Inclusion Criteria:

1. Participants with pathologically confirmed MM with measurable M-protein: serum and/or 24 hour urine, serum-free light chains or measurable isolated plasmacytoma
2. Have an Eastern Cooperative Oncology Group (ECOG) performance status score of 2 or less
3. Must have adequate hematologic, hepatic, renal, and cardiac functions

Exclusion Criteria:

1. Active malignant central nervous system involvement
2. Uncontrolled infection requiring systemic antibiotic therapy or other serious infection prior to C1D1
3. History of autoimmune disease requiring systemic immunosuppressive therapy
4. Any concurrent or uncontrolled medical, comorbid, psychiatric or social condition that would limit compliance with study procedures, interfere with the study results, substantially increase the risk of AEs, compromise ability to provide written informed consent or, in the opinion of the Investigator, constitute a hazard for participating in this study.
5. Female subjects who are lactating and breastfeeding or have a positive pregnancy test during the screening period or on Day 1 before first dose of ISB 2001.