Tucatinib with trastuzumab has also demonstrated activity across tumor types with an ORR of 39% and DCR of 71% in selected patients with HER2-expressing refractory colon cancer; ORR of 47% and DCR of 77% in patients with previously treated HER2-expressing biliary tract cancers [9, 35]. The gene discussed is ERBB2; the disease is biliary tract cancer.