The purpose of this study is to determine whether TSE-424 (bazedoxifene acetate), an investigational drug, is safe and effective in the prevention of osteoporosis in postmenopausal women.

Primary objective: To evaluate the safety and efficacy of 3 doses of TSE-424 (bazedoxifene acetate), an investigational drug, in comparison with those of placebo and raloxifene in preventing osteoporosis in postmenopausal women.

Secondary objective: To evaluate the effect of TSE-424 (bazedoxifene acetate), an investigational drug, in comparison with that of placebo and raloxifene on endometrium, metabolic parameters, vasomotor symptoms, adverse events, and quality of life. Samples will be collected for population pharmacokinetic (PK) analysis.

Inclusion Criteria:

• Generally healthy women 45 years of age or older who are at least 1 year postmenopausal.
• Subjects must qualify for one of the following categories (a or b): a) Greater than 1 year but less than 5 years postmenopausal with at least one of the osteoporosis risk factors. b) Greater than 5 years postmenopausal with BMD T-score at lumbar spine or femoral neck between -1 and -2.5 (inclusive) with at least one osteoporosis risk factor.

Exclusion Criteria:

• One (1) or more osteoporotic vertebral fractures (T4-L4).
• Diseases that may affect bone metabolism.
• Past history or active nontraumatic venous thromboembolic events, including deep vein thrombosis, pulmonary embolism, and retinal vein thrombosis.