8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March 4, 2024

PASSAGE BIO, INC.

(Exact name of registrant as specified in its charter)

Delaware	001-39231	82-2729751
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

One Commerce Square 2005 Market Street, 39th Floor Philadelphia, PA	19103
(Address of principal executive offices)	(Zip Code)

(267) 866-0311

(Registrant’s telephone number, including area code)

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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	PASG	The Nasdaq Stock Market LLC (Nasdaq Global Select Market)

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

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. ☐

Item 2.02 Results of Operations and Financial Condition.

On March 4, 2024, Passage Bio, Inc. (the “Company”) issued a press release announcing its financial results for the year ended December 31, 2023. A copy of the press release is attached as Exhibit 99.1 to this report.

The information in this Item 2.02, including Exhibit 99.1 to this report, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”). The information contained in this Item 2.02 and in the accompanying Exhibit 99.1 shall not be incorporated by reference into any other filing under the Exchange Act or under the Securities Act, except as shall be expressly set forth by specific reference in such filing.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Appointment of Chief Financial Officer

On March 1, 2024 (the “Effective Date”), Kathleen Borthwick, the Company’s current Senior Vice President and Interim Chief Financial Officer was appointed to serve as Chief Financial Officer. In this role, Ms. Borthwick will continue to serve as the Company’s Principal Financial Officer and Principal Accounting Officer.

Ms. Borthwick, age 48, has served as the Company’s Senior Vice President and Chief Financial Officer since the Effective Date. From July 2023 to February 2024, Ms. Borthwick served as our Senior Vice President and Interim Chief Financial Officer. Prior to that, from November 2021 to July 2023, Ms. Borthwick served as our Vice President of Finance. From June 1997 to October 2021, Ms. Borthwick served in various leadership roles of increasing responsibility at Johnson & Johnson. During her tenure at Johnson & Johnson, she worked in Finance in support of Research & Development, Manufacturing, Business Development, Treasury and commercial operations for global Pharmaceutical and Medical Technology business segments. Ms. Borthwick earned her B.S. in Economics with concentrations in Accounting and Health Care Management at the Wharton School of University of Pennsylvania, and her M.B.A. from the Tuck School of Business at Dartmouth College.

Pursuant to her employment agreement, Ms. Borthwick will (i) receive an annual base salary of $422,240 and (ii) be eligible to receive a cash bonus of up to 40% of her annual base salary, subject to the achievement of certain performance criteria. Ms. Borthwick will also receive a stock option to purchase 227,000 shares of common stock at an exercise price equal to the closing sale price of the common stock on the date of grant, as reported by the Nasdaq Global Select Market, which will vest as to 1/48th of the shares on the date that is one month following the Effective Date and 1/48th of the shares monthly thereafter until fully vested, subject to her continued service to the Company.

Additionally, pursuant to Ms. Borthwick’s employment agreement (the “Borthwick Employment Agreement”), if she is terminated without “cause” or resigns for “good reason” (as such terms are defined in her employment agreement), and subject to her execution and non-revocation of a release of claims, she will be entitled to (i) a lump-sum payment equal to nine months of her base salary if such termination occurs within the first year after the Effective Date or 12 months of her base salary if such termination occurs thereafter, and (ii) a taxable lump-sum payment equal to 12 months of COBRA premiums she would be required to pay to maintain group healthcare coverage as in effect on the date of termination. In the event that a successor company does not assume or substitute the equity awards held by Ms. Borthwick in connection with a “change in control”, or if she is terminated without “cause” or resigns for “good reason” within two months prior to, or 12 months following, a “change in control” (as such terms are defined in her respective employment agreement), then, in addition to the severance noted above, she will receive 100% of her then current target bonus, payable in a lump sum and her then outstanding unvested options and other equity awards will become fully vested and exercisable, as applicable, and any forfeiture restrictions thereon will lapse. Unless otherwise set forth in an applicable grant agreement, any performance conditions applicable to such equity awards will be deemed achieved at the greater of target or actual performance.

2

Ms. Borthwick is also party to the Company’s standard form of indemnification agreement. The form of the indemnification agreement was previously filed by the Company as Exhibit 10.1 to the Company’s Registration Statement on Form S-1 filed with the Securities and Exchange Commission on February 3, 2020 and incorporated by reference herein.

There are no arrangements or understandings between Ms. Borthwick and any other persons, pursuant to which she was appointed as Chief Financial Officer. There are also no family relationships between Ms. Borthwick and any director or executive officer of the Company, nor does Ms. Borthwick have a direct or indirect material interest in any transaction required to be disclosed pursuant to Item 404(a) of Regulation S-K.

Item 7.01 Regulation FD Disclosure.

On March 4, 2024, the Company updated its corporate presentation. A copy of the corporate presentation is attached as Exhibit 99.2 to this Current Report on Form 8-K.

