Key Inclusion Criteria:

        Phase 1 Key Inclusion Criteria

          1. Has Eastern Cooperative Oncology Group (ECOG) Performance Status ≤1.

          2. ≥ 1 measurable lesion per RECIST v1.1.

          3. Has adequate organ function.

          4. phase 1- Patients with histologically or cytologically confirmed advanced, metastatic,
             unresectable solid tumors who have previously received standard systemic therapy or
             for which treatment is not available, not tolerated or refused.

        Phase 1b Key Inclusion Criteria

          1. Signed informed consent form (ICF) and able to comply with study requirements.

          2. Age ≥ 18 years (or the legal age of consent) at the time the ICF is signed.

          3. Histologically or cytologically confirmed tumor types in the following disease
             cohorts:

             Cohort 1: stage IV squamous NSCLC Cohort 2: stage IV non-squamous NSCLC Cohort 3:
             stage IV squamous or non-squamous NSCLC with PD-L1 positive. Cohort 4: extensive-stage
             SCLC Cohort 5: stage IIIB, IIIC or IV NSCLC Cohort 6: stage IV ESCC Cohort 7: stage IV
             EAC Cohort 8: recurrent or metastatic HNSCC incurable by local therapies Cohort 9:
             stage IV G/GEJ adenocarcinoma.

          4. ECOG Performance Status ≤ 1

          5. Adequate organ function

          6. Willing to use highly effective method of birth control

        Phase 1 Key Exclusion Criteria:

          1. Active brain or leptomeningeal metastasis.

          2. Active autoimmune diseases or history of autoimmune diseases that may relapse.

          3. With severe chronic or active infections requiring systemic antibacterial, antifungal
             or antiviral therapy, including tuberculosis infection, etc. (antiviral therapy is
             permitted for patients with hepatocellular carcinoma).

          4. Concurrent participation in another therapeutic clinical trial.

          5. Received prior therapies targeting TIGIT.

        Phase 1b Key Exclusion Criteria:

          1. Patients with any prior therapy for recurrent/metastatic disease.

          2. Non-squamous NSCLC patients with sensitizing epidermal growth factor receptor (EGFR)
             mutation, anaplastic lymphoma kinase (ALK) fusion, and c-ros oncogene 1 (ROS1) fusion.

          3. Gastric cancer patients with squamous or with positive HER2 expression.

          4. Prior therapy with any drug specifically targeting T-cell co-stimulation or checkpoint
             pathways. (anti-PD(L)1 exception for Cohort 5).

          5. Active leptomeningeal disease or uncontrolled brain metastasis.

          6. Active autoimmune diseases or history of autoimmune diseases that may relapse.

          7. With severe chronic or active infections requiring systemic antibacterial, antifungal
             or antiviral therapy, including tuberculosis infection, etc. (antiviral therapy is
             permitted for patients with hepatocellular carcinoma).

          8. Concurrent participation in another therapeutic clinical study.

        NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.