ERBB2 and breast cancer: Interestingly, inhibition of ataxia telangiectasia and Rad3-related kinase (ATR), a member of the phosphatidylinositol 3-kinase-related kinase (PIKKs) family and involved in DNA repair in response to DNA damage and replication stress [141,142], is currently being tested in combination with trastuzumab deruxtecan in HER2 advanced or metastatic BC pretreated with chemotherapy and anti-HER2 therapy in a phase I/Ib trial (DASH, NCT04704661).