A Trial to Evaluate Safety and Tolerability of TST001 in Advanced or Metastatic Solid Tumors

Part A of the trial will consist of two cohorts, one dosed every 2 weeks and one dosed every 3 weeks in a standard 3+3 design. Part A is the dose finding portion of the trial. 18 to 36 participants will be enrolled. Part B consists of 3 cohorts: Cohort A is for patients with previously untreated, unresectable, locally advanced or metastatic GC/GEJ adenocarcinoma. Patients will receive TST001 at 2mg/kg or 4mg/kg Q2W plus Nivolumab and mFOLFOX6. Alternative allocation of patients between the 2 doses will be performed. The first 6 patients at each dose level as the lead-in phase will not be selected on the basis of their tumor's CLDN18.2 expression. Approximately 12-42 patients will be enrolled in Cohort A. Cohort B is for patients with GC/GEJ adenocarcinoma who have radiologically progressed following one or two prior systemic therapies. Patient will receive TST001 plus Nivolumab. No selection based on CLDN18.2 expression will be required for the safety run-in (3-6 patients). Patients with CLDN18.2 expression in tumor tissue tested by the central laboratory will be enrolled in the expansion phase. Safety run-in phase will follow 3+3 rule with two dose levels, TST001 3mg/kg and 6mg/kg Q3W combined with nivolumab. Approximately 30 patients will be enrolled in Cohort B including the patients in the safety run-in phase. Cohort C is for patients with previously untreated, unresectable, locally advanced or metastatic histologically confirmed pancreatic adenocarcinoma; Patients will receive TST001 at 2mg/kg or 4mg/kg Q2W plus gemcitabine and albumin-bound paclitaxel. Alternative allocation of patients between the 2 doses will be performed. The first 6 patients at each dose level as the lead-in phase will not be selected on the basis of their tumor's CLDN18.2 expression. Approximately 12-42 patients will be enrolled in Cohort C.