ERBB2 and breast cancer: HER2-targeted drugs for BC are categorized based on their mechanisms of action into three main types: monoclonal antibodies (Trastuzumab, Pertuzumab), anti-body-drug conjugates/ADCs (Trastuzumab Emtansine, Trastuzumab Deruxtecan), and small-molecule tyrosine kinase inhibitors/TKIs (Neritinib, Tucatinib, and Lapatinib).