The B-cell maturation antigen (BCMA) CD3-targeted bispecific antibody (BsAb) was given Priority Review in February and had previously received Breakthrough Therapy Designation for relapsed or refractory multiple myeloma (RRMM), according to Pfizer.
FDA approval was based on favorable response and duration of response rates in the single-arm, phase 2 MagnetisMM-3 trial. The trial showed meaningful responses in heavily pretreated patients with RRMM who received elranatamab as their first BCMA-directed therapy.
The overall response rate in 97 BCMA-naive patients (cohort A) who previously received at least four lines of therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 monoclonal antibody, was 58%, with an estimated 82% maintaining the response for 9 months or longer. Median time to first response was 1.2 months.
In 63 patients who received at least four prior lines of therapy, which also included a BCMA-directed therapy, the overall response rate was 33% after median follow-up of 10.2 months. An estimated 84% maintained a response for at least 9 months.
Elranatamab was given subcutaneously at a dose of 76 mg weekly on a 28-day cycle with a step-up priming dose regimen. The priming regimen included 12 mg and 32 mg doses on days 1 and 4, respectively, during cycle 1. Patients who received at least six cycles and showed at least a partial response for 2 or more months had a biweekly dosing interval.
Elranatamab carries a boxed warning for cytokine release syndrome (CRS) and neurologic toxicity, as well as warnings and precautions for infections, neutropenia, hepatotoxicity, and embryo–fetal toxicity. Therefore, the agent is available only through a restricted Risk Evaluation and Mitigation Strategy (REMS).
The boxed warning is included in the full prescribing information.
A confirmatory trial to gather additional safety and efficacy data was launched in 2022. Continued FDA approval is contingent on confirmed safety and efficacy data.
A version of this article first appeared on.