Enhertu, also known as DS-8201 or T-DXd, is HER2-targeted ADC for the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer who have received two or more prior anti-HER2 based regimens in the metastatic setting.206 It is composed of a humanized HER2 antibody (trastuzumab) conjugated to a novel topoisomerase I inhibitor (DXd) as payload through a enzymatically cleavable tetrapeptide-based linker with an average DAR of 7–8. The gene discussed is ERBB2; the disease is breast cancer.