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Bazedoxifene Prevents Fractures
Abstract & Commentary
By Leon Speroff, MD, Editor, Professor of Obstetrics and Gynecology, Oregon Health and Science University, Portland, is Editor for OB/GYN Clinical Alert.
Synopsis: Bazedoxifene treatment reduces fractures in postmenopausal women with osteoporosis.
Source: Silverman SL, et al. Efficacy of bazedoxifene in reducing new vertebral fracture risk in postmenopausal women with osteoporosis: Results from a 3-year, randomized, placebo-, and active-controlled clinical trial. J Bone Miner Res 2008;23:1923-1934.
A 3-year randomized, double-blind clinical trial in 206 sites throughout the world compared bazedoxifene (20 mg or 40 mg) and raloxifene (60 mg) with placebo. A total of 7492 postmenopausal women, age 55-85, with established osteoporosis were enrolled in the study, and about 1200 completed treatment in each group. The results are provided in the Table (above, below).
The approximately 40% reduction in new vertebral fractures compared with placebo was statistically significant. In a subgroup of women at higher risk for fractures, bazedoxifene had a reduced risk of nonvertebral fractures (50% reduction with 20 mg), compared with both raloxifene and placebo. The only adverse event that differed with treatment was an increase in venous thrombosis with treatment compared with placebo (13, 12, and 10 cases with 20 mg bazedoxifene, 40 mg bazedoxifene, and raloxifene, respectively; 5 cases with placebo).
Bazedoxifene belongs to the selective estrogen receptor modulator (SERM) family of drugs. It has favorable effects on bone and lipids, but does not affect the endometrium or the breast. The results of this trial indicate that the effect of bazedoxifene on bone should be comparable to that of estrogen and bisphosphonates.
The reduction of nonvertebral fractures with bazedoxifene compared with raloxifene should not be ignored. We have known for some time that even with 8 years of follow-up, raloxifene has no impact on the risk of hip fractures. This is presumably because raloxifene is less potent, and thus the hip, with a mixture of cortical and trabecular bone, is more resistant to raloxifene's effects compared with the spinal column that is composed of sensitive, trabecular bone. In this clinical trial, this difference was also observed in the bone mineral density responses at the hip; bazedoxifene was significantly better.
There were fewer cases of breast cancer and benign breast disease in the bazedoxifene groups, but the numbers were too small to give any confidence to this conclusion.
Wyeth has partnered bazedoxifene with estrogen, and called it TSEC (tissue-selective estrogen complex). The idea is to gain the benefits of estrogen (bazedoxifene has little impact on hot flushes), protect the endometrium and possibly the breast, and enhance some actions of estrogen, such as a reduction in fractures. This approach to postmenopausal hormone therapy would eliminate the need for progestational agents. Phase III trials are complete with this combination, and FDA approval is pending.