A Study to Learn About the Effects of the Combination of Elranatamab (PF-06863135) and Iberdomide in Patients With Relapsed or Refractory Multiple Myeloma (MagnetisMM-30)

Inclusion Criteria: * Prior diagnosis of multiple myeloma as defined by IMWG criteria * Measurable disease based on IMWG criteria as defined by at least 1 of the following: * Serum M-protein ≥0.5 g/dL by SPEP * Urinary M-protein excretion ≥200 mg/24 hour by UPEP * Serum immunoglobulin FLC ≥10 mg/dL (≥100 mg/L) AND abnormal serum immunoglobulin kappa to lambda FL ratio (\<0.26 or \>1.65) * Part 1: Received 2-4 prior lines of therapy for multiple myeloma, consisting of at least 1 immunomodulatory drug and 1 proteasome inhibitor. * Part 2: Received 1-3 prior lines of therapy for multiple myeloma, consisting of at least 1 immunomodulatory drug and 1 proteasome inhibitor. * ECOG performance status 0-1 * Resolved acute effects of any prior therapy to baseline severity or CTCAE Grade ≤1 Exclusion Criteria: * Plasma cell leukemia, Smoldering multiple myeloma, Waldenström's macroglobulinemia, Amyloidosis, POEMS Syndrome * Impaired cardiovascular function or clinically significant cardiovascular diseases * Stem cell transplant within 12 weeks prior to enrollment or active graft vs host disease * Participants with any active, uncontrolled bacterial, fungal, or viral infection * Any other active malignancy within 3 years prior to enrollment, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ * Previous treatment with: * BCMA-directed or CD3 redirecting therapy * Iberdomide (CC-220) or Mezigdomide * Administration of strong inhibitor or inducer of CYP3A4/5 within 2 weeks prior to dosing and during the study * Administration with an investigational product within 30 days preceding the first dose of study intervention * Participant is unable or unwilling to undergo protocol required thromboembolism prophylaxis