A Study of Subcutaneous Daratumumab Regimens in Combination With Bispecific T Cell Redirection Antibodies for the Treatment of Participants With Multiple Myeloma

Prior treatment

• Treatment in the prior 3 months with an anti- cluster of differentiation 38 (CD38) therapy (example, daratumumab), or discontinuation of a prior anti-CD38 therapy at any time due to an adverse event related to the anti-CD38 therapy
• Live, attenuated vaccine within 4 weeks prior to the first dose of study drug unless approved by sponsor

Other illness

• Seropositive for hepatitis B (defined by a positive test for hepatitis B surface antigen \[HBsAg\]). Participants with resolved infection must be screened using real-time polymerase chain reaction (PCR) measurement of hepatitis B virus (HBV) deoxyribonucleic acid (DNA) levels. Those who are PCR positive will be excluded
• Active hepatitis C infection as measured by positive hepatitis C virus- ribonucleotide (HCV)-RNA testing. Participants with a history of Hepatitis C virus antibody positivity must undergo HCV-RNA testing

Other

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

• Documented initial diagnosis of multiple myeloma according to International Myeloma Working Group (IMWG) diagnostic criteria
• Must have either of the following: a) received at least 3 prior lines of therapy including a proteasome inhibitor (PI) (greater than or equal to \[\>=\] 2 cycles or 2 months of treatment) and an immunomodulatory drug (IMiD) (\>=2 cycles or 2 months of treatment) in any order during the treatment or b) disease that is double refractory to a PI and an IMiD
• Measurable disease at screening as defined by any of the following: Serum monoclonal protein (M-protein) level \>=1.0 grams per deciliter (g/dL) (in non- immunoglobulin G (IgG) myeloma, an M-protein level \>=0.5 g/dL); or Urine M-protein level \>=200 milligrams (mg)/24 hours; or Light chain multiple myeloma: Serum immunoglobulin (Ig) free light chain (FLC) \>=10 milligrams per deciliter (mg/dL) and abnormal serum Ig kappa lambda FLC ratio
• Eastern Cooperative Oncology Group (ECOG) performance status grade of 0 or 1 at screening and at Cycle 1, Day 1 predose
• Female participants of childbearing potential must have a negative highly-sensitive serum beta-human chorionic gonadotropin (beta-hCG) pregnancy test (less than \[\<\] 5 international units per milliliter \[IU/mL\]) at screening and a negative urine or serum pregnancy test within 1 day before the first dose of study drug