A Study of Talquetamab in Participants With Relapsed or Refractory Multiple Myeloma

Inclusion Criteria

• Documented initial diagnosis of multiple myeloma according to international myeloma working group (IMWG) diagnostic criteria
• Part 3: Measurable disease cohort A, cohort B, cohort C, and cohort D: multiple myeloma must be measurable by central laboratory assessment
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 2
• Women of childbearing potential must have a negative pregnancy test at screening and prior to the first dose of study drug using a highly sensitive pregnancy test either serum (beta human chorionic gonadotropin [hCG]) or urine
• Willing and able to adhere to the prohibitions and restrictions specified in this protocol

Exclusion Criteria

• Part 3 only: Cohort A and Cohort C only: exposed to a CAR-T or T cell redirection therapy at any time. Cohort B and Cohort D: T cell redirection therapy within 3 months
• Toxicities from previous anticancer therapies should have resolved to baseline levels or to Grade 1 or less except for alopecia or peripheral neuropathy
• Received a cumulative dose of corticosteroids equivalent to >= 140 milligram (mg) of prednisone within the 14-day period before the first dose of study drug (does not include pretreatment medication)
• Stroke or seizure within 6 months prior to signing the informed consent form (ICF)