UK-447,841

UK-447,841 is an investigational oral small molecule phosphodiesterase type 5 (PDE5) inhibitor developed by Pfizer for the treatment of female sexual arousal disorder (FSAD). The compound was designed to enhance genital blood flow by inhibiting the degradation of cyclic guanosine monophosphate (cGMP) in vaginal and clitoral tissues, thereby addressing the physiological components of arousal. It reached Phase 2 clinical development, where it was evaluated in post-menopausal women using vaginal photoplethysmography to measure changes in vaginal blood flow. Pfizer ultimately discontinued the development of UK-447,841 and its broader FSAD research program in the mid-2000s after clinical results failed to demonstrate sufficient efficacy to support regulatory approval.