The information in this Item 7.01, including Exhibit 99.2 to this Current Report on Form 8-K, shall not be deemed to be “filed” for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act. The information contained in this Item 7.01 and in the accompanying Exhibit 99.2 shall not be incorporated by reference into any other filing under the Exchange Act or under the Securities Act, except as shall be expressly set forth by specific reference in such filing.

Item 9.01 Financial Statements and Exhibits.

(d)Exhibits

Exhibit No.	Description
99.1	Press release issued by Passage Bio, Inc. regarding its financial results for the year ended December 31, 2023, dated March 4, 2024.
99.2	Corporate Presentation.
104	Cover Page Interactive Data File (formatted as Inline XBRL).

3

SIGNATURE

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 hereunto duly authorized.

	PASSAGE BIO, INC.
Date: March 4, 2024	By:	/s/ Kathleen Borthwick
		Kathleen Borthwick
		Chief Financial Officer

4

EX-99.1

Exhibit 99.1

PASSAGE BIO REPORTS FOURTH QUARTER AND FULL-YEAR 2023 FINANCIAL RESULTS AND PROVIDES RECENT BUSINESS HIGHLIGHTS

● Continued momentum in upliFT-D trial of PBFT02 for the treatment of patients with frontotemporal dementia (FTD) with granulin mutations (GRN) with clinical trial site expansion into Europe and seven global sites now activated

● Pursuing new indications for PBFT02, including adult neurodegenerative diseasesFTD-C9orf72, amyotrophic lateral sclerosis (ALS) and Alzheimer’s disease

● Ended 2023 with robust balance sheet sufficient to deliver meaningful clinical data; with cash runway into Q4 2025

PHILADELPHIA – March 4, 2024 – Passage Bio, Inc. (Nasdaq: PASG), a clinical-stage genetic medicines company focused on improving the lives of patients with neurodegenerative diseases, today reported financial results for the fourth quarter and year ended December 31, 2023 and provided recent business highlights.

"In 2023, we achieved a significant milestone by announcing encouraging data from three patients in Cohort 1 of our FTD-GRN program. This data showcased the ability of PBFT02 to raise CSF progranulin to supraphysiologic levels, even at the lowest dose, Dose 1, and positions PBFT02 as a potential best-in-class treatment for FTD-GRN. Our global upliFT-D study continues to see strong momentum, and we're excited to announce the activation of our first clinical trial site in Europe to further bolster recruitment efforts. We are on track to complete dosing for Cohort 1 patients in the first half of this year and share 6-month additional safety and biomarker data from Cohort 1 in the second half of 2024," said Will Chou, M.D., president and chief executive officer of Passage Bio. "Buoyed by this promising data and additional evidence supporting progranulin's role in neurodegeneration, we are optimistic about expanding the application of PBFT02 beyond FTD-GRN and into new indications with significant unmet needs, including FTD-C9orf72, ALS, and Alzheimer's disease. We eagerly anticipate a catalyst-rich 2024, supported by our robust balance sheet, bringing us closer to improving patient outcomes across neurodegenerative diseases."

Recent Highlights

● Sustained momentum in global Phase 1/2 upliFT-D clinical trial evaluating PBFT02 for frontotemporal dementia (FTD) with granulin mutations (GRN), marked by the activation of two new trial sites and expansion into Europe: Initial data from the first three patients in Cohort 1 demonstrated elevated CSF progranulin levels to supraphysiologic levels at the lowest tested dose, Dose 1, up to six months post-treatment (n=1). Additionally, Dose 1 of PBFT02 continued to be generally well-tolerated in patients who received an enhanced steroid regimen for immunosuppression. In the first half of 2024, the company expects to complete dosing for Cohort 1 patients and report 6-month safety and biomarker data in the second half of 2024. Following the positive data, multiple GRN+ patients have been identified and are being evaluated for eligibility across seven clinical trial sites in Brazil, Canada, the United States and Europe.

● Expansion of PBFT02 into additional adult neurodegenerative indications: In response to the promising initial data for PBFT02 in FTD-GRN and evidence supporting progranulin’s role in neurodegeneration, the company is currentlyevaluating the therapeutic potential of PBFT02 in additional indications, including FTD-C9orf72, ALS, and Alzheimer’s disease. The company is preparing for regulatory discussions and expects to obtain regulatory feedback on the clinical pathway to treating FTD-C9orf72 and ALS patients with PBFT02 in 2H 2024.

● Robust balance sheet to support operations: The company’s decision to focus resources on the exploration of PBFT02 in additional indications, while simultaneously pursuing potential out-licensing opportunities for clinical-stage pediatric programs in GM1 gangliosidosis, Krabbe disease and metachromatic leukodystrophy, provides sufficient cash runway into Q4 2025 to execute through critical value-inflecting milestones.

