Trastuzumab Deruxtecan (T-DXd) is an Antibody-drug conjugate (ADC) in which the anti-HER2 antibody trastuzumab is linked to the topoisomerase I inhibitor deruxtecan via a linker, and it shows high efficacy against HER2-positive breast cancer [29, 30]. The gene discussed is ERBB2; the disease is breast carcinoma.