Arcellx Announces New Positive Data for Its iMMagine-1 Study in Patients With Relapsed or Refractory Multiple Myeloma to be Presented During an Oral Presentation at the 66th ASH Annual Meeting and Exposition

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 Phase 2 pivotal 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 66th American Society of Hematology (ASH) Annual Meeting and Exposition on Monday, December 9, 2024 at 5:30 p.m. PT. Anito-cel is partnered with Kite, a Gilead Company. Additional presentations during ASH are also noted below.

The Phase 2 iMMagine-1 data are from an October 31, 2024 data cutoff date, with a median follow-up of 9.5 months for the efficacy evaluable population. At the time of the data cut, 86 patients were evaluable for efficacy based on a follow-up of at least two months after treatment with anito-cel, and 98 patients were evaluable for safety based on a follow-up of at least one month after treatment with anito-cel. All patients received a single infusion of anito-cel (target dose of 115×10⁶ CAR+ viable T cells). In the safety evaluable population, 85 of 98 patients (87%) were triple refractory, and 41 of 98 patients (42%) were penta refractory. Patients received a median of four prior lines of therapy, with 45 of 98 patients (46%) having received three prior lines.

Overall response rate (ORR) was 97% (83/86) with a complete response/stringent complete response (CR/sCR) rate of 62% (53/86) and a very good partial response or higher (>VGPR) rate of 81% (70/86), per International Myeloma Working Group (IMWG) criteria as investigator-assessed. Of those evaluable for minimal residual disease (MRD) testing, 93.1% (54/58) achieved MRD negativity at a minimum of 10^-5 sensitivity. Median progression-free survival (mPFS) and overall survival (OS) were not reached; 6-month PFS and OS rates were 93.3% and 96.5%, respectively, and 12-month PFS and OS rates were 78.5% and 96.5%, respectively.

No delayed or non-ICANS neurotoxicities, including no Parkinsonism, no cranial nerve palsies, and no Guillain-Barré syndrome, have been observed to date in more than 150 patients dosed with anito-cel. Of the safety evaluable population, 86% (84/98) had Grade ≤1 cytokine release syndrome (CRS), including 17% of patients with no CRS. Among patients experiencing CRS, the median onset was four days (range: 1-17 days). Eight percent of patients (8/98) were treated as outpatient. Ninety-one percent (89/98) of patients had no ICANS. Any Grade ICANS was observed in 9 patients (9%; Gr3 1%), with all cases resolved without sequelae. Three deaths occurred due to treatment-emergent adverse events (TEAEs) (related or unrelated to anito-cel: retroperitoneal hemorrhage, CRS, and fungal infection). No additional treatment or therapy-related deaths or Grade ≥3 CRS or ICANs events have occurred to date. Cytopenias were the most common Grade ≥3 TEAEs; 53 patients (54%) had Grade ≥3 neutropenia, 20 (20%) had Grade ≥3 thrombocytopenia, and 22 (22%) had Grade ≥3 anemia.