Emtrastuzumab is an antibody-drug coupling targeting HER-2, and the antibody part is humanized anti-HER-2, IgG1 trastuzumab, which is similar to trastuzumab. Emtrastuzumab inhibits HER-2 receptor signaling, exerts antibody-dependent cell-mediated cytotoxic effects, and inhibits the overexpression of HER-2 in human breast cancer cells, as well as the shedding of HER-2 extracellular structural domains. Emtrastuzumab monotherapy is indicated for the adjuvant treatment of patients with HER-2-positive early-stage breast cancer who have received paclitaxel-based neoadjuvant therapy in combination with trastuzumab and still have residual invasive lesions. Patients may be at risk of hepatotoxicity, liver failure, and death after dosing. Liver function should be monitored before starting the drug, and at each dose, and the dose should be adjusted as needed, or the treatment should be permanently discontinued. It may also cause a decrease in left ventricular ejection fraction; therefore, left ventricular ejection fraction should be assessed prior to initiation of therapy, monitored as needed, and dosing should be suspended or discontinued.