Inclusion Criteria:

          -  For Ph1a monotherapy and combination cohorts, histologic or cytologic confirmation of
             advanced solid tumor.

          -  For Phase 1a and 1b, prior PD-1 or PD-L1 therapy or other immunotherapy is allowed, if
             the following criteria are met:

               -  Must not have experienced a toxicity that led to permanent discontinuation of
                  prior immunotherapy.

               -  Must have completely recovered or recovered to baseline prior to screening from
                  any prior AEs occurring while receiving prior immunotherapy.

          -  Must have provided tumor tissue sample, as follows:

               -  For participants entering Ph1a: have submitted, if available, an archival tumor
                  tissue sample.

               -  For participants entering Ph1b: have submitted, a sample from a newly obtained
                  core or excisional biopsy of a tumor lesion or a recent biopsy defined by 6
                  months of study enrollment (Ph1b).

          -  Must have a performance status of 0 to 1 on the Eastern Cooperative Oncology Group
             (ECOG) scale.

          -  Must have adequate organ function.

          -  Have an estimated life expectancy of 12 weeks, in judgement of the investigator.

        Exclusion Criteria:

          -  Have symptomatic or uncontrolled brain metastases, spinal cord compression, or
             leptomeningeal disease requiring concurrent treatment, including but not limited to
             surgery, radiation, and/or corticosteroids (participants receiving anticonvulsants are
             eligible).

          -  Have received a live vaccine within 30 days before the first dose of study treatment.

          -  If female, is pregnant, breastfeeding, or planning to become pregnant.

          -  Have a history or current evidence of any condition, therapy, or laboratory
             abnormality that might interfere with the participant's participation.

          -  Have moderate or severe cardiovascular disease.

          -  Have a serious concomitant systemic disorder that would compromise the participant's
             ability to adhere to the protocol, including active or chronic infection with human
             immunodeficiency virus (HIV), active hepatitis B virus (HBV), active hepatitis C virus
             (HCV), active autoimmune disorders, or prior documented severe autoimmune or
             inflammatory disorders requiring immunosuppressive treatment.

          -  Use of escalating or chronic supraphysiologic doses of corticosteroids or
             immunosuppressive agents (such as, cyclosporine). [Use of topical, ophthalmic,
             inhaled, and intranasal corticosteroids permitted].

          -  Bowel obstruction, history or presence of inflammatory enteropathy or extensive
             intestinal resection.

          -  Evidence of interstitial lung disease or noninfectious pneumonitis.