As of May 24, 2023, 70 pts received BMS-986393 at doses of 25 (n = 6), 75 (n = 10), 150 (n = 26), 300 (n = 17), and 450 (n = 11) × 10 6 CAR T cells. 32 pts (46%) had high-risk cytogenetics (del[17p], t[4;14], and/or t[14;16]), 40 (57%) had 1q21amp, and 30 (43%) had extramedullary plasmacytomas; 32 (46%) pts had received prior BCMA-targeted therapy, including BCMA-directed CAR T-cell therapy in 25 (36%) pts. 24 (34%) pts had penta-refractory MM.

Grade (G) 3/4 treatment-emergent adverse events (AEs) occurred in 64/70 (91%) pts; the most frequent were neutropenia (69%), anemia (31%), and thrombocytopenia (30%). Any-grade infections occurred in 30 (43%) pts (G 3/4 in 11 [16%] pts). Cytokine release syndrome (CRS) occurred in 59 (84%) pts (G ≥ 3 in 3 [4%] pts, with 1 [1%] G5 event); 3 (4%) pts had hemophagocytic lymphohistiocytosis, all G3. On-target off-tumor treatment-related AEs (TRAEs), all G1/2, included skin (17 [24%]) and nail (11 [16%]) TRAEs and dysgeusia/dysphagia (2 [3%]). Immune effector cell-associated neurotoxicity syndrome (ICANS)-type neurotoxicity occurred in 8 (11%) pts (G3 in 2 [3%] pts). The most frequent non-ICANS neurologic TRAEs were headache (10 [14%]), dizziness (6 [9%]), ataxia (5 [7%]), dysarthria (3 [4%]), neurotoxicity (3 [4%], including events termed cerebellar toxicity in 2 pts), and paresthesia, gait disturbance, and nystagmus (1 pt each [1%]). Aside from headache and paresthesia, incidence of the listed non-ICANS neurologic TRAEs appeared to be dose-related, and reversibility of some events was observed.

Overall response rate (ORR) across doses was 86% (55/64) in efficacy-evaluable pts and 75% (21/28) in pts treated with prior BCMA-directed therapies, including CAR T cells. Complete response (CR) rate was 38% (24/64). In pts refractory to prior BCMA-directed therapies, ORR was 85% (11/13), and CR rate was 46% (6/13). Median follow-up for all treated pts was 5.9 mo (range, 0.0-24.0). At the time of data cutoff, 75% of responses (41/55) were ongoing. All 10 pts (100%) with available minimal residual disease (MRD) data and a best overall response of CR were MRD-negative (10 −5 depth) at ≥ month 3. BMS-986393 reduced soluble BCMA levels (indicative of tumor burden reduction) across all dose levels and showed a dose-dependent increase in cellular expansion.