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): December 9, 2022

Arcellx, Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware	001-41259	47-2855917
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

25 West Watkins Mill Road, Suite A

Gaithersburg, MD 20878

(Address of principal executive offices, including zip code)

(240) 327-0603

(Registrant’s telephone number, including area code)

Not Applicable

(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, $0.001 par value per share	ACLX	The Nasdaq Stock Market LLC

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 1.01 Entry into a Material Definitive Agreement.

Collaboration and License Agreement

On December 9, 2022, Arcellx, Inc. (“Arcellx”) entered into a Collaboration and License Agreement (the “Collaboration Agreement”) with Kite Pharma, Inc., a Gilead Company (“Kite”), pursuant to which Arcellx and Kite will collaborate on the development and commercialization of (i) Arcellx’s CAR T-cell therapy product known at Arcellx as “CART-ddBCMA,” which is currently the subject of Arcellx’s iMMagine-1 program (such product, the “Existing Product”, and the D-domain BCMA binder used in such product, the “Existing BCMA Binder”); (ii) next generation autologous CAR T-cell therapy products utilizing the Existing BCMA Binder (“NextGen Products”); and (iii) non-autologous cell therapy products using the Existing BCMA Binder (“Non-Auto Products”, and collectively with the Existing Product and the NextGen Products, Inc., “Licensed Products”), in each case for myeloma. Arcellx will also grant to Kite an option to negotiate the expansion of Licensed Products to include autologous CAR T-cell therapy products that utilize Arcellx’s ARC-SparX platform (“ARC-SparX Products”) that are directed to BCMA (known at Arcellx as “ACLX-001”) and ARC-SparX Products directed to CS1.

The consummation of the Collaboration Agreement is subject to obtaining any necessary consents and approvals, including review by the appropriate regulatory agencies under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (the “Hart-Scott-Rodino Act”).

Following the consummation of the Collaboration Agreement, Arcellx will receive a $225 million upfront cash payment. In addition, based on the development and commercialization plan of the Licensed Products, Arcellx will be eligible to receive up to approximately $3.9 billion in clinical, regulatory, and commercial milestone payments. In the United States, Arcellx and Kite will equally share profits and losses from the commercialization of the Existing Product and any NextGen Product for which Arcellx has exercised its option to co-promote (the “Co-Promote Products”). For Co-Promote Products outside of the United States and for any Licensed Product that is not a Co-Promote Product (the “Non-Co-Promote Products”), Arcellx will be eligible for tiered royalties in the low to mid teen percentages.

Arcellx and Kite will jointly develop the Co-Promote Products in accordance with mutually agreed development plans and development budgets. Arcellx will conduct the iMMagine-1 Program for the Existing Product and Kite will conduct all other development of Co-Promote Products. Other than certain items expressly set forth in the Collaboration Agreement, the out-of-pocket development costs for activities conducted in the United States for Co-Promote Products will be shared equally by Arcellx and Kite and the out-of-pocket development costs for activities conducted outside the United States as part of a global clinical study for Co-Promote Products will be borne 60% by Kite and 40% by Arcellx, however Kite will be solely responsible for the costs for country-specific clinical studies and CMC commercial readiness. Kite will be solely responsible for the conduct of development of the Non-Co-Promote Products at its sole cost.

In the United States, Arcellx and Kite will be jointly responsible for commercialization of the Co-Promote Products. Kite will be responsible, at its sole cost, for commercialization of the Co-Promote Products outside the United States and the Non-Co-Promote Products worldwide.

Kite will manufacture the Licensed Products and bear the CMC commercial readiness costs and capital expenses, except that Arcellx is responsible for manufacturing the Existing Product prior to transferring the manufacturing process to Kite.

Unless earlier terminated, the Collaboration Agreement will continue in effect until no Licensed Products are being developed or commercialized. The Collaboration Agreement is subject to customary termination provisions including termination by a party for the other party’s uncured, material breach. In the event of certain terminations of the Collaboration Agreement, Arcellx is entitled to certain reversionary rights with respect to the terminated products.

The Collaboration Agreement contains customary representations, warranties, covenants, and terms governing the prosecution and enforcement of intellectual property.

The foregoing description of the terms of the Collaboration Agreement is not complete and is qualified in its entirety by reference to the full text of the Collaboration Agreement, a copy of which Arcellx intends to file as an exhibit to a subsequent periodic report.

