Multiple myeloma (MM) is a type of blood cancer that affects plasma cells. These cells are found in the bones and bone marrow. This study examines the effects of a new drug called etentamig compared to usual treatments for adults with MM that has come back or not improved. There are two groups in the study. In **Arm A**, participants receive etentamig through an IV (a tube that goes into a vein) every 28 days over 3.5 years. In **Arm B**, participants get the usual treatment chosen by the doctor.

Participants will have regular check-ups at a hospital or clinic. Doctors will monitor the effect of the treatments through medical tests, blood work, and questionnaires. This study might be more demanding than regular care.

• The study lasts for 3.5 years and involves regular hospital visits.
• Participants will receive either etentamig or standard treatment.
• Participants should be ready for frequent check-ups and monitoring.