, or to cease some aspect of our business operations, which could harm our business significantly. We might also be forced to redesign or modify our product candidates so that we no longer infringe the third-party intellectual property rights, which may result in significant cost or delay to us, or which redesign or modification could be impossible or technically infeasible. Even if we were ultimately to prevail, any of these events could require us to divert substantial financial and management resources that we would otherwise be able to devote to our business. In addition, if the breadth or strength of protection provided the patents and patent applications we own or in-license is threatened, it could dissuade companies from collaborating with us to license, develop or commercialize current or future product candidates.

If we or one of our licensors were to initiate legal proceedings against a third party to enforce a patent covering one of our product candidates, the defendant could counterclaim that our patent is invalid or unenforceable. In patent litigation in the United States and in Europe, defendant counterclaims alleging invalidity or unenforceability are commonplace. Grounds for a validity challenge could be an alleged failure to meet any of several statutory requirements, for example, lack of novelty, obviousness or non-enablement. Third parties might allege unenforceability of our patents because during prosecution of the patent an individual connected with such prosecution withheld relevant information, or made a misleading statement. The outcome of proceedings involving assertions of invalidity and unenforceability during patent litigation is unpredictable. With respect to the validity of patents, for example, we cannot be certain that there is no invalidating prior art of which we and the patent examiner were unaware during prosecution, but that an adverse third party may identify and submit in support of such assertions of invalidity. If a defendant were to prevail on a legal assertion of invalidity or unenforceability, we would lose at least part, and perhaps all, of the patent protection on our product candidates. Our patents and other intellectual property rights also will not protect our technology if competitors design around our protected technology without infringing our patents or other intellectual property rights.

Even if resolved in our favor, litigation or other legal proceedings relating to intellectual property claims may cause us to incur significant expenses and could distract our technical and management personnel from their normal responsibilities. In addition, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during this type of litigation. There could also be public announcements of the results of hearings, motions or other interim proceedings or developments, and if securities analysts or investors view these announcements in a negative light, the price of our common stock could be adversely affected. Such litigation or proceedings could substantially increase our operating losses and reduce our resources available for development activities. We may not have sufficient financial or other resources to adequately conduct such litigation or proceedings. Some of our competitors may be able to sustain the costs of such litigation or proceedings more effectively than we can because of their substantially greater financial resources. Uncertainties resulting from the initiation and continuation of patent litigation or other proceedings could have an adverse effect on our ability to compete in the marketplace.

We may not identify relevant third-party patents or may incorrectly interpret the relevance, scope or expiration of a third-party patent which might adversely affect our ability to develop, manufacture and market our product candidates.

We cannot guarantee that any of our or our licensors’ patent searches or analyses, including but not limited to the identification of relevant patents, analysis of the scope of relevant patent claims or determination of the expiration of relevant patents, are complete or thorough, nor can we be certain that we have identified each and every third-party patent and pending application in the United States, Europe and elsewhere that is relevant to or necessary for the commercialization of our product candidates in any jurisdiction. For example, in the United States, applications filed before November 29, 2000 and certain applications filed after that date that will not be filed outside the United States remain confidential until patents issue. Patent applications in the United States, EU and elsewhere are published approximately 18 months after the earliest filing for which priority is claimed, with such earliest filing date being commonly referred to as the priority date. Therefore, patent applications covering our product candidates could be filed by others without our knowledge. Additionally, pending patent applications that have been published can, subject to certain limitations, be later amended in a manner that could cover our product candidates or the use of our product candidates. After issuance, the scope of patent claims remains subject to construction as determined by an interpretation of the law, the written disclosure in a patent and the patent’s prosecution history. Our interpretation of the relevance or the scope of a patent or a pending application may be incorrect, which may negatively impact our ability to market our product candidates. We may incorrectly determine that our product candidates are not covered by a third-party patent or may incorrectly predict whether a third party’s pending application will issue with claims of relevant scope. Our determination of the expiration date of any patent in the United States, the EU or elsewhere that we consider relevant may be incorrect, which may negatively impact our ability to develop and market our product candidates. Our failure to identify and correctly interpret relevant patents may negatively impact our ability to develop and market our product candidates.

If we fail to correctly identify or interpret relevant patents, we may be subject to infringement claims. We cannot guarantee that we will be able to successfully settle or otherwise resolve such infringement claims. If we fail in any such dispute, in addition to being forced to pay monetary damages, we may be temporarily or permanently prohibited from commercializing our product candidates. We might, if possible, also be forced to redesign our product candidates in a manner that no longer infringes third-party intellectual

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property rights. Any of these events, even if we were ultimately to prevail, could require us to divert substantial financial and management resources that we would otherwise be able to devote to our business.

Changes in patent laws or patent jurisprudence could diminish the value of patents in general, thereby impairing our ability to protect our product candidates.

As is the case with other biotechnology companies, our success is heavily dependent on intellectual property, particularly patents. Obtaining and enforcing patents in the biotechnology and genetic medicines industries involve both technological complexity and legal complexity. Therefore, obtaining and enforcing biotechnology and genetic medicines patents is costly, time-consuming and inherently uncertain. In addition, the America Invents Act, or the AIA, which was passed in September 2011, resulted in significant changes to the U.S. patent system.

An important change introduced by the AIA is that, as of March 16, 2013, the United States transitioned from a “first-to-invent” to a “first-to-file” system for deciding which party should be granted a patent when two or more patent applications are filed by different parties claiming the same invention. Under a “first-to-file” system, assuming the other requirements for patentability are met, the first inventor to file a patent application generally will be entitled to a patent on the invention regardless of whether another inventor had made the invention earlier. A third party that files a patent application in the USPTO after that date but before us could therefore be awarded a patent covering an invention of ours even if we made the invention before it was made by the third party. This will require us to be cognizant going forward of the time from invention to filing of a patent application and diligent in filing patent applications, but circumstances could prevent us from promptly filing patent applications on our inventions.

Among some of the other changes introduced by the AIA are changes that limit where a patentee may file a patent infringement suit and providing opportunities for third parties to challenge any issued patent in the USPTO. This applies to all of our U.S. patents, even those issued before March 16, 2013. Because of a lower evidentiary standard in USPTO proceedings as compared to the evidentiary standard in U.S. federal courts necessary to invalidate a patent claim, a third party could potentially provide evidence in a USPTO proceeding sufficient for the USPTO to hold a claim invalid even though the same evidence would be insufficient to invalidate the claim if first presented in a district court action.

Accordingly, a third party may attempt to use the USPTO procedures to invalidate our patent claims that would not have been invalidated if first challenged by the third party as a defendant in a district court action. It is not clear what, if any, impact the AIA will have on the operation of our business. However, the AIA and its implementation could increase the uncertainties and costs surrounding the prosecution of our or our licensors’ patent applications and the enforcement or defense of our or our licensors’ issued patents.

We may become involved in opposition, interference, derivation, inter partes review or other proceedings challenging our or our licensors’ patent rights, and the outcome of any proceedings are highly uncertain. An adverse determination in any such proceeding could reduce the scope of, or invalidate, our owned or in-licensed patent rights, allow third parties to commercialize our technology or products and compete directly with us, without payment to us, or result in our inability to manufacture or commercialize products without infringing third-party patent rights.

Additionally, the U.S. Supreme Court has ruled on several patent cases in recent years either narrowing the scope of patent protection available in certain circumstances or weakening the rights of patent owners in certain situations, and there are other open questions under patent law that courts have yet to decisively address. In addition to increasing uncertainty with regard to our ability to obtain patents in the future, this combination of events has created uncertainty with respect to the value of patents, once obtained. Depending on decisions by Congress, the federal courts and the USPTO, the laws and regulations governing patents could change in unpredictable ways and could weaken our ability to obtain new patents or to enforce our existing patents and patents that we might obtain in the future. In addition, the European patent system is relatively stringent in the type of amendments that are allowed during prosecution, but, the complexity and uncertainty of European patent laws has also increased in recent years. Complying with these laws and regulations could limit our ability to obtain new patents in the future that may be important for our business.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment and other requirements imposed by governmental patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

The USPTO and European and other patent agencies require compliance with a number of procedural, documentary, fee payment and other similar provisions during the patent application process. In addition, periodic maintenance and annuity fees on any issued patent are due to be paid to the USPTO and European and other patent agencies over the lifetime of a patent. While an inadvertent failure to make payment of such fees or to comply with such provisions can in many cases be cured by additional payment

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of a late fee or by other means in accordance with the applicable rules, there are situations in which non-compliance with such provisions will result in the abandonment or lapse of the patent or patent application, and the partial or complete loss of patent rights in the relevant jurisdiction. Non-compliance events that could result in abandonment or lapse of a patent or patent application include failure to respond to official actions within prescribed time limits, non-payment of fees and failure to properly legalize and submit formal documents within prescribed time limits. If we or our licensors fail to maintain the patents and patent applications covering our product candidates or if we or our licensors otherwise allow our patents or patent applications to be abandoned or lapse, it can create opportunities for competitors to enter the market, which would hurt our competitive position and could impair our ability to successfully commercialize our product candidates in any indication for which they are approved.

We enjoy only limited geographical protection with respect to certain patents and we may not be able to protect our intellectual property rights throughout the world.

Filing, prosecuting and defending patents covering our product candidates in all countries throughout the world would be prohibitively expensive, and our intellectual property rights in some countries outside the United States can be less extensive than those in the United States. In-licensing patents covering our product candidates in all countries throughout the world may similarly be prohibitively expensive, if such opportunities are available at all. And in-licensing or filing, prosecuting and defending patents even in only those jurisdictions in which we develop or commercialize our product candidates may be prohibitively expensive or impractical. Competitors may use our and our licensors’ technologies in jurisdictions where we have not obtained patent protection or licensed patents to develop their own products and, further, may export otherwise infringing products to territories where we and our licensors have patent protection, but enforcement is not as strong as that in the United States or the EU. These products may compete with our product candidates, and our or our licensors’ patents or other intellectual property rights may not be effective or sufficient to prevent them from competing.

In addition, we intend to abandon certain national and regional patent applications while they are still pending. The grant proceeding of each national or regional patent is an independent proceeding which may lead to situations in which applications may be rejected by the relevant patent office, while substantively similar applications are granted by others. For example, relative to other countries, China has a heightened requirement for patentability and specifically requires a detailed description of medical uses of a claimed drug. Furthermore, generic drug manufacturers or other competitors may challenge the scope, validity or enforceability of our or our licensors’ patents, requiring us or our licensors to engage in complex, lengthy and costly litigation or other proceedings. Generic drug manufacturers may develop, seek approval for and launch generic versions of our products. It is also quite common that depending on the country, the scope of patent protection may vary for the same product candidate or technology.

The laws of some jurisdictions do not protect intellectual property rights to the same extent as the laws or regulations in the United States and the EU, and many companies have encountered significant difficulties in protecting and defending proprietary rights in such jurisdictions. Moreover, the legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents, trade secrets or other forms of intellectual property, which could make it difficult for us to prevent competitors in some jurisdictions from marketing competing products in violation of our proprietary rights generally. Proceedings to enforce our patent rights in foreign jurisdictions, whether or not successful, are likely to result in substantial costs and divert our efforts and attention from other aspects of our business, and additionally could put at risk our or our licensors’ patents of being invalidated or interpreted narrowly, could increase the risk of our or our licensors’ patent applications not issuing, or could provoke third parties to assert claims against us. We may not prevail in any lawsuits that we initiate, while damages or other remedies may be awarded to the adverse party, which may be commercially significant. If we prevail, damages or other remedies awarded to us, if any, may not be commercially meaningful. Accordingly, our efforts to enforce our intellectual property rights around the world may be inadequate to obtain a significant commercial advantage from the intellectual property that we develop or license. Furthermore, while we intend to protect our intellectual property rights in our expected significant markets, we cannot ensure that we will be able to initiate or maintain similar efforts in all jurisdictions in which we may wish to market our product candidates. Accordingly, our efforts to protect our intellectual property rights in such countries may be inadequate, which may have an adverse effect on our ability to successfully commercialize our product candidates in all of our expected significant foreign markets. If we or our licensors encounter difficulties in protecting, or are otherwise precluded from effectively protecting, the intellectual property rights important for our business in such jurisdictions, the value of these rights may be diminished and we may face additional competition in those jurisdictions.

In some jurisdictions, compulsory licensing laws compel patent owners to grant licenses to third parties. In addition, some countries limit the enforceability of patents against government agencies or government contractors. In these countries, the patent owner may have limited remedies, which could materially diminish the value of such patent. If we or any of our licensors are forced to grant a license to third parties under patents relevant to our business, or if we or our licensors are prevented from enforcing patent rights against third parties, our competitive position may be substantially impaired in such jurisdictions.

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If we do not obtain patent term extension in the United States under the Hatch-Waxman Act and in foreign countries under similar legislation, thereby potentially extending the term of marketing exclusivity for our product candidates, our business may be materially harmed.

The term of any individual patent depends on applicable law in the country where the patent is granted. In the United States, provided all maintenance fees are timely paid, a patent generally has a term of 20 years from its application filing date or earliest claimed non-provisional filing date. Extensions may be available under certain circumstances, but the life of a patent and, correspondingly, the protection it affords is limited. Even if we or our licensors obtain patents covering our product candidates, when the terms of all patents covering a product expire, our business may become subject to competition from competitive medications, including generic medications. Given the amount of time required for the development, testing and regulatory review and approval of new product candidates, patents protecting such candidates may expire before or shortly after such candidates are commercialized. As a result, our owned and licensed patent portfolio may not provide us with sufficient rights to exclude others from commercializing products similar or identical to ours.

In the United States, a patent that covers an FDA-approved drug or biologic may be eligible for a term extension designed to restore the period of the patent term that is lost during the premarket regulatory review process conducted by the FDA. Depending upon the timing, duration and conditions of FDA marketing approval of our product candidates, one or more of our U.S. patents may be eligible for limited patent term extension under the Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Act, which permits a patent term extension of up to five years for a patent covering an approved product as compensation for effective patent term lost during product development and the FDA regulatory review process. In the EU, our product candidates may be eligible for term extensions based on similar legislation. In either jurisdiction, however, we may not receive an extension if we fail to apply within applicable deadlines, fail to apply prior to expiration of relevant patents or otherwise fail to satisfy applicable requirements. Even if we are granted such extension, the duration of such extension may be less than our request. If we are unable to obtain a patent term extension, or if the term of any such extension is less than our request, the period during which we can enforce our patent rights for that product will be in effect shortened and our competitors may obtain approval to market competing products sooner. The resulting reduction of years of revenue from applicable products could be substantial.

Our proprietary rights may not adequately protect our technologies and product candidates, and do not necessarily address all potential threats to our competitive advantage.

The degree of future protection afforded by our intellectual property rights is uncertain because intellectual property rights have limitations, and may not adequately protect our business, or permit us to maintain our competitive advantage. The following examples are illustrative:

•others may be able to make products that are the same as or similar to our product candidates but that are not covered by the claims of the patents that we own or have exclusively licensed;

•others, including inventors or developers of our owned or in-licensed patented technologies who may become involved with competitors, may independently develop similar technologies that function as alternatives or replacements for any of our technologies without infringing our intellectual property rights;

•we or our licensors or our other collaboration partners might not have been the first to conceive and reduce to practice the inventions covered by the patents or patent applications that we own, license or will own or license;

•we or our licensors or our other collaboration partners might not have been the first to file patent applications covering certain of the patents or patent applications that we or they own or have obtained a license, or will own or will have obtained a license;

•we or our licensors may fail to meet obligations to the U.S. government with respect to in-licensed patents and patent applications funded by U.S. government grants, leading to the loss of patent rights;

•it is possible that our pending patent applications will not result in issued patents;

•it is possible that there are prior public disclosures that could invalidate our or our licensors’ patents;

•issued patents that we own or exclusively license may not provide us with any competitive advantage, or may be held invalid or unenforceable, as a result of legal challenges by our competitors;

•our competitors might conduct research and development activities in countries where we do not have patent rights, or in countries where research and development safe harbor laws exist, and then use the information learned from such activities to develop competitive products for sale in our major commercial markets;

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•ownership, validity or enforceability of our or our licensors’ patents or patent applications may be challenged by third parties; and

•the patents of third parties or pending or future applications of third parties, if issued, may have an adverse effect on our business.

We depend on proprietary technology licensed from others. If we lose our existing licenses or are unable to acquire or license additional proprietary rights from third parties, we may not be able to continue developing our products.

We currently in-license certain intellectual property from COH. In the future we may in-license intellectual property from other licensors. We rely on certain of these licensors to file and prosecute patent applications and maintain patents and otherwise protect the intellectual property we license from them. We have limited control over these activities or any other intellectual property that may be related to our in-licensed intellectual property. For example, we cannot be certain that such activities by these licensors have been or will be conducted in compliance with applicable laws and regulations or will result in valid and enforceable patents and other intellectual property rights. We have limited control over the manner in which our licensors initiate an infringement proceeding against a third-party infringer of the intellectual property rights, or defend certain of the intellectual property that is licensed to us. It is possible that the licensors’ infringement proceeding or defense activities may be less vigorous than had we conducted them ourselves. The licensing and acquisition of third-party intellectual property rights is a competitive practice, and companies that may be more established, or have greater resources than we do, may also be pursuing strategies to license or acquire third-party intellectual property rights that we may consider necessary or attractive in order to commercialize our product candidates. More established companies may have a competitive advantage over us due to their larger size and cash resources or greater clinical development and commercialization capabilities. There can be no assurance that we will be able to successfully complete such negotiations and ultimately acquire the rights to the intellectual property surrounding the additional product candidates that we may seek to acquire.

If we fail to comply with our obligations under our patent licenses with third parties, we could lose license rights that are important to our business.

We are a party to a license agreement with COH, pursuant to which we in-license patents and technology for our product candidates. This existing license imposes various diligence, milestone payment, royalty, insurance and other obligations on us. If we fail to comply with these obligations or otherwise materially breach a license agreement, our licensors may have the right to terminate the license, in which event we would not be able to develop or market the products covered by such licensed intellectual property. In addition, any claims asserted against us by our licensors may be costly and time-consuming, divert the attention of key personnel from business operations or otherwise have a material adverse effect on our business.

Our reliance on third parties may require us to share our trade secrets, which increases the possibility that our trade secrets will be misappropriated or disclosed, and confidentiality agreements with employees and third parties may not adequately prevent disclosure of trade secrets and protect other proprietary information.

