Ospemifene (FC1271a) was first reported as a metabolite of toremifene [
T2832] which is an antiestrogen and a hormonal antitumor agent. Ospemifene is the first non-hormonal estrogen receptor agonist/antagonist or selective estrogen receptor modulator (SERM). It specifically binds to the estrogen receptor α and β with affinity closely similar to that of toremifene and tamoxifen [
T2510]. Ospemifene is currently used for treatment of vulvovaginal atrophy (VVA). In addition, the antiestrogenic activity of ospemifene in several breast cancer animal models has been reported. (The product is for research purpose only.)