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.
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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 Medscape.com.