Study Purpose: This study aims to test the safety of combining two drugs, elranatamab and iberdomide, for treating relapsed or refractory multiple myeloma, a type of cancer in white blood cells.

Study Details: The study has two parts: Part 1 checks safety, and Part 2 finds the right dose for patients. Participants receive elranatamab as a shot and take iberdomide pills for 21 of 28 days in a cycle. They will continue until their disease worsens, they have unacceptable side effects, or they choose to stop.

Eligibility: Participants need a prior multiple myeloma diagnosis and have had 1-4 previous treatments. They must not have other active cancers or recent severe heart issues.

• **Duration:** Participants will be in the study until disease progression or withdrawal.
• **Visits:** Regular visits are necessary for monitoring treatment effects.
• **Risks:** Possible side effects from the study drugs.

This study will help determine if the drug combination is safe and effective for treating multiple myeloma.