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

The purpose of this study is to evaluate the efficacy and safety of talquetamab in participants with relapsed or refractory multiple myeloma at the recommended Phase 2 dose(s) (RP2Ds) (Part 3).

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; Cohort E: Multiple myeloma must be measurable by local 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, Cohort D and Cohort E: 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)