Common Stock Purchase Agreement

In connection with the Collaboration and License Agreement, Arcellx entered into a common stock purchase agreement (the “Purchase Agreement”) with Gilead Sciences, Inc. (“Gilead”) on December 9, 2022, pursuant to which Arcellx agreed to issue and sell, and Gilead has agreed to purchase, 3,478,261 shares of Arcelllx’s common stock (the “Shares”) for an aggregate purchase price of $100 million pursuant to the terms and conditions thereof. We expect to close the sale of the Shares within three business days following the satisfaction of the closing conditions set forth in the Purchase Agreement, which includes consummation of the Collaboration Agreement and the satisfaction of customary closing conditions, including expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Act.

Pursuant to the terms of a standstill and stock restriction agreement (the “Standstill Agreement”) to be entered into between Gilead and Arcellx at the closing of the sale of the Shares, Gilead will agree to certain transfer and standstill restrictions. In addition, Gilead will be entitled to certain registration rights with respect to the Shares following termination of the transfer restrictions.

The foregoing descriptions of the terms of the Purchase Agreement and Standstill Agreement (together, the “Agreements”) do not purport to be complete and are qualified in their entirety by reference to the full text of such Agreements, each of which will be filed as exhibits to a subsequent periodic report.

Item 3.02 Unregistered Sales of Equity Securities.

The information set forth above in Item 1.01 of this Current Report on Form 8-K under the heading “Common Stock Purchase Agreement” is hereby incorporated by reference into this Item 3.02.

Upon the closing of the sale of Shares pursuant to the above-referenced Purchase Agreement, Gilead will purchase the Shares in a private placement in reliance on Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”). Arcellx relied upon these exemptions from registration based in part on representations made by Gilead in the Purchase Agreement. Gilead will acquire the Shares for investment only and not with a view to or for sale in connection with any distribution thereof, and appropriate legends will be affixed to the Shares.

Item 7.01 Regulation FD Disclosure.

On December 9, 2022, Arcellx issued press releases announcing the collaboration with Kite and continued long-term responses from its CART-ddBCMA Phase 1 expansion trial in patients with relapsed or refractory multiple myeloma. Copies of the press releases are attached hereto as Exhibit 99.1 and Exhibit 99.2, and incorporated herein by reference.

The information furnished in this Item 7.01 and Item 9.01 (including Exhibits 99.1 and 99.2) 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, nor shall it be deemed incorporated by reference into any filing under the Securities Act or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Cautionary Note Regarding Forward-looking Statements

This report contains forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. All statements in this report that are not purely historical are forward-looking statements, including, without limitation, statements regarding the anticipated completion of the proposed transaction, including the closing of a proposed concurrent equity investment; potential payments that may be received by Arcellx in connection with the collaboration, including potential milestones and royalties; and Arcellx’s and Kite’s respective rights and obligations under the Collaboration Agreement. The forward-looking statements contained herein are based upon Arcellx’s current expectations and involve assumptions that may never materialize or may prove to be incorrect. These forward-looking statements are neither promises nor guarantees and are subject to a variety of risks and uncertainties, including that the proposed transaction will be completed in a timely manner or at all, the possibility that certain closing conditions to the proposed transaction will not be satisfied; uncertainty as to whether the anticipated benefits and opportunities of the proposed collaboration may not be realized or make take longer to realize or may cost more than expected; risks of unexpected hurdles, costs or delays; challenges in technology transfer and cell therapy manufacturing, particularly scaling up to commercial supply volumes, can limit the benefits of the collaboration; challenges inherent in new product candidate development, including the uncertainty of clinical success and obtaining regulatory approvals; challenges associated with collaborating with third parties, including intellectual property, operational, financial and other risks; uncertainty of commercial success for new products; the ability of Arcellx and Kite to successfully execute their strategic plans; and other risks that may be found in the section entitled Part II, Item 1A (Risk Factors) in the Quarterly Report on Form 10-Q for the period ended September 30, 2022, filed with the Securities and Exchange Commission (SEC), and other documents that Arcellx files from time to time with the SEC. These forward-looking statements are made as of the date of this report, and Arcellx assumes no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

Exhibit No.	Description
99.1	Press Release dated December 9, 2022.
99.2	Press Release dated December 9, 2022.
104	Cover Page Interactive Data File (formatted as Inline XBRL)

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 hereunto duly authorized.

