Alnuctamab, a bivalent B-cell maturation antigen-targeting T cell engager for patients with relapsed or refractory multiple myeloma: results from a phase 1, first-in-human study

B-cell maturation antigen (BCMA)-targeting therapies provide a new approach to treating multiple myeloma (MM). Alnuctamab (ALNUC) is a 2 + 1 immunoglobulin G1-based bispecific antibody binding BCMA and CD3ε receptors on myeloma and T cells, respectively. CC-93269-MM-001 is a first-in-human, phase 1 dose escalation/expansion study investigating ALNUC in relapsed/refractory MM. Patients had ≥3 prior regimens, disease progression ≤60 days of last regimen, and were BCMA-directed therapy-naïve. ALNUC was administered intravenously (IV) and subcutaneously (SC); however, SC was selected for further evaluation due to the more favorable safety profile. Ninety-five patients received ALNUC SC; at data cutoff, 44.2% remained on treatment and median follow-up was 8.0 months. The recommended phase 2 dose was 30 mg. The most common treatment emergent adverse events (any grade/grade 3/4) were CRS (57.9%/0%), and neutropenia (53.7%/43.2%). Infections were also frequent (64.2%/14.7%). ORR was 58.9% for all ALNUC SC-treated patients and 71.4% for the 30-mg cohort; 47/95 (49.5%) were measurable residual disease (MRD) negative. Overall, the safety and efficacy of ALNUC SC were comparable to other BCMA-targeted therapies. These results support improved safety of SC versus IV, and corroborate a step-up dosing strategy to mitigate CRS. Importantly, a schedule that de-intensifies over time provides favorable toxicity that may be applicable to other bispecific engagers.