Tucatinib has been shown to be efficacious in HER2-positive breast and colorectal cancers [65,66], and the phase II/III MONTAINEER-02 trial will assess tucatinib, trastuzumab, ramucirumab and paclitaxel as second-line treatment in HER2-positive gastric cancers (NCT0449924) [67]. Here, ERBB2 is linked to gastric cancer.