We consider proprietary trade secrets, confidential know-how and unpatented know-how to be important to our business. We may rely on trade secrets and confidential know-how to protect our technology, especially where patent protection is believed by us to be of limited value. However, trade secrets and confidential know-how are difficult to protect, and we have limited control over the protection of trade secrets and confidential know-how used by our licensors, collaborators and suppliers. Because we expect to rely on third parties to manufacture our current and future product candidates, and we expect to collaborate with third parties on the development of our current and future product candidates, we may, at times, share trade secrets with them. We also conduct joint research and development programs that may require us to share trade secrets under the terms of our research and development collaborations or similar agreements. Under such circumstances, trade secrets and confidential know-how can be difficult to maintain as confidential.

To protect this type of information against disclosure or appropriation by competitors, our policy is to require our employees, consultants, contractors and advisors to enter into confidentiality agreements and, if applicable, material transfer agreements, consulting agreements or other similar agreements with us prior to beginning research or disclosing proprietary information. These agreements typically limit the rights of the third parties to use or disclose our confidential information, including our trade secrets. However, current or former employees, consultants, contractors and advisers may unintentionally or willfully disclose our confidential information to competitors, and confidentiality agreements may not provide an adequate remedy in the event of unauthorized disclosure of confidential information. The need to share trade secrets and other confidential information increases the risk that such trade secrets become known by our competitors, are inadvertently incorporated into the technology of others, or are disclosed or used in violation of these agreements. Given that our competitive position is based, in part, on our know-how and trade secrets, a competitor’s discovery of our trade secrets or other unauthorized use or disclosure would impair our competitive position and may

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have an adverse effect on our business and results of operations. Enforcing a claim that a third party obtained illegally and is using trade secrets and/or confidential know-how is expensive, time consuming and unpredictable, and the enforceability of confidentiality agreements may vary from jurisdiction to jurisdiction.

In addition, these agreements typically restrict the ability of our advisors, employees, third-party contractors and consultants to publish data potentially relating to our trade secrets, although our agreements may contain certain limited publication rights. Despite our efforts to protect our trade secrets, our competitors may discover our trade secrets, either through breach of our agreements with third parties, independent development or publication of information by any of our third-party collaborators. A competitor’s discovery of our trade secrets would impair our competitive position and have an adverse impact on our business.

If our trademarks and trade names are not adequately protected, then we may not be able to build name recognition in our markets of interest and our business may be adversely affected.

If our trademarks and trade names are not adequately protected, then we may not be able to build name recognition in our markets of interest and our business may be adversely affected. As of September 30, 2023, we own four registered trademarks and one pending trademark applications in the United States, as well as 39 registered trademarks and five pending trademark applications in other countries around the world. We may not be able to protect our rights to these trademarks and trade names, which we need to build name recognition among potential partners or customers in our markets of interest. At times, competitors may adopt trade names or trademarks similar to ours, thereby impeding our ability to build brand identity and possibly leading to market confusion. In addition, there could be potential trade name or trademark infringement claims brought by owners of other registered trademarks or trademarks that incorporate variations of our unregistered trademarks or trade names. Over the long term, if we are unable to successfully register our trademarks and trade names and establish name recognition based on our trademarks and trade names, then we may not be able to compete effectively and our business may be adversely affected. Our efforts to enforce or protect our proprietary rights related to trademarks, trade secrets, domain names, copyrights or other intellectual property may be ineffective and could result in substantial costs and diversion of resources and could adversely impact our financial condition or results of operations.

We may be subject to claims that our employees, consultants or independent contractors have wrongfully used or disclosed confidential information of their former employers or other third parties.

We employ individuals who were previously employed at other biotechnology or pharmaceutical companies. Although we seek to protect our ownership of intellectual property rights by ensuring that our agreements with our employees, collaborators and other third parties with whom we do business include provisions requiring such parties to assign rights in inventions to us, we may be subject to claims that we or our employees, consultants or independent contractors have inadvertently or otherwise used or disclosed confidential information of our employees’ former employers or other third parties. We may also be subject to claims that former employers or other third parties have an ownership interest in our patents. Litigation may be necessary to defend against these claims. There is no guarantee of success in defending these claims, and if we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights, such as exclusive ownership of, or right to use, valuable intellectual property. Even if we are successful, litigation could result in substantial cost and reputational loss and be a distraction to our management and other employees.

Risks Related to Employee Matters and Other Risks Related to Our Business

Our recent reduction in force undertaken to significantly reduce our ongoing operating expenses may not result in our intended outcomes and may yield unintended consequences and additional costs.

In July 2023, we implemented a reduction in force affecting approximately 80 employees, or 86% of our workforce, in order to reduce our ongoing operating costs, extend our cash runway and maximize shareholder value as we consider strategic options. In connection with this corporate restructuring, the Company recorded a restructuring charge for severance and related costs of $6.9 million in the Company's condensed consolidated statements of operations included elsewhere in this Quarterly Report on Form 10-Q during the three months ended September 30, 2023. In addition, the Company had previously granted certain of the terminated employees restricted stock units that vest in annual installments based on continued service to the Company, as well as options to purchase shares of the Company’s common stock that typically vest over a period of four years. In connection with the reduction in workforce, the Company agreed to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates, and also modify the stock options for terminated employees such that subject to the satisfaction of severance conditions, the terminated employees’ vested options will remain outstanding and exercisable until the first anniversary of each employee’s termination date. These equity modifications resulted in a net reduction to stock based compensation expense of $0.3 million reflected

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within restructuring and other charges in the Company's condensed consolidated statements of operations included elsewhere in this Quarterly Report on Form 10-Q during the three months ended September 30, 2023.

The reduction in force may result in unintended consequences and additional costs, such as the loss of institutional knowledge and expertise, attrition beyond the intended number of employees, decreased morale among our remaining employees, and the risk that we may not achieve the anticipated benefits of the reduction in force. In addition, while positions have been eliminated certain functions necessary to our operations remain, and we may be unsuccessful in distributing the duties and obligations of departed employees among our remaining employees. The reduction in workforce could also make it difficult for us to pursue, or prevent us from pursuing, new opportunities and initiatives due to insufficient personnel, or require us to incur additional and unanticipated costs to hire new personnel to pursue such opportunities or initiatives. If we are unable to realize the anticipated benefits from the reduction in force, or if we experience significant adverse consequences from the reduction in force, our business, financial condition, and results of operations may be materially adversely affected.

Our future success depends on our ability to retain our key personnel and to attract, retain and motivate qualified personnel.

Our industry has experienced a high rate of turnover of management personnel in recent years. We are highly dependent on the development, regulatory, commercialization and business development expertise of certain principal members of our management team. Although we have formal employment agreements with our executive officers, these agreements do not prevent them from terminating their employment with us at any time.

If we are unable to retain one or more of our executive officers or key employees, our ability to implement our business strategy successfully could be seriously harmed. Furthermore, replacing executive officers and key employees may be difficult and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to develop, gain regulatory approval of and commercialize product candidates successfully. Competition to hire from the limited pool of skilled workers discussed above is intense, and in the future we may be unable to hire, train, retain or motivate these additional key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. In the future we may also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be engaged by entities other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to attract and retain high quality personnel in the future, our ability to develop and commercialize product candidates may be limited.

We or the third parties upon whom we depend may be adversely affected by natural disasters, public health emergencies and other natural catastrophic events, and our business continuity and disaster recovery plans may not adequately protect us from a serious disaster.

Natural disasters could severely disrupt our operations and have a material adverse effect on our business, results of operations, financial condition and prospects. If a natural disaster, public health emergency, such as the COVID-19 pandemic, power outage or other event occurred that prevented us from using all or a significant portion of our headquarters, that damaged critical infrastructure, such as our manufacturing facilities, or that otherwise disrupted operations, it may be difficult or, in certain cases, impossible for us to continue our business for a substantial period of time. The disaster recovery and business continuity plans we have in place may prove inadequate in the event of a serious disaster or similar event. We may incur substantial expenses as a result of the limited nature of our disaster recovery and business continuity plans, which could have a material adverse effect on our business. For example, following Hurricane Maria, shortages in production and delays in a number of medical supplies produced in Puerto Rico resulted, and any similar interruption due to a natural disaster affecting us or any of our third-party manufacturers could materially delay our operations.

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COVID-19 has and could continue to adversely impact our business, including our preclinical studies and clinical trials to the extent we resume such activities.

Disruptions caused by COVID-19 previously resulted in delays in enrolling our Phase 1/2 pheNIX clinical trial. In addition, many clinical sites are under-resourced as a result of COVID-19 and other factors, impacting the sites’ ability to advance clinical trials in a timely manner. Should we resume development of our product candidates, we could experience disruptions in conducting or completing our other ongoing and planned preclinical and clinical trials and could incur unforeseen costs as a result of preclinical study or clinical trial delays. It is possible that COVID-19 may have an impact in the future on our CROs’ ability to complete critical studies required for the progression of these programs. Moreover, it is possible that COVID-19 and response efforts may have an impact in the future on our third-party suppliers and CMOs’ ability to manufacture our product candidates or materials needed for our preclinical studies and clinical trials.

Moreover, COVID-19 has resulted in, and may continue to result in, significant disruption of global financial markets, which could reduce our ability to access capital and negatively affect our liquidity. In addition, the recession or market correction resulting from the spread of COVID-19 could materially affect our business.

Risks Related to Our Common Stock

Our executive officers and directors and their respective affiliates, if they choose to act together, will continue to have the ability to control or significantly influence all matters submitted to stockholders for approval.

Our executive officers and directors and their respective affiliates, in the aggregate, hold shares representing approximately 11% of our outstanding voting stock as of September 30, 2023. As a result, if these stockholders choose to act together, they would be able to control or significantly influence all matters submitted to our stockholders for approval, as well as our management and affairs. For example, these persons, if they choose to act together, could control or significantly influence the election of directors, the composition of our management and approval of any merger, consolidation or sale of all or substantially all of our assets.

A significant portion of our total outstanding shares are eligible, or will soon become eligible, to be sold into the market, which could cause the market price of our common stock to drop significantly, even if our business is doing well.

Sales of a substantial number of shares of our common stock in the public market, or the perception in the market that the holders of a large number of shares intend to sell shares, could reduce the market price of our common stock. We have registered all shares of common stock that we may issue under our equity compensation plans, which can be freely sold in the public market upon issuance, subject to volume limitations applicable to affiliates.

We are an “emerging growth company,” and the reduced disclosure requirements applicable to emerging growth companies may make our common stock less attractive to investors.

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act, and may remain an emerging growth company until the last day of the fiscal year following the fifth anniversary of the closing of the initial public offering of our common stock. However, if certain events occur prior to the end of such five-year period, including if we become a “large accelerated filer,” our annual gross revenues exceed $1.235 billion or we issue more than $1.0 billion of non-convertible debt in any three-year period, we will cease to be an emerging growth company prior to the end of such five-year period. For so long as we remain an emerging growth company, we are permitted and intend to rely on exemptions from certain disclosure requirements that are applicable to other public companies that are not emerging growth companies. These exemptions include:

•not being required to comply with the auditor attestation requirements in the assessment of our internal control over financial reporting;

•not being required to comply with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit firm rotation or a supplement to the auditor’s report providing additional information about the audit and the financial statements;

•reduced disclosure obligations regarding executive compensation; and

•exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and stockholder approval of any golden parachute payments not previously approved.

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We cannot predict whether investors will find our common stock less attractive if we rely on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be reduced or more volatile. In addition, the JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. This allows an emerging growth company to delay the adoption of these accounting standards until they would otherwise apply to private companies. We have elected to take advantage of this extended transition period.

Provisions in our restated certificate of incorporation and amended and restated bylaws and under Delaware law could make an acquisition of our Company, which may be beneficial to our stockholders, more difficult and may prevent attempts by our stockholders to replace or remove our current management.

Provisions in our restated certificate of incorporation and our amended and restated bylaws may discourage, delay or prevent a merger, acquisition or other change in control of our Company that stockholders may consider favorable, including transactions in which you might otherwise receive a premium for your shares. These provisions could also limit the price that investors might be willing to pay in the future for shares of our common stock, thereby depressing the market price of our common stock. In addition, because our board of directors is responsible for appointing the members of our management team, these provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our board of directors. Among other things, these provisions include those establishing:

•a classified board of directors with three-year staggered terms, which may delay the ability of stockholders to change the membership of a majority of our board of directors;

•no cumulative voting in the election of directors, which limits the ability of minority stockholders to elect director candidates;

•the exclusive right of our board of directors to elect a director to fill a vacancy created by the expansion of the board of directors or the resignation, death or removal of a director, which prevents stockholders from filling vacancies on our board of directors;

•the ability of our board of directors to authorize the issuance of shares of preferred stock and to determine the terms of those shares, including preferences and voting rights, without stockholder approval, which could be used to significantly dilute the ownership of a hostile acquirer;

•the ability of our board of directors to alter our bylaws without obtaining stockholder approval;

•the required approval of the holders of at least two-thirds of the shares entitled to vote at an election of directors to adopt, amend or repeal our bylaws or repeal the provisions of our restated certificate of incorporation regarding the election and removal of directors;

•a prohibition on stockholder action by written consent, which forces stockholder action to be taken at an annual or special meeting of our stockholders;

•the requirement that a special meeting of stockholders may be called only by the chairman of the board of directors, the chief executive officer, the president or the board of directors, which may delay the ability of our stockholders to force consideration of a proposal or to take action, including the removal of directors; and

•advance notice procedures that stockholders must comply with in order to nominate candidates to our board of directors or to propose matters to be acted upon at a stockholders’ meeting, which may discourage or deter a potential acquirer from conducting a solicitation of proxies to elect the acquirer’s own slate of directors or otherwise attempting to obtain control of us.

Moreover, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the General Corporation Law of the State of Delaware, which prohibits a person who owns in excess of 15% of our outstanding voting stock from merging or combining with us for a period of three years after the date of the transaction in which the person acquired in excess of 15% of our outstanding voting stock, unless the merger or combination is approved in a prescribed manner.

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Our certificate of incorporation designates the Court of Chancery of the State of Delaware, subject to certain exceptions, as the sole and exclusive forum for certain types of actions and proceedings that may be initiated by our stockholders and our bylaws designate the federal district courts of the United States as the exclusive forum for actions arising under the Securities Act of 1933, as amended, which could limit our stockholders’ ability to obtain a favorable judicial forum for disputes with us or our directors, officers or employees.

Our restated certificate of incorporation specifies that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for most legal actions involving claims brought against us by stockholders. In addition, our bylaws provide that the federal district courts of the United States are the exclusive forum for any complaint raising a cause of action arising under the Securities Act of 1933, as amended. Any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock shall be deemed to have notice of and to have consented to the provisions of our restated certificate of incorporation and bylaws described above.

We believe these choice of forum provisions benefit us by providing increased consistency in the application of Delaware law by chancellors particularly experienced in resolving corporate disputes, efficient administration of cases on a more expedited schedule relative to other forums and protection against the burdens of multi-forum litigation. However, the provision may have the effect of discouraging lawsuits against our directors, officers, employees and agents as it may limit any stockholder’s ability to bring a claim in a judicial forum that such stockholder finds favorable for disputes with us or our directors, officers, employees or agents. The enforceability of similar choice of forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that, in connection with any applicable action brought against us, a court could find the choice of forum provisions contained in our restated certificate of incorporation or bylaws to be inapplicable or unenforceable in such action. If a court were to find the choice of forum provisions contained in our restated certificate of incorporation or bylaws to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could adversely affect our business, financial condition or results of operations.

Our ability to use net operating losses and research and development credits to offset future taxable income or income tax liabilities may be subject to certain limitations.

As of December 31, 2022, we had federal and state net operating loss carryforwards, or NOLs, of approximately $283.5 million and $272.1 million, respectively. Our state NOLs, and federal NOLs generated in taxable years beginning before January 1, 2018, are subject to expiration and will expire at various dates through 2041. Federal NOLs generated in taxable periods beginning after December 31, 2017 may be carried forward indefinitely but may only be used to offset 80% of our taxable income in taxable years beginning after December 31, 2020, which may require us to pay federal income taxes in future years despite generating federal NOLs in prior years. As of December 31, 2022, we also had federal and state research and development and other tax credit carryforwards, or credits, including the orphan drug credit, of approximately $55.1 million and $14.8 million, respectively, available to reduce future income tax liabilities. The federal and state credits expire at various dates through 2041. These NOLs and credits could expire unused and be unavailable to offset future taxable income or income tax liabilities, to the extent subject to expiration. In addition, in general, under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, or the Code, a corporation that undergoes an “ownership change” is subject to limitations on its ability to utilize its pre-change NOLs or credits to offset future taxable income or income tax liabilities. For these purposes, an ownership change generally occurs where the aggregate change in stock ownership of one or more stockholders or groups of stockholders owning at least 5% of a corporation’s stock exceeds 50 percentage points over a rolling three-year period. Our existing NOLs or credits may be subject to limitations arising from previous ownership changes, if any. In addition, future changes in our stock ownership, many of which are outside of our control, could result in an ownership change. Our state NOLs or credits may also be impaired or subject to limitations under state law. Accordingly, even if we attain profitability, we may not be able to utilize a material portion of our NOLs or credits.

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Because we do not anticipate paying any cash dividends on our common shares in the foreseeable future, capital appreciation, if any, would be your sole source of gain.

We have never declared or paid any cash dividends on our common shares. We anticipate that we will retain future earnings for the development and operation of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. As a result, capital appreciation, if any, of our common shares would be your sole source of gain on an investment in our common shares for the foreseeable future.

General Risk Factors

The market price of our common stock may be volatile and fluctuate substantially, which could result in substantial losses for purchasers of our common stock.