		ARCELLX, INC.
Date: December 9, 2022	By:	/s/ Rami Elghandour
		Rami Elghandour Chief Executive Officer

EX-99.1

Exhibit 99.1

Arcellx and Kite Announce Strategic Collaboration to Co-Develop and Co-Commercialize Late-

Stage Clinical CART-ddBCMA in Multiple Myeloma

— Collaboration leverages expertise across both companies, including Kite’s global cell therapy

leadership and industry leading reliable manufacturing —

— Arcellx to receive $225M upfront payment; $100M equity investment; and up to $3.9B in total contingent consideration —

— Companies to co-commercialize and split profits in the U.S.; Arcellx to receive low to mid-teen royalties outside the U.S. —

— Arcellx to continue independently progressing its development pipeline and researching new

product candidates beyond myeloma —

— Arcellx to host a conference call and webcast today at 5:45 a.m. PT —

REDWOOD CITY, Calif., and SANTA MONICA, Calif., (PRNEWSWIRE) — Arcellx, Inc. (NASDAQ: ACLX) and Kite, a Gilead Company (NASDAQ: GILD), today announced a global strategic collaboration to co-develop and co-commercialize Arcellx’s lead late-stage product candidate, CART-ddBCMA, for the treatment of patients with relapsed or refractory multiple myeloma. Multiple myeloma is an incurable disease for most patients and the need remains for effective, safe, and broadly accessible therapies.

“This collaboration marks a significant achievement for the myeloma field and Arcellx,” said Rami Elghandour, Arcellx’s Chairman and Chief Executive Officer. “Combining our potentially best-in-class CART-ddBCMA therapy for multiple myeloma with Kite’s global leadership in cell therapy provides the foundation for us to commercialize our therapy at scale. Most importantly this collaboration is focused on accelerating access for patients in need. The synergies between the two companies are a natural fit. We both bring complementary expertise to the collaboration allowing each company to contribute to the partnership without duplication or competing interests, which is critical for building long-term value.”

Currently in Phase 2 clinical development, CART-ddBCMA is an investigational cell therapy product comprising autologous T cells that have been genetically modified to target multiple myeloma. CART-ddBCMA utilizes Arcellx’s novel D-Domain binder. Kite and Arcellx will jointly advance the CART-ddBMCA asset.

“The collaboration with Arcellx enables Kite to expand into a new area of high unmet need and bring a potentially best-in-class cell therapy to help many patients,” said Christi Shaw, Chief Executive Officer of Kite. “Cell therapy has proven it can change the way cancer is treated by creating a potentially curative therapy for an individual patient, engineered from their own T cells. To deliver cell therapy globally, and at scale, it requires a highly coordinated, vertically integrated organization from R&D to commercialization to manufacturing, dedicated to the unique needs of this very complex field. The Kite team is excited to engage on this meaningful program in the multiple myeloma field, alongside Arcellx’s talented team.”

Upon closing, Arcellx will receive an upfront cash payment of $225 million and $100 million equity investment. Both companies will share development, clinical trial, and commercialization costs for CART-ddBCMA and will jointly commercialize and split U.S. profits 50/50. Outside the US, Kite will commercialize the product and Arcellx will receive royalties on sales. Kite will be responsible for the development and commercialization costs for any product under the collaboration that is not co-commercialized. After completion of the technical transfer, Kite will be responsible for manufacturing.

Terms of the Collaboration

• Upfront: Upon closing, Arcellx will receive an upfront cash payment of $225 million and $100 million equity investment from Kite.

• Manufacturing: After completion of the technical transfer, Kite will be responsible for manufacturing. Kite will be responsible for all manufacturing expenses associated with commercial readiness.

• Development: U.S. and global study costs for the iMMagine-1, iMMagine-2 and future clinical studies for CART-ddBCMA and any other co-commercialized product will be shared 50/50 in the U.S. and 60 to Kite / 40 to Arcellx in the Ex U.S. territory.

• U.S. Commercialization: 50/50 profit split for products co-commercialized by Arcellx and Kite; Kite will commercialize all other products and Arcellx will receive low to mid teen royalties.

• Ex-U.S. Commercialization: Kite will commercialize the product and Arcellx will receive low to mid-teen royalties on sales.

• NextGen, Non-Autologous, and ARC-SparX Programs: Arcellx and Kite to collaborate on next generation autologous and non-autologous programs incorporating ddBCMA. Arcellx to receive an option to co-develop and co-commercialize next generation autologous programs and Kite to receive an option to selected ARC-SparX programs in myeloma.

Bank of America is acting as financial advisor to Kite. Wilson Sonsini Goodrich & Rosati is serving as legal counsel to Arcellx.

The transaction is expected to close in the first quarter of 2023. Closing of the transaction is subject to expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions.

