This study is testing a new medicine combination for people with relapsed or refractory multiple myeloma (RRMM), a type of cancer affecting white blood cells. The study will compare two treatment options: Mezigdomide with carfilzomib and dexamethasone (MeziKD) versus only carfilzomib and dexamethasone (Kd). Mezigdomide is an experimental drug being tested to see if it works better with the other two drugs.

To join, you need to have multiple myeloma with measurable disease, have tried other treatments before, and your cancer must have returned or not responded to those treatments. You cannot join if you've had certain transplants or if you've been treated with mezigdomide or carfilzomib before.

• The study involves comparing two different drug treatments.
• You must have tried other cancer treatments before joining.
• Previous treatment with mezigdomide or carfilzomib disqualifies you.

If you have questions or want to join, talk to your doctor to see if this study could be right for you.