Our stock price is likely to be volatile. The stock market in general and the market for smaller biopharmaceutical companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, you may not be able to sell your shares of common stock at or above the price at which you purchased them. The market price for our common stock may be influenced by many factors, including:

•the success of competitive products or technologies;

•actual or expected changes in our growth rate relative to our competitors;

•results of clinical trials of our product candidates or those of our competitors;

•developments related to our existing or any future collaborations;

•regulatory actions with respect to our product candidates or our competitors’ products and product candidates;

•regulatory or legal developments in the United States and other countries;

•development of new product candidates that may address our markets and make our product candidates less attractive;

•changes in physician, hospital or healthcare provider practices that may make our product candidates less useful;

•announcements by us, our collaborators or our competitors of significant acquisitions, strategic collaborations, joint ventures or capital commitments;

•developments or disputes concerning patent applications, issued patents or other proprietary rights;

•the recruitment or departure of key personnel;

•the level of expenses related to any of our product candidates or clinical development programs;

•failure to meet or exceed financial estimates and projections of the investment community or that we provide to the public;

•the results of our efforts to discover, develop, acquire or in-license additional product candidates or products;

•actual or expected changes in estimates as to financial results, development timelines or recommendations by securities analysts;

•variations in our financial results or those of companies that are perceived to be similar to us;

•changes in the structure of healthcare payment systems;

•market conditions in the pharmaceutical and biotechnology sectors;

•general economic, industry and market conditions; and

•the other factors described in this “Risk Factors” section.

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We expect to continue to incur costs as a result of operating as a public company, and our management is required to devote substantial time to new compliance initiatives and corporate governance practices.

As a public company, we have incurred and expect to continue to incur significant legal, accounting and other expenses that we did not incur as a private company. The Sarbanes-Oxley Act of 2002, the Dodd-Frank Wall Street Reform and Consumer Protection Act, the listing requirements of The Nasdaq Global Select Market and other applicable securities rules and regulations impose various requirements on public companies, including establishment and maintenance of effective disclosure and financial controls and corporate governance practices. Our management and other personnel devote a substantial amount of time to these compliance initiatives. Moreover, these rules and regulations have increased our legal and financial compliance costs and have made some activities more time-consuming and costly. For example, we expect that these rules and regulations may make it more difficult and more expensive for us to obtain director and officer liability insurance, which in turn could make it more difficult for us to attract and retain qualified members of our board of directors.

We continue to evaluate these rules and regulations, and cannot predict or estimate the amount of additional costs we may incur or the timing of such costs. These rules and regulations are often subject to varying interpretations, in many cases due to their lack of specificity, and, as a result, their application in practice may evolve over time as new guidance is provided by regulatory and governing bodies. This could result in continuing uncertainty regarding compliance matters and higher costs necessitated by ongoing revisions to disclosure and governance practices.

Pursuant to Section 404 of the Sarbanes-Oxley Act of 2002, or Section 404, we are required to furnish a report by our management on our internal control over financial reporting. However, while we remain an emerging growth company, we will not be required to include an attestation report on internal control over financial reporting issued by our independent registered public accounting firm. To achieve compliance with Section 404 within the prescribed period, we have engaged in a process to document and evaluate our internal control over financial reporting, which has been both costly and challenging. We will need to continue to dedicate internal resources, engage outside consultants, adopt a detailed work plan to assess and document the adequacy of internal control over financial reporting, continue steps to improve control processes as appropriate, validate through testing whether such controls are functioning as documented, and implement a continuous reporting and improvement process for internal control over financial reporting. Despite our efforts, there is a risk that we will not be able to conclude that our internal control over financial reporting is effective as required by Section 404. If we identify one or more material weaknesses, it could cause us to need to restate our previously issued financial statements and result in an adverse reaction in the financial markets due to a loss of confidence in the reliability of our financial statements.

There can be no assurance that we will be able to comply with the continued listing standards of Nasdaq.

If we fail to satisfy Nasdaq’s continued listing requirements, Nasdaq may take steps to delist our securities. Such a delisting would likely have a negative effect on the price of the securities and would impair stockholders’ ability to sell or purchase the securities when they wish to do so. In the event of a delisting, we can provide no assurance that any action taken by us to restore compliance with listing requirements would allow our securities to become listed again, stabilize the market price or improve the liquidity of our securities, or prevent future non-compliance with Nasdaq’s listing requirements.

In the future, we may engage in acquisitions that could disrupt our business, cause dilution to our stockholders or reduce our financial resources.

In the future, we may enter into transactions to acquire other businesses, products or technologies. If we do identify suitable candidates, we may not be able to make such acquisitions on favorable terms, or at all. Any acquisitions we make may not strengthen our competitive position, and these transactions may be viewed negatively by customers or investors. We may decide to incur debt in connection with an acquisition or issue our common stock or other equity securities to the stockholders of the acquired company, which would reduce the percentage ownership of our existing stockholders. We could incur losses resulting from undiscovered liabilities of the acquired business that are not covered by the indemnification we may obtain from the seller. In addition, we may not be able to successfully integrate the acquired personnel, technologies and operations into our existing business in an effective, timely and nondisruptive manner. Acquisitions may also divert management attention from day-to-day responsibilities, increase our expenses and reduce our cash available for operations and other uses. We cannot predict the number, timing or size of future acquisitions or the effect that any such transactions might have on our operating results.

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Unstable global political or economic conditions may have serious adverse consequences on our business, financial condition and share price.

The global economy, including credit and financial markets, has recently experienced extreme volatility and disruptions, including severely diminished liquidity and credit availability, rising interest and inflation rates, declines in consumer confidence, declines in economic growth, increases in unemployment rates and uncertainty about economic stability. There can be no assurance that further deterioration in credit and financial markets and confidence in economic conditions will not occur. If the equity and credit markets continue to deteriorate, or the United States enters a recession, it may make any necessary debt or equity financing more difficult to obtain in a timely manner or on favorable terms, more costly or more dilutive. In addition, international terrorism and conflicts could disrupt or otherwise adversely impact our operations and those of third parties upon which we rely. Related sanctions, export controls or other actions have and may in the future be initiated by nations including the U.S., the EU or Russia (e.g., potential cyberattacks, disruption of energy flows, etc.), which could adversely affect our business and/or our supply chain, our CROs, CMOs and other third parties with which we conduct business. Any of the foregoing could harm our business, results of operations and the price of our common stock may be adversely affected.

We are exposed to fluctuations in inflation, which could negatively affect our business, financial condition and results of operations.

The United States has recently experienced historically high levels of inflation. According to the U.S. Department of Labor, the annual inflation rate for the United States was approximately 8.0% for 2022. If the inflation rate continues to increase, it will likely affect our expenses, including, but not limited to, increased cost of drug product from OXB Solutions and other future potential contract manufacturing organizations, supplies and employee compensation expenses. To the extent inflation results in rising interest rates and has other adverse effects on the market, it may adversely affect our business, financial condition and results of operations.

The increasing focus on environmental sustainability and social initiatives could increase our costs, harm our reputation and adversely impact our financial results.

There has been increasing public focus by investors, environmental activists, the media and governmental and nongovernmental organizations on a variety of environmental, social and other sustainability matters. We may experience pressure to make commitments relating to sustainability matters that affect us, including the design and implementation of specific risk mitigation strategic initiatives relating to sustainability. If we are not effective in addressing environmental, social and other sustainability matters affecting our business, or setting and meeting relevant sustainability goals, our reputation and financial results may suffer. In addition, we may experience increased costs in order to execute upon our sustainability goals and measure achievement of those goals, which could have an adverse impact on our business and financial condition.

Moreover, this emphasis on environmental, social and other sustainability matters has resulted and may result in the adoption of new laws and regulations, including new reporting requirements. If we fail to comply with new laws, regulations or reporting requirements, our reputation and business could be adversely impacted.

Item 2. Unregistered Sales of Equity Securities, Use of Proceeds, and Issuer Purchases of Equity Securities.

Not applicable.

Item 3. Defaults Upon Senior Securities.

Not applicable.

Item 4. Mine Safety Disclosures.

Not applicable.

Item 5. Other Information.

a)None.

b)None.

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c)We are a smaller reporting company as defined in Rule 12b-2 of the Exchange Act and are not required to provide the information otherwise required under Item 408(a) of Regulation S-K.

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Item 6. Exhibits.

Exhibit Number	Description	Form	File No.	Exhibit	Filing Date	Filed/Furnished Herewith
3.1	Restated Certificate of Incorporation of Homology Medicines, Inc.	8-K	001-38433	3.1	4/3/2018
3.2	Amended and Restated Bylaws of Homology Medicines, Inc.	8-K	001-38433	3.1	12/18/2020
31.1	Certification of Principal Executive Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.					*
31.2	Certification of Principal Financial Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.					*
32.1	Certification of Principal Executive Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.					**
32.2	Certification of Principal Financial Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.					**
101.INS	Inline XBRL Instance Document- the Instance Document does not appear in the interactive data file because its XBRL tags are embedded within the Inline XBRL document					*
101.SCH	Inline XBRL Taxonomy Extension Schema Document					*
101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document					*
101.DEF	Inline XBRL Taxonomy Extension Definition Linkbase Document					*
101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document					*
101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document					*
104	Cover Page Interactive Data File (formatted as Inline XBRL and contained in Exhibit 101)					*

* Filed herewith.

** Furnished herewith.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	HOMOLOGY MEDICINES, INC.
Date: November 14, 2023	By:	/s/ Albert Seymour, Ph.D.
		Albert Seymour, Ph.D.
		President, Chief Executive Officer and Director (principal executive officer)

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Date: November 14, 2023	By:	/s/ W. Bradford Smith
		W. Bradford Smith
		Chief Financial and Business Officer and Treasurer (principal financial officer and principal accounting officer)

95

EX-31.1

Exhibit 31.1

CERTIFICATION

I, Albert Seymour, Ph.D., certify that:

1.I have reviewed this Quarterly Report on Form 10-Q of Homology Medicines, Inc.;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5.The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: November 14, 2023	By:	/s/ Albert Seymour, Ph.D.
		Albert Seymour, Ph.D.
		President, Chief Executive Officer and Director  (principal executive officer)

EX-31.2

Exhibit 31.2

CERTIFICATION

I, W. Bradford Smith, certify that:

1.I have reviewed this Quarterly Report on Form 10-Q of Homology Medicines, Inc.;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5.The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: November 14, 2023	By:	/s/ W. Bradford Smith
		W. Bradford Smith
		Chief Financial and Business Officer and Treasurer (principal financial officer and principal accounting officer)

EX-32.1

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, Albert Seymour, Ph.D., Chief Executive Officer of Homology Medicines, Inc. (the “Company”), hereby certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge:

(1) The Quarterly Report on Form 10-Q of the Company for the period ended September 30, 2023 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

November 14, 2023	By:	/s/ Albert Seymour, Ph.D.
		Albert Seymour, Ph.D.
		President, Chief Executive Officer and Director (principal executive officer)

EX-32.2

Exhibit 32.2

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, W. Bradford Smith, Chief Financial and Business Officer of Homology Medicines, Inc. (the “Company”), hereby certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge:

(1) The Quarterly Report on Form 10-Q of the Company for the period ended September 30, 2023 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

November 14, 2023	By:	/s/ W. Bradford Smith
		W. Bradford Smith
		Chief Financial and Business Officer and Treasurer (principal financial officer and principal accounting officer)

XML

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Nov. 07, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2023
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2023
Entity Registrant Name	Homology Medicines, Inc
Entity Central Index Key	0001661998
Trading Symbol	FIXX
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		57,934,332
Entity File Number	001-38433
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-3468154
Entity Address, Address Line One	One Patriots Park
Entity Address, City or Town	Bedford
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01730
City Area Code	781
Local Phone Number	301-7277
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false

XML

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 29,111	$ 33,986
Short-term investments	74,187	141,040
Assets held for sale	314	0
Prepaid expenses and other current assets	3,023	5,989
Total current assets	106,635	181,015
Equity method investment	13,957	25,814
Property and equipment, net	0	1,078
Right-of-use assets	19,471	20,563
Total assets	140,063	228,470
Current liabilities:
Accounts payable	7,803	1,144
Accrued expenses and other liabilities	15,711	18,715
Operating lease liabilities	1,778	1,561
Deferred revenue	0	1,156
Total current liabilities	25,292	22,576
Non-current liabilities:
Operating lease liabilities, net of current portion	26,560	27,916
Total liabilities	51,852	50,492
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized; no shares issued and outstanding at September 30, 2023 and December 31, 2022	0	0
Common stock, $0.0001 par value; 200,000,000 shares authorized; 57,902,210 and 57,483,910 shares issued and outstanding as of September 30, 2023 and December 31, 2022, respectively	6	6
Additional paid-in capital	614,220	607,513
Accumulated other comprehensive loss	(36)	(404)
Accumulated deficit	(525,979)	(429,137)
Total stockholders’ equity	88,211	177,978
Total liabilities and stockholders' equity	$ 140,063	$ 228,470

XML

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	57,902,210	57,483,910
Common stock, shares outstanding	57,902,210	57,483,910

XML

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Collaboration revenue	$ 0	$ 802	$ 1,156	$ 2,406
Operating expenses:
Research and development	17,519	25,854	60,489	71,202
General and administrative	6,842	7,810	23,355	29,991
Restructuring and other charges	6,640	0	6,640	0
Total operating expenses	31,001	33,664	90,484	101,193
Loss from operations	(31,001)	(32,862)	(89,328)	(98,787)
Other income
Gain on sale of business	0	0	0	131,249
Interest income	1,423	1,269	4,403	1,775
Total other income	1,423	1,269	4,403	133,024
Income (loss) before income taxes	(29,578)	(31,593)	(84,925)	34,237
Benefit from (provision for) income taxes	0	46	0	(816)
Loss from equity method investment	(3,376)	(2,179)	(11,917)	(4,131)
Net income (loss)	$ (32,954)	$ (33,726)	$ (96,842)	$ 29,290
Net income (loss) per share-basic	$ (0.57)	$ (0.59)	$ (1.68)	$ 0.51
Net income (loss) per share-diluted	$ (0.57)	$ (0.59)	$ (1.68)	$ 0.51
Weighted-average common shares outstanding-basic	57,853,132	57,447,192	57,788,755	57,372,399
Weighted-average common shares outstanding-diluted	57,853,132	57,447,192	57,788,755	57,901,298

XML

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (32,954)	$ (33,726)	$ (96,842)	$ 29,290
Other comprehensive gain (loss):
Change in unrealized gain (loss) on available for sale securities, net	52	(416)	368	(450)
Total other comprehensive gain	52	(416)	368	(450)
Comprehensive income (loss)	$ (32,902)	$ (34,142)	$ (96,474)	$ 28,840

XML

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Equity Method Investee	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Equity Method Investee	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2021	$ 169,651		$ 6	$ 593,784		$ (7)	$ (424,132)
Beginning balance, Shares at Dec. 31, 2021			57,150,274
Issuance of common stock from RSU vesting			87,140
Issuance of common stock from option exercises	1			1
Issuance of common stock from option exercises, Shares			293
Issuance of common stock pursuant to employee stock purchase plan	439			439
Issuance of common stock pursuant to employee stock purchase plan, Shares			147,871
Stock-based compensation	4,051			4,051
Other comprehensive gain (loss)	7					7
Net income (loss)	92,105						92,105
Ending balance at Mar. 31, 2022	266,254		$ 6	598,275			(332,027)
Ending balance, Shares at Mar. 31, 2022			57,385,578
Beginning balance at Dec. 31, 2021	169,651		$ 6	593,784		(7)	(424,132)
Beginning balance, Shares at Dec. 31, 2021			57,150,274
Other comprehensive gain (loss)	(450)
Net income (loss)	29,290
Ending balance at Sep. 30, 2022	209,061		$ 6	604,354		(457)	(394,842)
Ending balance, Shares at Sep. 30, 2022			57,480,610
Beginning balance at Mar. 31, 2022	266,254		$ 6	598,275			(332,027)
Beginning balance, Shares at Mar. 31, 2022			57,385,578
Stock-based compensation	3,143	$ 21		3,143	$ 21
Other comprehensive gain (loss)	(41)					(41)
Net income (loss)	(29,089)						(29,089)
Ending balance at Jun. 30, 2022	240,288		$ 6	601,439		(41)	(361,116)
Ending balance, Shares at Jun. 30, 2022			57,385,578
Issuance of common stock from RSU vesting			16,450
Issuance of common stock pursuant to employee stock purchase plan	124			124
Issuance of common stock pursuant to employee stock purchase plan, Shares			78,582
Stock-based compensation	2,771	20		2,771	20
Other comprehensive gain (loss)	(416)					(416)
Net income (loss)	(33,726)						(33,726)
Ending balance at Sep. 30, 2022	209,061		$ 6	604,354		(457)	(394,842)
Ending balance, Shares at Sep. 30, 2022			57,480,610
Beginning balance at Dec. 31, 2022	177,978		$ 6	607,513		(404)	(429,137)
Beginning balance, Shares at Dec. 31, 2022			57,483,910
Issuance of common stock from RSU vesting			194,525
Issuance of common stock pursuant to employee stock purchase plan	150			150
Issuance of common stock pursuant to employee stock purchase plan, Shares			116,332
Stock-based compensation	2,369	24		2,369	24
Other comprehensive gain (loss)	222					222
Net income (loss)	(28,844)						(28,844)
Ending balance at Mar. 31, 2023	151,899		$ 6	610,056		(182)	(457,981)
Ending balance, Shares at Mar. 31, 2023			57,794,767
Beginning balance at Dec. 31, 2022	177,978		$ 6	607,513		(404)	(429,137)
Beginning balance, Shares at Dec. 31, 2022			57,483,910
Other comprehensive gain (loss)	368
Net income (loss)	(96,842)
Ending balance at Sep. 30, 2023	88,211		$ 6	614,220		(36)	(525,979)
Ending balance, Shares at Sep. 30, 2023			57,902,210
Beginning balance at Mar. 31, 2023	151,899		$ 6	610,056		(182)	(457,981)
Beginning balance, Shares at Mar. 31, 2023			57,794,767
Issuance of common stock from option exercises	2			2
Issuance of common stock from option exercises, Shares			3,366
Stock-based compensation	2,402	22		2,402	22
Other comprehensive gain (loss)	94					94
Net income (loss)	(35,044)						(35,044)
Ending balance at Jun. 30, 2023	119,375		$ 6	612,482		(88)	(493,025)
Ending balance, Shares at Jun. 30, 2023			57,798,133
Issuance of common stock from RSU vesting			86,592
Issuance of common stock pursuant to employee stock purchase plan	18			18
Issuance of common stock pursuant to employee stock purchase plan, Shares			17,485
Stock-based compensation	1,706	$ 14		1,706	$ 14
Other comprehensive gain (loss)	52					52
Net income (loss)	(32,954)						(32,954)
Ending balance at Sep. 30, 2023	$ 88,211		$ 6	$ 614,220		$ (36)	$ (525,979)
Ending balance, Shares at Sep. 30, 2023			57,902,210

XML

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net income (loss)	$ (96,842)	$ 29,290
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	578	997
Noncash lease expense	1,091	969
Loss from equity method investment	11,917	4,131
Stock-based compensation expense	6,477	9,965
Accretion of discount on short-term investments	(2,279)	(872)
Loss on disposal of property and equipment	68	0
Gain on sale of business	0	(131,249)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	2,966	(5,301)
Accounts payable	6,659	2,711
Accrued expenses and other liabilities	(2,996)	5,672
Deferred revenue	(1,156)	(2,406)
Operating lease liabilities	(1,138)	(369)
Net cash used in operating activities	(74,655)	(86,462)
Cash flows from investing activities:
Purchases of short-term investments	(73,240)	(157,460)
Maturities of short-term investments	142,740	47,461
Proceeds from sale of business	0	130,000
Proceeds from sale of property and equipment	338	0
Purchases of property and equipment	(228)	(1,276)
Net cash provided by investing activities	69,610	18,725
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to employee stock purchase plan	168	563
Proceeds from issuance of common stock from option exercises	2	1
Net cash provided by financing activities	170	564
Net change in cash, cash equivalents and restricted cash	(4,875)	(67,173)
Cash, cash equivalents and restricted cash, beginning of period	33,986	110,335
Cash, cash equivalents and restricted cash, end of period	29,111	43,162
Supplemental disclosures of noncash investing and financing activities:
Property and equipment additions included in accrued expenses and other liabilities	0	8
Unrealized loss on available for sale securities, net	$ 368	$ (450)

XML

Nature of Business and Basis of Presentation

9 Months Ended

Sep. 30, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

NATURE OF BUSINESS AND BASIS OF PRESENTATION

1. NATURE OF BUSINESS AND BASIS OF PRESENTATION

Nature of Business—Homology Medicines, Inc. (the “Company” or "Homology") is a clinical-stage genetic medicines company historically focused on transforming the lives of patients suffering from rare diseases by addressing the underlying cause of the disease with one-time gene therapy and gene editing treatments. The Company was founded in March 2015 as a Delaware corporation. Its principal offices are in Bedford, Massachusetts.