Conference Call and Webcast Details

The live webcast and conference call will be accessible under the Events & Presentations in the Investors section of the company’s website www.arcellx.com. To participate in the conference call, dial 1-888-440-3310 (domestic) or 1-646-960-0513 (international) and reference conference ID# 1012518. The archived audio webcast will be available on Arcellx’s website following the call and will be available for 30 days.

About Multiple Myeloma

Multiple Myeloma (MM) is a type of hematological cancer in which diseased plasma cells proliferate and accumulate in the bone marrow, crowding out healthy blood cells and causing bone lesions, loss of bone density, and bone fractures. These abnormal plasma cells also produce excessive quantities of an abnormal immunoglobulin fragment, called a myeloma protein (M protein), causing kidney damage and impairing the patient’s immune function. Multiple myeloma is the third most common hematological malignancy in the United States and Europe, representing approximately 10% of all hematological cancer cases and 20% of deaths due to hematological malignancies. The median age of patients at diagnosis is 69 years with one-third of patients diagnosed at an age of at least 75 years. Because MM tends to afflict patients at an advanced stage of life, patients often have multiple co-morbidities and toxicities that can quickly escalate and become life-endangering.

About CART-ddBCMA

CART-ddBCMA is Arcellx’s BCMA-specific CAR-modified T-cell therapy utilizing the company’s novel binding domain for the treatment of patients with relapsed or refractory multiple myeloma. CART-ddBCMA is currently being investigated in a pivotal Phase 2 study called iMMagine-1. Arcellx’s proprietary binding domains are novel synthetic proteins designed to bind specific therapeutic targets. CART-ddBCMA has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy Designations by the U.S. Food and Drug Administration.

About Arcellx

Arcellx, Inc. is a clinical-stage biotechnology company reimagining cell therapy by engineering innovative immunotherapies for patients with cancer and other incurable diseases. Arcellx believes that cell therapies are one of the forward pillars of medicine and Arcellx’s mission is to advance humanity by developing cell therapies that are safer, more effective, and more broadly accessible. Arcellx’s lead product candidate, CART-ddBCMA, is being developed for the treatment of relapsed or refractory multiple myeloma (r/r MM) in an ongoing Phase 2 study. CART-ddBCMA has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy designations by the U.S. Food and Drug Administration.

Arcellx is also advancing its dosable and controllable CAR-T therapy, ARC-SparX, through two programs: a Phase 1 study of ACLX-001 for r/r MM, initiated in the second quarter of 2022; and a Phase 1 study of ACLX-002 in relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome, initiated in the fourth quarter of 2022. For more information on Arcellx, please visit www.arcellx.com.

About Kite

Kite, a Gilead Company, is a global biopharmaceutical company based in Santa Monica, California, focused on cell therapy to treat and potentially cure cancer. As the global cell therapy leader, Kite has treated more patients with CAR T-cell therapy than any other company. Kite has the largest in-house cell therapy manufacturing network in the world, spanning process development, vector manufacturing, clinical trial production and commercial product manufacturing. For more information on Kite, please visit www.kitepharma.com. Follow Kite on social media on Twitter (@KitePharma) and LinkedIn.

About Gilead Sciences

Gilead Sciences, Inc. is a biopharmaceutical company that has pursued and achieved breakthroughs in medicine for more than three decades, with the goal of creating a healthier world for all people. The company is committed to advancing innovative medicines to prevent and treat life-threatening diseases, including HIV, viral hepatitis and cancer. Gilead operates in more than 35 countries worldwide, with headquarters in Foster City, California. Gilead Sciences acquired Kite in 2017.

