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): June 19, 2023

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, Maryland	20878
(Address of Principal Executive Offices)	(Zip Code)

Registrant’s Telephone Number, Including Area Code: 240 327-0603

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 8.01 Other Events.

On June 19, 2023, Arcellx, Inc. (the “Company”) issued a press release announcing that the Company received a clinical hold notice from the U.S. Food and Drug Administration regarding the Company’s CART-ddBCMA investigational new drug for the treatment of patients with relapsed or refractory multiple myeloma. A copy of the Company’s press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.	Description
99.1	Press Release dated June 19, 2023
104	Cover Page Interactive Data File (embedded within the Inline XBRL Document)

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: June 20, 2023	By:	/s/ Rami Elghandour
		Rami Elghandour Chief Executive Officer

EX-99.1

Exhibit 99.1

Arcellx Announces Clinical Hold for its iMMagine-1 Phase 2 Clinical Program

— FDA has provided clearance to the company to continue dosing patients

who have already undergone lymphodepletion —

REDWOOD CITY, Calif., June 19, 2023 /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, announced today that it has received notification from the U.S. Food and Drug Administration (FDA) that a clinical hold has been placed on its CART-ddBCMA investigational new drug (IND) for the treatment of patients with relapsed or refractory multiple myeloma (rrMM).

The clinical hold was received on June 16, following a recent patient death. The company believes limitations on bridging therapy are a contributing factor and is working with FDA to amend the protocol to expand options for patients that are consistent with current clinical practice. The FDA has provided clearance to Arcellx to continue to dose patients who have undergone lymphodepletion.

“The safety and well-being of patients enrolled in our studies is our top priority,” said Rami Elghandour, Arcellx’s Chairman and Chief Executive Officer.“ In coordination with our investigators, data safety monitoring board (DSMB), and our partners at Kite Pharma, we are working with FDA to address the clinical hold. The expansion of bridging therapy regimens is consistent with what’s currently available in clinical practice and is in the best interest of patients. Additionally, we continue to evaluate other potential improvements to the study. We remain confident that CART-ddBCMA is a potential best-in-class therapy for the treatment of patients with rrMM based on the clinical profile observed in the patients dosed to date across our studies. The drug product release characteristics from iMMagine-1 are consistent with those from our Phase 1 study. The manufacturing success rate remains 100% while ramping Lonza, our cell therapy manufacturer, to full scale. Fourteen clinical sites have been opened and study enrollment is tracking to our expectations. We look forward to resolving this matter expeditiously and to continue to advance our therapy to the benefit of patients suffering from rrMM.”

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 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 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, without limitation: Arcellx’s belief regarding limitations on bridging therapy as a contributing factor to a recent patient death and bridging therapy being in the best interest of patients; Arcellx’s belief that the drug product release characteristics from iMMagine-1 are consistent with those from its Phase 1 study; Arcellx’s belief regarding the potential of CART-ddBCMA to be a best-in-class therapy for the treatment of patients with rrMM; and statements regarding the FDA’s clinical hold and related timing and potential resolution. 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 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 quarter ended March 31, 2023, as amended, filed with the Securities and Exchange Commission (SEC) on May 9, 2023, and the other documents that Arcellx may file 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.

Investor Contact:

Myesha Lacy

Arcellx, Inc.

ir@arcellx.com

510-691-6361

Media Contact:

Laura Morgan

Sam Brown Inc.

lauramorgan@sambrown.com

951-333-9110

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Cover [Abstract]
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Entity Central Index Key	0001786205
Document Type	8-K
Document Period End Date	Jun. 19, 2023
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