Arzoxifene, a new selective estrogen receptor modulator for chemoprevention of experimental breast cancer.

Arzoxifene ([6-hydroxy-3-[4-[2-(1-piperidinyl)-ethoxy]phenoxy]-2-(4-methoxyphenyl)]benzo[b]thiophene) is a selective estrogen receptor modulator (SERM) that is a potent estrogen antagonist in mammary and uterine tissue while acting as an estrogen agonist to maintain bone density and lower serum cholesterol. Arzoxifene is a highly effective agent for prevention of mammary cancer induced in the rat by the carcinogen nitrosomethylurea and is significantly more potent than raloxifene in this regard. Arzoxifene is devoid of the uterotrophic effects of tamoxifen, suggesting that, in contrast to tamoxifen, it is unlikely that the clinical use of arzoxifene will increase the risk of developing endometrial carcinoma.