New Bispecific Antibody Nabs Conditional FDA Approval for Myeloma

The FDA granted accelerated approval to the bispecific antibody elranatamab (Elrexfio) for relapsed/refractory multiple myeloma treated with at least four prior regimens.

A B-cell maturation antigen (BCMA)-directed T-cell engager, elranatamab is indicated for adults whose treatment history includes a proteasome inhibitor, an immunomodulator, and an anti-CD38 monoclonal antibody. As a conditional approval status, accelerated approval requires submission of additional supportive evidence of a drug’s safety and efficacy, typically from a new clinical trial.

“Most multiple myeloma patients will experience relapse or resistance of their disease to treatment, often facing increased symptom burden and lowering their chance of surviving longer with each attempted line of therapy,” said Ajay Nooka, MD, of the Winship Cancer Institute of Emory University in Atlanta, in a statement from Pfizer. “By offering durable clinical response with an established safety profile and the convenience of subcutaneous administration, Elrexfio provides a much-needed new option for heavily pretreated multiple myeloma patients who are struggling with relapsed myeloma.”

Primary support for the approval came from cohort A of the phase II, multicenter, single-arm MagnetisMM-3 trial, which had a primary endpoint of objective response in the 123 patients receiving elranatamab as their first BCMA-directed therapy. The overall response rate (ORR) reached 58% in the efficacy population — the 97 patients with at least four prior lines of therapy. Median duration of response (DOR) had not been reached after a median follow-up of 11.1 months. More than 90% of responses persisted for at least 6 months and 82.3% of responses were ongoing at 9 months.

An updated report involving all 123 patients in cohort A followed for 15 months showed an ORR of 61%, including complete responses in 35% of patients. Median DOR still had not been reached, but responding patients had a 71.5% probability of maintaining the response at 15 months.

According to the prescribing information, the most common adverse reactions (all grades, ≥20% of patients) were cytokine release syndrome (CRS), fatigue, injection-site reaction, diarrhea, upper respiratory tract infection, musculoskeletal pain, pneumonia, decreased appetite, rash, cough, nausea, and pyrexia. The most common grade 3/4 laboratory abnormalities were decreased lymphocytes, neutrophils, white blood cells, and platelets (each ≥20%).

Elranatamab labeling includes a boxed warning about the risk of CRS and neurologic toxicity, and the drug will be available through a risk evaluation and mitigation strategy (REMS) due to these risks. Other warnings and precautions include risks for severe infections, neutropenia, liver toxicity, and embryo-fetal toxicity.

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