CLDN18.2-positive Adenocarcinoma of the Gastroesophageal Junction

This study is a prospective, umbrella-design, Phase II clinical trial. Eligible participants with advanced or metastatic gastric cancer who are treatment-naïve for advanced-stage systemic therapy will undergo biomarker profiling (HER2, CLDN18.2, and PD-L1) via next-generation sequencing (NGS) or immunohistochemistry (IHC). Participants will be stratified into distinct molecular subtypes and assigned subtype-specific therapeutic regimens. The primary objectives are to assess treatment efficacy (e.g., objective response rate) and safety profiles across molecularly defined cohorts.