On July 27, 2023, the Company announced that it had completed a review of its business and the Company's Board of Directors had approved a plan to explore, review and evaluate a range of potential strategic options available to the Company, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Based on the current financing environment and the Company's anticipated clinical development timeline for its lead program, HMI-103, the Company also announced that it was stopping further development of its programs and reduced its workforce by 86% in an effort to significantly reduce its ongoing operating costs as it evaluates strategic alternatives. The workforce reduction was substantially completed in the third quarter of 2023 (see Note 8).

On March 9, 2023, the Company filed a Registration Statement on Form S-3 (File No. 333-270414) (the “Shelf”) with the SEC in relation to the registration of up to an aggregate of $250.0 million of its common stock, preferred stock, debt securities, warrants and/or units of any combination thereof for a period up to three years from the date of the filing. The Shelf became effective on March 17, 2023. The Company also simultaneously entered into a sales agreement with Cowen and Company, LLC (“Cowen”), as sales agent, providing for the offering, issuance and sale by the Company of up to an aggregate of $75.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf (the “ATM”). The Company did not sell any shares of common stock under the ATM during the nine months ended September 30, 2023. As of September 30, 2023, there remained $75.0 million of common stock available for sale under the ATM.

On March 10, 2022, the Company closed a transaction with Oxford Biomedica plc ("Oxford"), to establish a new adeno-associated virus ("AAV") vector manufacturing company, Oxford Biomedica Solutions ("OXB Solutions") that provides AAV vector process development and manufacturing services to biotechnology companies. Under the terms of the agreement, the Company contributed its manufacturing team of 125 employees, manufacturing facility and equipment, manufacturing-related intellectual property and know-how and certain other assets. Oxford paid the Company $130.0 million of upfront cash and invested $50.0 million of cash to fund OXB Solutions in exchange for an 80 percent ownership interest, while Homology retained a 20 percent ownership interest in the new company and received a put option on this ownership position (see Note 5).

Since its inception and until recently, the Company devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates through discovery, preclinical and clinical trials, developing and implementing manufacturing processes, building out manufacturing and research and development space, and maintaining and building its intellectual property portfolio. The Company is subject to a number of risks similar to those of other companies conducting high-risk, early-stage research and development of product candidates. Principal among these risks are dependency on key individuals and intellectual property, competition from other products and companies, and the technical and regulatory risks associated with the successful research, development and manufacturing of its product candidates.

To date, the Company has not generated any revenue from product sales and does not expect to generate any revenue from the sale of product in the foreseeable future. Through September 30, 2023, the Company has financed its operations primarily through public offerings of its common stock, the issuance of convertible preferred stock, and with proceeds from its transaction with Oxford (see Note 5), its collaboration and license agreement with a former collaboration partner and its private placement with Pfizer (see Note 12). During the nine months ended September 30, 2023, the Company incurred a loss from operations of $96.8 million and as of September 30, 2023, the Company had $526.0 million in accumulated deficit.

The Company has incurred and expects to continue to incur costs and expenditures in connection with the process of evaluating strategic alternatives. There can be no assurance, however, that the Company will be able to successfully consummate any particular strategic transaction. The process of evaluating strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges.

Based on current projections, management believes that the Company's existing cash and cash equivalents and short-term investments as of September 30, 2023 will enable the Company to continue its operations for at least one year from the date of this filing. However, due to the consideration of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as the Company's workforce reduction of all but a few custodial employees, management has concluded there is substantial doubt regarding the Company's ability to continue as a going concern for more than twelve months from the date that the unaudited condensed consolidated financial statements included in this Quarterly Report on Form 10-Q have been issued. These financial statements do not include any adjustments that might result from the outcome of this uncertainty. Should the Company resume the development of product candidates, it would need to obtain substantial additional funding in connection with continuing operations, particularly as the Company resumes its preclinical activities and clinical trials for its product candidates. There can be no assurance that the Company will be able to obtain sufficient capital to cover its costs on acceptable terms, if at all.

Basis of Presentation— The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2022, included in the Company's Annual Report on Form 10-K on file with the SEC.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position as of September 30, 2023, and consolidated results of operations for the three and nine months ended September 30, 2023 and 2022, and cash flows for the nine months ended September 30, 2023 and 2022. Such adjustments are of a normal and recurring nature. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023.

XML

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2023

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation—The Company’s condensed consolidated financial statements include the accounts of the Company and its subsidiary, Homology Medicines Securities Corporation, a wholly owned Massachusetts corporation, for the sole purpose of buying, selling, and holding securities on the Company’s behalf. All intercompany balances and transactions have been eliminated in the condensed consolidated financial statements.

Use of Estimates—The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, accrued research and development expenses and the valuation of the Company's equity method investment. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Comprehensive Income (Loss)—Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company’s only element of other comprehensive income (loss) is unrealized gains and losses on available-for-sale investments.

Cash and Cash Equivalents and Restricted Cash—Cash and cash equivalents consist of standard checking accounts, money market accounts and certain investments. The Company considers all highly liquid investments with original or remaining maturities at the time of purchase of 90 days or less to be cash equivalents. The Company did not have any restricted cash at September 30, 2023 or December 31, 2022.

Short-Term Investments—Short-term investments represent holdings of available-for-sale marketable securities in accordance with the Company’s investment policy and cash management strategy. Short-term investments have maturities of greater than 90 days at the time of purchase and mature within one year from the balance sheet date. Investments in marketable securities are recorded at fair value, with any unrealized gains and losses reported within accumulated other comprehensive income as a separate component of stockholders’ equity until realized or until a determination is made that an other-than-temporary decline in market value has occurred. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the

underlying security. Such amortization and accretion, together with interest on securities, are included in interest income in the Company’s condensed consolidated statements of operations. The cost of marketable securities sold is determined based on the specific identification method and any realized gains or losses on the sale of investments are reflected as a component of other income.

Assets Held for Sale—The Company classifies assets as held for sale when the following conditions are met: (1) management has committed to a plan to sell, (2) the assets are available for immediate sale in their present condition, (3) the Company has initiated an active program to identify a buyer, (4) it is probable that a sale will occur within one year, (5) the assets are actively marketed for sale at a reasonable price in relation to their current fair value, and (6) there is a low likelihood of significant changes to the plan or that the plan will be withdrawn. If all of the aforementioned criteria are met as of the balance sheet date, the assets are presented separately in the consolidated balance sheet as held for sale at the lower of the carrying amount or fair value less costs to sell. The assets are then no longer depreciated or amortized while classified as held for sale.

Equity Method Investment—The Company uses the equity method of accounting to account for an investment in an entity that it does not control, but in which it has the ability to exercise significant influence over operating and financial policies. The Company's proportionate share of the net income or loss of the entity is included in consolidated net loss. Judgments regarding the level of influence over the equity method investment include consideration of key factors such as the Company's ownership interest, representation on the board of directors or other management body and participation in policy-making decisions.

Under the equity method of accounting, the Company’s investment is initially recorded at fair value on the condensed consolidated balance sheets. Upon initial investment, the Company evaluates whether there are basis differences between the carrying value and fair value of the Company’s proportionate share of the investee’s underlying net assets. Typically, the Company amortizes basis differences identified on a straight-line basis over the underlying assets’ estimated useful lives when calculating the attributable earnings or losses, excluding the basis differences attributable to in-process research and development that has no alternative future use. If the Company is unable to attribute all of the basis differences to specific assets or liabilities of the investee, the residual excess of the cost of the investment over the proportional fair value of the investee’s assets and liabilities is considered to be equity method goodwill and is recognized within the equity investment balance, which is tracked separately within the Company’s memo accounts. The Company subsequently records in the condensed consolidated statements of operations its share of income or loss of the other entity within other income/expense, which results in an increase or decrease to the carrying value of the investment. If the share of losses exceeds the carrying value of the Company’s investment, the Company will suspend recognizing additional losses and will continue to do so unless it commits to providing additional funding; however, if there are intra-entity profits this can cause the investment balance to go negative.

The Company evaluates its equity method investments for impairment whenever events or changes in circumstances indicate that a decline in value has occurred that is other than temporary. Evidence considered in this evaluation includes, but would not necessarily be limited to, the financial condition and near-term prospects of the investee, recent operating trends and forecasted performance of the investee, market conditions in the geographic area or industry in which the investee operates and the Company’s strategic plans for holding the investment in relation to the period of time expected for an anticipated recovery of its carrying value. If the investment is determined to have a decline in value deemed to be other than temporary it is written down to estimated fair value.

At September 30, 2023, the Company accounted for its investment in OXB Solutions using the equity method of accounting (see Note 5).

Offering Costs—The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with equity financings as other current assets until the transactions are completed. After equity financings are complete, these costs are recorded in stockholders’ equity as a reduction of additional paid-in capital generated as a result of the offering.

Leases—The Company determines if an arrangement is a lease at contract inception. The Company’s contracts are determined to contain a lease when all of the following criteria based on the specific circumstances of the arrangement are met: (1) there is an identified asset for which there are no substantive substitution rights; (2) the Company has the right to obtain substantially all of the economic benefits from the identified asset; and (3) the Company has the right to direct the use of the identified asset.

At the commencement date, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of future lease payments over the expected lease term. The Company’s lease agreements do not provide an implicit rate. As a result, the Company utilizes an estimated incremental borrowing rate to discount lease payments, which is based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or lease incentives received. Operating lease cost is recognized over the expected term on a straight-line basis. The expected lease term includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as

periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option. Variable lease cost is recognized as incurred. Right-of-use assets are periodically evaluated for impairment.

The Company acts as sublessor related to a sublease of a substantial portion of the Company's headquarters that is now occupied by OXB Solutions. Fixed sublease payments received are recorded as a reduction to lease cost. Although Homology assigned all of its right, title and interest in, to and under this lease to OXB Solutions, the Company remained jointly and severally liable for the payment of rent under this lease as of and for the three and nine months ended September 30, 2023. Therefore, the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s condensed consolidated balance sheets as of September 30, 2023. The Company was released from being the primary obligor under such lease effective October 1, 2023 (see Note 14).

Research and Development Costs—Research and development costs are charged to expense as incurred. Research and development expense consists of expenses incurred in performing research and development activities, including salaries and benefits, materials and supplies, preclinical and clinical expenses, stock-based compensation expense, depreciation of equipment, contract services, and other outside expenses.

Costs for certain development activities are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense.

Income Taxes—The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s condensed consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. Since inception, the Company has provided a valuation allowance for the full amount of the net deferred tax assets as the realization of the net deferred tax assets has not been determined to be more likely than not.

The Company recorded an income tax benefit of less than $0.1 million and an income tax provision of $0.8 million for the three and nine months ended September 30, 2022, respectively. The year-to-date tax provision predominately resulted from the gain associated with the sale of the Company's manufacturing business due to the transaction with Oxford (see Note 5), offset by available federal and state net operating loss carryforwards and research and development tax credits which are subject to certain limitations as to their utilization. The Company did not record an income tax provision (benefit) for the three and nine months ended September 30, 2023.

Revenue Recognition—Revenue is recognized in accordance with FASB Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”).

Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer.

The promised goods or services in the Company’s arrangements would likely consist of a license, rights to the Company’s intellectual property or research, development and manufacturing services. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers

factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration and variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of consideration to which the Company expects to be entitled to. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

The Company’s contracts may include development and regulatory milestone payments that are assessed under the most likely amount method and constrained until it is probable that a significant revenue reversal would not occur. Milestone payments that are not within the Company’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and regulatory milestones and any related constraint, and if necessary, adjust its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from the Company’s collaboration arrangement.

The Company allocates the transaction price based on the estimated standalone selling price of each performance obligation. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress for its over-time arrangements at each reporting period and, if necessary, updates the measure of progress and revenue recognized.

Net Income (Loss) per Share—Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding during the period. Diluted net income (loss) per share is computed using the weighted-average number of common shares outstanding during the period and, if dilutive, the weighted-average number of potential shares of common stock. The weighted-average number of common shares included in the computation of diluted net income (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, restricted stock units and unvested shares of common stock.

Common stock equivalent shares are excluded from the computation of diluted net income (loss) per share if their effect is antidilutive. In periods in which the Company reports a net (loss) attributable to common stockholders, diluted net (loss) per share attributable to common stockholders is generally the same as basic net (loss) per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.

Recent Accounting Pronouncements—The Jumpstart Our Business Startups Act of 2012 permits an emerging growth company to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. As an emerging growth company, the Company has elected to take advantage of this extended transition period.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) to improve financial reporting by requiring more timely recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. ASU 2016-13 requires the measurement

of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. ASU 2016-13 also requires enhanced disclosures to help investors and other financial statement users better understand significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. The Company adopted ASU 2016-13 on January 1, 2023. The adoption of ASU 2016-13 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

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Short-Term Investments

9 Months Ended

Sep. 30, 2023

Investments Disclosure [Abstract]

SHORT-TERM INVESTMENTS

3. SHORT-TERM INVESTMENTS

The Company may invest its excess cash in fixed income instruments denominated and payable in U.S. dollars, including U.S. treasury securities, commercial paper, corporate debt securities and asset-backed securities in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital.

The following table summarizes the Company’s short-term investments as of September 30, 2023 and December 31, 2022:

As of September 30, 2023	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Commercial paper	$	3,965	$	—	$	(2	)	$	3,963
US Treasury securities		55,268		6		(7	)		55,267
Corporate debt securities		14,990		—		(33	)		14,957
Total	$	74,223	$	6	$	(42	)	$	74,187
As of December 31, 2022	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Commercial paper	$	57,138	$	—	$	—		$	57,138
US Treasury securities		65,160		—		(335	)		64,825
Corporate debt securities		19,146		—		(69	)		19,077
Total	$	141,444	$	—	$	(404	)	$	141,040

The Company utilizes the specific identification method in computing realized gains and losses. The Company had no realized gains and losses on its available-for-sale securities for the three and nine months ended September 30, 2023 and 2022. The contractual maturity dates of all of the Company’s investments are less than one year.

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Fair Value Measurements

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

4. FAIR VALUE MEASUREMENTS

The Company’s financial instruments consist of cash and cash equivalents, short-term investments, restricted cash and accounts payable. The carrying amount of cash, restricted cash and accounts payable are each considered a reasonable estimate of fair value due to the short-term maturity.

Assets measured at fair value on a recurring basis were as follows:

Description	September 30, 2023		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	28,375	$	28,375	$	—	$	—
Total cash equivalents	$	28,375	$	28,375	$	—	$	—
Short-term investments:
Commercial paper	$	3,963	$	—	$	3,963	$	—
US Treasury securities		55,267		—		55,267		—
Corporate debt securities		14,957		—		14,957		—
Total short-term investments	$	74,187	$	—	$	74,187	$	—
Total financial assets	$	102,562	$	28,375	$	74,187	$	—
Description	December 31, 2022		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	33,967	$	33,967	$	—	$	—
Total cash equivalents	$	33,967	$	33,967	$	—	$	—
Short-term investments:
Commercial paper	$	57,138	$	—	$	57,138	$	—
US Treasury securities		64,825		—		64,825		—
Corporate debt securities		19,077		—		19,077		—
Total short-term investments	$	141,040	$	—	$	141,040	$	—
Total financial assets	$	175,007	$	33,967	$	141,040	$	—

Short-term securities are valued using models or other valuation methodologies that use Level 2 inputs. These models are primarily industry-standard models that consider various assumptions, including time value, yield curve, volatility factors, default rates, current market and contractual prices for the underlying financial instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace.

There were no transfers between fair value measurement levels during the three and nine months ended September 30, 2023 and 2022.

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Equity Method Investment

9 Months Ended

Sep. 30, 2023

Equity Method Investment, Summarized Financial Information [Abstract]

EQUITY METHOD INVESTMENT

5. EQUITY METHOD INVESTMENT

Summary of Transaction

On March 10, 2022, the Company closed a transaction with OXB Solutions, Oxford Biomedica (US), Inc., ("OXB"), and Oxford, pursuant to the Equity Securities Purchase Agreement (the "Purchase Agreement"), dated as of January 28, 2022, by and among Homology, OXB Solutions and Oxford, whereby, among other things, Homology and Oxford agreed to collaborate to operate OXB Solutions, which provides AAV vector process development and manufacturing services to pharmaceutical and biotechnology companies (the "OXB Solutions Transaction").

