Trastuzumab Deruxtecan for Subjects With HER2-Positive Gastric Cancer or Gastro-Esophageal Junction Adenocarcinoma After Progression on or After a Trastuzumab-Containing Regimen (DESTINY-Gastric04)

This study will assess the efficacy and safety of T-DXd compared with Ram + PTX in participants with HER2-positive (defined as immunohistochemistry \[IHC\] 3+ or IHC 2+/in situ hybridization \[ISH\]+) gastric or GEJ adenocarcinoma (based on \[American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines who have progressed on or after a trastuzumab-containing regimen and have not received any additional systemic therapy. Participants will be randomized 1:1 to either T-DXd or Ram + PTX treatment. The primary objective will assess overall survival. Secondary objectives will further assess progression-free survival, objective response rate, duration of response, disease control rate, safety, pharmacokinetics, and immunogenicity of T-DXd.