Identification of Keratinocyte Cytoprotectants against Toxicity by the Multikinase Inhibitor Sorafenib Using Drug Repositioning

Hand–foot skin reaction is the most common adverse event of multikinase inhibitors, such as sorafenib. Although hand–foot skin reaction is not life threatening, severe cases impair quality of life because of pain and reduced activities of daily living. However, the pathological mechanisms of hand–foot skin reaction have not yet been elucidated in detail, and there is currently no effective treatment. We aimed to identify keratinocyte cytoprotectants against sorafenib toxicity. The screening of cytoprotectants against sorafenib toxicity was performed using cultured normal human epidermal keratinocytes or a reconstructed human epidermis model and off-patent approved drugs in the Prestwick Chemical library. Among 1273 drugs in the chemical library, 8 dose-dependently increased cell viability by >200% in the presence of sorafenib. In the presence of sorafenib, the number of proliferating cell nuclear antigen–positive cells was significantly higher in clofazimine-, cyclosporin A–, and itraconazole-treated reconstructed human epidermis models than in sorafenib-treated models, and candidate drugs suppressed sorafenib-induced apoptosis in normal human epidermal keratinocytes. In addition, clofazimine, itraconazole, and pyrvinium pamoate significantly recovered the phosphorylation of extracellular signal–regulated kinase 1/2 in the presence of sorafenib. Collectively, hit drugs promoted cell viability and normalized keratinocyte proliferation in the presence of sorafenib. These candidate drugs have potential as treatments for multikinase inhibitor–induced hand–foot skin reaction.