ERBB2 and breast cancer: Nowadays, the trastuzumab backbone has been used for the synthesis of two FDA- and EMA-approved ADCs, ado-trastuzumab emtansine (T-DM1, Kadcyla®; Genentech) and fam-trastuzumab deruxtecan (T-Dxd, Enhertu®, Daiichi Sankyo, Astrazeneca), which have improved the OS in the second and third-line settings and are currently used for the treatment of HER2+ early/metastatic and HER2+ low BC, respectively (Ferraro et al., 2021; Rassy et al., 2022).