Fam-trastuzumab deruxtecan-nxki is a HER2 antibody drug conjugate combined with irinotecan-type chemotherapy drug, which belongs to the ADC-type drug. It is used to treat adult patients with unresectable or metastatic HER2-positive breast cancer who have previously received two or more anti-HER2-based regimens. This evidence concerns the gene ERBB2 and breast cancer.