As a second-line treatment of HER2-positive G/GEJ adenocarcinoma, trials of tucatinib in combination with several agents are currently recruiting patients (NCT04499924, NCT05190445), and the results of a phase I trial of tucatinib alone have just been published (NCT05382364) [94]. Here, ERBB2 is linked to gastroesophageal junction adenocarcinoma.