Efficacy and safety of elranatamab in patients with relapsed/refractory multiple myeloma (RRMM) and prior B-cell maturation antigen (BCMA)-directed therapies: A pooled analysis from MagnetisMM studies.

8008 Background: Studies in the MagnetisMM program (MM-1, NCT03269136; MM-3, NCT04649359; MM-9, NCT05014412) enrolled pts treated with prior BCMA-directed therapies. A pooled analysis from these studies evaluated the efficacy and safety of elranatamab in pts with RRMM and prior exposure to BCMA-directed therapy. Methods: Eligible pts received at least 1 PI, 1 IMiD, 1 anti-CD38 antibody, and 1 BCMA-directed therapy (ADC and/or CAR-T cells). Pooled analysis included pts in MM-1 (n = 13) who received SC elranatamab 215−1000 µg/kg; MM-3 (n = 64) and MM-9 (n = 9) who received the RP2D, SC 76 mg QW. Efficacy endpoints were assessed by investigator per IMWG criteria. TEAEs were graded by CTCAE (MM-1, v4.03; MM-3 CRS and ICANS were graded by ASTCT criteria. Results include data up through ~10 months after last pt initial dose in all pooled studies. Results: In total, 86 pts were included. Median age was 66.0 y (range, 40−84); 47.7% male. At baseline, 69.8% had an ECOG PS ≥1; 24.4% had high risk cytogenetics; 54.7% had extramedullary disease. Pts received a median of 7.0 (3−19) prior lines of therapy, including BCMA-directed ADC (67.4%), CAR T-cells (41.9%), 9.3% received both. 96.5% and 54.7% of pts were triple-class and penta-drug refractory, respectively; among pts who received ADC and CAR-T cells respectively, 79.3% and 27.8% were refractory to ADC and CAR-T cells. After a median follow-up of 10.3 mo (0.3−32.3), median duration of treatment was 3.3 mo (0.03−30.4). At data cut-off, 24.4% of pts remained on treatment; most common reason for permanent treatment discontinuation was progressive disease (44.2%). ORR was 45.3% (95% CI 34.6−56.5), with ≥CR achieved in 17.4% of pts. ORR for pts with prior BCMA-directed ADC and CAR-T cells was 41.4% (95% CI 28.6−55.1) and 52.8% (95% CI 35.5−69.6), respectively. Among responders, median time to objective response was 1.9 mo (0.3−9.3). Median DOR was not reached by 10 mo; the DOR rate at 9 mo was 72.4% (95% CI 54.7−84.2). DOR rate (95% CI) for pts with prior BCMA-directed ADC and CAR-T cells were 67.3% (43.1−83.0) and 78.9% (53.2−91.5) at 9 mo, respectively. Median PFS was 4.8 mo (95% CI 1.9−7.7), and median OS was not reached by 10 mo, with a rate of 60.1% (95% CI 48.9−69.6) at 9 mo. Most common (≥25% of pts) TEAEs were CRS (65.1% G3 1.2%), anemia (59.3% G3/4, 46.5%), neutropenia (44.2% G3/4, 40.7%), thrombocytopenia (40.7% G3/4, 29.1%), diarrhea (33.7% G3/4, 0%, and lymphopenia (32.6% G3/4, 30.2%). ICANS was reported in 5.8% (G3, 2.3%) of pts. Conclusions: In pts with RRMM and prior exposure to BCMA-directed therapies, elranatamab was efficacious and well tolerated; no new safety signals were observed vs the BCMA-naïve population. Results support treatment with elranatamab in pts with RRMM post BCMA-directed therapy. Clinical trial information: NCT03269136 , NCT04649359 , NCT05014412 .