A total of 55 pts received single-agent elranatamab SC at a dose ≥215 μg/kg as of 22-Jun-2022. Median age was 64 (range 42-80) years, and 27% of pts were Black/African American or Asian. Median number of prior regimens was 5 (range 2-14), 91% were triple-class refractory, 69% had prior stem cell transplantation, 29% had high cytogenetic risk, and 24% received prior BCMA-targeted therapy. The most common TEAEs regardless of causality included CRS, neutropenia, anemia, injection site reaction, and lymphopenia. With pre-medication and a single priming dose (600µg/kg or 44mg), the overall incidence of CRS at the recommended dose (1000µg/kg or 76mg) was 67% and limited to Grade 1 (33%) or Grade 2 (33%), with no events Grade 3 or higher. Elranatamab exposure was dose dependent. Cytokine increases occurred with the first dose and were reduced by pre-medication. Soluble BCMA decreased with disease response, elranatamab therapy was associated with increased peripheral T-cell proliferation, and median time to response was 36 days (range 7-262). With a median follow-up of 12.0 months (range 0.3-29.0) and including only IMWG confirmed responses, the objective response rate (ORR) was 64% (95% CI 50-75%) with 56% of pts (31/55) achieving very good partial response (VGPR) or better and 38% of pts (21/55) achieving complete response (CR) or better. Among 13 pts with prior BCMA-directed therapy (antibody drug conjugate, chimeric antigen receptor T-cell therapy, or both), 54% (7/13) achieved response including 46% (6/13) with VGPR or better. For responders (n=35), the probability of being event-free at 12 months was 59% (95% CI 39-74%) and the Kaplan-Meier estimate for median duration of response was 17.1 months (95% CI 10.6-NE). Single-agent elranatamab induced durable clinical and molecular responses, and 100% (12/12) of evaluable pts with confirmed CR or better achieved MRD negativity at a sensitivity of 1×10-5 including 2 pts with MRD negativity and ongoing stringent CR beyond 2 years.