Sildenafil (ViagraTM), a Potent and Selective Inhibitor of Type 5 CGMP Phosphodiesterase with Utility for the Treatment of Male Erectile Dysfunction.

Abstract 5-(2′-Alkoxyphenyl)pyrazolo[4,3-d]pyrimidin-7-ones, and in particular our preferred compound, sildenafil (VIAGRATM), discovered through a rational drug design programme, are potent and selective inhibitors of the type 5 cGMP phosphodiesterase from both rabbit platelets and human corpus cavernosum. Sildenafil is currently in the clinic for the oral treatment of male erectile dysfunction.