Part 1: Number of participants with Adverse Events (AE) by Seriousness and Relationship to 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.

Assessed from baseline up to 90 days after last dose of study treatment

Part 1 and Part 2: Number of Participants with Adverse Events (AE) characterized by type, frequency, severity

An AE was any untoward medical occurrence in a participant who received study drug without regard to possibly of causal relationship

Assessed from baseline up to 90 days after last dose of study treatment

Part 1 and Part 2: Number of Participants with Clinically Significant Change from Baseline in Laboratory Abnormalities

Laboratory abnormalities as characterized by type, frequency, severity

Assessed from baseline up to 90 days after last dose of study treatment

Part 1 and Part 2: Percentage of Participants with Objective Response Rate (ORR)

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

Assessed for approximately 2 years

Part 1 and Part 2: Percentage of Participants with Complete Response Rate (CRR)

Percent of participants having Complete Response/ Stringent Complete Response (CR+sCR) per IMWG criteria as determined by investigator

Assessed for approximately 2 years

Part 1 and Part 2: Time to Response (TTR)

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

Assessed for approximately 2 years

Part 1 and Part 2: Duration of Response (DOR)

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

Assessed for approximately 2 years

Part 1 and Part 2: Duration of Complete Response (DOCR)

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

Assessed for approximately 2 years

Part 1 and Part 2: Time of Progression Free Survival (PFS)

Progression free survival (IMWG criteria)

Assessed for approximately 2 years

Part 1 and Part 2: Time of Overall Survival (OS)

The duration of time from first dose of study treatment to death

Assessed for approximately 2 years

Part 1 and Part 2: Minimal Residual Disease (MRD) Negativity Rate

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.

Assessed for approximately 2 years

Part 1 and Part 2: Concentrations of elranatamab

Pre-dose and post-dose concentrations of elranatamab

Assessed for approximately 2 years

Part 1 and Part 2: Concentrations of iberdomide

Pre-dose concentrations of iberdomide

Assessed for approximately 4 months

Part 1 and Part 2: Percentage of participants with positive anti-drug antibodies (ADA) against elranatamab

Percent of participants with positive ADA to elranatamab when given in combination with iberdomide

Assessed for approximately 2 years