A Study to Determine the Recommended Dose and Schedule, and Evaluate the Safety and Preliminary Efficacy of Mezigdomide in Combination With Elranatamab in Participants With Relapsed and/or Refractory Multiple Myeloma

Inclusion Criteria: * Age ≥18 with history of relapsed and refractory multiple myeloma (RRMM) treated with 2 to 4 prior lines of anti-myeloma therapy (Phase 1) or 1 to 3 prior lines of anti-myeloma therapy (Phase 2). * Measurable MM by local laboratory. * Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 to 1. * Adherence to contraception requirements. Exclusion Criteria: * Prior treatment with mezigdomide. * Prior treatment with T cell engaging or T cell engager (TCE). * Prior treatment with B cell-maturation antigen (BCMA)-targeting therapy, with the exception of participants who have received autologous BCMA-targeted CART-cell therapy\> 6 months from the start of study therapy * Other protocol-defined Inclusion/Exclusion criteria apply.