-- A more recent data cut will be shared during an oral presentation for the iMMagine-1 study --

-- To date, no delayed neurotoxicities, including no Parkinsonism, no cranial nerve palsies, no Guillain-Barré syndrome, and no immune effector cell-associated enterocolitis have been observed with anito-cel --

-- FDA pre-BLA meeting for anito-cel has occurred; reiterating planned 2026 commercial launch --

-- Company to host a live webcast event with an expert panel of clinicians during ASH 2025 --

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 it will share two presentations at the 67th American Society of Hematology (ASH) Annual Meeting and Exposition taking place December 6-9, 2025, in Orlando, Florida, including updated clinical data from iMMagine-1, its Phase 2 pivotal study (publication #256) of anitocabtagene autoleucel (anito-cel) in patients with relapsed and/or refractory multiple myeloma (RRMM). Additionally, an abstract (publication #7644) describing the fast off-rate of anito-cel’s D-Domain binder will be published in a supplemental issue of Blood in November 2025. The company will also have a medical affairs booth (#1363) at the Orange County Convention Center.

“We’re pleased to share that, along with our partners at Kite, we conducted our pre-BLA meeting with the FDA and remain confident in our planned 2026 commercial launch of anito-cel,” said Rami Elghandour, Arcellx’s Chairman and Chief Executive Officer. “This milestone marks a significant step toward bringing our innovative therapy to the multiple myeloma community. We look forward to sharing updated clinical data from our iMMagine-1 study in an oral presentation at ASH. These are exciting times at Arcellx!”

ASH Presentation Details:

Title: Phase 2 registrational study of anitocabtagene autoleucel for the treatment of patients with relapsed and/or refractory multiple myeloma: Updated results from iMMagine-1

Speaker: Krina K. Patel, MD, MSc, MD Anderson Cancer Center

Session Name: 655. Multiple Myeloma: Cellular Therapies: Clinical Trial Advances in CAR T-Cell Therapy for Multiple Myeloma

Session Date: Saturday, December 6, 2025

Session Time: 2:00 p.m. – 3:30 p.m. ET

Presentation Time: 2:45 p.m. ET

Location: OCCC – West Hall E1

Publication Number: 256

Submission ID: abs25-4541

Title: Visualizing geographic variation and systemic inequities of disease burden and CAR T-cell therapy access in multiple myeloma in the US

Speaker: Brandon Blue, MD, Moffitt Cancer Center

Session Name: 907. Outcomes Research: Plasma Cell Disorders: Poster III

Session Date: Monday, December 8, 2025

Session Time: 6:00 p.m. – 8:00 p.m. ET

Location: OCCC – West Halls B3-B4

Publication Number: 6344

Submission ID: abs25-2093

Title: The fast off-rate of anito-cel’s D-Domain binder contributes to its distinctive pharmacology profile in preclinical models of multiple myeloma

Disposition: Online Publication

Publication Number: 7644

Submission ID: abs25-1695

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. MM 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 Anitocabtagene Autoleucel (anito-cel)

Anitocabtagene autoleucel (anito-cel, previously CART-ddBCMA) is the first BCMA-directed CAR T-cell therapy to be investigated in multiple myeloma that utilizes Arcellx’s novel and compact binder known as the D-Domain. The small, stable D-Domain binder enables high CAR expression without tonic signaling and is designed to quickly release from the BCMA target. This combination may allow for the effective elimination of multiple myeloma cells without severe immunotoxicity. Anito-cel has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy Designations by the U.S. Food and Drug Administration.

About Arcellx and Kite Collaboration

Arcellx and Kite, a Gilead Company, formed a global strategic collaboration and license agreement to co-develop and co-commercialize anito-cel for patients with multiple myeloma. Anito-cel is currently being developed in a Phase 2 registrational pivotal study and a global Phase 3 randomized controlled study for relapsed and/or refractory multiple myeloma (RRMM). Kite and Arcellx will jointly commercialize the anito-cel asset in the United States, and Kite will commercialize the product outside the United States.

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. For more information on Arcellx, please visit www.arcellx.com. Follow Arcellx on X @arcellx and LinkedIn.

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, statements regarding: anticipated announcements of additional data; anito-cel pharmacology profile, tolerability and toxicity trends; the potential of anito-cel for providing meaningful benefit in patients suffering from multiple myeloma; the potential commercial launch of anito-cel, subject to FDA approval, in partnership with Kite; and the potential impact of Arcellx’s product candidates and platforms on patients and cell therapy. 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 fiscal quarter ended June 30, 2025, filed with the Securities and Exchange Commission (SEC) on August 7, 2025, 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.

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