ERBB2 and breast cancer: HER2-targeted regimens are firstly used in HER2-positive breast and gastric cancers, and two HER2-targeting ADCs, trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd, DS-8201), have been approved for the treatment of HER2-positive breast cancer and gastric cancers.