Inclusion Criteria:

          -  Male or female, age 18 years or older.

          -  Willingness to provide written informed consent for the study.

          -  Part 1a: Subjects with histologically or cytologically confirmed advanced or
             metastatic solid tumors that have failed prior standard therapy (including subject
             refusal or intolerance).

          -  Part 1b: Subjects with endometrial cancer, gastric cancer, head and neck squamous cell
             carcinoma, melanoma, microsatellite unstable colorectal cancer, non-small cell lung
             cancer, pancreatic ductal adenocarcinoma, renal cell carcinoma, triple negative breast
             cancer, or transitional cell carcinoma of the genitourinary tract that have had
             disease progression after available therapies for metastatic disease that are known to
             confer clinical benefit, been intolerant to treatment, or refused standard treatment.

          -  Part 1b: Must have documented confirmed disease progression on a prior programmed cell
             death-1 (PD-1) pathway targeted agent or must be PD-1 pathway-targeted treatment
             naïve.

          -  Part 2: Subjects with HNSCC, NSCLC, pancreatic ductal adenocarcinoma, salivary gland
             cancer, and transitional cell carcinoma of the genitourinary tract that have had
             disease progression after available therapies for advanced or metastatic disease that
             are known to confer clinical benefit, have been intolerant to treatment, or have
             refused standard treatment.

          -  Willingness to undergo a pre-treatment and on-treatment tumor biopsy to obtain the
             specimen.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

        Exclusion Criteria:

          -  Laboratory parameters not within the protocol-defined range.

          -  Receipt of anticancer medications or investigational drugs within a defined interval
             before the first administration of study drug.

          -  Received an immune-suppressive based treatment for any reason within 14 days prior to
             the first dose of study treatment.

          -  Has not recovered from toxic effect of prior therapy to < Grade 1.

          -  Active or inactive autoimmune process.

          -  Has received a live vaccine within 30 days of planned start of study therapy.

          -  Active infection requiring systemic therapy.