● Appointed Kathleen Borthwick as Chief Financial Officer, effective March 1, 2024: Ms. Borthwick previously served as the company’s Senior Vice President, Finance and Interim CFO and brings 25 years of pharmaceutical and biotech strategic financial leadership experience.

Anticipated Upcoming Milestones:

FTD-GRN

● Initiate dosing for Cohort 2 FTD-GRN patients in 1H 2024

● Report 6-month safety and biomarker data from Cohort 1 patients in 2H 2024

● Announce 12-month follow-up data from Cohort 1 patients in 1H 2025

● Report initial safety and biomarker data from Cohort 2 patients in 1H 2025

FTD-C9orf72 and ALS

● Obtain regulatory feedback on the pathway to treating FTD-C9orf72 and ALS patients with PBFT02 in 2H 2024

Fourth Quarter and Full-Year 2023 Financial Results

● Cash Position: Cash, cash equivalents and marketable securities were $114.3 million as of December 31, 2023, as compared to $189.6 million as of December 31, 2022. The company expects current cash, cash equivalents and marketable securities to fund operations into Q4 2025.

● Research and Development (R&D) Expenses: R&D expenses were $12.1 million for the quarter ended December 31, 2023, and $61.4 million for the year ended December 31, 2023, compared to $17.7 million and $86.1 million for the same quarter and year ended in 2022, respectively.

● General and Administrative (G&A) Expenses: G&A expenses were $6.3 million for the quarter ended December 31, 2023, and $41.6 million for the year ended December 31, 2023, compared to $10.6 million and $49.3 million for the same quarter and year ended in 2022, respectively.

● Net Loss: Net loss was $16.8 million, or $0.30 per basic and diluted share, for the quarter ended December 31, 2023 and $102.1 million, or $1.86 per basic and diluted share, for the year ended December 31, 2023, compared to a net loss of $27.1 million, or $0.50 per basic and diluted share, for the quarter ended December 31, 2022 and $136.1 million, or $2.50 per basic and diluted share, for the year ended December 31, 2022.

About Passage Bio

Passage Bio (Nasdaq: PASG) is a clinical stage genetic medicines company on a mission to improve the lives of patients with neurodegenerative diseases. Our primary focus is the development and advancement of cutting-edge, one-time therapies designed to target the underlying pathology of these conditions. Passage Bio’s lead product candidate, PBFT02, seeks to treat neurodegenerative conditions, including frontotemporal dementia, by elevating progranulin levels to restore lysosomal function and slow disease progression. 

To learn more about Passage Bio and our steadfast commitment to protecting patients and families against loss in neurodegenerative conditions, please visit: www.passagebio.com.

Forward-Looking Statements
This press release contains “forward-looking statements” within the meaning of, and made pursuant to the safe harbor provisions of, the Private Securities Litigation Reform Act of 1995, including, but not limited to: our expectations about timing and execution of anticipated milestones, including the progress of clinical trials and the availability of clinical data from such trials; our expectations about our collaborators’ and partners’ ability to execute key initiatives; our expectations about manufacturing plans and strategies; our expectations about cash runway; our expectations about potential out-licensing opportunities related to PBGM01, PBKR03 and PBML04; and the ability of our product candidates to treat their respective target CNS disorders. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” “believe,” “could,” “estimate,” “expect,” “forecast,” “goal,” “intend,” “may,” “might,” “plan,” “potential,” “possible,” “will,” “would,” and other words and terms of similar meaning. These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements, including: our ability to develop and obtain regulatory approval for our product candidates; the timing and results of preclinical studies and clinical trials; risks associated with clinical trials, including our ability to adequately manage clinical activities, unexpected concerns that may arise from additional data or analysis obtained during clinical trials, regulatory authorities may require additional information or further studies, or may fail to approve or may delay approval of our drug candidates; the occurrence of adverse safety events; the risk that positive results in a preclinical study or clinical trial may not be replicated in subsequent trials or success in early stage clinical trials may not be predictive of results in later stage clinical trials; failure to protect and enforce our intellectual property, and other proprietary rights; our dependence on collaborators and other third parties for the development and manufacture of product candidates and other aspects of our business, which are outside of our full control; risks associated with current and potential delays, work stoppages, or supply chain disruptions; and the other risks and uncertainties that are described in the Risk Factors section in documents the company files from time to time with the Securities and Exchange Commission (SEC), and other reports as filed with the SEC. Passage Bio undertakes no obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise.

Passage Bio, Inc.

