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)