ERBB2 and breast cancer: HER2 is the most prominent target for ADC development globally, and Ado-trastuzumab emtansine (Kadcyla), Trastuzumab deruxtecan (Enhertu), and Trastuzumab emtansine (T-DM1), which are designed to target HER2-positive cancer cells, have been approved for use in treating HER2-positive breast cancer and other types of cancer.