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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

December 8, 2024 – Biotechnology, Clinical Trials, Drug Discovery, Pharmaceutical – ASH 2024, Arcellx, clinical trial, clinical trials, relapsed or refractory multiple myeloma

Preliminary results from 86 patients enrolled in the Phase 2 pivotal iMMagine-1 study of anito-cel demonstrated 97% ORR and 62% CR/sCR at a median follow-up of 9.5 months
No delayed neurotoxicities have been observed to date with anito-cel, including no Parkinsonism, no cranial nerve palsies, and no Guillain-Barré syndrome in more than 150 patients dosed across the Phase 1 and iMMagine-1 studies
30.2-month median progression-free survival with a median follow-up of 38.1 months in the Phase 1 study of anito-cel; median overall survival not reached
Company highlights additional presentations during the ASH Annual Meeting
Company to host a live webcast event with an expert panel of clinicians on Monday, December 9, 2024 at 8 p.m. PT

8 December 2024 — California, US — Arcellx, Inc, 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 115×10⁶CAR+ 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^-5sensitivity. 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.

Conclusions

Preliminary results from the Phase 2 iMMagine-1 study demonstrate deep and durable responses with a predictable and manageable safety profile in a high-risk 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, have been observed with anito-cel to date.

Ciara Freeman, M.D., Ph.D., Assistant Member, Department of Blood and Marrow Transplant and Cellular Immunotherapy, Moffitt Cancer Center said, “The data from the iMMagine-1 study demonstrate that this is a highly active product with impressive depth of responses achieved in patients with relapsed or refractory multiple myeloma. As a physician who treats many patients both inpatient and in the outpatient setting, the emerging safety profile of anito-cel is encouraging, in particular the absence of any delayed neurotoxicities reported to date. We are excited to begin enrolling patients in the iMMagine-3 study and in the near future having anito-cel as an approved treatment option.”

Arcellx’s Chairman and Chief Executive Officer, Rami Elghandour, said, “It’s exciting to reach this momentous milestone in our pivotal study and present these compelling data. These data, along with the data from our Phase 1 study, which demonstrated a 30.2-month median PFS and zero cases of delayed neurotoxicity or other non-ICANS neurotoxicity with all patients having more than two years of follow-up, continue to support our conviction that anito-cel has the potential to be a best-in-class treatment option for patients with RRMM. Additionally, with iMMagine-3 underway in earlier lines in a patient population representing an unmet clinical need, we expect to further position anito-cel as a differentiated CAR-T treatment option for RRMM. Separately, this year is Arcellx’s 10th anniversary! I’m grateful for the incredible people who make up the fabric of Arcellx and have poured themselves into developing this life-saving therapy for the patients most in need. And I’m proud of how we’ve done it, leaning into our diversity as a cornerstone of our culture, which underpins our success. I especially appreciate the partnership, collaboration, and trust of the Phase 1 and iMMagine-1 clinicians who helped enroll patients in these studies and allowed us to demonstrate the potential benefit of anito-cel. I’m also grateful to those who believed in us, our founding investors and scientists, our investors who helped us go public nearly three years ago in a challenging market, and those who have joined us along the way. To our colleagues at Kite, we thank you for your partnership. To everyone who’s been part of this incredible journey, thank you! We’re just getting started!”

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.