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

Inclusion Criteria: * Male or female ≥ 18 years. * Patients with histologically or cytologically confirmed, locally advanced or metastatic solid tumors. Part A only: \* Patients must be: a) progressed after standard therapies, b) intolerant of standard therapies, or c) with a tumor type without standard therapy. Part B only: * Cohort A: Patients with previously untreated, unresectable, locally advanced or metastatic GC/GEJ adenocarcinoma; prior adjuvant or neoadjuvant therapy are allowed only if disease progressed or recurred at least 6 months after completion of these treatments. Patients may have received one infusion of mFOLFOX6 plus nivolumab during the screening period. * Cohort B: Patients with GC/GEJ adenocarcinoma who have radiologically progressed following one or two prior systemic therapies; adjuvant or neoadjuvant therapy could be regarded as one line of therapy only if disease progressed or recurred during these treatments or within 6 months or less after completion of these treatments. * Cohort C: Patients with previously untreated, unresectable, locally advanced or metastatic histologically confirmed pancreatic adenocarcinoma; prior adjuvant or neoadjuvant therapy are allowed only if disease progressed or recurred at least 6 months after completion of these treatments. Patients may have received up to 2 infusions of Gemcitabine + albumin-bound paclitaxel (with one week between each infusion) during the screening period. * Eastern Cooperative Oncology Group Performance Status (ECOG PS): 0-1 . * Patients with adequate cardiac, liver, renal function, etc. Exclusion Criteria * Symptomatic central nervous system metastases. * Prior treatment with any CLDN18.2 target agents * Allergy or sensitivity to TST001 or known allergies to comparable drugs * Documented history of multiple other allergies requiring interventions * Severe cardiovascular disease, including CVA, TIA, myocardial infarction, or unstable angina, NYHA class III or IV heart failure or uncontrolled arrhythmia within 6 months of study entry, severe QTc prolongation, concomitant risks for QTc prolongation. * Concurrent malignancy within 5 years prior to entry except adequately treated certain types of cancer * Active and clinically significant infections, known uncontrolled infections with hepatitis B, hepatitis C, known human immunodeficiency virus with acquired immunodeficiency syndrome related illness * Any condition that the investigator or primary physician believes may not be appropriate for participating in the study. Other protocol-defined Inclusion/Exclusion Criteria could apply. .