ERBB2 and breast cancer: From trastuzumab to trastuzumab–emtansine, moving to trastuzumab–deruxtecan and combinations with immunotherapy, endocrine therapies, cyclin-dependent kinase inhibitors, among others, preclinical, clinical, and safety data supporting further testing of anti-HER2 drugs for the treatment of HER2-low BC patients are reviewed and put into perspective below.