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

INTERVENTION: Arm A1: Iberdomide Dose 1 Arm A2: Iberdomide Dose 2 Arm A3: Iberdomide Dose 3 Arm B: Lenalidomide Specified dose on specified days CONDITION: Multiple Myeloma PRIMARY OUTCOME: Progression‐free survival (PFS) [ Time Frame: Up to 6 years ] 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, or bortezomib, cyclophosphamide, dexamethasone (VCd), and followed by a single or tandem autologous stem cell transplantation (ASCT). Post‐stem cell transplant consolidation is permitted ‐ Participants within 12 months 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 SECONDARY OUTCOME: 1. Achieving minimal residual disease (MRD) negativity in participants with complete response (CR) or better at 12 (+‐ 3) months of maintenance treatment [ Time Frame: Up to 6 years ]; 2. Overall Survival [ Time Frame: Up to 12 years ]; 3. Recommended iberdomide dose for Stage 2 [ Time Frame: Up to 1 year ]; 4. Area under the iberdomide plasma concentration‐time curve from time zero to tau [ Time Frame: Up to 1 year ]; 5. Area under the iberdomide plasma concentration‐time curve within a dosing interval AUC (TAU) [ Time Frame: Up to 1 year ]; 6. Maximum iberdomide concentration (Cmax) [ Time Frame: Up to 1 year ]; 7. Time to maximum iberdomide plasma concentration (Tmax) [ Time Frame: Up to 1 year ]; 8. Number of participants with adverse events (AEs) [ Time Frame: Up to 6 years ]; 9.Progression‐free survival on next line of treatment (PFS2) [ Time Frame: Up to 6 years ]; 10.Achieving MRD negativity in participants with CR or better at any time after the date of randomization [ Time Frame: Up to 6 years ]; 11. Conversion from MRD positive to MRD negative in participants with CR or better [ Time Frame: Up to 6 years ]; 12. Achievement of CR or better and maintaining MRD‐negative status in 2 bone marrow aspirate assessments that are a minimum of 6 months or 1 year apart, without any examination showing MRD positive status in between assessments [ Time Frame: Up to 6 years ]; 13. Time to progression (TTP) [ Time Frame: Up to 6 years ]; 14. Time to next treatment (TTNT) [ Time Frame: Up to 6 years ]; 15. Best response achieved prior to progressive disease (PD) [ Time Frame: Up to 6 years ]; 16. Patient‐reported health‐related quality of life (HRQoL) outcomes and multiple myeloma‐related symptoms as measured by the European Organization for Research and Treatment of Cancer [EORTC] Quality of Life C30 questionnaire (QLQ‐C30) [ Time Frame: Up to 6 years ]; 17. Patient‐reported HRQoL outcomes and multiple myeloma‐related symptoms as measured by the EORTC Quality of Life Multiple Myeloma Module (QLQ‐MY20) [ Time Frame: Up to 6 years ]