Bhagirathbhai R. Dholaria, MD, on Evaluating P-BCMA-ALLO1 in R/R Myeloma

This article originally appeared on our sister site, OncLive®.

“We did not report any grade 3 or [higher] cytokine release syndrome or immune effector cell–associated neurotoxicity syndrome.”

Poseida Therapeutics is currently evaluating P-BCMA-ALLO1, an allogeneic BCMA-directed chimeric antigen receptor T-cell (CAR-T) therapy, in an ongoing phase 1/1b clinical trial (NCT04960579) for the treatment of relapsed/refractory (r/r) multiple myeloma (MM). Data from the trial were recently presented at the 2025 Tandem Meetings |Transplantation & Cellular Therapy Meetings of ASTCT and CIBMTR, held in Honolulu, Hawaii, February 12 to 15, 2025. The presentation focused on findings from the study's optimized lymphodepletion cohort (Arm C).

Arm C included patients with r/r MM who had been previously treated with at least 3 prior lines of therapy, including a proteasome inhibitor, an immunomodulatory drug, and an antiCD38 monoclonal antibody. The arm allowed for inclusion patients who had previously received a BCMA-directed therapy. In an interview with CGTLive®'s sister site OncLive®, Bhagirathbhai R. Dholaria, MD, an associate professor of medicine in malignant hematology & stem cell transplantation at Vanderbilt University Medical Center, discussed the results presented at the conference.

The study included 32 evaluable patients in Arm C, and findings demonstrated an overall response rate (ORR) of 88%. Among specific subgroups, patients who were naive to BCMA-directed therapy (n = 16) achieved an ORR of 100% . Those who previously had received 1 or more BCMA-targeted therapies (n = 12) experienced an ORR of 75%, and patients with prior exposure to both BCMA- and GPRC5D-directed therapies (n = 9) achieved an ORR of 78%. Notably, responses were rapid, with a median time to response of 16 days for patients across cohorts A, B, and C. In cohorts A and B, the median duration of response was 214 days; most patients in arm C had been enrolled within 6 months of data cutoff.

Safety data for P-BCMA-ALLO1 in cohort C showed that no cases of grade 3 or higher cytokine release syndrome (CRS) or immune effector cell–associated neurotoxicity syndrome (ICANS) were reported. Additionally, no patients experienced Parkinsonism, movement disorders, or hemophagocytic lymphohistiocytosis. The overall incidence of CRS was 42%, with all cases limited to grade 1 or 2 in severity. ICANS occurred in 14% of patients, but all events were grade 1 and resolved with minimal steroid intervention.

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