Balance Sheets

	December 31,
(in thousands, except share and per share data)	2023		2022
Assets
Current assets:
Cash and cash equivalents	$	21,709	$	34,601
Marketable securities		92,585		155,009
Prepaid expenses and other current assets		923		926
Prepaid research and development		2,742		6,508
Total current assets		117,959		197,044
Property and equipment, net		15,295		22,515
Right of use assets - operating leases		16,858		19,723
Other assets		433		4,267
Total assets	$	150,545	$	243,549
Liabilities and stockholders’ equity
Current liabilities:
Accounts payable	$	1,298	$	4,065
Accrued expenses and other current liabilities		11,670		11,011
Operating lease liabilities		3,373		3,275
Total current liabilities		16,341		18,351
Operating lease liabilities – noncurrent		22,921		23,832
Total liabilities		39,262		42,183
Stockholders’ equity:
Preferred stock, $0.0001 par value: 10,000,000 shares authorized; no shares issued and outstanding at both December 31, 2023 and December 31, 2022		—		—
Common stock, $0.0001 par value: 300,000,000 shares authorized; 54,944,130 shares issued and outstanding at December 31, 2023 and 54,614,690 shares issued and outstanding at December 31, 2022		5		5
Additional paid‑in capital		705,789		694,733
Accumulated other comprehensive income (loss)		(43)		(966)
Accumulated deficit		(594,468)		(492,406)
Total stockholders’ equity		111,283		201,366
Total liabilities and stockholders’ equity	$	150,545	$	243,549

Passage Bio, Inc.

Statements of Operations and Comprehensive Loss

	Year Ended December 31,
(in thousands, except share and per share data)	2023		2022
Operating expenses:
Research and development	$	61,419	$	86,053
Acquired in‑process research and development		—		3,000
General and administrative		41,580		49,341
Impairment of long-lived assets		5,390		—
Loss from operations		(108,389)		(138,394)
Other income (expense), net		6,327		2,269
Net loss	$	(102,062)	$	(136,125)
Per share information:
Net loss per share of common stock, basic and diluted	$	(1.86)	$	(2.50)
Weighted average common shares outstanding, basic and diluted		54,743,490		54,429,023
Comprehensive loss:
Net loss	$	(102,062)	$	(136,125)
Unrealized gain (loss) on marketable securities		923		(553)
Comprehensive loss	$	(101,139)	$	(136,678)

For further information, please contact:

Investors:

Stuart Henderson

Passage Bio

267.866.0114

shenderson@passagebio.com

Media:

Mike BeyerSam Brown Inc. Healthcare Communications312.961.2502MikeBeyer@sambrown.com

EX-99.2

Exhibit 99.2

Nasdaq: PASG © 2024 Passage Bio. All rights reserved. Corporate Presentation March 2024

2 Forward-Looking Statement This presentation includes “forward-looking statements” within the meaning of, and made pursuant to the safe harbor provisions of, the Private Securities Litigation Reform Act of 1995, including, but not limited to: our expectations about timing and execution of anticipated milestones, including the progress of clinical trials and the availability of clinical data from such trials; our expectations about our collaborators’ and partners’ ability to execute key initiatives; our expectations about manufacturing plans and strategies; our expectations about cash runway; our expectations about potential outlicensing opportunities related to PBGM01, PBKR03 and PBML04; and the ability of our product candidates to treat their respective target CNS disorders. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” “believe,” “could,” “estimate,” “expect,” “forecast,” “goal,” “intend,” “may,” “might,” “plan,” “potential,” “possible,” “will,” “would,” and other words and terms of similar meaning. These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements, including: our ability to develop and obtain regulatory approval for our product candidates; the timing and results of preclinical studies and clinical trials; risks associated with clinical trials, including our ability to adequately manage clinical activities, unexpected concerns that may arise from additional data or analysis obtained during clinical trials, regulatory authorities may require additional information or further studies, or may fail to approve or may delay approval of our drug candidates; the occurrence of adverse safety events; the risk that positive results in a preclinical study or clinical trial may not be replicated in subsequent trials or success in early stage clinical trials may not be predictive of results in later stage clinical trials; failure to protect and enforce our intellectual property, and other proprietary rights; our dependence on collaborators and other third parties for the development and manufacture of product candidates and other aspects of our business, which are outside of our full control; risks associated with current and potential delays, work stoppages, or supply chain disruptions; and the other risks and uncertainties that are described in the Risk Factors section in documents the company files from time to time with the Securities and Exchange Commission (SEC), and other reports as filed with the SEC. Passage Bio undertakes no obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise.

