Abstract
Gastric and gastroesophageal junction (G/GEJ) adenocarcinomas remain among the most aggressive and lethal malignancies globally. Most patients are diagnosed at advanced stages and respond poorly to conventional chemotherapy, highlighting the urgent demand for more effective, novel treatment strategies such as monoclonal antibody therapies targeting drivers of tumor progression. This review examines the mechanisms, safety profiles, and clinical trial outcomes of three targeted agents-bemarituzumab, zolbetuximab, and ramucirumab-which inhibit tumor growth through the FGFR2b, CLDN18.2, and VEGFR2 pathways, respectively. We also compare traditional versus adaptive clinical trial designs, explore emerging challenges such as therapeutic resistance and treatment-related toxicities, and consider implications for personalized medicine. Collectively, these agents represent a paradigm shift from empiric chemotherapy toward biomarker-driven immunotherapy, with the potential to significantly improve survival and quality of life in patients with advanced G/GEJ cancers.