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 will be presented during an oral presentation at the EHA2025 Congress in Milan on June 14, 2025. Anito-cel is partnered with Kite, a Gilead Company.

The Phase 2 iMMagine-1 data are from a May 1, 2025 data cutoff date, including all 117 patients with a median follow-up of 12.6 months and a minimum follow-up of four months after treatment with anito-cel. All patients received a single infusion of anito-cel (target dose of 115×10⁶ CAR+ viable T cells). 101 of 117 patients (86%) were triple refractory, and 48 of 117 patients (41%) were penta refractory. Patients received a median of three prior lines of therapy, with 60 of 117 patients (51%) having received three prior lines.

Overall response rate (ORR) was 97% (114/117) with a complete response/stringent complete response (CR/sCR) rate of 68% (79/117) and a very good partial response or higher (>VGPR) rate of 85% (100/117), per International Myeloma Working Group (IMWG) criteria as investigator-assessed. Of those evaluable for minimal residual disease (MRD) testing at the time of this data cut, 93.3% (70/75) achieved MRD negativity at a minimum of 10^-5 sensitivity. Six-month progression-free survival (PFS) and overall survival (OS) rates were 91.9% and 96.6%, respectively, and 12-month PFS and OS rates were 78.8% and 95.2%, respectively. Median PFS and median OS have not been reached.

No delayed or non-immune effector cell-associated neurotoxicity syndrome (ICANS) neurotoxicities, including no Parkinsonism, no cranial nerve palsies, and no Guillain-Barré syndrome, and no immune-mediated enterocolitis have been observed to date with anito-cel. No additional treatment- or therapy-related deaths or Grade ≥3 cytokine release syndrome (CRS) or ICANS events have occurred since the previous data presentation in December 2024.

Conclusions

Preliminary results from the Phase 2 iMMagine-1 study 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-class refractory disease. Notably, no delayed or non-ICANS neurotoxicities, including no Parkinsonism, no cranial nerve palsies, and no Guillain-Barré syndrome, and no immune-mediated enterocolitis have been observed with anito-cel to date.