A Dose Escalation and Expansion Study of ABBV-383 in Combination with Anti-Cancer Regimens for the Treatment of Patients with Relapsed/Refractory Multiple Myeloma

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 etentamig (ABBV-383) when co-administered with pomalidomide-dexamethasone
(Pd), lenalidomide-dexamethasone (Rd), or daratumumab-dexamethasone (Dd), in adult
participants with relapsed/refractory (R/R) multiple myeloma (MM). Adverse events and
change in disease activity will be assessed.

Etentamig is an investigational drug being developed for the treatment of R/R MM. Study
doctors put the participants in groups called treatment arms. Etentamig co-administered
with Pd, Rd, or Dd, 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 etentamig, followed by a dose
expansion phase to confirm the dose. Approximately 320 adult participants with R/R MM
will be enrolled in the study in approximately 48 sites worldwide.

Participants will receive intravenous (IV) etentamig co-administered with oral/IV Pd,
oral/IV Rd, or oral/IV/subcutaneous (SC) Dd 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.

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 last
treatment regimen based on the investigator's determination of the International
Myeloma Working Group (IMWG) criteria.

- Must have measurable disease as determined by central lab as outlined in the
protocol.

- Must be naïve to treatment with Etentamig.

- Must have never received BCMA-targeted therapy. Participants who have received
targeted 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 an
allogeneic SCT within 1 year of the first dose of study treatment.

- Unresolved adverse event (AE)s >= Grade 2 (National Cancer Institute [NCI] Common
Terminology Criteria for Adverse Events [CTCAE] version 5.0) from prior anticancer
therapy.

- 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 skin
changes (POEMS) syndrome.

- Major surgery within 4 weeks prior to first dose or planned study
participation.

- 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 prior
to first dose.