3 Our Vision To improve patient lives with neurodegenerative diseases by delivering genetic medicines that will permanently redefine the course of their conditions. Potential best in class progranulin raising FTD-GRN gene therapy program Established manufacturing and process analytics capabilities Strong cash position with runway expected into 4Q 2025* Portfolio expansion into additional adult neurodegenerative diseases * Based on cash, cash equivalents and marketable securities as of December 31, 2023

4 Pipeline with Potential to Address Multiple Neurodegenerative Diseases Program Indication US/EU prevalence Discovery Pre-clinical Phase 1/2 Pivotal PBFT02 Frontotemporal dementia - GRN 18,0001-3 Frontotemporal dementia - C9orf72 21,0002-4 Amyotrophic lateral sclerosis 72,6005-6 Alzheimer’s disease with rs5848 SNP 3.9M7-8 Unnamed Huntington’s disease 60,0009 PBGM01 GM1 gangliosidosis PBKR03 Krabbe disease PBML04 Metachromatic leukodystrophy Pursuing outlicensing opportunities Sources: [1] Greaves CV, et al. J Neurol 2019; 266:2075-2086, [2] Galvin JE, et al. Neurology 2017; 89:2049-2056, [3] Onyike CU, et al. Int Rev Psychiatry 2013; 25:130-137, [4] Moore KM, et al. Lancet Neurol 2020; 19: 145–156, [5] Brown et al. Neuroepi 2021; 55:342-353, [6] CDC ALS Registry Dashboard, [7] Sheng J, et al. Gene 2014; 141-145, [8] Alz Assoc. 2023 Alzheimer’s Disease Facts and Figures. Alzheimers Dement 2023;19, [9] Crowell et al. Neuroepi. 2021; 55:361-368

5 • One time therapy • Durable, supraphysiologic CSF PGRN levels • Administration directly to CSF with nonsurgical injection Lead Clinical Program: PBFT02 Has Demonstrated Best in Class Potential in FTD-GRN Differentiated, Potential Best in Class Product Profile Initial Data from First 3 Treated Patients • Supraphysiologic CSF PGRN levels greater than 2-3x normal healthy adult levels in all patients at 30 days following treatment (n=3)* • Supraphysiologic CSF PGRN levels maintained at up to 6 months following treatment (n=1) Global Dose-Escalation Study of PBFT02 in FTD-GRN *Reference range for normal, healthy adult controls’ PGRN levels in CSF (range: 3.28 – 8.15 ng/mL, mean: 4.76 ng/mL, n = 61) (Passage Bio data)

6 Discovery UPenn GTP Research Analytics and Vector Engineering Process/Analytic Development Passage CMC R&D Lab Proven Analytical Capabilities Integrated Process Development GMP QC Capabilities Strong Regulatory CMC Scientific Expertise Scale-up Capability GMP Manufacturing Longstanding Partnership with Catalent End-to-End Clinical Supply Chain Leading CMC Capabilities Via a Hybrid Approach External Manufacturing Partnerships and End-to-End Supply Chain Key Strategic Partnerships Internal State-of-the-Art CMC Capabilities Partnerships In House Critical analytical and development capabilities maintained in-house

PBFT02 Frontotemporal Dementia — GRN

8 FTD-GRN: A Devastating Adult Disease 10pt Calibri footer OVERVIEW • Devastating form of dementia caused by a GRN gene mutation resulting in progranulin (PGRN) deficiency and haploinsufficiency • No disease-modifying therapies are currently approved EPIDEMIOLOGY • Approximately 5–10% of all FTD is caused by a GRN mutation, with an estimated prevalence in the U.S. and E.U. of ~18,000 patients CLINICAL SYMPTOMS • Disease progression is rapid and degenerative including loss of speech, loss of expression, severe behavioral changes and immobility

9 Progranulin Deficiency is the Defining Characteristic of FTD-GRN and Leads to Neurodegeneration Progranulin is critical to maintaining CNS cell homeostasis Source: Rhinn H et al. Trends Pharm Sci. 2022, 43:641-652

10 PBFT02 • Proprietary AAV1 construct delivering functional GRN gene encoding progranulin (PGRN) • Potential therapeutic benefit of a one-time approach • Delivered directly to the CSF via a single intra-cisterna magna (ICM) injection: –Allows for broad CNS biodistribution –Lower doses compared to IV systemic delivery –Reduced impact of neutralizing antibodies • Able to achieve supraphysiologic levels of CSF progranulin, based on preclinical and initial clinical evidence • Received Orphan Drug and Fast Track designations by FDA and Orphan designation by EC Potential transformative therapy

11 Preclinical: PBFT02 Achieved Supraphysiologic Levels of CSF Progranulin in NHPs • AAV1 increased CSF PGRN levels ~5x more than AAV5 and AAVhu68 (proprietary AAV9 variant) vectors, without further elevating peripheral levels Left, right: Two adult rhesus macaques per treatment received ICM AAV.hPGRN High dose, 3.0 x 1013 GC / 3.3 x 1011 GC/g brain) on study day 01. Shading: Reference range for healthy adult controls’ PGRN levels in CSF (n = 61) and plasma (n = 56) (Passage Bio data). Production of Human PGRN in Plasma AAV1 transgene delivery led to supraphysiologic hPGRN levels in CSF CSF PGRN (ng/mL) 0 10 20 30 40 CSF 0.1 1 10 100 Day AAVhu68 AAVhu68 (v2) AAV5 AAV1 Normal LLOQ Plasma Plasma PGRN (ng/mL) 0 10 20 30 40 0.1 1 10 100 Normal Day 1,000

