Pfizer says ELREXFIO outperformed comparator in multiple myeloma trial

Key Facts

Pfizer said its Phase 3 MagnetisMM-32 trial met its primary endpoint, with ELREXFIO showing a statistically significant and clinically meaningful reduction in the risk of disease progression or death compared with investigator's choice of treatment. An independent, blinded central review committee measured progression-free survival, the study's primary endpoint. The trial included adults who had previously received at least one line of therapy that included an anti-CD38 treatment, such as daratumumab or isatuximab, as well as lenalidomide. ELREXFIO monotherapy was compared with one of three regimens selected by the investigator: EloPd, PVd or Kd. Pfizer published the topline results in an announcement via Business Wire and said the data would be submitted to global health authorities. The comparison tests the drug in patients previously treated with at least one line of therapy, at an earlier point in treatment than covered by the original U.S. approval.

Median progression-free survival had not been reached at the prespecified interim analysis, but more than 75% of patients receiving ELREXFIO had not experienced disease progression or death from any cause by that point. The company estimated 18-month progression-free survival at 68%. These figures reflect an early readout of the study endpoint, while overall survival, a key secondary endpoint, had not yet matured. Pfizer said follow-up would continue until the next prespecified overall-survival analysis. The treatment's effect on total lifespan therefore remains unclear in this readout, despite meeting the primary endpoint related to disease progression. The company plans to submit the data to global health authorities, share details at a future medical meeting and submit them for publication, without specifying a timeline in its announcement.

Safety data showed differences in infection rates by severity and treatment group. Grade 3 or higher infections were reported in 27.5% of patients receiving ELREXFIO, compared with 18.1% in the investigator's-choice group. Grade 5 infections were reported in 0.8% with ELREXFIO, compared with 1.6% in the other group. Pfizer said the safety profile in MagnetisMM-32 was consistent with the drug's known profile and that the study found no new safety signals. It added that infection-prevention measures began at the start of the trial to help reduce risks. These differences in severe infections are one factor in weighing clinical outcomes against treatment risks, while follow-up continues.

ELREXFIO has had accelerated U.S. approval since 14 August 2023 for adults with relapsed or refractory multiple myeloma after at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent and an anti-CD38 treatment. The approval was based on the open-label, single-arm MagnetisMM-3 trial, where the objective response rate was 57.7% among 97 patients in the efficacy population. In an update announced by Pfizer in 2024 after more than two years, the overall response rate was 61.0%, median progression-free survival was 17.2 months, and median duration of response had not been reached. In Europe, Pfizer said the European Commission granted the drug conditional marketing authorization in December 2023 for patients who had received at least three prior treatments and whose disease progressed during their last treatment. MagnetisMM-32 tests ELREXFIO alone after at least one line of therapy that included an anti-CD38 treatment and lenalidomide, and compares it directly with three treatment regimens. Pfizer shares (PFE) closed at $29.79 on 26 October 2026.

Known safety considerations for the drug include cytokine release syndrome and neurotoxicity, including ICANS. In the Food and Drug Administration's review of MagnetisMM-3, cytokine release syndrome occurred in 58% of patients receiving the recommended dose, neurotoxicity in 59%, and ICANS in 3.3%. The U.S. label carries a boxed warning for cytokine release syndrome and neurotoxicity, and restricts access to ELREXFIO through a Risk Evaluation and Mitigation Strategy (REMS) program. The announced MagnetisMM-32 data indicate that the company found no new safety signals, alongside the severe infection rates reported in the trial. Pfizer said next steps include continuing follow-up through the prespecified overall-survival analysis, while submitting the data to health authorities, sharing details at a future medical meeting and publishing them. The company did not provide a timeline for these steps or announce a new regulatory approval.