∙ General

• Age ≥18 years, or ≥ minimum legal age to attend a clinical study.

• Be willing and able to provide written informed consent/assent for the trial.

• Ability to comply with requirements of the protocol, as assessed by the investigator.

• Disease-Specific Inclusion Criteria All subjects must have unresectable locally advanced or metastatic tumors that have histologic or cytological documentation confirmed.

‣ Phase Ib: subjects with advanced HCC, GC or GEJ adenocarcinoma, Urothelial transitional cell Carcinoma and Esophagus Carcinoma who have progressed despite standard therapies, are intolerant of standard therapy, or for whom no standard therapy exists;

⁃ Phase II: subjects with tumor of specific types:

∙ Cohort# Indication Inclusion criteria

• HCC, 2L Unresectable histologic confirmed primary hepatocellular carcinoma. Subjects with radiological diagnosis may also be enrolled in the study.

• Documented radiographic or clinical disease progression during or after 1st line therapy, including Sorafenib, Lenvatinib and Atezolizumab plus Bevacizumab and other 1st line standard care per local clinical practice.

• Patient has a Child-Pugh score of 5 or 6 points and no encephalopathy and/or clinically apparent ascites. (Note: Child-Pugh score should be evaluated within 7 days of first dose of study drug)

• GC or GEJ adenocarcinoma, 3L Unresectable locally advanced or metastatic GC or GEJ carcinoma and have histologically confirmed adenocarcinoma.

• At least 50% subjects with PD-L1 expression (CPS) on ≥ 1% will be enrolled in this cohort.

• Has experienced documented objective radiographic or clinical disease progression during or after standard first line Platinum- and fluoropyrimidine-based two or three cytotoxic drug chemotherapy and second line NCCN recommended treatment regimen therapy or other 1st and 2nd line standard care per local clinical practice. (Note: subjects with discontinuation due to AEs prior to disease progression are not considered as treatment failure unless disease progression is confirmed by documentation.) Disease progression during or within 6 months following the last dose of adjuvant or neo-adjuvant therapy will be considered as 1st line failure.

• UC, 2L Histologically or cytologically confirmed urothelial carcinoma of the renal pelvis, ureter, bladder, or urethra that showed predominantly transitional-cell features Has experienced documented progression or recurrence after at least the 1st line platinum-based chemotherapy or recurrence within 12 months after the receipt of platinum-based adjuvant or neoadjuvant therapy for localized muscle-invasive disease.

∙ Note: Primary chemoradiation for unresectable muscle-invasive bladder cancer with the aim of bladder preservation will not be considered a prior line of systemic therapy for the purposes of determining study eligibility.

∙ 4 ESCC 2L Histologically confirmed, unresectable squamous cell carcinoma of the esophagus.

∙ The primary tumor must originate in the esophagus. Tumors that involve the GE junction must meet Sievert Type 1 criteria, 1-5 cm above the EGJ. For the purposes of this protocol, this will be interpreted as: greater than 50% of the tumor must be above the GE junction.

∙ Patients must have received at least one prior therapy for unresectable disease. Patients with recurrence within 6 months of completion of neoadjuvant or adjuvant therapy may be considered as having received one prior therapy for unresectable disease.

∙ 5\. Patient must have at least one measurable lesion by CT or MRI per RECIST 1.1. Tumor lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions. Loco-regional treated lesion cannot be selected as a target lesion.

∙ 6\. ECOG performance status score of 0 or 1. 7. Life expectancy ≥ 12 weeks. 8. At screening, patients in Phase II part must agree to provide archival tumor tissue, if available, for biomarker testing. When archival tissue is not available, it is optional for patients to undergo fresh biopsy judged medically safe by the investigator.

• Archival tumor tissue can be formalin-fixed paraffin embedded (FFPE) tissue block (preferably collected within 12 months before the first dose) or at least 5 freshly sectioned unstained slides. Tissue block is preferred over unstained slides.

• Acceptable tissue sample include core needle punctured, resected or incisional biopsy, or surgical sample. (Note: Fine needle aspirational cytology (FNAC) sample is not acceptable. Tumor tissue from bone metastases is not evaluable for determination of PD-L1 expression and is therefore also not acceptable.) 9. Any toxic effects of prior anti-cancer therapy or surgical procedures resolved to baseline severity or NCI-CTCAE version 5 Grade ≤ 1 (except alopecia or other toxicities not considered a safety risk for the patient at investigator's discretion).

∙ Clinical Laboratory Inclusion Criteria

∙ 10\. Subject must have adequate organ function as indicated by the following laboratory values \[had not received blood transfusion, erythropoietin (EPO), granulocyte colony stimulating factor (G-CSF) or other relevant medical support within 14 days before the administration of the investigational product\]:

∙ Absolute neutrophil count (ANC) ≥ 1.5×109/L Platelets ≥ 100 ×109/L (≥ 60 ×109/L for HCC subjects) Hemoglobin ≥ 9 g/dL or ≥ 5.6 mmol/L Serum creatinine ≤ 1.5 × upper limit of normal (ULN); AND calculated creatinine clearance (CrCL) \> 50 mL/min (Cockcroft-Gault formula) Total bilirubin ≤ 1.5 × ULN OR ≤2.5 × ULN for HCC OR ≤ 2 × ULN in case of known Gilbert disease AST (SGOT) and ALT (SGPT) ≤ 2.5 × ULN OR ≤ 5 × ULN for HCC patients or patients with liver metastases Serum albumin ≥ 28 g/L (no albumin transfusion within 14 days) International Normalized Ratio (INR) or Prothrombin Time (PT) ≤ 1.5 × ULN Activated Partial Thromboplastin Time (aPTT) ≤ 1.5 × ULN

∙ 11\. Subjects with hepatitis B virus (HBV) infection must have HBV DNA \< 2000 IU/mL at screening.

∙ Subjects with positive HBsAg and/or positive HBV DNA that requires anti-HBV treatment for at least 2 weeks prior to the first dose of study drugs and are willing to continue receiving antiviral treatment.

∙ 12\. Women of childbearing potential (WOCBP) must have a negative pregnancy test result. Either Female or male patients must agree to use adequate contraceptive measures from signing informed consent and for 180 days after last investigational product administration, except for a patient with documented surgical sterilization or a postmenopausal female.