12 Supraphysiologic PGRN Increases Potential for Improved Cellular Function • Progranulin is a secreted protein that binds to cell membrane receptors to affect multiple intracellular pathways –Major role is regulating intracellular lysosomal activity –Extracellular progranulin is endocytosed via multiple receptors • Driving supraphysiologic progranulin levels in the extracellular space increases the amount of progranulin available to enter target CNS cells Sources: Paushter et al., Acta Neuropathol. 2018;136(1):1-17., Rhinn et al., Trends in Pharmacological Sciences 2022; 43.8:641-652.

13 Preclinical: Higher CSF PGRN May Confer Reduction in Inflammatory Response Thalamus data shown above. Thalamic atrophy is a key feature commonly found in FTD PBFT02 reduced lipofuscin at all doses, suggesting correction of underlying mechanism of disease • Lipofuscin: increased levels associated with lysosomal dysfunction • Correlated with underlying mechanism of FTD-GRN *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, one-way ANOVA followed by Tukey’s multiple comparisons test Microgliosis reduction strongest at highest PBFT02 dose / PGRN level • Microgliosis: inflammatory response to pathogenic insults in the CNS • CD68: marker of activated microglia Murine FTD Model Murine FTD Model

14 Preclinical: PBFT02 Showed Dose-Related Increases in CSF Progranulin in NHPs Adult rhesus macaques received ICM PBFT02 (n = 3/dose) or vehicle (n =2) on study day 0. CSF was sampled 14 days post-dose. Human PGRN Levels in CSF of NHPs 14 days post-ICM Dose 0 2 4 6 8 10 12 High Dose Medium Dose Low Dose Vehicle Human PGRN (ng/ml) Equivalent Clinical Dose Dose 1 Dose 2 Dose 3 (optional) • NHP immune response to hPGRN limits follow-up period to 14-days and may underestimate hPGRN levels achieved in CSF post-ICM administration

15 upliFT-D: Global Phase 1/2 Trial with PBFT02 OPTIONAL DOSE 3 DOSE 2 (1.1e11 GC/g)* DOSE 1 (3.3e10 GC/g)* COHORT 1 COHORT 2 OPTIONAL COHORT 3 Trial Design Phase 1/2, multicenter, open-label, dose escalation study; up to 15 patients across 3 cohorts Duration 2 years; with additional 3 years of follow-up for safety and durability of effect Primary Endpoints • Safety and tolerability Secondary Endpoints Biomarkers: • Progranulin (CSF, plasma) • GFAP (CSF, plasma) • vMRI • Retinal nerve fiber layer and retinal lipofuscin deposits via OCT • NfL (CSF, plasma) Clinical: • CDR + NACC FTLD sum of boxes Exploratory Biomarkers • Cathepsin D (CSF) • LAMP 1 (CSF) • Lys-GL1 (CSF) *Genome copies per gram of estimated brain weight IDMC review Recruiting

16 upliFT-D: Interim Data from First 3 Treated Patients • Patient 1 experienced two SAEs consistent with an immune response; study protocol was revised to increase steroid regimen • Patient 2 & Patient 3 received a higher level of steroid immunosuppression and did not experience SAEs; only mild-to-moderate treatment emergent AEs were reported • No evidence of DRG toxicity, as measured by nerve conduction studies • No complications related to ICM administration observed SAE: serious adverse event; AE: adverse event; DRG: dorsal root ganglion; ICM: intracisterna magna; NHP: non-human primate *Patient safety follow-up ranged from 2 to 8 months post-dosing as of data cutoff of Feb 14, 2024 Safety* Efficacy / Target Engagement • Interim data demonstrates PBFT02 potential for best-in-class efficacy at the low dose • In all patients, Dose 1 achieved supraphysiologic CSF PGRN levels at Day 30: >2-3x normal healthy adult levels • CSF PGRN levels exceeded levels observed in NHPs

