Bazedoxifene: a new selective estrogen receptor modulator for the treatment of postmenopausal osteoporosis.

Bazedoxifene acetate (WAY-140424; TSE-424) is an oral, nonsteroidal, indole-based selective estrogen receptor modulator (SERM) being developed for the prevention and treatment of osteoporosis. Preclinical studies on bazedoxifene have demonstrated estrogen agonist effects on the skeleton and lipid metabolism but not on breast and uterine endometrium. In combination with estrogen, bazedoxifene antagonizes the stimulatory action of estrogens on proliferation of breast cancer cells and endometrium. Phase III clinical studies have shown favorable effects on the skeleton without stimulation of endometrium and breast. Bazedoxifene prevents bone loss in postmenopausal women without osteoporosis and reduces vertebral fractures in women with postmenopausal osteoporosis. In women at high risk of fracture with multiple risk factors, bazedoxifene reduces nonvertebral fracture risk in post-hoc analysis. Bazedoxifene in combination with conjugated estrogens represents a new form of therapeutic agents for the treatment of postmenopausal symptoms and prevention of postmenopausal osteoporosis. Clinical trials with bazedoxifene/conjugated estrogens have shown beneficial effects on bone mineral density and bone turnover markers with improvement in vasomotor symptoms and little or no stimulation of breast and endometrium.