Arcellx, Inc. Forward-looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements in this press release that are not purely historical are forward-looking statements, including the potential benefits, synergies and results that may be achieved through the proposed collaboration; the anticipated completion of the proposed transaction including the closing of a proposed concurrent equity investment; the anticipated payments expected to be received by Arcellx in connection with the collaboration, including potential milestones and royalties; expectations regarding the timing and outcomes of clinical trials for its product candidates; the expected capabilities, including in manufacturing and commercialization, of Kite and Arcellx to complete clinical development, obtain regulatory approval, and if approved, commercialize the product candidates; the collaboration’s impact on Arcellx’s research and development, clinical and commercial activities, expenditures, capabilities and financials; Kite’s rights around certain ARC-SparX programs; and Arcellx’s research and development pipeline plans in autologous and allogeneic programs and beyond myeloma. The forward-looking statements contained herein are based upon Arcellx’s current expectations and involve assumptions that may never materialize or may prove to be incorrect. These forward-looking statements are neither promises nor guarantees and are subject to a variety of risks and uncertainties, including the ability to complete the proposed transaction, including the concurrent equity investment, in a timely manner or at all, including the possibility that a governmental entity may prohibit, delay or refuse to grant approval for the consummation of the transaction; the possibility that certain closing conditions to the proposed transaction will not be satisfied; uncertainty as to whether the anticipated benefits and opportunities of the proposed collaboration may not be realized or make take longer to realize or may cost more than expected; challenges in technology transfer and cell therapy manufacturing, particularly in scaling up to commercial supply volumes, that can limit the benefits of the collaboration; challenges inherent in new product candidate development, including the uncertainty of clinical success and obtaining regulatory approvals; challenges associated with collaborating with third parties, including intellectual property, operational, financial and other risks; uncertainty of commercial success for new products; the ability of Arcellx and Kite to successfully execute their strategic plans; the risk that the collaboration can be terminated; potential for other unexpected hurdles, costs or delays; and other risks that may be found in the section entitled

Part II, Item 1A (Risk Factors) in the Quarterly Report on Form 10-Q for the period ended September 30, 2022, filed with the Securities and Exchange Commission (SEC), and other documents that Arcellx files from time to time with the SEC. These forward-looking statements are made as of the date of this press release, and Arcellx assumes no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

Gilead Forward-looking Statements

This press release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks, uncertainties and other factors, including the ability of the parties to complete the transaction in a timely manner or at all; the possibility that various closing conditions for the transaction may not be satisfied or waived, including the possibility that a governmental entity may prohibit, delay or refuse to grant approval for the consummation of the transaction; difficulties or unanticipated expenses in connection with the collaboration, including with respect to the co-development, co-commercialization, and manufacturing of CART-ddBCMA or other programs subject of the collaboration and associated funding; the risk that Gilead and Kite may not realize the anticipated benefits of the collaboration with Arcellx; the possibility that the parties may make a strategic decision to terminate this collaboration at any time; the risk that Gilead’s investment in Arcellx will lose value for any number of reasons; uncertainties relating to regulatory applications and related filing and approval timelines for CART-ddBCMA or other programs subject of the collaboration, including the risk that FDA may not approve any such programs on the currently anticipated timelines or at all, and any marketing approvals, if granted, may have significant limitations on its use; the potential effect of any of the foregoing on Gilead and Kite’s earnings; and any assumptions underlying any of the foregoing. These and other risks, uncertainties and other factors are described in detail in Gilead’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2022, as filed with the U.S. Securities and Exchange Commission. These risks, uncertainties and other factors could cause actual results to differ materially from those referred to in the forward-looking statements. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. The reader is cautioned that any such forward-looking statements are not guarantees of future performance and involve risks and uncertainties, and is cautioned not to place undue reliance on these forward-looking statements. All forward-looking statements are based on information currently available to Gilead and Kite, and Gilead and Kite assume no obligation and disclaim any intent to update any such forward-looking statements.

Arcellx Contacts:    

Investors:    

Myesha Lacy

ir@arcellx.com

510-418-2412

Media:

Andrea Cohen

Sam Brown Inc.

andreacohen@sambrown.com

917-209-7163

Kite Contacts:

Investors:

Jacquie Ross

investor_relations@gilead.com

Media:

Tracy Rossin

trossin@kitepharma.com

EX-99.2

Exhibit 99.2

Arcellx Announces Continued Robust Long-Term Responses from its CART-ddBCMA Phase 1

Expansion Trial in Patients with Relapsed or Refractory Multiple Myeloma and Additional

Pipeline Progress

— 100% ORR at both CART-ddBCMA dose levels; deep and durable responses observed in patients with poor prognostic factors —

— 27 of 38 (71%) evaluable patients reached CR/sCR; 20 of 25 patients (80%) dosed > 12 months

ago or had their 12-month follow-up visit by November 22, 2022 have reached CR/sCR —

— No cases of Grade >3 CRS at RP2D and no delayed neurotoxicity or parkinsonian-like events —

— First patients dosed in iMMagine-1 Phase 2 clinical trial with pivotal drug product —

— Initiated the Phase 1 clinical trial of ACLX-002 for the treatment of patients with AML/MDS —

— Management to host a live webcast event with an expert panel of clinicians to discuss the

CART-ddBCMA clinical results on Sunday, December 11, 2022, at 11:00 AM CT —

REDWOOD CITY, Calif., December 9, 2022 /PRNewswire/ — Arcellx, Inc. (NASDAQ: ACLX), a biotechnology company reimagining cell therapy through the development of innovative immunotherapies for patients with cancer and other incurable diseases, today announced continued robust long-term responses from its CART-ddBCMA Phase 1 expansion trial in patients with relapsed or refractory multiple myeloma, dosing of first patients in its iMMagine-1 Phase 2 clinical trial with pivotal drug product, and the initiation of the Phase 1 clinical trial of ACLX-002 for the treatment of patients with relapsed or refractory acute myeloid leukemia (AML) and high-risk myelodysplastic syndromes (MDS).

