A Safety Study of SEA-BCMA in Patients With Multiple Myeloma

Inclusion Criteria:

   - Histologically confirmed diagnosis of MM

   - Must have MM that is relapsed or refractory

   - Has received a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38
   antibody

   - Measurable disease, as defined by at least one of the following: (1) serum M protein
   0.5 g/dL or higher, (2) urine M protein 200 mg/24 hour or higher, and (3) serum
   immunoglobulin free light chain (FLC) 10 mg/dL or higher and abnormal serum
   immunoglobulin kappa lambda FLC ratio.

   - Eastern Cooperative Oncology Group (ECOG) status score of 0 or 1

   - Life expectancy of greater than 3 months in the opinion of the investigator

   - Adequate hematologic, renal, and hepatic function

Exclusion Criteria:

   - Parts A and D: Prior treatment with a BCMA-directed therapy

   - History of another malignancy within 3 years

   - Active cerebral or meningeal disease related to the underlying malignancy

   - Uncontrolled Grade 3 or higher infection

   - Prior antitumor therapy that is not completed at least 4 weeks prior to first dose of
   study drug, or at least 2 weeks if progressing. Prior CAR-T-cell therapy must be
   completed 8 weeks before first dose of study drug.

   - Combination therapy only:

      1. Known intolerance to corticosteroids

      2. Uncontrolled psychoses