In May 2020, DS-8201, a HER2-directed antibody and topoisomerase inhibitor conjugate, received Breakthrough Therapy Designation (BTD) from the U.S. FDA for the treatment of patients with HER2 positive unresectable or metastatic gastric or GEJ adenocarcinoma who have received two or more prior regimens including trastuzumab based on the results of DESTINY-Gastric01 clinical trial [17]. This evidence concerns the gene ERBB2 and gastroesophageal junction adenocarcinoma.