58 pts received elranatamab SC as a single agent (n=50) or in combination with either LEN (n=4) or POM (n=4) as of 4-Feb-2021. Pts had a median (range) age of 64 (32-86) years, and 26% were Black/African American or Asian. Pts had a median of 6 prior regimens, 98% had triple-class relapsed/refractory disease, 45% had prior high-dose chemotherapy with stem cell transplantation, and 22% had prior BCMA-targeted therapy. The most common all causality TEAEs included CRS (n=48, 83%; none higher than G2), lymphopenia (n=37, 64%; 12% G3, 52% G4), neutropenia (n=37, 64%; 31% G3, 29% G4), anemia (n=32, 55%; 38% G3, 0% G4), injection site reaction (n=31, 53%; none higher than G2), and thrombocytopenia (n=30, 52%; 14% G3, 17% G4). At the RP2D of 1000μg/kg, median duration of CRS decreased by 50% from 4 days to 2 days with priming. Two of 58 pts had DLT including G4 thrombocytopenia (Part 1.1) and G4 neutropenia (POM). Exposure increased with dose, cytokine increases occurred with the first dose, and increased T-cell proliferation was observed in peripheral blood. Median duration of follow-up was 7.5, 2.3, and 1.9 months for the dose escalation, priming, and LEN/POM combination cohorts, respectively. For pts treated across the efficacious dose range (215–1000μg/kg) in Part 1, confirmed overall response rate (ORR) was 70% (14/20) with complete response (CR)/stringent CR (sCR) rate of 30% (6/20). For the 14 pts with confirmed responses, median duration of response had not yet been reached; the probability (95% CI) of responders being event free at 6 months was 92.3% (56.7–98.9). Confirmed ORR at the RP2D was 83% (5/6). Responses in this RRMM population included sCR (n=5), CR (n=1), very good partial response (VGPR; n=7), and partial response (n=1). Median time to response was 22 days. Importantly, 100% (4/4) of evaluable pts with baseline dominant sequence and on-treatment sample at CR/sCR achieved MRD negativity at 1×10-5 by IMWG criteria, and 75% (3/4) of pts with prior BCMA-targeted therapy achieved response (1 sCR, 2 VGPR). Updated efficacy, safety, and MRD results will be presented for SC parts of the study.