38 patients were evaluable for efficacy and safety analysis as of the October 31, 2022 cutoff date, based on follow-up of at least one month, following treatment. These evaluable patients comprised the dose escalation cohorts for the first dose level (100 (+/- 20) million CAR+ T cells, n=6) and the second dose level (300 (+/- 20) million CAR+ T cells, n=6), and a dose expansion cohort at 100 (+/- 20) million CAR+ T cells (n=26). The median dose administered to patients in the first dose level and dose expansion cohorts was 115 million CAR+ T cells. All patients evaluable for this analysis have poor prognostic factors with 38 of 38 (100%) patients triple-refractory, 26 of 38 (68%) penta-refractory, and 22 of 38 (58%) with at least one high-risk prognostic factor (extramedullary disease (EMD), ISS Stage 3 [beta-2-microglobulin ≥5.5], bone marrow plasma cells (BMPC) ≥60%). All 38 patients had at least 3 prior lines of therapy.

The interim CART-ddBCMA Phase 1 clinical results (October 31, 2022 cutoff date) demonstrate deep and durable responses in patients with poor prognostic factors. Based on these data, the recommended Phase 2 dose (RP2D) was selected to be 115 (+/- 10) million CAR+T cells.

All Patients:

Of the 38 evaluable patients with median follow-up of 15 months

• 100% overall response rate (ORR) achieved in all patients per International Myeloma Working Group criteria

• 27 of 38 (71%) evaluable patients achieved complete response (CR) or a stringent complete response (sCR)

• 7 of 38 (18%) patients achieved very good partial response (VGPR)

• 4 of 38 (11%) patients achieved a partial response (PR)

• 34 of 38 (89%) patients achieved > VGPR

• 22 of 38 (58%) had high risk features (EMD, ISS stage 3, and/or BMPC ≥60%)

• 13 of 38 (34%) patients have extramedullary disease

Patients dosed 12 months prior or had their 12-month follow-up visit by November 22, 2022:

• 25 of 25 (100%) ORR

• 20 of 25 (80%) CR/sCR

• 3 of 25 (12%) VGPR

• 2 of 25 (8%) PR

• 23 of 25 (92%) > VGPR

Patients dosed 18 months prior or had their 18-month follow-up visit by November 22, 2022:

• 16 of 16 (100%) ORR

• 13 of 16 (81%) CR/sCR

• 1 of 16 (6%) VGPR

• 2 of 16 (13%) PR

• 14 of 16 (88%) > VGPR

CART-ddBCMA dosed at RP2D (115 million (+/- 10) CAR+ T cells) continues to be well-tolerated:

• No tissue-targeted toxicities observed

• No cases of delayed neurotoxicity events or parkinsonian symptoms

• No cases of grade 3 (or greater) CRS and only one case (3%) of grade 3 ICANS event with no additional cases from previously reported

• Based on the observed safety and efficacy of CART-ddBCMA, a dose of 115 (+/- 10) million CAR+ T cells was selected as the recommended phase 2 dose (RP2D)

Matthew J. Frigault, M.D., CART-ddBCMA study investigator and Assistant Director of the Cellular Therapy Service at Mass General Cancer Center and Instructor at Harvard Medical School said, “CART-ddBCMA continues to demonstrate deep responses. It is encouraging to see these clinical results with an autologous cell therapy, particularly in a population with high-risk features. Accessibility to treat multiple myeloma patients with CAR-T therapy remains an issue.”

Arcellx’s Chairman and Chief Executive Officer, Rami Elghandour continued, “We’re excited by these long-term data as they are indicative of the potential for CART-ddBCMA to make a meaningful impact for patients and the physicians who need available therapies to treat them. These results supported the initiation of our iMMagine-1 Phase 2 pivotal trial where we recently dosed the first patients in this study. We look forward to completing enrollment of iMMagine-1 and advancing towards a BLA filing. Additionally, we are excited to have initiated our Phase 1 clinical trial for ACLX-002 utilizing our ARC-SparX platform for the treatment of patients with AML or MDS. Given the heterogeneity of these diseases, we believe that by leveraging the controllability and adaptability of ARC-SparX we can overcome a degree of the toxicity issues observed with traditional single antigen CAR-T therapies.”

