A Study to Assess Adverse Events and Change in Disease Activity of Intravenously (IV) Infused Etentamig (ABBV-383) in Combination With Anti-Cancer Regimens for the Treatment of Adult Participants With Relapsed/Refractory Multiple Myeloma

Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) performance of <= 2.

• Must have confirmed diagnosis of Relapsed/Refractory (R/R) Multiple Myeloma (MM)with documented evidence of progression during or after the participant's lasttreatment regimen based on the investigator's determination of the InternationalMyeloma Working Group (IMWG) criteria.

• Must have measurable disease as determined by central lab as outlined in theprotocol.

• Must be naïve to treatment with Etentamig.

• Must have never received BCMA-targeted therapy. Participants who have receivedtargeted therapy against non-BCMA targets will not be excluded.

• Arms A, B and C: Participant has received at least 3 prior lines of MM treatment.

• Arm E: Participant has received 1-3 prior lines of MM treatment.

Exclusion Criteria:

• Received a peripheral autologous stem cell transplant (SCT) within 12 weeks, or anallogeneic SCT within 1 year of the first dose of study treatment.

• Unresolved adverse event (AE)s >= Grade 2 (National Cancer Institute [NCI] CommonTerminology Criteria for Adverse Events [CTCAE] version 5.0) from prior anticancertherapy.

• Has any of the following conditions:

• Nonsecretory Multiple Myeloma (MM).

• Active Plasma cell leukemia i.e., either 20% of peripheral white blood cells or > 2.0 × 10^9L circulating plasma cells by standard differential.

• Waldenstrom's macroglobulinemia.

• Light chain amyloidosis.

• Polyneuropathy, organomegaly, endocrinopathy, monoclonal protein and skinchanges (POEMS) syndrome.

• Major surgery within 4 weeks prior to first dose or planned studyparticipation.

• Acute infections within 14 days prior to first dose of study requiring therapy (antibiotic, antifungal or antiviral).

• Uncontrolled diabetes or hypertension within 14 days prior to first dose.

• Peripheral neuropathy >= Grade 3 or >= Grade 2 with pain within 2 weeks priorto first dose.