Pursuant to the terms of the Purchase Agreement and a contribution agreement (the "Contribution Agreement") entered into between Homology and OXB Solutions prior to the closing of the OXB Solutions Transaction (the "Closing"), Homology contributed its manufacturing team of 125 employees and assigned and transferred to OXB Solutions all of its assets that are primarily used in the manufacturing of AAV vectors for use in gene therapy and gene editing products, including its manufacturing facility and equipment and manufacturing-related intellectual property and know-how, but excluding certain assets related to manufacturing or testing of Homology's proprietary AAV vectors (collectively, the "Transferred Assets"), in exchange for 175,000 common equity units in OXB Solutions ("Units"), representing 100 percent (100%) of the ownership interest of OXB Solutions, and OXB Solutions assumed from the Company, and agreed to pay, perform and discharge when due, all of the Company's duties, obligations, liabilities, interests and commitments of any kind under, arising out of or relating to the Transferred Assets.

Effective as of the Closing, Homology sold to OXB, and OXB purchased from Homology, 130,000 Units, (the "Transferred Units") in exchange for $130.0 million of cash consideration. In connection with the Closing, OXB contributed $50.0 million in cash to OXB Solutions in exchange for an additional, newly issued 50,000 Units. Immediately following the Closing, (i) OXB owned 180,000 Units, representing 80 percent (80%) of the fully diluted equity interests in OXB Solutions, and (ii) Homology owned 45,000 Units, representing 20 percent (20%) of the fully diluted equity interests in OXB Solutions.

Pursuant to the Amended and Restated Limited Liability Company Agreement of OXB Solutions (the "OXB Solutions Operating Agreement") which was executed in connection with the Closing, at any time following the three-year anniversary of the Closing, (i) OXB will have an option to cause Homology to sell and transfer to OXB, and (ii) Homology will have an option to cause OXB to purchase from Homology, in each case all of Homology's equity ownership interest in OXB Solutions at a price equal to 5.5 times the revenue for the immediately preceding 12-month period (together, the "Options"), subject to a maximum amount of $74.1 million. Pursuant to the terms of the OXB Solutions Operating Agreement, Homology is entitled to designate one director to the board of directors of OXB Solutions, currently Albert Seymour, Homology's Chief Executive Officer.

Pursuant to the OXB Solutions Transaction, the Company also assigned all of its right, title and interest in, to and under its facility lease to OXB Solutions. However, as the Company remained jointly and severally liable for the payment of rent under the facility lease, the Company had not been released from being the primary obligor under such lease as of September 30, 2023 and therefore the related right-of-use asset and lease liability were not derecognized and remained on the Company’s balance sheet. The Company determined that the expected disposal of the fixed assets did not qualify for reporting as a discontinued operation since it did not represent a strategic shift that has or will have a major effect on the Company's operations and financial results. Subsequently, the Company was released from being the primary obligor under such lease effective as of October 1, 2023 (see Note 14).

Equity Method of Accounting

The Company has significant influence over, but does not control, OXB Solutions through its noncontrolling representation on OXB’s board of directors and the Company’s equity interest in OXB Solutions. In addition, the Company and OXB Solutions have intra-entity transactions through a series of agreements entered into in conjunction with the OXB Solutions Transaction, OXB Solutions granted certain licenses to the Company, and the Company has representation on the joint steering committee which oversees the activities governed by the Supply Agreement. Accordingly, the Company does not consolidate the financial statements of OXB Solutions and accounts for its investment using the equity method of accounting.

The Company recorded its equity method investment in OXB Solutions at fair value upon deconsolidation of OXB Solutions as of the Closing. The fair value of the equity method investment was determined based on the market approach. This approach estimated the fair value of OXB Solutions based on the implied value for the entity using the consideration paid, including the Options, for a controlling interest in OXB Solutions at the entity’s formation. As part of its fair value analysis, the Company determined that the Options are embedded in the common equity units because the Options are not legally detachable or separately exercisable. Accordingly, the equity method investment and the Options represent one unit of account and the fair value recorded reflects the value of the equity interest and the Options. The valuation included certain subjective assumptions including discounts for lack of control and marketability given the consideration paid for OXB Solutions was for a controlling interest in the entity and the Company owns a noncontrolling interest. As of March 10, 2022, the Closing, the fair value of the Company’s investment in OXB Solutions was $31.2 million and the Company recorded a gain of $131.2 million on the sale of its manufacturing business in other income in the Company's condensed consolidated statements of operations. The gain was computed as follows:

(in thousands)	March 10, 2022
Cash received	$	130,000
Plus: Fair value of equity method investment		31,223
Less: Carrying value of transferred assets		(29,974	)
Gain on sale of business	$	131,249

During the nine months ended September 30, 2023, the Company determined that the fair value of its investment in OXB Solutions was negatively impacted due to a change in OXB Solutions' forecasted performance relative to expected performance when the Company initially invested in OXB Solutions. The Company determined that the decline in value was deemed to be other than temporary and recorded an impairment charge of $3.8 million to reduce its equity method investment to fair value. The impairment charge is included in the loss on equity method investment in the Company's condensed consolidated statements of operations.

In addition, the Company records its share of income or losses from OXB Solutions on a quarterly basis. For the nine months ended September 30, 2023, the Company recorded $8.1 million representing its share of OXB Solution's net loss for the period. As of September 30, 2023, the carrying value of the equity method investment was $14.0 million.

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Property and Equipment, Net

9 Months Ended

Sep. 30, 2023

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT, NET

6. PROPERTY AND EQUIPMENT, NET

Property and equipment, net consists of the following:

	As of
	September 30, 2023		December 31, 2022
	(in thousands)
Laboratory equipment	$	—	$	6,025
Computers and purchased software		—		644
Furniture and fixtures		—		645
Property and equipment, at cost		—		7,314
Less: accumulated depreciation and amortization		—		(6,236	)
Property and equipment, net	$	—	$	1,078

In August 2023, consistent with its decision to stop further development of its programs and explore, review and evaluate a range of potential strategic options available to the Company, the Company committed to a plan to sell its remaining property and equipment and therefore has classified the amount as assets held for sale on the consolidated balance sheet as of September 30, 2023. The assets held for sale were reported at the lower of the carrying amount or fair value with no depreciation expense taken after August 2023.

Depreciation expense for the three and nine months ended September 30, 2023 was approximately $0.1 million and $0.6 million, respectively, compared to $0.3 million and $1.0 million, respectively for the three and nine months ended September 30, 2022. The Company had approximately $0.4 million of disposals of property and equipment during the three and nine months ended September 30, 2023. The Company had no disposals of property and equipment during the three and nine months ended September 30, 2022.

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Accrued Expenses and Other Liabilities

9 Months Ended

Sep. 30, 2023

Payables and Accruals [Abstract]

ACCRUED EXPENSES AND OTHER LIABILITIES

7. ACCRUED EXPENSES AND OTHER LIABILITIES

Accrued expenses and other liabilities consist of the following:

	As of
	September 30, 2023		December 31, 2022
	(in thousands)
Accrued research and development expenses	$	8,198	$	9,447
Accrued compensation and benefits		6,660		5,953
Accrued professional fees		648		1,052
Accrued other		205		2,263
Total accrued expenses and other liabilities	$	15,711	$	18,715

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Restructuring and Other Charges

9 Months Ended

Sep. 30, 2023

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND OTHER CHARGES

8. RESTRUCTURING AND OTHER CHARGES

On July 25, 2023, the Company's Board of Directors approved a process to explore, review and evaluate a range of potential strategic options available to the Company, including, without limitation, an acquisition, merger, reverse merger, sale of assets, strategic partnerships or other transactions. Therefore, based on cost-reduction initiatives intended to reduce the Company’s ongoing operating expenses and maximize shareholder value as the Company plans to pursue strategic options, the Company's Board of Directors also approved a reduction in the Company’s workforce by approximately 80 employees, or 86% of the Company's workforce as of July 2023. In connection with this corporate restructuring, the Company recorded a restructuring charge for severance and related costs of $6.9 million in the Company's condensed consolidated statements of operations during the three months ended September 30, 2023.

The Company’s restructuring liability, which was included in accrued compensation and benefits, consisted of the following:

(in thousands)	Employee-Related Costs
Accrued restructuring balance at January 1, 2023	$	-
Expenses incurred		6,895
Payments		(2,154	)
Accrued restructuring balance at September 30, 2023	$	4,741

The Company had previously granted certain of the terminated employees restricted stock units (“RSUs”) that vest in annual installments based on continued service to the Company, as well as options to purchase shares of the Company’s common stock that typically vest over a period of four years. In connection with the reduction in workforce, the Company agreed to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates, and also modify the stock options for terminated employees such that subject to the satisfaction of severance conditions, the terminated employees’ vested options will remain outstanding and exercisable until the first anniversary of each employee’s termination date. These equity modifications, described in detail in Note 10, resulted in a net reduction to stock based compensation expense of $0.3 million reflected within restructuring and other charges in the Company's condensed consolidated statements of operations during the three months ended September 30, 2023.

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Commitments and Contingencies

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

9. COMMITMENTS AND CONTINGENCIES

Operating Leases—In December 2017, the Company entered into a noncancelable operating lease for approximately 67,000 square feet of research and development, manufacturing and general office space in Bedford, Massachusetts. Prior to a subsequent amendment described below, the lease was set to expire in February 2027 with an option for an additional five-year term. Rent became due under the lease in two phases; rent on the first 46,000 square feet started in September 2018 and rent on the remaining 21,000 square feet started in March 2019. The initial annual base rent was $39.50 per square foot and increases by three percent annually. The Company is obligated to pay, on a pro-rata basis, real estate taxes and operating costs related to the premises. The lease agreement allowed for a tenant improvement allowance not to exceed $10.9 million, which the Company received in full, to be applied to the total cost of tenant improvements to the leased premises. The unamortized balance of the tenant improvement allowance was included in deferred rent incentives and recorded as a reduction to operating right-of-use asset upon adoption of the new leasing standards.

In November 2021, the Company entered into an amendment of its December 2017 lease agreement (the “Lease Amendment”) for its corporate headquarters in Bedford, Massachusetts. The Lease Amendment increases the space under lease by approximately 23,011 square feet (the "Expansion Premises") and extended the expiration date of the existing premises under the lease from February 2027 to June 2030. The payment term with respect to the Expansion Premises commenced on May 1, 2022 and continues for a period of ten years and five months. The term of the Expansion Premises and the existing premises are not coterminous. Annual base rent for the existing premise under the Lease Amendment is approximately $4.7 million beginning on March 1, 2027, and increases by three percent annually; annual base rent for the Expansion Premises is approximately $1.4 million per year and increases by three percent annually. The Lease Amendment allows for tenant improvement allowances not to exceed $6.3 million in the aggregate. The Lease Amendment was accounted for as a lease modification and the right-of-use asset and operating lease liability for the existing premises were remeasured at the modification date, which resulted in an increase of $10.9 million to both the right-of-use asset and operating lease liabilities. In February 2022, the Company revised its assumption for when it expects to utilize the tenant improvement allowances. This change in assumption was accounted for as a lease modification and the right-of-use asset and operating lease liability for the existing premises were remeasured at the modification date, which resulted in an increase of $0.2 million to both the right-of-use asset and operating lease liabilities.

In March 2022, in accordance with its transaction with OXB Solutions, the Company assigned all of its right, title and interest in, to and under its corporate headquarters lease to OXB Solutions and entered into a sublease agreement whereby OXB Solutions subleased certain premises in its facility to Homology. The Company was not released from being the primary obligor under such lease as of September 30, 2023 and therefore the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s balance sheet and the Company acted as sublessor to OXB Solutions for accounting purposes. See Note 5 for details. During the nine months ended September 30, 2023, the Company received $2.3 million in sublease payments from OXB Solutions, which is recorded as a reduction to lease cost. In October 2023, the Company was released from being primary obligor under the lease (see Note 14).

In September 2022, the Company concluded that 100% of the tenant improvement allowances would be utilized by OXB Solutions. This change in assumption was accounted for as a lease modification and the right-of-use asset and operating lease liability for the existing premises were remeasured at the modification date, which resulted in an increase of $6.1 million to both the right-of-use asset and operating lease liabilities.

The following table summarizes operating lease costs and variable lease costs, as well as sublease income:

	Nine months ended September 30,
	2023			2022
	(in thousands)
Operating lease costs	$	3,263		$	2,826
Variable lease costs		1,551			1,698
Sublease income		(2,312	)		(1,210	)
Net lease cost	$	2,502		$	3,314

The maturities of the Company's operating lease liabilities and minimum lease payments as of September 30, 2023 were as follows:

For the Years Ending December 31,	Amount (in thousands)
2023		1,134
2024		4,578
2025		4,715
2026		4,857
Thereafter		26,265
Total undiscounted lease payments	$	41,549
Less: imputed interest		(13,211	)
Present value of operating lease liabilities	$	28,338

The following table summarizes the lease term and discount rate as of September 30, 2023:

	September 30, 2023
Weighted-average remaining lease term (years)
Operating leases		7.5
Weighted-average discount rate
Operating leases		10.6	%

The following table summarizes the supplemental cash flow information related to the Company's operating lease:

	Nine months ended September 30,
	2023		2022
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities	$	3,310	$	2,226
Increase in lease liabilities and right-of-use assets due to lease remeasurements	$	—	$	6,262

Legal Proceedings—On March 25, 2022, the Company and certain of its executives were named as defendants in a putative securities class action lawsuit filed in the United States District Court for the Central District of California; Pizzuto v. Homology Medicines, Inc., No. 2:22–CV–01968 (C.D. Cal 2022). The complaint alleges that the Company failed to disclose certain information regarding efficacy and safety in connection with a Phase I/II HMI-102 clinical trial, and seeks damages in an unspecified amount. The

case is in its early stages. The Company believes the claims alleged lack merit and filed a motion to transfer venue (filed September 2, 2022) and a motion to dismiss (filed October 17, 2022). On April 18, 2023, the court granted the motion to transfer, finding that venue was not proper in the Central District of California and transferring the case to the District of Massachusetts. Following the transfer, the case number changed to 1:23-cv-10858-AK (D. Mass.). On May 9, 2023, the Massachusetts court issued an order permitting the parties to submit updated briefs in connection with the motion to dismiss, which were submitted on June 8, 2023, July 13, 2023, and August 3, 2023. The motion to dismiss remains pending. As the outcome is not presently determinable, any loss is neither probable nor reasonably estimable.

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Stock Incentive Plans

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

STOCK INCENTIVE PLANS

. STOCK INCENTIVE PLANS

2015 Stock Incentive Plan

In December 2015, the Company’s Board of Directors adopted the 2015 Stock Incentive Plan (the “2015 Plan”), which provided for the grant of incentive stock options, nonqualified stock options and restricted stock awards to the Company’s employees, officers, directors, advisors, and outside consultants. Stock options granted under the 2015 Plan generally vest over a four-year period and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the 2015 Plan. At September 30, 2023, there were no additional shares available for future grant under the 2015 Plan.

2018 Incentive Award Plan

In March 2018, the Company’s Board of Directors adopted and the Company’s stockholders approved the Homology Medicines, Inc. 2018 Incentive Award Plan (the “2018 Plan” and, together with the 2015 Plan, the “Plans”), which became effective on the day prior to the first public trading date of the Company’s common stock. Upon effectiveness of the 2018 Plan, the Company ceased granting new awards under the 2015 Plan.

The 2018 Plan provides for the grant of incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock or cash-based awards to employees and consultants of the Company and certain affiliates and directors of the Company. The number of shares of common stock initially available for issuance under the 2018 Plan was 3,186,205 shares of common stock plus the number of shares subject to awards outstanding under the 2015 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company on or after the effective date of the 2018 Plan. In addition, the number of shares of common stock available for issuance under the 2018 Plan is subject to an annual increase on the first day of each calendar year beginning on January 1, 2019, and ending on and including January 1, 2028, equal to the lesser of (i) 4% of the Company’s outstanding shares of common stock on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as determined by the Company’s Board of Directors, provided that not more than 20,887,347 shares of common stock may be issued under the 2018 Plan upon the exercise of incentive stock options. Therefore, on January 1, 2023, an additional 2,299,356 shares were added to the 2018 Plan, representing 4% of total common shares outstanding at December 31, 2022. As of September 30, 2023, there were 1,978,793 shares available for future grant under the 2018 Plan.

2018 Employee Stock Purchase Plan

In March 2018, the Company’s Board of Directors adopted and the Company’s stockholders approved the Homology Medicines, Inc. 2018 Employee Stock Purchase Plan (the “2018 ESPP”). The 2018 ESPP allows employees to buy Company stock through after-tax payroll deductions at a discount from market value. The 2018 ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. The number of shares of common stock initially available for issuance under the 2018 ESPP was 353,980 shares of common stock plus an annual increase on the first day of each calendar year, beginning on January 1, 2019, and ending on and including January 1, 2028 equal to the lesser of (i) 1% of the Company’s outstanding shares of common stock on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as determined by the Company’s Board of Directors, provided that not more than 4,778,738 shares of common stock may be issued under the 2018 ESPP. Therefore, on January 1, 2023, an additional 574,839 shares were added to the 2018 ESPP, representing 1% of total common shares outstanding at December 31, 2022. As of September 30, 2023, there were 2,693,911 shares available for future issuance under the 2018 ESPP.

Under the 2018 ESPP, employees may purchase common stock through after-tax payroll deductions at a price equal to 85% of the lower of the fair market value on the first trading day of an offering period or the last trading day of an offering period. The 2018 ESPP generally provides for offering periods of six months in duration that end on the final trading day of each February and August. In accordance with the Internal Revenue Code, no employee will be permitted to accrue the right to purchase stock under the 2018

ESPP at a rate in excess of $25,000 worth of shares during any calendar year during which such a purchase right is outstanding (based on the fair market value per share of the Company’s common stock as of the first day of the offering period).

During the nine months ended September 30, 2023, 133,817 shares were issued under the 2018 ESPP for aggregate proceeds to the Company of approximately $0.2 million. During the nine months ended September 30, 2022, 226,453 shares were issued under the 2018 ESPP for aggregate proceeds to the Company of approximately $0.6 million. Pursuant to the 2018 ESPP, the Company recorded stock-based compensation of less than $0.1 million during the three and nine months ended September 30, 2023 and 2022, respectively.