17 Following Protocol Update to Increase Steroids, Patients 2 & 3 had no SAEs or Evidence of Significant Immune Response Patient 1 Patient 2 Patient 3 Immunosuppression1 Day -1-60: 60 mg oral prednisone Days 1-3: 1,000 mg IV methylprednisolone Days 4-60: 60 mg oral prednisone LFTs Day 14-21 and Day 51-55: elevated2 asymptomatic No significant change from baseline Imaging Findings Day 55: venous sinus thrombosis asymptomatic None None DRG Toxicity None None None ICM Complications None None None Length of Follow-up (as of Feb 14, 2024) 2 months (subject withdrew from study at week 10) 8 months 4 months Summary • 2 SAEs: both asymptomatic and consistent with immune response 1. Hepatotoxicity (resolved with methylprednisolone) 2. Venous sinus thrombosis • No SAEs • No hepatotoxicity or significant LFT changes from baseline • No venous sinus thrombosis or inflammation on MRIs • No clinically significant immune response requiring adjustment to immunosuppression regimen • All treatment emergent AEs mild to moderate in severity LFT: liver function test; SAE: serious adverse event 1 Day minus one refers to the day prior to dosing. 2 Day 14-21 LFT elevations were mild and self-resolved; Day 51-55 LFT elevations: ALT 16x upper limit of normal (ULN), AST 4x ULN, alkaline phosphatase 2x ULN, GGT 10x ULN; total bilirubin was normal. Resolving with methylprednisolone at time of patient study withdrawal.

18 • Dose 1 resulted in supraphysiologic levels of CSF PGRN at Day 30 for all patients –Greater than 2-3x normal healthy adult levels at Day 30 following treatment (n=3) • Increase in CSF PGRN was sustained at 6- months (n=1) • Results exceeded what was observed in NHPs Shading: Reference range for healthy adult controls’ PGRN levels in CSF (range: 3.28 – 8.15 ng/mL, mean: 4.76 ng/mL, n = 61) (Passage Bio data) CSF= Cerebrospinal Fluid Initial Patients Treated with PBFT02 Have Seen a Substantial Increase in CSF PGRN 0 3 6 9 12 15 18 21 24 27 30 0 30 180 CSF PGRN, ng/mL Time (days) Dose 1 Progranulin, CSF Patient 1 Patient 2 Patient 3 At Dosing D30 D180 Patient 1 1.9 12.7 N/A Patient 2 2.8 17.3 27.3 Patient 3 2.9 10.7 N/A CSF Progranulin (ng/mL)

19 Shading: Lower limit of normal of reference range for healthy adult controls’ PGRN levels in plasma (91.6 – 372.4 ng/mL, n = 56) (Passage Bio data) • Plasma PGRN levels remained below normal levels at up to 6 months post-dose • PGRN increased only in the CSF where it has potential to correct deficit associated with neurodegeneration Plasma PGRN Levels Remained Below Normal Levels Post-Dose 0 10 20 30 40 50 60 70 80 90 100 0 7 14 30 90 180 Plasma PGRN, ng/mL Time (days) Dose 1 Progranulin, Plasma Patient 1 Patient 2 Patient 3

20 Summary AEs=adverse events; ICM=intra-cisterna magna 1 Patient safety follow-up ranged from 2 to 8 months post-dosing as of data cutoff of Feb 14, 2024 *Reference range for normal, healthy adult controls’ PGRN levels in CSF (range: 3.28 – 8.15 ng/mL, mean: 4.76 ng/mL, n = 61) (Passage Bio data) SAFETY1 PBFT02 Dose 1 generally well-tolerated to date in Patients 2 & 3, who received revised steroid regimen following protocol amendment • No serious AEs • All AEs mild to moderate in intensity • No evidence of clinically significant immune response, hepatotoxicity or venous sinus thrombosis • No evidence of DRG toxicity • No complications observed related to ICM injection BIOMARKERS Evidence of target engagement with >2-3x normal* levels of CSF progranulin in all participants on Day 30 post treatment • Outperforming NHP data at this dose level No increase in plasma PGRN levels up to Day 180 Supraphysiologic CSF PGRN levels maintained at 6 months (n=1) ANTICIPATED NEXT STEPS •Initiate dosing of Cohort 2 patients in 1H 2024 • Additional 6-month data from Cohort 1 in 2H 2024 • 12-month follow-up data from Cohort 1 patients in 1H 2025 •Initial data from Cohort 2 in 1H 2025

Looking Ahead

22 PBFT02 has Potential to Correct Underlying Pathology in FTD-GRN, FTD-C9orf72, and ALS Elevating PGRN in TDP-43 models results in: • Normalized cytoplasmic TDP-43 accumulation • Improved survival2 Supraphysiologic PGRN ameliorates TDP-43 pathology in preclinical models 1Rhinn H et al. Trends Pharm Sci. 2022, 43:641-652; 2Beel S et al. Mol Neurodeg. 2018, 13:55. TDP-43 pathology is a hallmark of multiple neurodegenerative diseases1 • TDP-43 mislocalizes from nucleus to cytoplasm • Forms inclusion bodies associated with neurodegeneration

