REDWOOD CITY, Calif. — 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 that new clinical data from its Phase 1 study of CART-ddBCMA in patients with relapsed or refractory multiple myeloma will be presented at the 65th American Society of Hematology (ASH) Annual Meeting and Exposition taking place December 9-12, 2023 in San Diego, California. The data in the ASH abstract published today is from a June 2, 2023 data cut. The oral presentation at ASH will be on Monday, December 11, 2023 at 5 p.m. PT and will include new data with a median follow-up of 26.5 months. The company will also have a medical affairs booth (#748) in Hall E of the San Diego Convention Center.
As detailed in the abstract (#1023), 38 patients were evaluable for efficacy and safety analysis as of the June 2, 2023 cutoff date, based on a median follow-up of 22 months following treatment. These evaluable patients comprised the dose escalation cohorts for the first dose level (100 (+/- 20) million CAR+ T cells, n=6) and the second dose level (300 (+/- 20) million CAR+ T cells, n=6), and a dose expansion cohort at 100 (+/- 20) million CAR+ T cells (n=26). The median dose administered to patients in the first dose level and dose expansion cohorts was 115 million CAR+ T cells. All patients evaluable for this analysis have poor prognostic factors with 38 of 38 (100%) patients triple-refractory, 26 of 38 (68%) penta-refractory, and 34 of 38 (89%) refractory to last-line of treatment by International Myeloma Working Group (IMWG) criteria. Additionally, 9 of 38 patients (24%) patients had high tumor burden with >60% bone marrow plasma (BMPC) cells, 13 of 38 patients (34%) patients had extramedullary disease (EMD), and 11 of 38 (29%) patients had high-risk cytogenetics (Del 17p, t(14;16), t(4;14)) at baseline. At baseline, 24 of 38 (63%) had at least one high risk clinical feature, defined as presence of EMD, BMPC >60% or B2M >5.5. All 38 patients had at least three prior lines of therapy.
The interim CART-ddBCMA Phase 1 clinical results (June 2, 2023 cutoff date) demonstrate deep and durable responses in patients with poor prognostic factors.
All Patients:
Of the 38 evaluable patients with a median follow-up of 22 months
- 100% overall response rate (ORR) achieved in all patients per IMWG criteria
- 29 of 38 evaluable patients achieved a complete response (CR) or a stringent complete response (sCR) (> CR rate, 76%)
- 35 patients achieved a very good partial response or higher (>VGPR rate, 92%)
Median duration of response, progression free survival (PFS), and overall survival were not reached at the time of the June 2, 2023 data cut because 25 of 38 (66%) evaluable patients had ongoing responses.
The Kaplan-Meier method estimated PFS rates for 6, 12, and 18 months were 92%, 74%, and 67% respectively. Durable responses were also observed in patients with high-risk features (EMD, BMPC ≥60%, or B2M ≥5.5 mg/L at baseline) and high-risk cytogenetics.
PFS rates at 6-, 12-, and 18 months by Kaplan-Meier method were:
| PFS Rates (%) | |||
| 6-month | 12-month | 18-month | |
| All dosed (n=38) | 92.1 | 74.3 | 67.5 |
| Age ≥65 years (n=20) | 95.0 | 84.4 | 78.4 |
| Complete responders (n=29) | 96.4 | 88.8 | 84.6 |
| High Risk Features* (n=24) | 91.7 | 73.3 | 68.1 |
| Extramedullary Disease (n=13) | 92.3 | 64.6 | 64.6 |
| High Risk Cytogenetics (n=11) | 81.8 | 70.1 | 70.1 |
| *High risk features defined as presence of EMD, BMPC ≥60, or B2M ≥5.5 mg/L. Note: increased from prior presentation from 22 to 24 subjects as a result of database update based on monitoring and query resolution. | |||
CART-ddBCMA dosed at RP2D (115 million (+/- 10) CAR+ T cells) continues to be well-tolerated at the time of the data cut:
- Adverse events with CART-ddBCMA, including CRS and ICANS, were manageable
- No tissue-targeted toxicities were observed
- No cases of delayed neurotoxicity events or parkinsonian symptoms were observed
About Multiple Myeloma
Multiple Myeloma (MM) is a type of hematological cancer in which diseased plasma cells proliferate and accumulate in the bone marrow, crowding out healthy blood cells and causing bone lesions, loss of bone density, and bone fractures. These abnormal plasma cells also produce excessive quantities of an abnormal immunoglobulin fragment, called a myeloma protein (M protein), causing kidney damage and impairing the patient’s immune function. 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 of patients at diagnosis is 69 years with one-third of patients diagnosed at an age of at least 75 years. Because MM tends to afflict patients at an advanced stage of life, patients often have multiple co-morbidities and toxicities that can quickly escalate and become life-endangering.
About CART-ddBCMA
CART-ddBCMA is Arcellx’s BCMA-specific CAR-modified T-cell therapy utilizing the company’s novel BCMA-targeting binding domain for the treatment of patients with relapsed or refractory multiple myeloma. CART-ddBCMA is currently in a Phase 2 study. Arcellx’s proprietary binding domains are novel synthetic proteins designed to bind specific therapeutic targets. CART-ddBCMA has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy Designations by the U.S. Food and Drug Administration.
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. Arcellx’s lead product candidate, CART-ddBCMA, is being developed for the treatment of relapsed or refractory multiple myeloma (rrMM) in a Phase 2 pivotal trial. CART-ddBCMA has been granted Fast Track, Orphan Drug, and Regenerative Medicine Advanced Therapy designations by the U.S. Food and Drug Administration.
Arcellx is also advancing its dosable and controllable CAR-T therapy, ARC-SparX, through two clinical-stage programs: a Phase 1 study of ACLX-001 for rrMM, initiated in the second quarter of 2022; and ACLX-002 in relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome, initiated in the fourth quarter of 2022.
Contact
Andrea Cohen
Sam Brown Inc.
[email protected]
917-209-7163