ERBB2 and breast cancer: Trastuzumab-deruxtecan (T-DXd), another HER2-directed ADC containing a topoisomerase I inhibitor, demonstrated an impressive PFS benefit in HER2-positive pretreated breast cancer patients also in earlier lines, as emerged by the data of DESTINY-Breast 03 trial presented at ESMO 2021 congress (Cortes et al., 2021).