In clinical trials, the antibody-drug conjugates trastuzumab deruxtecan, trastuzumab plus pertuzumab, and zanidatamab (an antibody targeting two distinct ERBB2 (HER2) epitopes) have shown beneficial effects on ERBB2-positive (with a mutation and/or amplification) gastroesophageal junction cancer, breast cancer, lung cancer, biliary tract cancer, and RAS/BRAF wild type metastatic colorectal cancer [27–31]. The gene discussed is ERBB2; the disease is biliary tract neoplasm.