Inclusion Criteria:

          -  Dose escalation: Patients with histologically proven, unresectable, locally advanced
             or metastatic solid tumors for whom no approved therapy with demonstrated clinical
             benefit is available or patients who are intolerant to standard therapy.

          -  Cohort Expansion Phase:

          -  Checkpoint inhibitor-naïve squamous cell NSCLC, including:

               1. Patients that have progressed during or following treatment with platinum-based
                  chemotherapy for advanced disease. Patients harboring an activating epidermal
                  growth factor receptor (EGFR) mutation or anaplastic lymphoma kinase (ALK)
                  rearrangement must have progressed following at least one available EGFR or ALK
                  targeted therapy.

               2. Patients with previously untreated squamous cell NSCLC without activating
                  mutations for whom checkpoint inhibitor therapy is not approved or available.

          -  Advanced non-microsatellite instability-high colorectal cancer (CRC) with recurrence,
             progression, or intolerance to standard therapy consisting of at least 2 prior
             standard regimens. CRC harboring an activating EGFR mutation must have progressed
             during or following at least one available EGFR targeted therapy. Patients who are
             inappropriate candidates for or have refused treatment with these regimens are also
             eligible. Patients should have received no more than 4 prior lines of systemic
             therapy.

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

          -  Life expectancy ≥ 12 weeks.

          -  Measurable disease as per RECIST 1.1 for the purpose of response assessment must
             either (a) not reside in a field that has been subjected to prior radiotherapy or (b)
             have demonstrated clear evidence of radiographic progression since the completion of
             prior radiotherapy and prior to study enrollment.

          -  All patients must have an identified formalin-fixed, paraffin embedded (FFPE) tumor
             specimen (up to 20 slides or a block) for immunohistochemical evaluation of
             pharmacodynamic markers of interest.

          -  Acceptable laboratory parameters and adequate organ reserve.

        Exclusion Criteria:

          -  In patients who have previously received an immune checkpoint inhibitor (e.g.,
             anti-PD-L1, anti-PD-1, anti-CTLA-4), toxicities related to the checkpoint inhibitor
             must have resolved to ≤ Grade 1 or baseline. Patients with well controlled immune
             endocrinopathies secondary to prior checkpoint therapy are eligible.

          -  Patients with symptomatic CNS metastases. Patients with history of prior CNS
             metastasis must have been treated, must be asymptomatic, and must not have concurrent
             treatment for the CNS disease, progression of CNS metastases on magnetic resonance
             imaging (MRI) or computed tomography (CT) for at least 14 days after last day of prior
             therapy for the CNS metastases, or concurrent leptomeningeal disease or cord
             compression.

          -  Patients who sustained the following Grade 3 immune checkpoint inhibitor related AEs
             are ineligible: Ocular AE, changes in liver function tests that met the criteria for
             Hy's law (> 3 × ULN of either ALT or AST with concurrent > 2 × ULN of total bilirubin
             and without alternate etiology), neurologic toxicity, colitis, renal toxicity,
             pneumonitis.

          -  Patients who have received prior therapy with a combination of monoclonal antibodies
             against PD-1/PD-L1 and CTLA-4 will be excluded in the Cohort Expansion.

          -  Patients with any history of known or suspected autoimmune disease with certain
             exceptions

          -  History of prior allogeneic bone marrow, stem-cell, or solid organ transplantation.

          -  History of trauma, major surgical procedure, systemic antineoplastic therapy, or
             investigational therapy within the 4 weeks prior to initiation of study drug
             administration.

          -  Treatment with radiation therapy within 2 weeks prior to initiation of study drug
             administration.