A Study to Compare Iberdomide Maintenance Versus Lenalidomide Maintenance Therapy Following Autologous Stem Cell Transplant in Participants With Newly Diagnosed Multiple Myeloma

Inclusion Criteria * Confirmed diagnosis of symptomatic multiple myeloma (MM). * Eastern Cooperative Oncology Group performance status (ECOG) score of 0, 1, or 2. * Received 3 to 6 cycles of an induction therapy that includes a proteasome inhibitor (PI) and immunomodulatory (IMiD) \[eg, bortezomib thalidomide and dexamethasone (VTd), lenalidomide, bortezomib and dexamethasone (RVd)\] with or without a CD38 monoclonal antibody, daratumumab + bortezomib/thalidomide/dexamethasone \[D-VTd\] and daratumumab + bortezomib/ lenalidomide/dexamethasone \[D-VRd\]), or VCd / daratumumab + bortezomib/cyclophosphamide/dexamethasone \[D-VCd\], and followed by a single or tandem autologous stem cell transplantation (ASCT). Post-stem cell transplant consolidation is permitted. * Participants within 12 months (single transplant) or 15 months (tandem transplant) from initiation of induction therapy who achieved at least a partial response (PR) after autologous stem cell transplantation (ASCT) with or without consolidation, according to International Myeloma Working Group (IMWG 2016) criteria. Exclusion Criteria * Progressive disease or clinical relapse (as defined by IMWG response criteria) following ASCT with or without consolidation or is not responsive to primary therapy. * Smoldering myeloma, solitary plasmacytoma or nonsecretory myeloma. * Known central nervous system/meningeal involvement of MM. * Prior history of malignancies, other than MM, unless the participant has been free of the disease for ≥ 5 years. * Other protocol-defined Inclusion/Exclusion criteria apply.