A Study to Assess Adverse Events and Change in Disease Activity of Oral Surzetoclax Alone or in Combination With Subcutaneous and/or Oral Antimyeloma Agents in Adult Participants With Multiple Myeloma (MM)

Inclusion Criteria: * Documented diagnosis of multiple myeloma (MM) based on standard international myeloma working group (IMWG) diagnostic criteria. * All participants must have measurable disease per central laboratory with at least 1 of the following assessed within 28 days prior to enrollment: * Serum M-protein \>= 0.5 g/dL (\>= 5g/L); OR * Urine M-protein \>= 200 mg/24 hours; OR * For participants without measurable serum and urine M-protein: Serum free light chain (sFLC) \>= 10 mg/dL (100 mg/L), provided sFLC ratio is abnormal. * B-cell lymphoma (BCL)-2 inhibitor treatment naïve. * t(11;14) positive status and/or BCL2 high status. * Must have confirmed diagnosis of relapsed or refractory (R/R) multiple myeloma (MM) with documented evidence of progression during or after the participant's last treatment regimen, based on the investigator's determination of the international myeloma working group (IMWG) 2016 criteria. Exclusion Criteria: * Major surgery within 4 weeks of study treatment or planned during study participation. * Recent infection requiring systemic treatment that was completed \<= 14 days before first dose of study treatment and/or uncontrolled active systemic infection.