ERBB2 and breast cancer: Most recently, trastuzumab deruxtecan (DS-8201), a novel HER2-targeting antibody-drug conjugate with a novel DNA topoisomerase I inhibitor, demonstrated a significant improvement in overall survival (OS) and progression-free survival (PFS) in HER2+ metastatic BC previously treated with Herceptin, confirming as the standard of care in the second-line setting 3, 4.