A Study of ABBV-428, an Immunotherapy, in Subjects With Advanced Solid Tumors

Inclusion Criteria:

- Participants must have an advanced solid tumor that has progressed on standard
therapies known to provide clinical benefit or the participants are intolerant to such
therapies.

- Participants have adequate bone marrow, renal, hepatic and coagulation function.

- For all dose expansion arms, participants must have measurable disease per Response
Evaluation Criteria in Solid Tumors (RECIST) Version 1.1

- Participants in combination therapy cohorts must have an advanced solid tumor where
the use of nivolumab is standard therapy.

Exclusion Criteria:

- Active or prior documented autoimmune disease in the last 2 years. Participants with
childhood atopy or asthma, vitiligo, alopecia, Hashimoto syndrome, Grave's disease, or
psoriasis not requiring systemic treatment (within the past 2 years) are not excluded.

- Current or prior use of immunosuppressive medication within 14 days prior to the first
dose (with certain exceptions).

- History of primary immunodeficiency, bone marrow transplantation, chronic lymphocytic
leukemia, solid organ transplantation, or previous clinical diagnosis of tuberculosis.

- Confirmed positive test results for human immunodeficiency virus (HIV), or
participants with chronic or active hepatitis B or C. Participants who have a history
of hepatitis B or C who have undetectable HBV DNA or HCV RNA after anti-viral therapy
may be enrolled.

- Prior grade greater than or equal to 3 immune-mediated neurotoxicity or pneumonitis
(or any other unresolved or symptomatic adverse event in the last 3 months) while
receiving immunotherapy.

- Male participants who are considering fathering a child or donating sperm during the
study or for at least 3 or 5 months (for monotherapy and combination therapy
participants, respectively) after the last dose of study drug.