Arcellx, Inc. (NASDAQ: ACLX) has announced promising new data from its pivotal Phase 2 iMMagine-1 study evaluating anitocabtagene autoleucel (anito-cel) in patients with relapsed or refractory multiple myeloma (RRMM). The results, which will be presented at the upcoming EHA2025 Congress in Milan on June 14, 2025, demonstrate strong efficacy and a manageable safety profile.
The study included 117 patients with a median follow-up of 12.6 months. All patients received a single infusion of anito-cel at a target dose of 115×10^6 CAR+ viable T cells. The patient population was heavily pretreated, with 86% being triple-class refractory and 41% penta-refractory. Patients had received a median of three prior lines of therapy.
Impressive Efficacy Results
The data revealed an overall response rate (ORR) of 97%, with 114 of 117 patients responding to treatment. The complete response/stringent complete response (CR/sCR) rate was 68% (79/117), and 85% of patients (100/117) achieved a very good partial response or better.
Dr. Gurbakhash Kaur, Assistant Professor of Internal Medicine at Mount Sinai Health System and presenter of the upcoming EHA data, noted, "These results demonstrate deep and durable responses in a patient population with limited treatment options."
Minimal residual disease (MRD) testing showed that 93.3% (70/75) of evaluable patients achieved MRD negativity at a sensitivity of at least 10^-5, indicating the elimination of detectable cancer cells.
Survival data was equally encouraging, with six-month progression-free survival (PFS) and overall survival (OS) rates of 91.9% and 96.6%, respectively. At the 12-month mark, PFS was 78.8% and OS was 95.2%. Neither median PFS nor median OS had been reached at the time of data cutoff.
Favorable Safety Profile
A key highlight of the anito-cel data is the absence of certain toxicities that have been observed with other CAR-T therapies. No delayed neurotoxicities, including Parkinsonism, cranial nerve palsies, and Guillain-Barré syndrome, have been reported. Additionally, no immune-mediated enterocolitis has been observed to date.
No additional treatment- or therapy-related deaths or Grade ≥3 cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) events have occurred since the previous data presentation in December 2024.
Novel Technology Platform
Anito-cel is the first BCMA-directed CAR-T cell therapy to utilize Arcellx's proprietary D-Domain binder technology. This novel approach features a small, stable binder that enables high CAR expression without tonic signaling and is designed to quickly release from the BCMA target.
"These clinical data from our registrational study continue to support our belief that anito-cel has the potential to address the needs of myeloma patients and the physicians who serve them," said Rami Elghandour, Arcellx's Chairman and Chief Executive Officer. "There is no cure for multiple myeloma. We believe there remains an unmet medical need for CAR-T therapies that are efficacious, safe, and accessible."
Strategic Partnership and Commercialization Plans
Anito-cel is being developed in collaboration with Kite, a Gilead Company. Under this global strategic partnership, the companies will jointly commercialize anito-cel in the United States, while Kite will handle commercialization outside the U.S.
"Our 2026 commercial launch plans for anito-cel with our partners at Kite are well underway and we are excited for the opportunity to advance anito-cel in support of the myeloma community," Elghandour added.
Multiple Myeloma: A Significant Unmet Need
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 at diagnosis is 69 years, with one-third of patients diagnosed at 75 years or older.
The disease is characterized by abnormal plasma cells that proliferate in the bone marrow, causing bone lesions, fractures, and producing excessive quantities of abnormal immunoglobulin fragments that can lead to kidney damage and immune dysfunction.
Despite advances in treatment, multiple myeloma remains incurable, with patients eventually relapsing after each line of therapy. The development of new treatment options, particularly for heavily pretreated patients, represents a critical area of need.
Regulatory Status and Next Steps
Anito-cel has received Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy Designations from the U.S. Food and Drug Administration, highlighting its potential to address significant unmet medical needs.
In addition to the Phase 2 iMMagine-1 study, anito-cel is being evaluated in a global Phase 3 randomized controlled study for relapsed and/or refractory multiple myeloma. The complete data from the iMMagine-1 trial will be presented during an oral session at the EHA2025 Congress on June 14, 2025, with Arcellx planning to host a live webcast event featuring an expert panel of clinicians during the conference.
With these promising results and ongoing development efforts, anito-cel appears positioned to potentially become an important addition to the treatment landscape for multiple myeloma patients who have exhausted other therapeutic options.
