A Study Comparing Pre- and Post-Change Teclistamab in Participants With Relapsed or Refractory Multiple Myeloma

Prior treatment

• Received any bispecific antibody and/or chimeric antigen receptor T cell (CAR-T) cell therapy
• Received a live, attenuated vaccine within 4 weeks before the first dose of study drug. Non-live or non-replicating vaccines authorized for emergency use by local health authorities are allowed
• Participant had major surgery or had significant traumatic injury within 2 weeks prior to randomization, or will not have fully recovered from surgery, or has major surgery planned during the time the participant is expected to be treated in the study

Other illness

• Contraindications or life-threatening allergies, hypersensitivity, or intolerance to any study drug or its excipients

Other

• Central nervous system involvement or clinical signs of meningeal involvement of multiple myeloma. If either is suspected, negative whole brain magnetic resonance imaging (MRI) and lumbar cytology may be required

• Documented diagnosis of multiple myeloma as defined by the criteria below: (a) Multiple myeloma diagnosis according to International Myeloma Working Group (IMWG) diagnostic criteria (b) Measurable disease at screening as defined by any of the following: (1) Serum M-protein level greater than or equal to (\>=) 0.5 grams per deciliter (g/dL) (central laboratory); or (2) Urine M-protein level \>=200 milligrams (mg)/24 hours (central laboratory); or (3) Serum immunoglobulin free light chain \>=10 milligrams per deciliter (mg/dL) (central laboratory) and abnormal serum immunoglobulin kappa lambda free light chain ratio
• Received 1 to 3 prior lines of antimyeloma therapy, including a minimum of 2 consecutive cycles each of a protease inhibitor (PI), lenalidomide, and an anti-cluster of differentiation 38 (CD38) monoclonal antibody (or minimum of 6 doses if anti CD38 monoclonal antibody was only part of a maintenance regimen) in any prior line
• Documented evidence of progressive disease or failure to achieve a response to last line of therapy based on investigator's determination of response by IMWG criteria
• Have an eastern cooperative oncology group (ECOG) performance status score of 0 to 2
• A female participant of childbearing potential must have a negative highly sensitive serum pregnancy test at screening and within 24 hours of the start of study treatment and must agree to further serum or urine pregnancy tests during the study