ERBB2 and breast cancer: To date, two ADCs directed against HER2—trastuzumab emtansine (T-DM1, Kadcyla) [15] and trastuzumab deruxtecan (T-DXd, DS-8201a, Enhertu) [16]—have been approved by the Food and Drug Administration (FDA) and other regulatory agencies throughout the world for the management of HER2-positive breast cancer.