First data from planned interim analysis of pivotal phase II MagnetisMM-3 trial of BCMA-CD3 bispecific antibody elranatamab for relapsed/refractory multiple myeloma.- Pfizer
Pfizer Inc. announced new data from a planned interim analysis of the Phase II MagnetisMM-3 registration-enabling trial of elranatamab in people with relapsed/refractory multiple myeloma (RRMM) whose disease is refractory to at least one agent in each of three major classes of medications approved for the disease.
These data were presented during an oral abstract session at the 2022 American Society of Clinical Oncology Annual Meeting (ASCO) (Abstract # 8006). Elranatamab is an investigational B-cell maturation antigen (BCMA) CD3-targeted bispecific antibody in development for the treatment of multiple myeloma (MM). MagnetisMM-3 is an open-label, multicenter, single arm, Phase II study evaluating the safety and efficacy of elranatamab monotherapy in patients with RRMM.
The participants included in this study represent a particularly difficult-to-treat MM patient population: 95.7% of participants in the current interim analysis population had triple-class refractory disease and 39.4% had penta-drug refractory disease.
In this interim analysis, safety and efficacy was analyzed in 94 patients who had received at least one dose of elranatamab (Cohort A – BCMA-naïve) as of the data cutoff on March 23, 2022. Patients received subcutaneous (SC) elranatamab 76 mg weekly (QW) with a 2-step-up priming dose regimen administered during the first week. With a median follow up of 3.71 months, initial efficacy results showed that the objective response rate for elranatamab was 60.6%. As of the data cut-off, 89.5% of objective responders were ongoing without confirmed progression or death.
The results also suggested 76 mg of elranatamab QW may have a manageable safety profile in patients with triple-class refractory MM. The most common treatment emergent adverse events (TEAEs) were hematologic AEs- anemia (43.6%), neutropenia (38.3%), thrombocytopenia (28.7%) and lymphopenia (25.5%); and cytokine release syndrome (CRS) (60.6%). The 2-step-up priming regimen is intended to help mitigate the rate and severity of CRS, and the CRS profile appears to be predictable with the majority of events confined to the first two doses (88.4%) or first three doses (98.6%). Of the 90 patients who received the 2-step-up priming regimen, all CRS were Grade 1 (40.0%) or 2 (18.9%). Additionally, immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 2.2% of patients, all Grade 2 or less.
These results presented at ASCO are the first data to be disclosed from the MagnetisMM-3 study. The trial is still ongoing to the primary endpoint analysis with results expected later this year, which, if positive, would form the basis of potential regulatory filings. These data also support continued development of elranatamab in the robust MagnetisMM program, with other trials planned or ongoing both as monotherapy and in combination with standard or novel therapies.