A Study of CC-95266 in Participants With Relapsed and/or Refractory Multiple Myeloma

Inclusion Criteria:

Age ≥ 18 years
Participant has a diagnosis of multiple myeloma (MM) with relapsed and/or refractory disease. Participants must have confirmed progressive disease (as per IMWG criteria) on or within 12 months of completing treatment with the last anti-myeloma treatment regimen before study entry or have confirmed progressive disease within 6 months prior to screening and who are subsequently determined to be refractory or non-responsive to their most recent anti-myeloma treatment regimen, except for participants with cellular therapy (e.g., Chimeric antigen receptor (CAR) T-cell therapy) as their last treatment, who may enroll beyond 12 months.

Participants in Part A, and Part B Cohort A, and Part B Cohort B must have received at least 3 prior anti-myeloma treatment regimens (note: induction with or without hematopoietic stem cell transplant (HSCT) and with or without maintenance therapy is considered one regimen).Subjects in Part B Cohort C only must have received at least 1 but not greater than 3 prior anti-myeloma treatment regimens, including a proteasome inhibitor and immunomodulatory agent including:

Autologous HSCT, unless the subject was ineligible
A regimen that included an immunomodulatory agent (e.g., thalidomide, lenalidomide, pomalidomide) and a proteasome inhibitor (e.g., bortezomib, carfilzomib, ixazomib), either alone or combination
Anti-CD38 (e.g., daratumumab), either alone or combination. Subjects in Cohort C do not require prior anti-CD38 antibody therapy.
Measurable disease
Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
Adequate organ function

Exclusion Criteria:

Known active or history of central nervous system (CNS) involvement of MM
Active or history of plasma cell leukemia, Waldenstrom's macroglobulinemia, POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome, or clinically significant amyloidosis
Active autoimmune disease requiring immunosuppressive therapy
History or presence of clinically significant CNS pathology such as seizure disorder, aphasia, stroke, severe brain injuries, dementia, Parkinson's disease, cerebellar disease, or psychosis

Other protocol-defined inclusion/exclusion criteria apply.