Pfizer says ELREXFIO improved progression-free survival in Phase 3 trial; results are interim

Pfizer said Tuesday that its Phase 3 MagnetisMM-32 trial showed ELREXFIO improved progression-free survival over standard regimens in adults with relapsed or refractory multiple myeloma, a result that could help move the drug into earlier lines of treatment beyond its current later-line U.S. approval.

The result, announced Oct. 27 in a company press release, came from a topline interim analysis rather than a full peer-reviewed dataset. Pfizer described MagnetisMM-32 as an open-label, multicenter, randomized trial that enrolled 523 adults in 26 countries. Patients had received at least one prior line of treatment that included an anti-CD38 antibody — daratumumab or isatuximab — and lenalidomide. The study tested ELREXFIO, known generically as elranatamab, as a monotherapy against investigator’s choice of three standard regimens: elotuzumab plus pomalidomide and dexamethasone, pomalidomide plus bortezomib and dexamethasone, or carfilzomib plus dexamethasone.

Pfizer said the trial met its primary endpoint of progression-free survival, or the length of time patients live without their disease worsening, as assessed by blinded independent central review. The company said ELREXFIO produced a statistically significant and clinically meaningful reduction in the risk of disease progression or death compared with investigator’s choice, but it did not disclose the hazard ratio, confidence intervals or other detailed efficacy data in the release. Pfizer did say that median progression-free survival was not yet reached for ELREXFIO at the time of the interim analysis, that more than 75% of patients in the ELREXFIO group had not experienced disease progression or death, and that estimated 18-month progression-free survival was 68%.

On safety, Pfizer said ELREXFIO’s profile was consistent with its known risks and that no new safety signals were identified. Still, severe infections were more common in the ELREXFIO arm, a notable point for a class of cancer immunotherapies already associated with infection risk. Grade 3 or higher infections occurred in 27.5% of patients receiving ELREXFIO, compared with 18.1% in the investigator’s-choice arm. Grade 5, or fatal, infections were reported in 0.8% of ELREXFIO patients and 1.6% of patients receiving investigator’s choice. Pfizer said infection prophylaxis measures were used in the study.

The finding matters because ELREXFIO is already on the U.S. market, but only for people whose disease has been treated much later in its course. The drug, a subcutaneous BCMA-CD3 bispecific antibody, received accelerated approval in the United States in August 2023 for adults with relapsed or refractory multiple myeloma after at least four prior lines of therapy. MagnetisMM-32 studied a broader, earlier-use population after prior anti-CD38 treatment and lenalidomide, potentially opening the door to a label expansion if regulators agree. BCMA-targeted bispecific antibodies are considered off-the-shelf immunotherapies, unlike personalized CAR-T treatments, though product labeling for the class also warns of risks including infections, cytokine release syndrome and neurologic toxicities.

Pfizer said it “plans to submit these data to global health authorities” and present detailed results at a future medical meeting, with publication to follow. Overall survival data remain immature, the company said, underscoring that Tuesday’s announcement reflects an early topline look at the trial rather than the complete dataset.