Raloxifene: a selective estrogen-receptor modulator for postmenopausal osteoporosis - a clinical update on efficacy and safety

Selective estrogen-receptor modulators are molecules with specific estrogen-receptor binding affinity. Each selective estrogen-receptor modulator induces a unique conformation in the ligand-receptor complex, which leads to transcriptional activation and/or inhibition. Raloxifene 60 mg/day, a benzothiophene selective estrogen-receptor modulator, is approved for the prevention and treatment of postmenopausal osteoporosis. This article provides an update on new studies and further analyses of clinical trial data for raloxifene. The Multiple Outcomes of Raloxifene Evaluation (MORE) trial of women with osteoporosis has described the efficacy of raloxifene in decreasing vertebral fracture risk over 4 years. The Continuing Outcomes Relevant to Evista((R)) (CORE) trial, designed to assess the effects of raloxifene on breast cancer prevention, is a 4-year continuation of MORE. The skeletal and cardiovascular effects of raloxifene in the CORE study were similar to those observed in MORE. The relative risk of developing breast cancer was significantly decreased in women treated with raloxifene, compared with placebo, after 4 years in MORE and 8 years in the CORE trial. The incidence of uterine bleeding, endometrial hyperplasia and endometrial cancer was similar between raloxifene and placebo after 8 years of treatment. Raloxifene use is associated with a higher incidence of hot flashes and leg cramps, and an increased risk of venous thromboembolic events.

Selective estrogen receptor modulators: an update on recent clinical findings

Recent clinical data on selective estrogen receptor modulators (SERMs) have provided the basis for reassessment of the SERM concept. The molecular basis of SERM activity involves binding of the ligand SERM to the estrogen receptor (ER), causing conformational changes which facilitate interactions with coactivator or corepressor proteins, and subsequently initiate or suppress transcription of target genes. SERM activity is intrinsic to each ER ligand, which accomplishes its unique profile by specific interactions in the target cell, leading to tissue selective actions. We discuss the estrogenic and anti-estrogenic effects of early SERMs, such as clomiphene citrate, used for treatment of ovulation induction, and the triphenylethylene, tamoxifen, which has ER antagonist activity in the breast, and is used for prevention and treatment of ER-positive breast cancer. Since the development of tamoxifen, other triphenylethylene SERMs have been studied for breast cancer prevention, including droloxifene, idoxifene, toremifene, and ospemifene. Other SERMs have entered clinical development more recently, including benzothiophenes (raloxifene and arzoxifene), benzopyrans (ormeloxifene, levormeloxifene, and EM-800), lasofoxifene, pipendoxifene, bazedoxifene, HMR-3339, and fulvestrant, an anti-estrogen which is approved for breast cancer treatment. SERMs have effects on tissues containing ER, such as the breast, bone, uterine and genitourinary tissues, and brain, and on markers of cardiovascular risk. Current evidence indicates that each SERM has a unique array of clinical activities. Differences in the patterns of action of SERMs suggest that each clinical end point must be evaluated individually, and conclusions about any particular SERM can only be established through appropriate clinical trials.