Pfizer's Elrexfio Meets Phase 3 Progression-Free Survival Goal in Relapsed Myeloma
Topline MagnetisMM-32 results compared the BCMA bispecific antibody with three standard regimens in patients previously treated with anti-CD38 therapy and lenalidomide.
These results come from a Phase 3 trial, the large trial usually needed before approval.
Key points
- Pfizer said Elrexfio (elranatamab) met the primary progression-free survival endpoint at a prespecified interim analysis of the Phase 3 MagnetisMM-32 trial in 523 patients.
- The estimated 18-month progression-free survival rate was 68% with Elrexfio; median PFS was not reached and overall survival data are immature.
- Grade 3 or higher infections occurred in 27.5% of Elrexfio patients versus 18.1% in the comparator arm, the company said.
Pfizer said on October 27 that its bispecific antibody Elrexfio (elranatamab) met the primary endpoint of the Phase 3 MagnetisMM-32 trial in adults with relapsed or refractory multiple myeloma, according to the company's announcement. The results are topline data from a prespecified interim analysis; Pfizer said detailed results will be shared at a future medical meeting and submitted for publication.
The trial enrolled patients who had received at least one prior line of treatment that included an anti-CD38 antibody, daratumumab or isatuximab, and lenalidomide. Pfizer said this group is growing as those medicines are used earlier in care.
Trial design
MagnetisMM-32 is an open-label, multicenter, randomized Phase 3 study that enrolled 523 adults across 26 countries. Patients received Elrexfio as monotherapy or the investigator's choice of one of three standard regimens: elotuzumab, pomalidomide and dexamethasone (EloPd); pomalidomide, bortezomib and dexamethasone (PVd); or carfilzomib and dexamethasone (Kd).
Elrexfio was given under the skin as two step-up priming doses followed by weekly doses in 28-day cycles, before moving to dosing every two weeks and then monthly. The primary endpoint was progression-free survival (PFS) assessed by blinded independent central review, and overall survival is the key secondary endpoint, OncLive reported. Patients who had previously received BCMA-directed or CD3-redirecting therapy were excluded, according to the outlet.
Results
Pfizer said Elrexfio produced a statistically significant and clinically meaningful reduction in the risk of disease progression or death versus the comparator regimens. It did not disclose a hazard ratio. More than 75% of patients receiving Elrexfio had not experienced disease progression or death at the time of the analysis, and the estimated PFS rate at 18 months was 68%. Median PFS had not been reached.
Overall survival data remain immature, and follow-up will continue to the next prespecified analysis, the company said.
Pfizer said the safety profile was consistent with Elrexfio's known profile and that no new safety signals were identified. Infection prophylaxis was used from the start of the study. Grade 3 or higher infections occurred in 27.5% of patients on Elrexfio and 18.1% of patients on investigator's choice, while Grade 5, or fatal, infections occurred in 0.8% and 1.6%, respectively.
"The MagnetisMM-32 results are particularly compelling given the rigorous and clinically relevant benchmark of three established standard-of-care regimens," said C. Ola Landgren, chief of the Myeloma Division and director of the Sylvester Myeloma Institute at the University of Miami Miller School of Medicine, in Pfizer's release.
Jeff Legos, Pfizer's chief oncology officer, said the findings "further strengthen the rationale for moving BCMA-directed therapy earlier in the treatment journey."
Regulatory status
Pfizer plans to submit the data to health authorities around the world. Elrexfio received accelerated approval from the FDA in August 2023 for adults with relapsed or refractory multiple myeloma who had received at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent and an anti-CD38 antibody, based on the Phase 2 MagnetisMM-3 trial, OncLive reported.
Pfizer said the MagnetisMM-32 data build on earlier positive topline results from MagnetisMM-5, the first Phase 3 study of Elrexfio to read out in patients previously exposed to two classes of myeloma drugs.