A Study to Evaluate Efficacy and Safety of Alnuctamab Compared to Standard of Care Regimens in Participants With Relapsed or Refractory Multiple Myeloma (RRMM)

Inclusion Criteria * Participant is willing and able to adhere to the study visit schedule and other protocol requirements including bone marrow aspirations and/or biopsies and hospitalization during the first cycle. * Documented diagnosis of multiple myeloma (MM), and must:. i) Received at least 1 but not more than 3 prior lines of anti-myeloma therapy. ii) Received prior treatment with lenalidomide and an anti-CD38 monoclonal antibody (for at least 2 consecutive cycles). iii) Achieved minimal response (MR) or better to at least 1 prior anti-myeloma therapy. iv) Documented PD during or after their last anti-myeloma therapy or failure to achieve response. * Must have measurable disease (as determined by central laboratory). * Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0, 1, or 2 at the time of the screening. Exclusion Criteria * Active, uncontrolled, or suspected infection. * Known current, or history of, central nervous system involvement of multiple myeloma. * History or presence of clinically relevant CNS pathology. * Received prior BCMA-targeted TCE or BCMA-targeted CAR-T therapy. * Previously received allogeneic stem cell transplantation at any time or received autologous stem cell transplantation within 3 months of initiating study intervention. * Other protocol-defined Inclusion/Exclusion criteria apply.