Additional Study Information: The purpose of this study is to test whether BMS-986393 in combination with other anti-cancer drugs is safe and effective at treating people with multiple myeloma (MM) that has come back after previous treatment (relapsed) or is not responding to current treatment (refractory). The researchers think that the combinations of alnuctamab, mezigdomide, or iberdomide with BMS-986393 in people with relapsed/refractory MM may improve their disease or keep their disease under control. This is an open-label, multicenter study that will recruit potential participants in the United States (USA) and Canada. This study consists of two parts: dose finding (Part 1) and dose expansion (Part 2), and will treat participants in three different treatment groups, called Arms. Participants will receive a different combination of treatments in each Arm. These combinations are considered investigational, which means they are not approved for your disease by the Food and Drug Administration (FDA).