Elranatamab (PF-06863135) is a humanized bispecific antibody that targets both BCMA-expressing MM cells and CD3-expressing T cells. MagnetisMM-3 (NCT04649359) is an open-label, multicenter, non-randomized, phase 2 study to evaluate the safety and efficacy of elranatamab monotherapy in pts with R/R MM. Initial safety results are presented.

MagnetisMM-3 enrolled pts who are refractory to at least 1 proteasome inhibitor, 1 immunomodulatory drug, and 1 anti-CD38 antibody. Pts were assigned to 1 of 2 independent, parallel cohorts: those naïve to BCMA-directed therapies (Cohort A) and those with previous exposure to BCMA-directed antibody-drug conjugates or CAR-T cells (Cohort B). Pts received SQ elranatamab 76 mg QW on a 28-d cycle with a 2-step-up priming dose regimen administered during the first wk. Dose modifications were permitted for toxicity. Treatment-emergent adverse events (TEAEs) were graded by CTCAE (v5.0), and cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) by ASTCT criteria.

As of the data cutoff on Dec 31, 2021, 60 pts in Cohort A had received ≥1 dose of elranatamab; the last pt's first dose was ̃2 mos prior to the cutoff. Median age was 69.0 yrs (range, 44-89), 48.3% were male, 63.3% were white, 18.3% were Asian and 11.7% were Black/African American. At baseline, 60.0% of pts had an ECOG performance status 1-2 and pts had received a median of 5 (range, 2-12) prior therapies. Median duration of elranatamab treatment was 9.57 wks (range, 0.1-46.1); median relative dose intensity was 87.4% (range, 23.1-101.4). TEAEs were reported in 100% (Grade [G] 3/4, 75.0%) of pts. Most common (≥30%) hematologic TEAEs were neutropenia (36.7% [G3/4, 35.0%]), anemia (36.7% [G3/4, 30.0%]) and thrombocytopenia (30.0% [G3/4, 21.7%]). Among pts who received the 2-step-up priming regimen (n = 56), CRS and ICANS, respectively, were reported in 58.9% (G3/4, 0%) and 3.6% (G3/4, 0%); of those pts, 57.6% (n = 19/33) and 100% (n = 2/2) received tocilizumab and/or steroids. Most common (≥30%) non-hematologic TEAE, other than CRS/ICANS, was fatigue (31.7% [G3/4, 3.3%]). Infections were reported in 46.7% (G3/4, 18.3%) of pts; most frequently reported were upper respiratory tract infections (11.7% [G3/4, 0%]). Discontinuations due to adverse events were reported in 5.0% of pts. No pts permanently discontinued treatment due to CRS or ICANS. There were 10 deaths; causes were MM progression (n = 8), septic shock (n = 1) and unknown (n = 1). Data will be updated at the time of presentation to include 90 pts.

Preliminary results in pts with R/R MM and no prior BCMA-targeted treatment suggest that 76 mg QW elranatamab with a 2-step-up priming regimen is well tolerated, with no G≥3 CRS or ICANS observed.

These results support the continued development of elranatamab monotherapy for pts with MM. The MagnetisMM program continues to evaluate elranatamab alone and in combination with other drugs for the treatment of pts with MM. ©2022 American Society of Clinical Oncology, Inc. Reused with permission. The abstract was accepted and previously presented at the 2022 ASCO Annual Meeting. All rights reserved. Also presented at the European Hematology Association 2022 Hybrid Congress.