Inclusion Criteria:  Diagnosis of multiple myeloma (IMWG criteria, Rajkumar et al, 2014)  Measurable disease, as defined by at least 1 of the following:  Serum M-protein >0.5 g/dL by SPEP Urinary M-protein excretion >200 mg/24 hours by UPEP Serum immunoglobulin FLC≥10 mg/dL (≥100 mg/L) AND abnormal serum immunoglobulin kappa to lambda FLC ratio Refractory to at least one IMiD Refractory to at least one PI Refractory to at least one anti-CD38 antibody Relapsed/refractory to last anti-myeloma regimen ECOG performance status ≤1 Resolved acute effects of any prior therapy to baseline severity or CTCAE Grade ≤1 Not pregnant and willing to use contraception  Exclusion Criteria:  Smoldering multiple myeloma Active Plasma cell leukemia POEMS syndrome Amyloidosis Stem cell transplant within 12 weeks prior to enrollment or active GVHD Active HBV, HCV, SARS-CoV2, HIV, or any active, uncontrolled bacterial, fungal, or viral infection Any other active malignancy within 3 years prior to enrollment, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ. Previous treatment with an anti-BCMA bispecific antibody. Live attenuated vaccine within 4 weeks of the first dose Previous administration with an investigational drug within 30 days or 5 half-lives preceding the first dose of study intervention used in this study (whichever is longer)