Key Inclusion Criteria:

          -  Eastern Cooperative Oncology Group (ECOG) performance status ≤1 Individual cases of
             patients with ECOG 2 performance status, whose ECOG status is expected to improve as a
             consequence of effective therapy, may be discussed with the medical monitor for
             potential enrollment

          -  Patients must have symptomatic myeloma at the time of study entry with myeloma-related
             organ damage or tissue dysfunction (such as hypercalcemia, renal insufficiency, bone
             lytic lesions, or anemia)

          -  Patients must have myeloma that is measurable by either serum or urine evaluation of
             the monoclonal component or by assay of serum free light chain (FLC)

          -  Measurable disease is defined as 1 or more of the following:

               1. Serum M-protein ≥1 g/dL,

               2. Urine M-protein ≥200 mg/24-hour, and/or

               3. FLC assay with involved FLC level ≥10 mg/dL with an abnormal serum FLC ratio

          -  A patient with Immunoglobulin A (IgA) myeloma but without measurable M-protein may be
             enrolled if quantitative IgA levels are elevated and can be followed longitudinally

          -  A patient with non-secretory MM may be considered for enrollment after discussion with
             the sponsor that includes the feasibility of an individualized plan for response
             assessment

          -  Patients with MM who have exhausted all therapeutic options that are expected to
             provide meaningful clinical benefit, either through disease relapse, treatment
             refractory disease, or intolerance or refusal of the therapy, and including either:

               1. Progression on or after at least 3 lines of therapy, or intolerance of therapy,
                  including a proteasome inhibitor, an IMiD, and an anti-CD38 antibody, OR

               2. Progression on or after an anti-CD38 antibody and have disease that is "double
                  refractory" to a proteasome inhibitor and an IMiD, or intolerance of therapy. The
                  anti-CD38 antibody may have been administered alone or in combination with
                  another agent such as a proteasome inhibitor. Refractory disease is defined as
                  lack of response or relapse within 60 days of last treatment.

          -  Adequate hematologic function as measured by:

               1. Platelet count > 50 x 109/L. A patient may not have received a platelet
                  transfusion within 7 days in order to meet this platelet eligibility requirement.

               2. ANC > 1.0 x 109/L. A patient may not have received granulocyte colony stimulating
                  factor (G-CSF) within 2 days in order to meet this absolute neutrophil count
                  eligibility requirement.

               3. Hemoglobin > 8.0 g/dL

          -  Adequate hepatic function, defined as:

               1. Total bilirubin ≤1.5 x ULN

               2. Transaminase (ALT, AST) ≤2.5 x ULN

               3. Alkaline phosphatase ≤2.5 x ULN

          -  Patients with Gilbert syndrome do not need to meet this total bilirubin requirement
             provided that the total bilirubin is unchanged from the baseline value.

             d. Serum creatinine clearance by Cockcroft-Gault >30 mL/min

          -  A patient with a creatinine clearance by Cockcroft-Gault who does not meet eligibility
             criteria may be considered for enrollment if a measured creatinine clearance (based on
             24-hour urine collection or other reliable method) is >30 mL/min

          -  Life expectancy of at least 6 months

        Key Exclusion Criteria:

          -  Patients with known MM brain lesions or meningeal involvement with MM (suspected
             central nervous system (CNS) myeloma should be excluded by radiographic imaging and/or
             lumbar puncture, as appropriate)

          -  History of neurodegenerative condition or CNS movement disorder

          -  Cardiac ejection fraction <40% by echocardiogram or multi-gated acquisition scan
             (MUGA)

          -  Prior treatment with any anti-BCMA antibody (including antibody-drug conjugate or
             bispecific antibody) or BCMA-directed CAR T therapy

          -  Uncontrolled infection with human immunodeficiency virus (HIV), hepatitis B virus
             (HBV) or hepatitis C virus (HCV) infection; or other uncontrolled infection

               1. Patients with HIV who have controlled infection (undetectable viral load and CD4
                  count above 350 cells/microliter either spontaneously or on a stable antiviral
                  regimen) are permitted.

               2. Patients with hepatitis B (Hepatitis B Surface Antigen Test positive [HepBsAg+])
                  who have controlled infection (serum HBV DNA polymerase chain reaction [PCR] that
                  is below the limit of detection AND receiving anti-viral therapy for hepatitis B)
                  are permitted.

               3. Patients who are HCV antibody-positive (HCV Ab+) who have controlled infection
                  (undetectable HCV RNA by PCR either spontaneously or in response to a successful
                  prior course of anti-HCV therapy) are permitted.

          -  History of allogeneic stem cell transplantation at any time, or autologous stem cell
             transplantation within 12 weeks of the start of study treatment

        NOTE: Other protocol defined Inclusion/Exclusion Criteria apply.