NECTIN4‐targeted antibody–drug conjugate is a potential therapeutic option for extramammary Paget disease

Extramammary Paget disease (EMPD) is a rare skin cancer mainly found in areas rich in apocrine sweat glands. Since the effective treatments for advanced and/or metastasized EMPD are limited, there is an urgent need to develop novel therapeutic approaches. Nectin cell adhesion molecule 4 (NECTIN4) is highly expressed in cancers and considered to be a promising therapeutic target. NECTIN4 is also expressed in EMPD, but its role and the efficacy of NECTIN4‐targeted therapy in EMPD remain unclear. This study investigated the potential of NECTIN4 as a novel therapeutic target for EMPD. NECTIN4 expression was immunohistochemically analysed in EMPD patients' primary (118 samples) and metastatic (21 samples) lesions. Using an EMPD cell line, KS‐EMPD‐1, the effects of NECTIN4 inhibition on cell proliferation and migration were investigated. NECTIN4 was expressed in primary and metastatic EMPD lesions, and the H‐score of NECTIN4 staining was significantly higher in metastatic lesions than in primary ones. Knockdown of NECTIN4 significantly inhibited cell proliferation and affected cell migration. The cytotoxic effects of NECTIN4‐targeted antibody–drug conjugate (ADC) were further evaluated, revealing a significant decrease in EMPD cell viability. In conclusion, NECTIN4 is a potential therapeutic target and NECTIN4‐targeted ADC is promising as a therapeutic option for EMPD.