23 PBFT02 has Potential to Modulate Alzheimer’s Disease • GRN SNP rs5848 carriers have reduced PGRN levels and increased risk for AD • AD patients with GRN SNP rs5848 show reduced PGRN levels and increased CSF tau Genetic risk1 SNP: single nucleotide polymorphism Third-party preclinical data. Sources: 1Chen Y et al. J Neurol. 2015, 262:814-22; Takahashi H et al. Acta Neuropathol. 2017, 133:785-807. 2Fenoglio C et al. J Alzheimers Dis. 2009, 18:603-612. 3Hosokawa M et al. J Neuropath Exp Neurol. 2015, 74:158-65; Minami SS et al. Nat Med. 2014, 20:1157-64; Van Kampen JM & Kay DG. PLoS ONE 2017, 12:e0182896 Supporting Preclinical Evidence3 Prevalence • PGRN ablation exacerbates AD pathology in mice • PGRN overexpression reduces pathology burden in AD models • GRN SNP rs5848 is estimated to occur in 30% of general population, with a similar prevalence rate among AD patients2

24 TIMING MILESTONE FTD-GRN 1H 2024 Initiate dosing of Cohort 2 patients 2H 2024 6-month safety and biomarker data from Cohort 1 patients 1H 2025 12-month follow-up data from Cohort 1 patients 1H 2025 Initial safety and biomarker data from Cohort 2 patients PBFT02 Additional Indications 2H 2024 Obtain regulatory feedback on clinical pathway for treating FTD-C9orf72 and ALS patients Upcoming Milestones and Corporate Updates PIPELINE • Pursuing outlicensing opportunities to advance pediatric clinical-stage programs (GM1, Krabbe, & MLD) • Continuing the Huntington’s disease preclinical program being executed through our Penn GTP partnership • BALANCE SHEET • Cash balance of $114 million as of 12/31/23* • Cash as of 12/31/23 expected to fund operations into 4Q 2025* * Cash, cash equivalents and marketable securities

25 Our Vision To improve patient lives with neurodegenerative diseases by delivering genetic medicines that will permanently redefine the course of their conditions. Potential best in class progranulin raising FTD-GRN gene therapy program Established manufacturing and process analytics capabilities Strong cash position with runway expected into 4Q 2025* Portfolio expansion into multiple adult neurodegenerative diseases * Based on cash, cash equivalents and marketable securities as of December 31, 2023

Thank You passagebio.com | NASDAQ: PASG

27 Demonstrated Leadership LEADERSHIP TEAM Deep experience in rare disease, CNS disorders and genetic medicines Eden Fucci SVP Technical Operations BOARD OF DIRECTORS Maxine Gowen, Ph.D. Chairwoman Athena Countouriotis, M.D. Avenzo Therapeutics Derrell Porter, M.D. cTRL Therapeutics Dolan Sondhi, Ph.D. Weill Cornell Medicine Sandip Kapadia Harmony Biosciences Saqib Islam, J.D. SpringWorks William Chou, M.D. President & Chief Executive Officer Stuart Henderson SVP Corporate Development & Investor Relations Mark Forman, M.D., Ph.D. Chief Medical Officer William Chou, M.D. President & Chief Executive Officer Chip Cale General Counsel & Corporate Secretary Kathleen Borthwick Chief Financial Officer Karl Whitney SVP Global Regulatory Affairs Sue Browne, Ph.D. SVP Research & Development

28 Intra-Cisterna Magna (ICM) Administration • Directly deliver vector into the CSF via a single injection to reach both CNS and peripheral tissues* –Allows for broad CNS biodistribution –Lower doses compared to IV systemic delivery –Reduced impact of neutralizing antibodies • Administered under anesthesia using modern neuroimaging to allow for precise delivery • Currently being used in several clinical studies in both pediatric and adult populations Cisterna magna *Hinderer et. al, Human Gene Therapy. 2018 Jan; 29(1):15-24

XML

Document and Entity Information	Mar. 04, 2024
Cover [Abstract]
Document Type	8-K
Document Period End Date	Mar. 04, 2024
Securities Act File Number	001-39231
Entity Registrant Name	PASSAGE BIO, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-2729751
Entity Address, Address Line One	One Commerce Square
Entity Address, Address Line Two	2005 Market Street, 39th Floor
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19103
City Area Code	267
Local Phone Number	866-0311
Written Communications	false
Soliciting Material	false
Pre-commencement Tender Offer	false
Pre-commencement Issuer Tender Offer	false
Title of 12(b) Security	Common Stock, $0.0001 Par Value Per Share
Trading Symbol	PASG
Security Exchange Name	NASDAQ
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Central Index Key	0001787297
Amendment Flag	false

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N-2	Mar. 04, 2024
Cover [Abstract]
Entity Central Index Key	0001787297
Amendment Flag	false
Securities Act File Number	001-39231
Document Type	8-K
Entity Registrant Name	PASSAGE BIO, INC.
Entity Address, Address Line One	One Commerce Square
Entity Address, Address Line Two	2005 Market Street, 39th Floor
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19103
City Area Code	267
Local Phone Number	866-0311
Entity Emerging Growth Company	true
Entity Ex Transition Period	false