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)

• Elranatamab (Drug), also known as PF-06863135: BCMA-CD3 bispecific antibody
• Iberdomide (Drug), also known as CC-220, BMS-986382: cereblon-modulating agent

Primary outcomes

• Part 1: Number of participants with dose limiting toxicity (DLT) [Cycle 1, about 28 days]: Dose limiting toxicity rate based on dose limiting toxicity evaluable participants
• Part 2: Number of participants with Adverse Events (AE) by Seriousness and Relationship to Treatment [Assessed from baseline up to 90 days after last dose of study treatment]: Number of participants with AE among participants who take at least 1 dose of study intervention. AEs are categorized by seriousness and relationship to treatment. Relatedness to study drug is assessed by investigator.

Secondary outcomes

• Part 1: Number of participants with Adverse Events (AE) by Seriousness and Relationship to Treatment [Assessed from baseline up to 90 days after last dose of study treatment]: Number of participants with AE among participants who take at least 1 dose of study intervention. AEs are categorized by seriousness and relationship to treatment. Relatedness to study drug is assessed by investigator.
• Part 1 and Part 2: Number of Participants with Adverse Events (AE) characterized by type, frequency, severity [Assessed from baseline up to 90 days after last dose of study treatment]: An AE was any untoward medical occurrence in a participant who received study drug without regard to possibly of causal relationship
• Part 1 and Part 2: Number of Participants with Clinically Significant Change from Baseline in Laboratory Abnormalities [Assessed from baseline up to 90 days after last dose of study treatment]: Laboratory abnormalities as characterized by type, frequency, severity
• Part 1 and Part 2: Percentage of Participants with Objective Response Rate (ORR) [Assessed for approximately 2 years]: Percent of participants having confirmed Stringent Complete Response (sCR), Complete Response (CR), Very Good Partial Response (VGPR), or Partial Response (PR) per IMWG criteria as determined by investigator
• Part 1 and Part 2: Percentage of Participants with Complete Response Rate (CRR) [Assessed for approximately 2 years]: Percent of participants having Complete Response/ Stringent Complete Response (CR+sCR) per IMWG criteria as determined by investigator
• Part 1 and Part 2: Time to Response (TTR) [Assessed for approximately 2 years]: For participants with an objective response per IMWG criteria, TTR is the time from first dose to the first documentation of objective response that is subsequently confirmed
• Part 1 and Part 2: Duration of Response (DOR) [Assessed for approximately 2 years]: For participants with an objective response per IMWG criteria, DOR is the time from first documentation of objective response that is subsequently confirmed until the first documentation of confirmed progressive disease (PD) per IMWG criteria
• Part 1 and Part 2: Duration of Complete Response (DOCR) [Assessed for approximately 2 years]: For participants with a Complete Response/ Stringent Complete Response (CR+sCR) per IMWG criteria, DOCR is the time from the first documentation of CR/sCR that is subsequently confirmed until the first documentation of confirmed progressive disease (PD) per IMWG criteria
• Part 1 and Part 2: Time of Progression Free Survival (PFS) [Assessed for approximately 2 years]: Progression free survival (IMWG criteria)
• Part 1 and Part 2: Time of Overall Survival (OS) [Assessed for approximately 2 years]: The duration of time from first dose of study treatment to death
• Part 1 and Part 2: Minimal Residual Disease (MRD) Negativity Rate [Assessed for approximately 2 years]: The proportion of participants achieving CR+sCR with negative MRD per IMWG sequencing criteria, from the date of first dose until the first documentation of confirmed progressive disease (PD), death, or start of new anticancer therapy.
• Part 1 and Part 2: Concentrations of elranatamab [Assessed for approximately 2 years]: Pre-dose and post-dose concentrations of elranatamab
• Part 1 and Part 2: Concentrations of iberdomide [Assessed for approximately 4 months]: Pre-dose concentrations of iberdomide
• Part 1 and Part 2: Percentage of participants with positive anti-drug antibodies (ADA) against elranatamab [Assessed for approximately 2 years]: Percent of participants with positive ADA to elranatamab when given in combination with iberdomide

Sex: All, ages: 18 Years to any

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

• Pfizer CT.gov Call Center, Study director, Pfizer