Stock Options

The fair value of each option award is estimated on the date of grant using the Black-Scholes option pricing model, with the assumptions noted in the table below. Expected volatility for the Company’s common stock was determined based on an average of the historical volatility of a peer group of publicly traded companies that are similar to the Company. The expected term of options was calculated using the simplified method, which represents the average of the contractual term of the option and the weighted-average vesting period of the option. The Company uses the simplified method because it does not have sufficient historical option exercise data to provide a reasonable basis upon which to estimate expected term. The assumed dividend yield is based upon the Company’s expectation of not paying dividends in the foreseeable future. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods commensurate with the expected term of the award. The Company recognizes forfeitures as they occur.

The assumptions used in the Black-Scholes option pricing model are as follows (note that there were no options granted during the three months ended September 30, 2023):

	Three months ended	Nine months ended September 30,
	September 30, 2022	2023	2022
Expected volatility	70.1%	69.2% - 69.7%	68.7% - 70.1%
Weighted-average risk-free interest rate	3.20% - 3.66%	3.45% - 4.22%	1.46% - 3.66%
Expected dividend yield	— %	— %	— %
Expected term (in years)	6.25	5.5 - 6.25	5.5 - 6.25
Underlying common stock fair value	$1.82-$2.82	$0.92-$1.60	$1.78-$4.17

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2023:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
								(in thousands)
Outstanding at January 1, 2023		9,865,734		$	10.96		7.2	$	493
Granted		3,188,150		$	1.53
Exercised		(3,366	)	$	0.47
Cancelled/Forfeited		(623,776	)	$	11.11
Outstanding at September 30, 2023		12,426,742		$	8.55		4.9	$	488
Vested and expected to vest at    September 30, 2023		12,426,742		$	8.55		4.9	$	488
Exercisable at September 30, 2023		7,566,304		$	11.80		4.5	$	421

The total intrinsic value of options exercised during the nine months ended September 30, 2023 and 2022 was insignificant for each period. The weighted-average grant date fair value per share of options granted during the nine months ended September 30, 2023 and 2022 was $1.01 and $1.72, respectively.

Stock Awards Modifications - Corporate Restructuring

In connection with the Company's corporate restructuring (see Note 8), the Company terminated approximately 80 employees and modified approximately 3.3 million existing stock options and approximately 0.4 million existing restricted stock units ("RSUs") granted to these terminated employees in prior periods. The modification of the vested stock options to permit terminated employees

up to one year following their termination date to exercise their options, rather than the 90-day window for terminated employees, is accounted for as a modification under FASB ASC Topic 718, Compensation—Stock Compensation ("ASC 718"). Accordingly, the Company recognized incremental compensation cost on the modification date in an amount equal to the difference between the fair value of the awards before and after the modification. The fair value of the awards immediately before assumes an expected term equal to 90 days from the termination date, whereas the fair value immediately after assumes an expected term equal to one year from the termination date. Total incremental compensation cost recognized in the three months ended September 30, 2023 related to awards that were vested as of the modification date was less than $0.1 million. All unvested stock options were forfeited upon termination and the Company reversed all compensation cost previously recorded on the forfeited awards. Total compensation cost reversed in the three months ended September 30, 2023 was less than $0.1 million.

The terminated employees' RSUs were modified to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates. The accelerated vesting of certain RSUs is accounted for as a Type III (improbable to probable) modification under ASC 718. Accordingly, the Company reversed all compensation cost previously recorded on the awards that are not expected to vest under the original terms. Total compensation cost reversed in the three months ended September 30, 2023 was approximately $0.2 million. Total compensation cost of less than $0.1 million, equal to the modification date fair value, was recognized over the remaining service period, beginning on the modification date and ending on each employee’s termination date.

Stock Awards Modifications - OXB Solutions Transaction

As part of the transaction with OXB Solutions (see Note 5), the Company transferred employees to OXB Solutions and modified approximately 1.6 million existing stock options and approximately 0.1 million existing restricted stock units granted to these transferred employees in prior periods in order to permit such individuals to continue vesting in their awards and exercise their vested options as long as they are employed by and provide services to OXB Solutions. The modification of the unvested stock awards to continue vesting was accounted for as a Type III (improbable to probable) modification under ASC 718. Accordingly, the Company reversed all compensation cost previously recorded on the awards that were not expected to vest under the original terms. Total compensation cost reversed in the three months ended March 31, 2022 was less than $0.1 million. Total compensation cost of $0.8 million, equal to the modification date fair value, will be recognized over the remaining service period. A portion of this total compensation cost will be included as a component of the loss from equity method investment.

The modification of the vested stock awards to permit transferred employees to exercise their options over the remaining life of the award, rather than the 90-day window for terminated employees, was accounted for as a modification under ASC 718. Accordingly, the Company recognized incremental compensation cost on the modification date in an amount equal to the difference between the fair value of the awards before and after modification. The fair value of the awards immediately before modification assumed a 90-day expected term, whereas the fair value immediately after assumed an expected term equal to the remaining life of the modified options. Total incremental compensation cost recognized in the year ended December 31, 2022 related to awards that were vested as of the modification date was $0.4 million.

Restricted Stock Units

The fair value of RSUs is based on the fair market value of the Company's common stock on the date of grant. Each RSU represents a contingent right to receive one share of the Company's common stock upon vesting. In general, RSUs vest annually in two or three equal installments on January 1st of each year after the grant date. The following table summarizes the Company's RSU activity for the nine months ended September 30, 2023:

	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2023		543,179		$	6.12
Granted		483,850		$	1.60
Vested		(281,117	)	$	5.31
Forfeited		(258,184	)	$	2.54
Outstanding at September 30, 2023		487,728		$	3.04

Stock-based Compensation Expense

The Company recognizes compensation expense for awards to employees based on the grant date fair value of stock-based awards on a straight-line basis over the period during which an award holder provides service in exchange for the award, which is generally the vesting period. The Company recorded stock-based compensation expense related to stock options, shares purchased under the 2018 ESPP, restricted stock units and stock award modifications as follows:

	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
	(in thousands)
Research and development	$	230	$	889	$	1,507	$	4,143
General and administrative		1,477		1,882		4,970		5,822
	$	1,707	$	2,771	$	6,477	$	9,965

As of September 30, 2023, there was $10.5 million of unrecognized compensation expense related to unvested employee and non-employee share-based compensation arrangements granted under the Plans. The unrecognized compensation expense is estimated to be recognized over a period of 2.2 years at September 30, 2023.

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Net Income (Loss) Per Share

9 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

NET INCOME (LOSS) PER SHARE

11. NET INCOME (LOSS) PER SHARE

Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding during the applicable period. Diluted net income (loss) per share incorporates the additional shares issuable upon assumed exercise of stock options and the vesting of restricted stock units, except in such case when their inclusion would be anti-dilutive.

	Three months ended September 30,						Nine months ended September 30,
(in thousands, except per share amounts)	2023			2022			2023			2022
Numerator:
Net income (loss)	$	(32,954	)	$	(33,726	)	$	(96,842	)	$	29,290
Denominator:
Weighted-average common shares outstanding-basic		57,853,132			57,447,192			57,788,755			57,372,399
Dilutive securities		—			—			—			528,899
Weighted-average common shares outstanding-diluted		57,853,132			57,447,192			57,788,755			57,901,298
Net income (loss) per share-basic	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51
Net income (loss) per share-diluted	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51

For the three and nine months ended September 30, 2023, as well as for the three months end September 30, 2022, the effect of dilutive securities including stock options, restricted stock units and unvested common stock from early exercise of options, was excluded from the denominator for the calculation of diluted net loss per share because the Company recognized a net loss for the periods and their inclusion would be anti-dilutive. Anti-dilutive securities excluded for the three months ended September 30, 2023 and 2022 were 12,993,266 and 9,933,508, respectively, and for the nine months ended September 30, 2023 and 2022 were 12,507,026 and 9,048,927, respectively.

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Pfizer Stock Purchase Agreement

9 Months Ended

Sep. 30, 2023

Pfizer Inc.

PFIZER STOCK PURCHASE AGREEMENT

12. PFIZER STOCK PURCHASE AGREEMENT

On November 9, 2020, the Company entered into a common stock purchase agreement (the “Stock Purchase Agreement”) with Pfizer Inc. (“Pfizer”), pursuant to which the Company agreed to issue and sell to Pfizer 5,000,000 shares of the Company’s common stock through a private placement transaction (the “Private Placement”) at a purchase price of $12.00 per share, for an aggregate purchase price of $60.0 million. The shares of common stock sold to Pfizer were subject to a one-year lock-up from closing, during which time Pfizer was prohibited from selling or otherwise disposing of such shares.

Under the Stock Purchase Agreement, Pfizer was granted an exclusive right of first refusal (the “ROFR”) for a 30-month period (the “ROFR Period”) beginning on the date of the closing of the Private Placement (collectively, the “ROFR Provision”), to negotiate a potential collaboration on the development and commercialization of HMI-102 and HMI-103. The ROFR Period expired on May 9, 2023. In addition to the ROFR, the Stock Purchase Agreement provided for an information sharing committee (the “Information Committee”), comprised of representatives of each company, which served as a forum for sharing information regarding the development of HMI-102 and HMI-103 during the ROFR Period.

The Company recorded the issuance of common stock at its estimated fair value of $52.0 million, which reflected a discount for the lack of marketability of the shares. The remaining $8.0 million of aggregate purchase price was allocated to the other elements of the Stock Purchase Agreement, which represented a contract with a customer. The Company concluded that the Information Committee represented the only performance obligation under the contract. The ROFR did not provide Pfizer with a material right and was therefore not a performance obligation. As such, the Company allocated the $8.0 million to the Information Committee obligation.

The Company recognizes revenue over time as the measure of progress, which it believes best depicts the transfer of control to Pfizer. The Information Committee met regularly over the ROFR Period to share information which resulted in recognition of the transaction price over the 30-month ROFR Period.

During the nine months ended September 30, 2023, the Company recognized collaboration revenue of $1.2 million, compared to $0.8 million and $2.4 million, respectively for the three and nine months ended September 30, 2022. As the ROFR Period expired in May 2023, there was no revenue recognized during the three months ended September 30, 2023. There was no deferred revenue related to the Company’s obligation to Pfizer as of September 30, 2023. As of December 31, 2022, there was approximately $1.2 million of deferred revenue related to the Company’s obligation to Pfizer.

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Related Party Transactions

9 Months Ended

Sep. 30, 2023

Related Party Transactions [Abstract]

RELATED PARTY TRANSACTIONS

13. RELATED PARTY TRANSACTIONS

Oxford Biomedica Solutions LLC

As described in Note 5, the Company has significant influence over, but does not control, OXB Solutions through its noncontrolling representation on OXB Solution’s board of directors and the Company’s equity interest in OXB Solutions. In March 2022, concurrently with the closing of the transaction with OXB Solutions, the Company entered into certain ancillary agreements with OXB Solutions including a supply agreement, a lease assignment and assumption agreement, a sublease agreement and a transitional services agreement.

Supply Agreement

Pursuant to the terms of the Manufacturing and Supply Agreement with OXB Solutions entered into in March 2022 (the "Supply Agreement"), the Company agreed to purchase from OXB Solutions at least 50% of its clinical supply requirements of AAV-based products during the initial term of the supply agreement. The Supply Agreement provides for an initial term of three years, which may be extended for an additional one-year term. Under the Supply Agreement, the Company is committed to purchase a minimum number of batches of drug substance and drug product, as well as process development services, totaling approximately $29.7 million by the fiscal year ending December 31, 2023. As of September 30, 2023, the Company had approximately $1.4 million in remaining purchase obligations to OXB Solutions pursuant to the Supply Agreement. There are no minimum purchase commitments in 2024 (year three) of the Supply Agreement. After the initial term, the Company will have the right to terminate the Supply Agreement for convenience or other reasons specified in the Supply Agreement upon prior written notice. Either party may terminate the Supply Agreement upon an uncured material breach by the other party or upon the bankruptcy or insolvency of the other party.

During the three and nine months ended September 30, 2023, the Company recorded purchases of drug substance from OXB Solutions related to the Supply Agreement of $8.4 million and $21.7 million, respectively, as well as purchases of process development services of approximately $3.1 million and $5.8 million, respectively, and stability services and other support services of approximately $0.4 million and $1.2 million, respectively. During the three and nine months ended September 30, 2022, the Company recorded purchases of drug substance from OXB Solutions related to the Supply Agreement of $6.0 million and $7.5 million, respectively, as well as purchases of process development services of approximately $2.2 million and $10.2 million, respectively. These amounts are included within research and development expenses on the Company's condensed consolidated statements of operations. The amounts due to OXB Solutions under the Supply Agreement were $12.6 million and $5.2 million as of September 30, 2023 and December 31, 2022, respectively, and were included in accounts payable and accrued expenses and other liabilities on the Company's condensed consolidated balance sheets.

Lease Assignment and Sublease Agreement

As described in Note 9, the Company leases space for research and development, manufacturing and general office space in Bedford, Massachusetts. In March 2022, the Company and OXB Solutions entered into a lease assignment and assumption agreement pursuant to which Homology assigned all of its right, title and interest in, to and under this lease to OXB Solutions and a sublease agreement whereby OXB Solutions subleased certain premises in its facility to Homology. However, as of and for the three and nine

months ended September 30, 2023, the Company remained jointly and severally liable for the payment of rent under this lease and had not been released from being the primary obligor under such lease and therefore the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s condensed consolidated balance sheets. Therefore, the Company is recording sublease income from OXB Solutions as if it were subleasing the space to OXB Solutions. On October 1, 2023, the Company was released from being the primary obligor under the lease (see Note 14).

During the three and nine months ended September 30, 2023, the Company recorded sublease income of $0.8 million and $2.3 million, respectively, related to the sublease agreement with OXB Solutions. During the three and nine months ended September 30, 2022, the Company recorded sublease income of $0.5 million and $1.2 million, respectively, related to the sublease agreement with OXB Solutions. This amount was recognized as a reduction to lease expense in the Company's condensed consolidated statements of operations.

During 2023, OXB Solutions assumed responsibility for paying the landlord for invoices related to the leased property and, as such, the Company began making direct payments to OXB Solutions for amounts due to OXB Solutions under the sublease. Therefore, as of September 30, 2023, the amount of sublease income payable to OXB Solutions was $0.1 million and was included in accrued expenses on the Company's condensed consolidated balance sheets. As of December 31, 2022, the amount of sublease income receivable from OXB Solutions was $0.5 million and was included in prepaid expenses and other current assets on the Company's condensed consolidated balance sheets.

Transitional Services Agreement

Under the transitional services agreement with OXB Solutions (the “Services Agreement”), the Company is performing certain services for the benefit of OXB Solutions and OXB Solutions is performing certain services for the benefit of the Company. The term of the Services Agreement will not exceed eighteen months and lasts until the earlier of termination for convenience, termination for cause in the event of an uncured material breach, termination as a result of bankruptcy of either party, and expiration or termination of the only remaining outstanding service as set forth in the Services Agreement. Each company is fully reimbursing the other for these services. The Services Agreement was substantially complete as of September 30, 2023.

Expenses incurred by the Company for services provided by OXB Solutions recognized under the Services Agreement totaled $0.3 million for the nine months ended September 30, 2023, and $0.2 million and $0.5 million for the three and nine months ended September 30, 2022, respectively, and are presented within research and development expenses in the condensed consolidated statements of operations as the services related to facilities support within the Company's research and development labs. As of September 30, 2023 and December 31, 2022, the amount due to OXB Solutions under the Services Agreement was $0.1 million at each balance sheet date, and was included in accrued expenses and other liabilities on the Company's condensed consolidated balance sheets.

The Company provided finance, human resources, IT and legal services to OXB Solutions under the Services Agreement and recognized $0.5 million for the nine months ended September 30, 2023, and $0.8 million and $1.7 million for the three and nine months ended September 30, 2022, respectively, for amounts reimbursed by OXB Solutions as a reduction to general and administrative expense in the Company's condensed consolidated statements of operations. The Company did not provide reimbursable services to OXB Solutions under the Services Agreement during the three months ended September 30, 2023. As of December 31, 2022, the Company had a receivable balance of $0.3 million from OXB Solutions which was recorded as a component of prepaid expenses and other current assets in the Company's condensed consolidated balance sheets. Pursuant to the Services Agreement, the Company has been paying vendors on OXB Solutions' behalf; this process will be fully transitioned to OXB Solutions in 2023. As of December 31, 2022, the amount receivable from OXB Solutions for amounts paid to vendors on their behalf was $1.1 million and was included in prepaid expenses and other current assets on the Company's condensed consolidated balance sheets.

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Subsequent Events

9 Months Ended

Sep. 30, 2023

Subsequent Events [Abstract]

SUBSEQUENT EVENTS

14. SUBSEQUENT EVENTS

On September 25, 2023, the Company signed and executed a release letter with its lessor related to its headquarters in Bedford, MA. The lessor agreed to release the Company of all obligations under the lease effective October 1, 2023 (the “Release Date”) in exchange for a $0.1 million cash payment. For accounting purposes, the release letter is not considered a modification of the lease until the Release Date as the Company is not released from its obligations under the lease until such date. As of September 30, 2023, the lease had a remaining right-of-use asset balance of $19.5 million and an operating lease liability balance of $28.3 million. On October 1, 2023, the Company will write off the right-of-use asset and operating lease liability and record the difference as a gain of $8.8 million within other income on the condensed consolidated statements of operations. Because the Company’s sublease agreement with OXB Solutions remains in effect after termination of the head lease, the Company will recognize a new right-of-use asset and an operating lease liability of $1.6 million, which equals the present value of the future sublease payments owed to OXB Solutions for

the remaining term of the sublease. The Company is actively searching for a subtenant to take over its sublease with OXB Solutions and is evaluating whether there is any impairment of the related right-of-use asset.

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Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2023

Accounting Policies [Abstract]

Basis of Presentation

Basis of Presentation— The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2022, included in the Company's Annual Report on Form 10-K on file with the SEC.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position as of September 30, 2023, and consolidated results of operations for the three and nine months ended September 30, 2023 and 2022, and cash flows for the nine months ended September 30, 2023 and 2022. Such adjustments are of a normal and recurring nature. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023.

