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