Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy bb21217 for relapsed and refractory multiple myeloma: results from the phase 1 CRB-402 study

Chimeric antigen receptor (CAR) T-cell therapy enriched for a memory-like phenotype may persist and function longer than a non-enriched product, thereby improving duration of response (DOR). We conducted a phase 1 study with bb21217 (NCT03274219), an anti-B-cell maturation antigen CAR T-cell therapy manufactured in the presence of bb007 (phosphoinositide 3-kinase inhibitor) to enrich for T cells with a memory-like phenotype, in patients with relapsed/refractory multiple myeloma. No new safety concerns were raised with bb21217 therapy. The objective response rate was 69.4% and median DOR was 23.8 (95% confidence interval, 16.8–34.8) months. Analysis of drug product established an association between early memory phenotype and robust expansion and depth of response. Examination of baseline characteristics indicated that tumor burden and prior therapies influenced DOR. This supports the generation of CAR T cells early in a disease course when tumor burden is lower and source material exhibits a more naïve phenotype. RNA-Seq was performed on pre-infusion bb21217 drug products (DPs) for 75 patients participating in CRB-402 (NCT03274219), a two-part, non-randomized, open-label, multi-site, phase 1 study of bb21217 in patients with relapsed/refractory (R/R) Multiple Myeloma (MM). In Part A (dose-escalation phase), 12 patients received a target dose of 150 × 106 CAR T cells, 6 received 300 × 106 cells and 6 received 450 × 106 cells. In Part B (dose-expansion phase), 8 patients received 300 × 106 cells and 40 patients received 450 × 106 cells. bb21217 Drug Product (DP) was manufactured by transducing autologous T cells with an anti-BCMA02 CAR lentiviral vector as described by Friedman et al. (2018) and culturing in the presence of bb007.