Principles of Consolidation

Principles of Consolidation—The Company’s condensed consolidated financial statements include the accounts of the Company and its subsidiary, Homology Medicines Securities Corporation, a wholly owned Massachusetts corporation, for the sole purpose of buying, selling, and holding securities on the Company’s behalf. All intercompany balances and transactions have been eliminated in the condensed consolidated financial statements.

Use of Estimates

Use of Estimates—The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, accrued research and development expenses and the valuation of the Company's equity method investment. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Comprehensive Income (Loss)

Comprehensive Income (Loss)—Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company’s only element of other comprehensive income (loss) is unrealized gains and losses on available-for-sale investments.

Cash and Cash Equivalents and Restricted Cash

Cash and Cash Equivalents and Restricted Cash—Cash and cash equivalents consist of standard checking accounts, money market accounts and certain investments. The Company considers all highly liquid investments with original or remaining maturities at the time of purchase of 90 days or less to be cash equivalents. The Company did not have any restricted cash at September 30, 2023 or December 31, 2022.

Short-Term Investments

Short-Term Investments—Short-term investments represent holdings of available-for-sale marketable securities in accordance with the Company’s investment policy and cash management strategy. Short-term investments have maturities of greater than 90 days at the time of purchase and mature within one year from the balance sheet date. Investments in marketable securities are recorded at fair value, with any unrealized gains and losses reported within accumulated other comprehensive income as a separate component of stockholders’ equity until realized or until a determination is made that an other-than-temporary decline in market value has occurred. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the

underlying security. Such amortization and accretion, together with interest on securities, are included in interest income in the Company’s condensed consolidated statements of operations. The cost of marketable securities sold is determined based on the specific identification method and any realized gains or losses on the sale of investments are reflected as a component of other income.

Assets Held for Sale

Assets Held for Sale—The Company classifies assets as held for sale when the following conditions are met: (1) management has committed to a plan to sell, (2) the assets are available for immediate sale in their present condition, (3) the Company has initiated an active program to identify a buyer, (4) it is probable that a sale will occur within one year, (5) the assets are actively marketed for sale at a reasonable price in relation to their current fair value, and (6) there is a low likelihood of significant changes to the plan or that the plan will be withdrawn. If all of the aforementioned criteria are met as of the balance sheet date, the assets are presented separately in the consolidated balance sheet as held for sale at the lower of the carrying amount or fair value less costs to sell. The assets are then no longer depreciated or amortized while classified as held for sale.

Equity Method Investment

Equity Method Investment—The Company uses the equity method of accounting to account for an investment in an entity that it does not control, but in which it has the ability to exercise significant influence over operating and financial policies. The Company's proportionate share of the net income or loss of the entity is included in consolidated net loss. Judgments regarding the level of influence over the equity method investment include consideration of key factors such as the Company's ownership interest, representation on the board of directors or other management body and participation in policy-making decisions.

Under the equity method of accounting, the Company’s investment is initially recorded at fair value on the condensed consolidated balance sheets. Upon initial investment, the Company evaluates whether there are basis differences between the carrying value and fair value of the Company’s proportionate share of the investee’s underlying net assets. Typically, the Company amortizes basis differences identified on a straight-line basis over the underlying assets’ estimated useful lives when calculating the attributable earnings or losses, excluding the basis differences attributable to in-process research and development that has no alternative future use. If the Company is unable to attribute all of the basis differences to specific assets or liabilities of the investee, the residual excess of the cost of the investment over the proportional fair value of the investee’s assets and liabilities is considered to be equity method goodwill and is recognized within the equity investment balance, which is tracked separately within the Company’s memo accounts. The Company subsequently records in the condensed consolidated statements of operations its share of income or loss of the other entity within other income/expense, which results in an increase or decrease to the carrying value of the investment. If the share of losses exceeds the carrying value of the Company’s investment, the Company will suspend recognizing additional losses and will continue to do so unless it commits to providing additional funding; however, if there are intra-entity profits this can cause the investment balance to go negative.

The Company evaluates its equity method investments for impairment whenever events or changes in circumstances indicate that a decline in value has occurred that is other than temporary. Evidence considered in this evaluation includes, but would not necessarily be limited to, the financial condition and near-term prospects of the investee, recent operating trends and forecasted performance of the investee, market conditions in the geographic area or industry in which the investee operates and the Company’s strategic plans for holding the investment in relation to the period of time expected for an anticipated recovery of its carrying value. If the investment is determined to have a decline in value deemed to be other than temporary it is written down to estimated fair value.

At September 30, 2023, the Company accounted for its investment in OXB Solutions using the equity method of accounting (see Note 5).

Offering Costs

Offering Costs—The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with equity financings as other current assets until the transactions are completed. After equity financings are complete, these costs are recorded in stockholders’ equity as a reduction of additional paid-in capital generated as a result of the offering.

Leases

Leases—The Company determines if an arrangement is a lease at contract inception. The Company’s contracts are determined to contain a lease when all of the following criteria based on the specific circumstances of the arrangement are met: (1) there is an identified asset for which there are no substantive substitution rights; (2) the Company has the right to obtain substantially all of the economic benefits from the identified asset; and (3) the Company has the right to direct the use of the identified asset.

At the commencement date, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of future lease payments over the expected lease term. The Company’s lease agreements do not provide an implicit rate. As a result, the Company utilizes an estimated incremental borrowing rate to discount lease payments, which is based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or lease incentives received. Operating lease cost is recognized over the expected term on a straight-line basis. The expected lease term includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as

periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option. Variable lease cost is recognized as incurred. Right-of-use assets are periodically evaluated for impairment.

The Company acts as sublessor related to a sublease of a substantial portion of the Company's headquarters that is now occupied by OXB Solutions. Fixed sublease payments received are recorded as a reduction to lease cost. Although Homology assigned all of its right, title and interest in, to and under this lease to OXB Solutions, the Company remained jointly and severally liable for the payment of rent under this lease as of and for the three and nine months ended September 30, 2023. Therefore, the related right-of-use asset and operating lease liability were not derecognized and remained on the Company’s condensed consolidated balance sheets as of September 30, 2023. The Company was released from being the primary obligor under such lease effective October 1, 2023 (see Note 14).

Research and Development Costs

Research and Development Costs—Research and development costs are charged to expense as incurred. Research and development expense consists of expenses incurred in performing research and development activities, including salaries and benefits, materials and supplies, preclinical and clinical expenses, stock-based compensation expense, depreciation of equipment, contract services, and other outside expenses.

Costs for certain development activities are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense.

Income Taxes

Income Taxes—The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s condensed consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. Since inception, the Company has provided a valuation allowance for the full amount of the net deferred tax assets as the realization of the net deferred tax assets has not been determined to be more likely than not.

The Company recorded an income tax benefit of less than $0.1 million and an income tax provision of $0.8 million for the three and nine months ended September 30, 2022, respectively. The year-to-date tax provision predominately resulted from the gain associated with the sale of the Company's manufacturing business due to the transaction with Oxford (see Note 5), offset by available federal and state net operating loss carryforwards and research and development tax credits which are subject to certain limitations as to their utilization. The Company did not record an income tax provision (benefit) for the three and nine months ended September 30, 2023.

Revenue Recognition

Revenue Recognition—Revenue is recognized in accordance with FASB Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”).

Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer.

The promised goods or services in the Company’s arrangements would likely consist of a license, rights to the Company’s intellectual property or research, development and manufacturing services. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers

factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration and variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of consideration to which the Company expects to be entitled to. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

The Company’s contracts may include development and regulatory milestone payments that are assessed under the most likely amount method and constrained until it is probable that a significant revenue reversal would not occur. Milestone payments that are not within the Company’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and regulatory milestones and any related constraint, and if necessary, adjust its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from the Company’s collaboration arrangement.

The Company allocates the transaction price based on the estimated standalone selling price of each performance obligation. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress for its over-time arrangements at each reporting period and, if necessary, updates the measure of progress and revenue recognized.

Net Income (Loss) per Share

Net Income (Loss) per Share—Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding during the period. Diluted net income (loss) per share is computed using the weighted-average number of common shares outstanding during the period and, if dilutive, the weighted-average number of potential shares of common stock. The weighted-average number of common shares included in the computation of diluted net income (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, restricted stock units and unvested shares of common stock.

Common stock equivalent shares are excluded from the computation of diluted net income (loss) per share if their effect is antidilutive. In periods in which the Company reports a net (loss) attributable to common stockholders, diluted net (loss) per share attributable to common stockholders is generally the same as basic net (loss) per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.

Recent Accounting Pronouncements

Recent Accounting Pronouncements—The Jumpstart Our Business Startups Act of 2012 permits an emerging growth company to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. As an emerging growth company, the Company has elected to take advantage of this extended transition period.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) to improve financial reporting by requiring more timely recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. ASU 2016-13 requires the measurement

of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. ASU 2016-13 also requires enhanced disclosures to help investors and other financial statement users better understand significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. The Company adopted ASU 2016-13 on January 1, 2023. The adoption of ASU 2016-13 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

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Short-Term Investments (Tables)

9 Months Ended

Sep. 30, 2023

Investments Disclosure [Abstract]

Summary of Short Term Investments

The following table summarizes the Company’s short-term investments as of September 30, 2023 and December 31, 2022:

As of September 30, 2023	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Commercial paper	$	3,965	$	—	$	(2	)	$	3,963
US Treasury securities		55,268		6		(7	)		55,267
Corporate debt securities		14,990		—		(33	)		14,957
Total	$	74,223	$	6	$	(42	)	$	74,187
As of December 31, 2022	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Commercial paper	$	57,138	$	—	$	—		$	57,138
US Treasury securities		65,160		—		(335	)		64,825
Corporate debt securities		19,146		—		(69	)		19,077
Total	$	141,444	$	—	$	(404	)	$	141,040

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Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on Recurring Basis

Assets measured at fair value on a recurring basis were as follows:

Description	September 30, 2023		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	28,375	$	28,375	$	—	$	—
Total cash equivalents	$	28,375	$	28,375	$	—	$	—
Short-term investments:
Commercial paper	$	3,963	$	—	$	3,963	$	—
US Treasury securities		55,267		—		55,267		—
Corporate debt securities		14,957		—		14,957		—
Total short-term investments	$	74,187	$	—	$	74,187	$	—
Total financial assets	$	102,562	$	28,375	$	74,187	$	—
Description	December 31, 2022		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	33,967	$	33,967	$	—	$	—
Total cash equivalents	$	33,967	$	33,967	$	—	$	—
Short-term investments:
Commercial paper	$	57,138	$	—	$	57,138	$	—
US Treasury securities		64,825		—		64,825		—
Corporate debt securities		19,077		—		19,077		—
Total short-term investments	$	141,040	$	—	$	141,040	$	—
Total financial assets	$	175,007	$	33,967	$	141,040	$	—

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Equity Method Investment (Tables)

9 Months Ended

Sep. 30, 2023

Equity Method Investment, Summarized Financial Information [Abstract]

Gain on sale of equity method investment

The gain was computed as follows:

(in thousands)	March 10, 2022
Cash received	$	130,000
Plus: Fair value of equity method investment		31,223
Less: Carrying value of transferred assets		(29,974	)
Gain on sale of business	$	131,249

During the nine months ended September 30, 2023, the Company determined that the fair value of its investment in OXB Solutions was negatively impacted due to a change in OXB Solutions' forecasted performance relative to expected performance when the Company initially invested in OXB Solutions. The Company determined that the decline in value was deemed to be other than temporary and recorded an impairment charge of $3.8 million to reduce its equity method investment to fair value

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Property and Equipment, Net (Tables)

9 Months Ended

Sep. 30, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consists of the following:

	As of
	September 30, 2023		December 31, 2022
	(in thousands)
Laboratory equipment	$	—	$	6,025
Computers and purchased software		—		644
Furniture and fixtures		—		645
Property and equipment, at cost		—		7,314
Less: accumulated depreciation and amortization		—		(6,236	)
Property and equipment, net	$	—	$	1,078

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Accrued Expenses and Other Liabilities (Tables)

9 Months Ended

Sep. 30, 2023

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Liabilities

Accrued expenses and other liabilities consist of the following:

	As of
	September 30, 2023		December 31, 2022
	(in thousands)
Accrued research and development expenses	$	8,198	$	9,447
Accrued compensation and benefits		6,660		5,953
Accrued professional fees		648		1,052
Accrued other		205		2,263
Total accrued expenses and other liabilities	$	15,711	$	18,715

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Restructuring and Other Charges (Tables)

9 Months Ended

Sep. 30, 2023

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Liability in Accrued Compensation and Benefits

The Company’s restructuring liability, which was included in accrued compensation and benefits, consisted of the following:

(in thousands)	Employee-Related Costs
Accrued restructuring balance at January 1, 2023	$	-
Expenses incurred		6,895
Payments		(2,154	)
Accrued restructuring balance at September 30, 2023	$	4,741

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Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of Operating Lease Costs, Variable Lease Costs and Sub Lease Income

The following table summarizes operating lease costs and variable lease costs, as well as sublease income:

	Nine months ended September 30,
	2023			2022
	(in thousands)
Operating lease costs	$	3,263		$	2,826
Variable lease costs		1,551			1,698
Sublease income		(2,312	)		(1,210	)
Net lease cost	$	2,502		$	3,314

Schedule of Operating Lease Liabilities and Minimum Lease Payments

The maturities of the Company's operating lease liabilities and minimum lease payments as of September 30, 2023 were as follows:

For the Years Ending December 31,	Amount (in thousands)
2023		1,134
2024		4,578
2025		4,715
2026		4,857
Thereafter		26,265
Total undiscounted lease payments	$	41,549
Less: imputed interest		(13,211	)
Present value of operating lease liabilities	$	28,338

Schedule of Lease Term and Discount Rate

The following table summarizes the lease term and discount rate as of September 30, 2023:

	September 30, 2023
Weighted-average remaining lease term (years)
Operating leases		7.5
Weighted-average discount rate
Operating leases		10.6	%

Schedule of Operating Lease Liabilities

The following table summarizes the supplemental cash flow information related to the Company's operating lease:

	Nine months ended September 30,
	2023		2022
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities	$	3,310	$	2,226
Increase in lease liabilities and right-of-use assets due to lease remeasurements	$	—	$	6,262

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Stock Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Options Valuation Assumptions Using a Black-Scholes Option Pricing Model

The assumptions used in the Black-Scholes option pricing model are as follows (note that there were no options granted during the three months ended September 30, 2023):

	Three months ended	Nine months ended September 30,
	September 30, 2022	2023	2022
Expected volatility	70.1%	69.2% - 69.7%	68.7% - 70.1%
Weighted-average risk-free interest rate	3.20% - 3.66%	3.45% - 4.22%	1.46% - 3.66%
Expected dividend yield	— %	— %	— %
Expected term (in years)	6.25	5.5 - 6.25	5.5 - 6.25
Underlying common stock fair value	$1.82-$2.82	$0.92-$1.60	$1.78-$4.17

Summary of Option Activity under Plans

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2023:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
								(in thousands)
Outstanding at January 1, 2023		9,865,734		$	10.96		7.2	$	493
Granted		3,188,150		$	1.53
Exercised		(3,366	)	$	0.47
Cancelled/Forfeited		(623,776	)	$	11.11
Outstanding at September 30, 2023		12,426,742		$	8.55		4.9	$	488
Vested and expected to vest at    September 30, 2023		12,426,742		$	8.55		4.9	$	488
Exercisable at September 30, 2023		7,566,304		$	11.80		4.5	$	421

Summary of Company's RSU Activity

The following table summarizes the Company's RSU activity for the nine months ended September 30, 2023:

	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2023		543,179		$	6.12
Granted		483,850		$	1.60
Vested		(281,117	)	$	5.31
Forfeited		(258,184	)	$	2.54
Outstanding at September 30, 2023		487,728		$	3.04

Schedule of Stock-Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options, shares purchased under the 2018 ESPP, restricted stock units and stock award modifications as follows:

	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
	(in thousands)
Research and development	$	230	$	889	$	1,507	$	4,143
General and administrative		1,477		1,882		4,970		5,822
	$	1,707	$	2,771	$	6,477	$	9,965

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Net Income (Loss) Per Share (Tables)

9 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Schedule of Anti-dilutive Effect Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders

Diluted net income (loss) per share incorporates the additional shares issuable upon assumed exercise of stock options and the vesting of restricted stock units, except in such case when their inclusion would be anti-dilutive.

