GS-9191 is a potent inhibitor of DNA polymerase alpha and ß , a prodrug of the novel nucleoside analogue 9-(2-phosphonomethoxyethyl)guanine (PMEG) , which penetrates the skin and is metabolized in the epithelium to an active nucleoside triphosphate analogue.GS-9191 has antiproliferative activity and reduces the size of papillomas in a dose-related manner.GS-9191 may be useful in the treatment of HPV-induced lesions.