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. ROS1 rearrangement or BRAF mutation must have progressed
                  following at least 1 available EGFR (including osimertinib for EGFR T790M-mutated
                  NSCLC), ALK, ROS1 or BRAF targeted therapy, respectively

               2. Patients that have progressed during or following treatment with platinum-based
                  chemotherapy for advanced disease and 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.

          -  Checkpoint inhibitor-naïve mCRPC that has progressed during or following no more than
             2 prior lines of an androgen receptor antagonist or androgen synthesis inhibitor
             (e.g., enzalutamide or abiraterone, respectively), if approved and available, with a
             PSA value of at least 2 ng/mL and meeting at least one of the following:

          -  Progression in measurable disease (RECIST v1.1).

          -  Appearance of 2 or more new bone lesions according to Prostate Cancer Working Group 2
             (PCWG-2).

          -  Rising PSA defined as at least two sequential rises in PSA.

          -  Eligible patients may have received prior chemotherapy (i.e. docetaxel), and patients
             with known homologous recombination (HRR) pathway gene alterations must have received
             the applicable approved therapy (e.g. olaparib).

          -  Cutaneous melanoma that has progressed during or following systemic treatment for
             unresectable, locally advanced, or metastatic disease. Patients will have received
             PD-(L)1 and/or CTLA-4 pathway inhibitors where available and indicated.

          -  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. Patients may undergo a fresh tumor biopsy during
             the screening period if a tumor sample is not available. Patients in the mCRPC
             expansion cohort with bone only disease not amenable to fresh biopsy may be eligible
             in consultation with the Sponsor.

          -  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 (this does not
             apply to the melanoma expansion cohort).

          -  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 or major surgical procedure within 4 weeks prior to initiation of
             study drug administration.

          -  Systemic antineoplastic therapy, or investigational therapy (for all tumor types) or
             androgen receptor antagonist/androgen synthesis inhibitor for mCRPC (e.g.,
             enzalutamide or abiraterone, respectively) 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.

          -  Radioligand (e.g., radium-223) within 6 months prior to initiation of study drug
             administration for mCRPC in the Cohort Expansion Phase.

          -  Serum testosterone > 50 ng/dl or > 1.7 nmol/L for mCRPC in the Cohort Expansion Phase.

          -  Confirmed or presumed COVID-19/SARS-CoV-2 infection. While SARS-CoV-2 testing is not
             mandatory for study entry, testing should follow local clinical practice
             guidelines/standards. Patients with a positive test result for SARS-CoV-2 infection,
             known asymptomatic infection, or presumed infection are excluded. Patients may be
             considered eligible after a resolved SARS-CoV-2 infection once he or she remains
             afebrile for at least 72 hours and after other SARS-CoV-2-related symptoms have fully
             recovered to baseline for a minimum of 72 hours