	Three months ended September 30,						Nine months ended September 30,
(in thousands, except per share amounts)	2023			2022			2023			2022
Numerator:
Net income (loss)	$	(32,954	)	$	(33,726	)	$	(96,842	)	$	29,290
Denominator:
Weighted-average common shares outstanding-basic		57,853,132			57,447,192			57,788,755			57,372,399
Dilutive securities		—			—			—			528,899
Weighted-average common shares outstanding-diluted		57,853,132			57,447,192			57,788,755			57,901,298
Net income (loss) per share-basic	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51
Net income (loss) per share-diluted	$	(0.57	)	$	(0.59	)	$	(1.68	)	$	0.51

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Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended						9 Months Ended
	Mar. 09, 2023	Mar. 10, 2022	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Jul. 31, 2023	Dec. 31, 2022
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from Sale of Equity Method Investments		$ 130,000
Reduction in workforce											86.00%
Net income			$ (32,954)	$ (35,044)	$ (28,844)	$ (33,726)	$ (29,089)	$ 92,105	$ (96,842)	$ 29,290
Loss from operations			(31,001)			$ (32,862)			(89,328)	$ (98,787)
Accumulated deficit			$ 525,979						$ 525,979			$ 429,137
Oxford Biomedica Plc
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Upfront Payment Received		130,000
Proceeds from Sale of Equity Method Investments		$ 50,000
Maximum
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceed from issuance of common stock	$ 250,000
ATM
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Issuance of common stock, net of discounts and issuance costs, Share									0
Proceeds through future financings									$ 75,000
ATM | Oxford Biomedica Plc
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Sale of Stock, Percentage of Ownership after Transaction		80.00%
ATM | Homology Member
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Sale of Stock, Percentage of Ownership after Transaction		20.00%
ATM | Maximum
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds through future financings	$ 75,000

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Summary of Significant Accounting Policies (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Tax positions, description			The Company determines whether it is more likely than not that a tax position will be sustained upon examination. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized.
Provision for income taxes	$ 0	$ (46)	$ 0	$ 816
Restricted cash	$ 0		$ 0		$ 0
Less Than [Member]
Provision for income taxes		$ (100)

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Short-Term Investments - Summary of Short Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule Of Cash Cash Equivalents And Available For Sale Securities [Line Items]
Cash equivalents and short-term investments, Amortized Cost	$ 74,223	$ 141,444
Cash equivalents and short-term investments, Unrealized Gains	6	0
Cash equivalents and short-term investments, Unrealized Losses	(42)	(404)
Cash equivalents and short-term investments, Fair Value	74,187	141,040
Commercial Paper
Schedule Of Cash Cash Equivalents And Available For Sale Securities [Line Items]
Cash equivalents and short-term investments, Amortized Cost	3,965	57,138
Cash equivalents and short-term investments, Unrealized Gains	0	0
Cash equivalents and short-term investments, Unrealized Losses	(2)	0
Cash equivalents and short-term investments, Fair Value	3,963	57,138
US Treasury Securities
Schedule Of Cash Cash Equivalents And Available For Sale Securities [Line Items]
Cash equivalents and short-term investments, Amortized Cost	55,268	65,160
Cash equivalents and short-term investments, Unrealized Gains	6	0
Cash equivalents and short-term investments, Unrealized Losses	(7)	(335)
Cash equivalents and short-term investments, Fair Value	55,267	64,825
Corporate Debt Securities
Schedule Of Cash Cash Equivalents And Available For Sale Securities [Line Items]
Cash equivalents and short-term investments, Amortized Cost	14,990	19,146
Cash equivalents and short-term investments, Unrealized Gains	0	0
Cash equivalents and short-term investments, Unrealized Losses	(33)	(69)
Cash equivalents and short-term investments, Fair Value	$ 14,957	$ 19,077

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Short-Term Investments - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Cash Cash Equivalents And Available For Sale Securities [Abstract]
Realized gains and losses on available-for-sale securities	$ 0	$ 0	$ 0	$ 0
Contractual maturity date of investments			less than one year

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Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 28,375	$ 33,967
Short-term investments	74,187	141,040
Financial assets, fair value	102,562	175,007
Money Market Mutual Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	28,375	33,967
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	3,963	57,138
US Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	55,267	64,825
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	14,957	19,077
Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	28,375	33,967
Financial assets, fair value	28,375	33,967
Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1) | Money Market Mutual Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	28,375	33,967
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	74,187	141,040
Financial assets, fair value	74,187	141,040
Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	3,963	57,138
Significant Other Observable Inputs (Level 2) | US Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	55,267	64,825
Significant Other Observable Inputs (Level 2) | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 14,957	$ 19,077

XML

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Transfers between fair value measure levels	$ 0	$ 0	$ 0	$ 0

XML

Equity Method Investment (Additional Information) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Mar. 10, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Gain on sale of business	$ 131,249	$ 0	$ 0	$ 0	$ 131,249
Loss from equity method investment		(3,376)	$ (2,179)	(11,917)	$ (4,131)
Equity method investment		13,957		13,957		$ 25,814
Maximum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equity method investment cash consideration		$ 74,100		74,100
OXB Solutions [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Fair value of investment	31,200
Gain on sale of business	$ 131,200
Loss from equity method investment				$ 8,100
Equity method investments, ownership description				The valuation included certain subjective assumptions including discounts for lack of control and marketability given the consideration paid for OXB Solutions was for a controlling interest in the entity and the Company owns a noncontrolling interest.
Equity method investment, description of principal activities	Homology will have an option to cause OXB to purchase from Homology, in each case all of Homology's equity ownership interest in OXB Solutions at a price equal to 5.5 times the revenue for the immediately preceding 12-month period (together, the "Options"), subject to a maximum amount of $74.1 million
Impairment Charge				$ 3,800
OXB
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Transferred units	130,000
Equity Securities Purchase Agreement | OXB Solutions [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common Unit, Issued	175,000
Contributed cash	$ 50,000
Additional units issued	50,000
Equity method investment, ownership percentage	100.00%
Equity Securities Purchase Agreement | Homology
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equity method investment, ownership percentage	20.00%
Ownership interests, units	45,000
Equity Securities Purchase Agreement | OXB
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Transferred units, value	$ 130,000
Equity method investment, ownership percentage	80.00%
Ownership interests, units	180,000

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Equity Method Investment - Schedule of equity method investment fair value (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Mar. 10, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Equity Method Investment, Summarized Financial Information [Abstract]
Cash received	$ 130,000
Plus: Fair value of equity method investment	31,223
Less: Carrying value of transferred assets	(29,974)
Gain on sale of business	$ 131,249	$ 0	$ 0	$ 0	$ 131,249

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Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 0	$ 7,314
Less: accumulated depreciation and amortization	0	(6,236)
Property and equipment, net	0	1,078
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, at cost	0	6,025
Computers and Purchased Software
Property Plant And Equipment [Line Items]
Property and equipment, at cost	0	644
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 0	$ 645

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Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Property Plant And Equipment [Line Items]
Depreciation	$ 100	$ 300	$ 578	$ 997
Depreciation expense on asset held for sale			0
Disposal of property and equipment	$ 400	$ 0	$ 400	$ 0

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Accrued Expenses and Other Liabilities - Schedule of Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued research and development expenses	$ 8,198	$ 9,447
Accrued compensation and benefits	6,660	5,953
Accrued professional fees	648	1,052
Accrued other	205	2,263
Total accrued expenses and other liabilities	$ 15,711	$ 18,715

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Restructuring and Other Charges - Accrued Compensation and Benefits (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Restructuring and Related Activities [Abstract]
Accrued restructuring, Beginning Balance	$ 0
Expenses incurred	6,895
Payments	(2,154)
Accrued restructuring, Ending Balance	$ 4,741

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Restructuring and Other Charges (Additional Information) (Details) $ in Millions		3 Months Ended	9 Months Ended
	Jul. 25, 2023 Employee	Sep. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)
Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Stock based compensation			$ 0.3
Corporate Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Vest over period			4 years
Corporate Restructuring [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance and related Cost		$ 6.9
Reduction in employee | Employee	80
Reduction in employee pecentage	86.00%

XML

Commitment and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended			9 Months Ended
	Feb. 28, 2022 USD ($)	Dec. 31, 2017 ft² Phase $ / ft²	Nov. 30, 2017 USD ($) ft²	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Commitment And Contingencies [Line Items]
Sublease income				$ 2,312	$ 1,210
Tenant improvement allowance			$ 6,300
Increase in Lease Liability				10,900
Increase (Decrease) in right-of-use asset	$ 200
OXB Solutions [Member]
Commitment And Contingencies [Line Items]
Sublease income				2,300
Increase (Decrease) in right-of-use asset				$ 6,100
Tenant improvement allowances percentage				100.00%
Maximum
Commitment And Contingencies [Line Items]
Tenant improvement allowance				$ 10,900
Bedford, Massachusetts
Commitment And Contingencies [Line Items]
Operating lease expiration year and month		2027-02	2027-02
Sublease aggregate base rent obligation			$ 1,400	$ 4,700
Office space leased | ft²		67,000	23,011
Lessee, operating lease, lease not yet commenced, renewal term		5 years
Number of phases | Phase		2
Initial annual base rent per square foot | $ / ft²		39.5
Percentage increase in initial annual base rent per square foot.		3.00%	3.00%
Bedford, Massachusetts | Phase One
Commitment And Contingencies [Line Items]
Office space leased | ft²		46,000
Rent due date		2018-09
Bedford, Massachusetts | Phase Two
Commitment And Contingencies [Line Items]
Office space leased | ft²		21,000
Rent due date		2019-03

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Commitment and Contingencies - Schedule of Operating Lease Costs, Variable Lease Costs and Sub Lease Income (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 3,263	$ 2,826
Variable lease costs	1,551	1,698
Sublease income	(2,312)	(1,210)
Net lease cost	$ 2,502	$ 3,314

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Commitments and Contingencies - Schedule of Operating Lease Liabilities and Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2023	$ 1,134
2024	4,578
2025	4,715
2026	4,857
Thereafter	26,265
Total undiscounted lease payments	41,549
Less: imputed interest	(13,211)
Present value of operating lease liabilities	$ 28,338

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Commitments and Contingencies - Schedule of Lease Term and Discount Rate (Details)	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years), Operating leases	7 years 6 months
Weighted-average discount rate, Operating leases	10.60%

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Commitments and Contingencies - Summary of Cash Paid for Company's Operating Lease Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 3,310	$ 2,226
Increase in lease liabilities and right-of-use assets due to lease remeasurements	$ 0	$ 6,262

XML

Stock Incentive Plans - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended			9 Months Ended
	Jan. 01, 2023 shares	Mar. 31, 2018 shares	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2023 USD ($) Employee $ / shares shares	Sep. 30, 2022 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate proceeds from shares issued under the plan | $						$ 168	$ 563
Stock-based compensation | $			$ 1,707	$ 2,771		$ 6,477	$ 9,965
Weighted-average grant date fair value per share for options granted | $ / shares						$ 1.01	$ 1.72
Share-Based Goods and Nonemployee Services Transaction, Modification of Terms, Incremental Compensation Cost | $			100			$ 400
Total compensation cost reversed | $			$ 100
Number of employees get terminated | Employee						80
2015 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting period						4 years
Stock options expiration period						10 years
Number of additional shares available for future grant | shares			0			0
2018 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for issuance | shares		3,186,205
Allowed annual percentage increase in shares authorized as percentage of outstanding shares of common stock	4.00%	4.00%
Maximum shares of common stock may be issued | shares		20,887,347
Number of shares outstanding available for future grant | shares	2,299,356		1,978,793			1,978,793
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for issuance | shares		353,980
Allowed annual percentage increase in shares authorized as percentage of outstanding shares of common stock	1.00%	1.00%
Number of shares outstanding available for future grant | shares	574,839		2,693,911			2,693,911
Maximum shares allowed to be issued under ESPP | shares		4,778,738
Purchase of common stock through payroll deductions expressed in percentage of fair market value						85.00%
Common stock offering period						6 months
Number of shares issued to the plan | shares						133,817	226,453
Aggregate proceeds from shares issued under the plan | $						$ 200	$ 600
Stock-based compensation | $			$ 100	$ 100		100	$ 100
Excess of accrued right to purchase stock | $						25,000
2015 and 2018 Stock Incentive Plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense | $			10,500			$ 10,500
Unrecognized compensation expense estimated to be recognized over period						2 years 2 months 12 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock award and exercise vested option to transferred employees | shares						400,000
Compensation cost, Total | $			100			$ 100
Total compensation cost reversed | $			200
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock award and exercise vested option to transferred employees | shares						3,300,000
OXB Solutions [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost, Total | $			$ 800			$ 800
Total compensation cost reversed | $					$ 100
OXB Solutions [Member] | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock award and exercise vested option to transferred employees | shares						100,000
OXB Solutions [Member] | Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock award and exercise vested option to transferred employees | shares						1,600,000

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Stock Incentive Plans - Schedule of Stock Options Valuation Assumptions Using a Black-Scholes Option Pricing Model (Details) - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum		69.20%	68.70%
Expected volatility, maximum		69.70%	70.10%
Expected volatility	70.10%
Weighted-average risk-free interest rate, minimum	3.20%	3.45%	1.46%
Weighted-average risk-free interest rate, maximum	3.66%	4.22%	3.66%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	6 years 3 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 years 3 months	6 years 3 months
Underlying common stock fair value	$ 2.82	$ 1.6	$ 4.17
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		5 years 6 months	5 years 6 months
Underlying common stock fair value	$ 1.82	$ 0.92	$ 1.78

XML

Stock Incentive Plans - Summary of Option Activity under Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Options, Outstanding at Beginning Balance	9,865,734
Number of Options, Granted	3,188,150
Number of Options, Exercised	(3,366)
Number of Options, Cancelled/Forfeited	(623,776)
Number of Options, Outstanding at Ending Balance	12,426,742	9,865,734
Number of Options, Vested and expected to vest at September 30, 2023	12,426,742
Number of Options, Exercisable at September 30, 2023	7,566,304
Weighted-Average Exercise Price per Share, Outstanding at Beginning Balance	$ 10.96
Weighted-Average Exercise Price per Share, Granted	1.53
Weighted-Average Exercise Price per Share, Exercised	0.47
Weighted-Average Exercise Price per Share, Cancelled/Forfeited	11.11
Weighted-Average Exercise Price per Share, Outstanding at Ending Balance	8.55	$ 10.96
Weighted-Average Exercise Price per Share, Vested and Expected to vest at September 30, 2023	8.55
Weighted-Average Exercise Price Per Share, Exercisable at September 30, 2023	$ 11.80
Weighted Average Remaining Contractual Term, Outstanding	4 years 10 months 24 days	7 years 2 months 12 days
Weighted Average Remaining Contractual Term, Vested and Expected to vest at September 30, 2023	4 years 10 months 24 days
Weighted Average Remaining Contractual Term, Exercisable at September 30, 2023	4 years 6 months
Aggregate Intrinsic Value, Outstanding Ending Balance	$ 488	$ 493
Aggregate Intrinsic Value, Vested and Expected to vest at September 30, 2023	488
Aggregate Intrinsic Value, Exercisable at September 30, 2023	$ 421

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Stock Incentive Plans - Summary of RSU Activity (Details) - $ / shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Outstanding at Beginning Balance	9,865,734
Number of Options, Granted	3,188,150
Number of Options, Outstanding at Ending Balance	12,426,742
Weighted-average grant date fair value per share for options granted	$ 1.01	$ 1.72
RSU Member
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Outstanding at Beginning Balance	543,179
Number of Options, Granted	483,850
RSU Vested	(281,117)
RSU, Forfeited	(258,184)
Number of Options, Outstanding at Ending Balance	487,728
Weighted-Average Grant Date Fair Value, Outstanding	$ 6.12
Weighted-average grant date fair value per share for options granted	1.6
Weighted-Average Grant Date Fair Value, Vested	5.31
Weighted-Average Grant Date Fair Value, Forfeited	2.54
Weighted-Average Grant Date Fair Value, Outstanding	$ 3.04

XML

Stock Incentive Plans - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 1,707	$ 2,771	$ 6,477	$ 9,965
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	230	889	1,507	4,143
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 1,477	$ 1,882	$ 4,970	$ 5,822

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Net Income (Loss) Per Share - Schedule of Anti-dilutive Effect Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Net income (loss)	$ (32,954)	$ (35,044)	$ (28,844)	$ (33,726)	$ (29,089)	$ 92,105	$ (96,842)	$ 29,290
Weighted-average common shares outstanding-basic	57,853,132			57,447,192			57,788,755	57,372,399
Dilutive securities	$ 0			$ 0			$ 0	$ 528,899
Weighted-average common shares outstanding-diluted	57,853,132			57,447,192			57,788,755	57,901,298
Net income (loss) per share-basic	$ (0.57)			$ (0.59)			$ (1.68)	$ 0.51
Net income (loss) per share-diluted	$ (0.57)			$ (0.59)			$ (1.68)	$ 0.51

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Net Income (Loss) Per Share (Additional Information) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Anti-dilutive securities	12,993,266	9,933,508	12,507,026	9,048,927

XML

Pfizer Stock Purchase Agreement - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Nov. 09, 2020	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Collaboration agreement revenue recognized		$ 0	$ 802	$ 1,156	$ 2,406
Pfizer Inc.
Common stock estimated fair value	$ 52,000
Stock purchase agreement remaining allocated value	8,000
Allocated Information Committee obligation	$ 8,000
Pfizer Inc. | Collaborative Arrangement [Member]
Collaboration agreement revenue recognized			$ 800	1,200	$ 2,400
Deferred revenue		$ 0		$ 0		$ 1,200
Private Placement
Issuance of common stock, net of discounts and issuance costs, Shares	5,000,000
Shares issued price per share	$ 12
Proceeds from issuance of common stock in follow-on public offering, net of discounts and issuance costs	$ 60,000
Common stock purchase agreement condition	The shares of common stock sold to Pfizer were subject to a one-year lock-up from closing, during which time Pfizer was prohibited from selling or otherwise disposing of such shares.

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Related Party Transactions (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Sublease income			$ 2,312	$ 1,210
General and administrative	$ 6,842	$ 7,810	23,355	29,991
Prepaid expenses and other current assets	3,023		3,023				$ 5,989
Oxford Biomedica [Member]
Related Party Transaction [Line Items]
Sublease income	800	500	2,300	1,200
Expenses recognized under the transitional services		(200)	(300)	(500)
Amount due to OXB Solutions	100		100				500
General and administrative		800	$ 500	1,700
Prepaid expenses and other current assets							300
Oxford Biomedica [Member] | Vendor [Member]
Related Party Transaction [Line Items]
Receivables from affiliates							1,100
Transitional Services Agreement [Member] | Oxford Biomedica [Member]
Related Party Transaction [Line Items]
Amount due to OXB Solutions							100
Supply Agreement [Member] | Oxford Biomedica [Member]
Related Party Transaction [Line Items]
Clinical supply requirements			50.00%
Purchases of drug substance	8,400	6,000	$ 21,700	7,500
Amount due to OXB Solutions	12,600		12,600				$ 5,200
Remaining purchase obligations	1,400		1,400
Supply Agreement [Member] | Oxford Biomedica [Member] | Forecast [Member]
Related Party Transaction [Line Items]
Purchase Commitment Amount					$ 0	$ 29,700
Supply Agreement [Member] | Oxford Biomedica [Member] | Process Development Services [Member]
Related Party Transaction [Line Items]
Recorded purchases	3,100	$ 2,200	5,800	$ 10,200
Supply Agreement [Member] | Oxford Biomedica [Member] | Stability and Other Support [Member]
Related Party Transaction [Line Items]
Recorded purchases	$ 400		$ 1,200

XML

Subsequent Events (Additional Information) (Details) - USD ($) $ in Thousands	Oct. 01, 2023	Sep. 30, 2023	Dec. 31, 2022
Subsequent Event [Line Items]
Right-of-use assets		$ 19,471	$ 20,563
Operating Lease Liability		$ 28,338
Subsequent Event [Member]
Subsequent Event [Line Items]
Gain on operating lease liability	$ 8,800
Cash payment for release operating lease	100
OXB Solutions [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Right Of Use Asset Obtained In Exchange For Operating Lease Liability	$ 1,600