Bispecific Antibodies and Antibody–Drug Conjugates in Advanced Gastric Adenocarcinoma

Advanced gastric (GAC) or gastroesophageal junction (GEJAC) adenocarcinoma continues to carry a poor prognosis. Understanding GAC/GEJAC at the molecular level has provided a new understanding and the basis for individualized approaches to treatment. The current biomarker-driven therapy focuses on four areas: microsatellite instability (MSI), human epidermal growth factor receptor-2 (HER2), programmed death ligand-1 (PD-L1) combined positive score, and claudin 18.2 (CLDN18.2). However, because of improving technology, the focus has shifted to cancer cell-surface proteins and peptides. Each of these GAC/GEJAC subgroups provides a different treatment pathway. The agents utilized to treat advanced GAC/GEJAC include immune checkpoint inhibitors (ICIs), chemotherapy, monoclonal antibodies (mAbs), and antibody–drug conjugate (ADC) therapy, as well as bispecific antibodies (BsAbs), but they are certainly not limited to the above. Drug development has shifted in recent years to establish different mechanisms that are attempting more sophisticated and targeted approaches, such as BsAbs and ADCs. Meanwhile, the development of cytotoxics has tapered off. Along with these developments in drug therapy, more therapies directed at CLDN18.2, HER2, MSI, EGFR, HER3 and trophoblast cell-surface antigen 2 (TROP2) are underway. Here we review future areas in advanced GAC, including zanidatamab’s potential role in HER2-positive advanced GAC and deciphering the abundance of anti-CLDN18.2, extending beyond investigative therapies.