CLDN18.2-Targeted Therapy in Gastrointestinal Cancers

Gastrointestinal cancers, including gastric, gastroesophageal junction, pancreatic, and biliary tract cancers, remain associated with poor outcomes due to late diagnosis and limited effective treatment options. Claudin-18.2 (CLDN18.2), a tight junction protein primarily found in the gastric epithelium and ectopically expressed in gastrointestinal tumors, has emerged as a promising therapeutic target across these diseases. This narrative review expands on existing discussions surrounding CLDN18.2-directed therapy in gastric and gastroesophageal cancer and provides a comprehensive, updated analysis of the rapidly evolving therapeutic landscape across multiple gastrointestinal malignancies, including pancreatic and biliary tract cancers. We summarize key developments following the approval of the monoclonal antibody zolbetuximab and critically evaluate emerging modalities, including bispecific antibodies, antibody–drug conjugates, and chimeric antigen receptor T-cell therapies, highlighting differences in mechanisms of action, efficacy, toxicity profiles, and mitigation strategies. We also discuss the clinical relevance of CLDN18.2 and PD-L1 co-expression, the rationale for pairing CLDN18.2-targeted therapy with immune checkpoint inhibitors, and early data supporting combination approaches. Additionally, we examine tumor heterogeneity, biomarker challenges, and emerging resistance mechanisms, alongside strategies to overcome them. Finally, we identify current limitations in the field, including inconsistent CLDN18.2 testing criteria, and outline prioritized future directions to optimize integration of CLDN18.2-directed therapies across gastrointestinal cancers. By looking beyond zolbetuximab and incorporating cross-platform comparison, immuno-oncology considerations, and multi-tumor context, this review provides a broad and forward-looking framework to guide clinical application and next-generation research in CLDN18.2-targeted therapy.