Phase 2 Study of Trastuzumab Deruxtecan in the Neoadjuvant Treatment, or Trastuzumab Deruxtecan Plus Capecitabine Plus Durvalumab(MEDI4736) in the Preoperative and Postoperative Adjuvant Treatment for Patients With HER2 Positive Gastric and Gastroesophageal Junction Adenocarcinoma

Inclusion criteria

• ✓. Histologically confirmed adenocarcinoma of the gastric or gastroesophageal junction.
• ✓. Has HER2 overexpression (IHC3+, or IHC2+ and ISH positive \[FISH or DISH\]). (HER2 Low expression: IHC1+, or IHC2+ and ISH-negative \[FISH or DISH\] with HER2-ECD \> 11.6 ng/mL in the exploratory cohort).
• ✓. Have previously untreated gastric and gastroesophageal junction adenocarcinoma and cT2-4 and/or cN+M0.according to the UICC TNM classification (8th edition),
• ✓. Age ≥ 20 years as the day of informed consent.
• ✓. Has an ECOG performance status (PS) of 0 or 1.
• ✓. Has a left ventricular ejection fraction (LVEF) ≥ 50% by either echocardiogram (ECHO) or multigated collecting acquisition (MUGA) scan within 28 days before enrollment (acceptable on the same day of the week).
• ✓. Has a corrected QT interval (QTc) ≦ 470 ms in females, or QTc ≦ 450 ms in males based on a 12-lead ECG screening within 28 days before enrollment (allowed on the same day of the week). \[Fridericia's correction is recommended\]
• ✓. Satisfies all of the following requirements within 14 days before enrollment (allowed on the same day of the week).

Exclusion criteria