Inclusion Criteria:

        Dose Optimization and Dose Expansion Inclusion Criteria:

          -  Willing and able to provide written informed consent.

          -  Male or female patients, age 18 years or older at the time of signing the informed
             consent form (ICF).

          -  Life expectancy > 12 weeks from the time of enrollment as determined by the
             Investigator.

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

          -  Oxygen saturation ≥ 92% on room air for all indications.

          -  Measurable disease per RECIST 1.1.

          -  Patients with brain metastases are eligible if certain criteria are met.

          -  Availability of fresh or archival tumor tissue

          -  Patients must have a minimum of 6 months of response to any nonpalliative
             cancer-directed treatment

        Dose Optimization Inclusion Criteria (Multiple Solid Tumors):

          -  Melanoma:

               -  Histologically confirmed stage IV (metastatic) melanoma.

          -  Non-small Cell Lung Cancer:

               -  Histologically confirmed diagnosis of stage IV NSCLC

               -  Must not have received systemic anti-PD-L1 therapy for metastatic disease.

               -  Patients with actionable mutations with approved targeted therapy in NSCLC are
                  excluded. Testing for mutations should be performed in accordance with standard
                  of care.

          -  Urothelial Carcinoma:

               -  Histologically confirmed diagnosis of metastatic urothelial carcinoma

          -  Head and Neck Squamous Cell Carcinoma (HNSCC)

               -  Histologically confirmed diagnosis of metastatic HNSCC

          -  Hepatocellular Carcinoma (HCC)

               -  Histologically confirmed diagnosis of metastatic HCC

        Dose Expansion Inclusion Criteria (Non-Small Cell Lung Cancer):

          -  Histologically confirmed diagnosis of stage IV NSCLC.

          -  Patients must have a minimum of 6 months of response to any nonpalliative
             cancer-directed treatment.

          -  Patients with actionable mutations with approved targeted therapy in NSCLC are
             excluded. Testing for mutations should be performed per standard of care.

          -  Must not have received anti-cancer therapy for treatment of metastatic lung cancer

          -  Must not have received prior immunotherapy

        Exclusion Criteria:

          -  Use of an investigational agent or an investigational device within 28 days before
             administration of first dose of study drug(s).

          -  Females who are pregnant or breastfeeding.

          -  Patients who have an active autoimmune disease

          -  History of allergy or hypersensitivity to study drug components

          -  Evidence of clinically significant interstitial lung disease or active, noninfectious
             pneumonitis.

          -  Prior surgery or radiotherapy within 14 days of therapy.

          -  For Dose Optimization Cohort 1 only: Chemotherapy or biological therapy within 28 days
             of enrollment. Targeted therapy (e.g., tyrosine kinase inhibitors) within 14 days of
             enrollment. Patients with ongoing AEs related to prior cancer therapies will be
             excluded.

          -  Participant's inability to adhere to or tolerate protocol or study procedures

        NOTE: Other protocol defined Inclusion/Exclusion criteria may apply