ERBB2 and breast cancer: Trastuzumab deruxtecan was approved by FDA in 2019 and by EMA in 2021 for treatment of patients with HER2-positive unresectable or metastatic BC, who have received two or more prior anti-HER2-based regimens in the metastatic settings; following positive results of the DESTINY-Breast03 study FDA and EMA have extended the recommendation also to second-line setting.