Furthermore, tucatinib plus trastuzumab showed a clinically meaningful antitumor effect in patients with HER2-overexpressing metastatic colorectal cancer who were previously untreated with anti-HER2 therapy (ORR: 38.1% ([complete response 4% and partial response 35%]), with manageable toxicities in a phase 2 trial [53]. The gene discussed is ERBB2; the disease is metastatic colorectal cancer.