Presentation Details:

Title: Phase 1 Study of CART-ddBCMA for the Treatment of Subjects with Relapsed and/or Refractory Multiple Myeloma

Speaker: Matthew J. Frigault, M.D., Assistant Director of the Cellular Therapy Service at Mass General Cancer Center, and Instructor at Harvard Medical School

Session Name: 704. Cellular Immunotherapies: Early Phase and Investigational Therapies: Poster II

Session Date: Sunday, December 11, 2022

Session Time: 6:00 – 8:00 p.m. CT

Location: Ernest N. Morial Convention Center, Hall D, New Orleans, LA Publication Number: 3313

The presentation can be accessed on the company’s corporate website here.

Webcast Event:

Arcellx will host a live webcast event with an expert panel of clinicians to discuss the clinical results on Sunday, December 11, 2022, at 11:00 a.m. CT. The event will be accessible from Arcellx’s website at www.arcellx.com in the Investors section. A replay of the webcast will be archived and available for 30 days following the event.

About Multiple Myeloma

Multiple Myeloma (MM) is a type of hematological cancer in which diseased plasma cells proliferate and accumulate in the bone marrow, crowding out healthy blood cells and causing bone lesions, loss of bone density, and bone fractures. These abnormal plasma cells also produce excessive quantities of an abnormal immunoglobulin fragment, called a myeloma protein (M protein), causing kidney damage and impairing the patient’s immune function. Multiple myeloma is the third most common hematological malignancy in the United States and Europe, representing approximately 10% of all hematological cancer cases and 20% of deaths due to hematological malignancies. The median age of patients at diagnosis is 69 years with one-third of patients diagnosed at an age of at least 75 years. Because MM tends to afflict patients at an advanced stage of life, patients often have multiple co-morbidities and toxicities that can quickly escalate and become life-endangering.

About CART-ddBCMA

CART-ddBCMA is Arcellx’s BCMA-specific CAR-modified T-cell therapy utilizing the company’s novel BCMA-targeting binding domain for the treatment of patients with relapsed or refractory multiple myeloma. CART-ddBCMA is currently in a Phase 2 study. Arcellx’s proprietary binding domains are novel synthetic proteins designed to bind specific therapeutic targets. CART-ddBCMA has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy Designations by the U.S. Food and Drug Administration.

About iMMagine-1

iMMagine-1 is a Phase 2 pivotal, open-label, multicenter clinical trial designed to evaluate CART-ddBCMA, a BCMA-specific CAR-modified T-Cell therapy utilizing Arcellx’s novel BCMA-targeted binding domain, for the treatment of adult patients with relapsed or refractory multiple myeloma. The primary objective of this study is to evaluate the overall response rate over a 24-month period. In addition to safety, secondary endpoints include depth of disease response, duration of response, and overall survival over a 24-month period.

About AML

Acute myeloid leukemia (AML), also referred to as acute myelogenous leukemia, arises from cells in the bone marrow that have accumulated genetic mutations that cause the mutated cells to grow uncontrollably and disrupt the development of healthy blood cells. The aggressive growth of AML in the bone marrow and blood and the lack of durable treatments leave AML patients with an ~30% five-year survival rate. The disease is the most common acute leukemia affecting adults. According to the National Cancer Institute SEER database, there were an estimated 69,700 people living with AML in the United States in 2019. In 2022, new cases were estimated at approximately 20,050, with 11,540 deaths. Current therapies for AML have many limitations including limited efficacy and, in some cases, significant toxicities, highlighting the critical need to develop new therapies with greater safety and efficacy.

About MDS

Myelodysplastic syndrome (MDS) is a closely related disease to AML in which a population of abnormal myeloid cells develop in and disrupt the bone marrow. Depending on the type of abnormal or dysplastic cell that emerges, patients may experience a specific decrease in red blood cells or in the disease-fighting cell population referred to as monocytes, neutrophils, and dendritic cells. While MDS is itself a type of cancer, about one-third of MDS patients will also subsequently become diagnosed with AML. MDS is more common in elderly patients often diagnosed in their 70s but can also occur in non-elderly patients. MDS has been estimated to be as low as 10,000 new cases per year in the United States. While stem cell transplant can cure MDS, most patients are not able to receive them due to the typical advanced age at time of disease onset and the presence of co-morbidities, resulting in new therapies being needed for MDS patients as well.

