This is an open-label, multicenter Phase 1/2 clinical study for participants with histologically or cytologically confirmed unresectable locally advanced or metastatic HCC or G/GEJ cancer. All participants will receive study treatment (s) until progressive disease (PD), unacceptable toxicity, death, withdrawal of consent, or study termination by sponsor. This study consists of the following phases.~Phase 1 (Dose escalation for sitravatinib as monotherapy and in combination with tislelizumab): Two dose levels of sitravatinib as monotherapy, 80 mg once daily and 120 mg once daily, will be evaluated in participants with unresectable locally advanced or metastatic HCC or G/GEJ cancer. A modified 3+3 design will be used in the dose escalation. Approximately 6 to 12 DLT evaluable participants will be treated with sitravatinib as monotherapy. The combination dose escalation of sitravatinib (80 mg once daily and 120 mg once daily; modified 3+3 design) with tislelizumab (200 mg every 3 weeks, in both cohorts) will be evaluated in participants with unresectable locally advanced or metastatic HCC or G/GEJ cancer. Approximately 12 to 24 DLT evaluable participants will be treated with sitravatinib in combination with tislelizumab.~Phase 2 (Dose expansion for sitravatinib as monotherapy and in combination with tislelizumab): Approximately 20 participants will be enrolled in each cohort. There will be a total of 4 cohorts in the study.~Cohort A: Anti-PD-1/PD-L1 Antibody Naïve or Refractory/Resistant HCC~Cohort B: Anti-PD-1/PD-L1 antibody naive HCC~Cohort C: Anti-PD-1/PD-L1 antibody refractory/resistant HCC~Cohort D: Anti-PD-1/PD-L1 antibody naive G/GEJ cancer
The purpose of this study is to evaluate the safety,tolerability, pharmacokinetics and preliminary antitumor activity of sitravatinib as monotherapy and in combination with tislelizumab in participants with unresectable locally advanced or metastatic hepatocellular carcinoma or gastric/gastroesophageal junction cancer.