Safety, Activity and Cell Kinetics of CYAD-211 in Patients With Relapsed or Refractory Multiple Myeloma

1. Documented diagnosis of MM with relapsed or refractory disease to at least two prior MM treatment regimens which should include exposure to IMiD and PIs either alone or in combination. 2. Presence of measurable disease as per International Myeloma Working Group (IMWG) Response Criteria 3. Eastern Cooperative Oncology Group (ECOG) below or equal 2 4. Adequate hematologic, renal, hepatic, pulmonary, and cardiac function Exclusion Criteria: 1. History or presence of clinically relevant central nervous system (CNS) tumor involvement. 2. Autologous stem cell transplant within 12 weeks of registration or an allogeneic stem cell transplant within 6 months of starting study treatment. 3. Any investigational agent within 3 weeks prior to the initiation of the non-myeloablative preconditioning chemotherapy). 4. Prior systemic therapy for MM within 14 days prior to the initiation of the non-myeloablative preconditioning chemotherapy. 5. Prior treatment with any BCMA-targeted therapy and which has not achieved at least a partial response.