About the ARC-SparX Platform Technology

The ARC-SparX platform is designed to allow for controllability and adaptability to potentially reduce toxicities that are often associated with serious dose-limiting adverse events and to overcome tumor heterogeneity. It is a modular therapy which utilizes a universal autologous ARC-T cell combined with one or more antigen-specific SparX protein to separate the tumor-recognition and tumor-killing functions. SparX (soluble protein antigen-receptor X-linkers) proteins utilize our D-Domain technology engineered to recognize antigens on the surface of diseased cells and flags those cells for detection by the ARC-T cells. ARC-T cells express a D-Domain-based CAR engineered to specifically recognize a unique TAG sequence in the SparX protein. ARC-T cells can be dosed separately and are designed to be activated to kill the target cell only when they encounter a SparX protein bound to the target antigen and thus can be controlled through dose modulation of the SparX protein. Arcellx has developed a collection of SparX proteins that bind different antigens on the surface of diseased cells. Multiple SparX proteins with different antigen specificity can be administered to potentially address antigen heterogeneity or antigen escape that contribute to relapsed and refractory disease.

About the Phase 1 Study Evaluating ACLX-002 for Patients with Acute Myeloid Leukemia or Myelodysplastic Syndrome (NCT05457010)

The Phase 1 study evaluating ACLX-002 in adults with relapsed and/or refractory acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS) is an open-label, multicenter, dose escalation clinical trial designed to evaluate the safety of ACLX-002. Secondary objectives are to measure anti-tumor activity and pharmacokinetics of both SparX-002 and ARC-T cells.

About Arcellx, Inc.

Arcellx, Inc. is a clinical-stage biotechnology company reimagining cell therapy by engineering innovative immunotherapies for patients with cancer and other incurable diseases. Arcellx believes that cell therapies are one of the forward pillars of medicine and Arcellx’s mission is to advance humanity by developing cell therapies that are safer, more effective, and more broadly accessible. Arcellx’s lead product candidate, CART-ddBCMA, is being developed for the treatment of relapsed or refractory multiple myeloma (r/r MM) in an ongoing Phase 2 study. CART-ddBCMA has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy designations by the U.S. Food and Drug Administration.

Arcellx is also advancing its dosable and controllable CAR-T therapy, ARC-SparX, through two programs: a Phase 1 study of ACLX-001 for r/r MM, initiated in the second quarter of 2022; and ACLX-002 in relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome, initiated in the fourth quarter of 2022.

Visit www.arcellx.com for more information.

Forward-looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements in this press release that are not purely historical are forward-looking statements, including Arcellx’s expectations regarding the timing and outcomes of clinical trials for its product candidates; the potential impact of its product candidates and platforms on patients and cell therapy; and the timing of achievement of its milestones. The forward-looking statements contained herein are based upon Arcellx’s current expectations and involve assumptions that may never materialize or may prove to be incorrect. These forward-looking statements are neither promises nor guarantees and are subject to a variety of risks and uncertainties, including those set forth in Part I, Item 1A (Risk Factors) of Arcellx’s Annual Report on Form 10-K and in other reports, such as Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, that Arcellx may file from time to time with the Securities and Exchange Commission. These forward-looking statements are made as of the date of this press release, and Arcellx assumes no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

Investor Contact:

Myesha Lacy

Arcellx

ir@arcellx.com

510-418-2412

Media Contact

Andrea Cohen

Sam Brown Inc.

andreacohen@sambrown.com

917-209-7163

###

XML

Document and Entity Information	Dec. 09, 2022
Cover [Abstract]
Amendment Flag	false
Entity Central Index Key	0001786205
Document Type	8-K
Document Period End Date	Dec. 09, 2022
Entity Registrant Name	Arcellx, Inc.
Entity Incorporation State Country Code	DE
Entity File Number	001-41259
Entity Tax Identification Number	47-2855917
Entity Address, Address Line One	25 West Watkins Mill Road
Entity Address, Address Line Two	Suite A
Entity Address, City or Town	Gaithersburg
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20878
City Area Code	(240)
Local Phone Number	327-0603
Written Communications	false
Soliciting Material	false
Pre Commencement Tender Offer	false
Pre Commencement Issuer Tender Offer	false
Security 12b Title	Common Stock, $0.001 par value per share
Trading Symbol	ACLX
Security Exchange Name	NASDAQ
Entity Emerging Growth Company	true
Entity Ex Transition Period	false