ABBV-383

Multiple myeloma (MM) is a plasma cell disease characterized by the growth of clonal plasma cells in the bone marrow. The purpose of this study is to assess the safety and toxicity of ABBV-383 when co-administered with pomalidomide-dexamethasone (Pd), lenalidomide-dexamethasone (Rd), daratumumab-dexamethasone (Dd), or nirogacestat (Niro) in adult participants with relapsed/refractory (R/R) multiple myeloma (MM). Adverse events and change in disease activity will be assessed.

ABBV-383 is an investigational drug being developed for the treatment of R/R MM. Study doctors put the participants in groups called treatment arms. ABBV-383 co-administered with Pd, Rd, Dd, or Niro will be explored. Each treatment arm receives a different treatment combination depending on stage of the study and eligibility. This study will include a dose escalation phase to determine the best dose of ABBV-383, followed by a dose expansion phase to confirm the dose. Approximately 270 adult participants with R/R MM will be enrolled in the study in approximately 45 sites worldwide.

Participants will receive intravenous (IV) ABBV-383 co-administered with oral/IV Pd, oral/IV Rd, oral/IV/subcutaneous (SC) Dd, or oral/IV Niro in 28-day cycles.

There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at an approved institution (hospital or clinic). The effect of the treatment will be frequently checked by medical assessments, blood tests, questionnaires and side effects.