Selective estrogen receptor modulators: a new category of therapeutic agents for extending the health of postmenopausal women.

Selective estrogen receptor modulators are a new category of therapeutic agents that bind with high affinity to estrogen receptors and mimic the effect of estrogens in some tissues but act as estrogen antagonists in others. Tamoxifen, a triphenylethylene derivative, was the first clinically available selective estrogen receptor modulator. It is a potent antiestrogen in the breast, and its use in breast cancer patients has made it the most prescribed antineoplastic drug worldwide. It has estrogen-like activity on bone metabolism, and it also reduces cholesterol. However, its ability to produce proliferation, polyp formation, and even carcinomas in the endometrium is well known. A new selective estrogen receptor modulator, raloxifene, a benzothiopene derivative, has a clinical profile similar to that of tamoxifen. However, both preclinical and clinical studies reveal that, unlike tamoxifen, it is a pure antiestrogen in the uterus. It has recently been approved by the Food and Drug Administration for prevention of osteoporosis in postmenopausal women. This report reviews pertinent preclinical and currently available clinical studies about this new selective estrogen receptor modulator and discusses clinical applicability.