Inclusion Criteria: 

• The patient must either have relapsed refractory multiple myeloma (RRMM) after receiving prior lines of anti-myeloma treatments that included at least lenalidomide (Revlimid®), pomalidomide (Pomalyst®), bortezomib (Velcade®), carfilzomib (Kyprolis®), and daratumumab (Darzalex®) (refractory MM is defined as the development of disease progression during therapy with an anti-myeloma regimen or within 60 days of the last dose of an anti-myeloma regimen or the achievement of less than a partial response (PR) after greater than or equal to 2 cycles; for relapsing patients the duration from the last dose of the last prior treatment regimen to relapse must be less than or equal to 12 months); OR have multiple myeloma that is refractory to or has relapsed within 1 year of receiving high-dose therapy [HDT]/autologous stem cell transplantation [ASCT] in first- or second-line (refractory is defined as the achievement of less than a PR at the Day 90 to 100 post-ASCT response assessment).
• Must have measurable disease as defined by the following:
  • Serum M-protein greater than or equal to 1 g/dL; OR
  • Urine M-protein greater than or equal to 200 mg/24 hours; OR
  • Serum free light chain (FLC) assay; involved FLC level greater than or equal to 10 mg/dL provided the serum FLC ratio is abnormal; OR
  • Greater than or equal to 30% clonal plasma cells in the bone marrow aspirate or biopsy sample.
• Must have a life expectancy of at least 12 weeks.
• Subjects should be willing and able to comply with the study schedule and protocols.
• Females of childbearing potential must have 2 negative pregnancy tests, agree to ongoing pregnancy testing during the study, and sexually active female and male subjects must be willing to use an effective method to avoid pregnancies.

Exclusion Criteria:

• Subjects who received anticancer therapy or investigational drug within 28 days of first dose.
• Subjects who received any approved anticancer chemotherapy within 21 days of first dose (exception cyclophosphamide as NMA conditioning).
• Subjects with unresolved toxicity greater than Grade 2 from previous therapies.
• Have myeloma involvement of central nervous system (CNS) or a history of brain metastasis or spinal cord compression.
• Subjects with an ECOG performance status greater than or equal to 3.
• Has received allogenic hematopoietic stem cell transplantation (HSCT) within 6 months, have active graft-versus-host disease (GVHD) following transplant, or receiving immunosuppressive therapy following a transplant.
• Has received any CAR cell line therapies.
• Has any clinically significant low baseline lab results for hemoglobin, platelet counts, and neutrophil counts, at screening unless resulting from underlying RRMM. 
• Has any clinically significant elevated baseline lab results for serum creatinine, AST, and total bilirubin (except for patients in whom hyperbilirubinemia is attributed to Gilbert's syndrome) at screening regardless of causality. 
• Known HIV or acquired immunodeficiency syndrome-related illness, acute or history of chronic hepatitis B or C.
• Female subjects who are pregnant or breastfeeding.
• Active bacterial, viral or fungal infections.
• Has active plasma cell leukemia.
• Has medical condition, abnormality, or psychiatric illness that would prevent study participation.
• Left ventricular ejection fraction (LVEF) less than 40%.