Adverse events induced by the subcutaneous HER2-targeted antibody-drug conjugate JSKN033 in a male patient with breast cancer: A case report.

JSKN033 is a fixed-dose combination of JSKN003 [a biparatopic HER2-directed antibody-drug conjugate (ADC)] and envafolimab (a programmed death-ligand 1 inhibitor). JSKN033 is formulated for subcutaneous administration and is currently in the investigational stage, with limited safety profile data. The present report highlights the case of a male patient with breast cancer with HER2 2+ expression who experienced disease progression after multiline therapy, including modified radical mastectomy, adjuvant chemotherapy, adjuvant radiotherapy and trastuzumab emtansine. Following enrollment in the JSKN033 clinical trial, the patient developed systemic and localized adverse reactions after treatment, including fatigue, diarrhea and injection-site reactions, such as pruritus, pain, skin indentation and induration. The present case report discusses potential etiologies of these adverse events and issues to consider during subcutaneous administration of HER2-directed ADCs, and provides supplementary clinical data to potentially advance the understanding of their adverse event profiles, mechanisms, prevention and management strategies.