Study of ISB 1342, a CD38/CD3 Bispecific Antibody, in Subjects With Previously Treated Multiple Myeloma

Inclusion Criteria: * Documented diagnosis of multiple myeloma with measurable disease (serum, urine, or free light chain) per International Myeloma Working Group (IMWG) criteria, including non-secretory or oligo-secretory multiple myeloma which has relapsed after or is refractory to prior therapies, including proteasome inhibitors (PIs), immunomodulators (IMiDs) and anti-CD38 targeted therapies (daratumumab, isatuximab). * Eastern Cooperative Oncology Group (ECOG) performance-status score of 2 or less and 1 or less (for France). * Adequate hematologic, renal, and hepatic functions * Seronegative for hepatitis B antigen; positive hepatitis B tests can be further evaluated by confirmatory tests, and if viral load is negative, the subject can be enrolled. * Seronegative for hepatitis C antibody; if positive, then further test for the presence of antigen by hepatitis C virus polymerase chain reaction (HCV PCR). If HCV antigen tests are negative, then the subject can be enrolled. * Oxygen saturation level ≥92% on room air. * Left ventricular ejection fraction (LVEF) ≥50% and no pericardial or pleural effusion at Screening Exclusion Criteria: * Active central nervous system involvement * Exposure to daratumumab or isatuximab within 2 months prior to the start of study treatment * Active plasma cell leukemia * Active infectious disease * Clinically significant cardiovascular and respiratory conditions * History of HIV infection * Subjects requiring prohibited concomitant medications