Inclusion Criteria:

          -  Diagnosis of multiple myeloma (IMWG criteria, Rajkumar et al, 2014)

          -  Measurable disease, as defined by at least 1 of the following:

               1. Serum M-protein >0.5 g/dL by SPEP

               2. Urinary M-protein excretion >200 mg/24 hours by UPEP

               3. 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

          -  Cohort A: has not received prior BCMA-directed therapy

          -  Cohort B: has received prior BCMA-directed therapy (ADC or CAR T cells)

          -  ECOG performance status ≤2

          -  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

          -  Amyloidosis

          -  POEMS syndrome

          -  Stem cell transplant within 12 weeks prior to enrollment

          -  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 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)