Arcellx Announces New Positive Data for Its iMMagine-1 Study in Patients with Relapsed and/or Refractory Multiple Myeloma

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 new positive data from its pivotal Phase 2 iMMagine-1 study of anitocabtagene autoleucel (anito-cel), in patients with relapsed or refractory multiple myeloma (RRMM). These data are being presented during an oral presentation at the 67th American Society of Hematology (ASH) Annual Meeting and Exposition on Saturday, December 6, 2025 at 2:45 p.m. ET. Anito-cel is partnered with Kite, a Gilead Company.

October 7, 2025, is the data cutoff date for this presentation and the BLA submission. These data are for all 117 patients with a median follow-up of 15.9 months. All patients received a single infusion of anito-cel (target dose of 115×10⁶ CAR+ viable T cells). Within the study population, 102 of 117 patients (87%) were triple refractory, 48 of 117 patients (41%) were penta refractory, 21 of 117 patients (18%) had extramedullary disease, and 47 of 117 patients (40%) had high risk cytogenetics. Patients received a median of three prior lines of therapy, with 65 of 117 patients (56%) having received three prior lines.

Overall response rate (ORR) was 96% (112/117) with a complete response/stringent complete response (CR/sCR) rate of 74% (86/117) and a very good partial response or higher (≥VGPR) rate of 88% (103/117), per Independent Review Committee (IRC) assessment. Of those evaluable for minimal residual disease (MRD) testing at the time of this data cut, 95% (91/96) achieved overall MRD negativity. Of the MRD evaluable group with sufficient follow up, 83% (54/65) sustained MRD negativity for >6 months, at a minimum of 10^-5 sensitivity. Six-month progression-free survival (PFS) and overall survival (OS) rates were 93.1% and 95.7%, respectively; 12-month PFS and OS rates were 82.1% and 94.0%, respectively; 18-month PFS and OS rates were 67.4% and 88.0% respectively, and 24-month PFS and OS rates were 61.7% and 83.0% respectively. Median PFS and median OS have not been reached.

To date, no delayed or non-ICANS 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 with all patients dosed more than 12 months ago.

Conclusions

Preliminary results from the Phase 2 iMMagine-1 study continue to demonstrate deep and durable responses with a predictable and manageable safety profile in a fourth-line or higher (4L+) RRMM population, including triple- and penta-refractory disease. Notably, no delayed or non-ICANS 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 to date.