Key Inclusion Criteria

        All Study Parts:

          -  Diagnosis of cancer that has been histologically or cytologically confirmed

          -  Eastern Cooperative Oncology Group Performance Status of 0 or 1

        Part A (1 of the following):

          -  Ovarian cancer, triple-negative breast cancer, head and neck squamous cell cancer,
             bladder cancer, metastatic colorectal cancer, pancreatic ductal adenocarcinoma, or
             gastric cancer that is measurable or evaluable, nonmeasurable as defined by RECIST
             v1.1 and meets 1 of the following criteria:

               -  is refractory to standard of care

               -  no standard therapy available

               -  patient refuses standard therapy

          -  Advanced, unresectable, or metastatic melanoma with or without prior treatment and
             measurable or evaluable, nonmeasurable disease as defined by RECIST v1.1

          -  Advanced/metastatic PD-L1-positive NSCLC (defined as a tumor proportion score [TPS] ≥
             50%) with measurable or evaluable, non-measurable disease as defined by RECIST v1.1 (1
             of the following):

               -  1) No prior systemic chemotherapy if tumor does not have EGFR or ALK genomic
                  aberrations

               -  2) Disease progression on or after platinum-containing chemotherapy;

               -  3) If tumor has EGFR or ALK genomic aberrations, disease progression on an
                  FDA-approved therapy for EGFR or ALK genomic tumor aberrations

        Phase 2 (1 of the following):

          -  Advanced/metastatic solid tumor with PD as defined by RECIST 1.1 or irRC on an
             anti-PD-1- or anti-PD-L1-containing regimen as their most recent prior therapy

          -  Advanced/metastatic epithelial ovarian cancer, peritoneal cancer or tubal cancer with
             measurable disease as defined by RECIST 1.1, that had progressed within 6 months of
             completing ≥ 4 cycles of platinum-based therapy

          -  Advanced/metastatic PDA that is locally advanced, unresectable or metastatic with
             measurable disease as defined by RECIST v1.1 in patients who have received at least
             one prior line of systemic therapy for their disease

        Key Exclusion Criteria

          1. Prior treatment as follows:

               -  Part A: an immune CPI (e.g., PD-1, PD-L1, or cytotoxic T-lymphocyte antigen 4
                  [CTLA-4] inhibitor).

             NOTE: For patients with melanoma, prior treatment with ipilimumab is allowed if it was
             administered as adjuvant therapy and treatment was completed at least 3 months prior
             to enrollment.

               -  Phase 2:

                    -  A CSF-1R inhibitor or CSF-1 (or MCSF) inhibitor.

                    -  prOVCA and PDA patients only: an immune CPI (e.g., PD-1, PD-L1, or CTLA-4
                       inhibitor)

          2. Symptomatic brain metastasis at screening

          3. Active autoimmune disease, documented history of autoimmune syndrome or disease, or a
             chronic medical condition that requires chronic steroid therapy or immunosuppressive
             medication

          4. History of pneumonitis or interstitial lung disease

          5. Severe, acute, or chronic medical or psychiatric condition or laboratory abnormality
             that may increase the risk associated with study participation or study drug
             administration or that may interfere with the interpretation of study results and, in
             the judgment of the Investigator, would make the patient an inappropriate candidate
             for the study

          6. Ocular melanoma