Effect of the ERα agonist GTx-758 on bone turnover markers in men with advanced prostate cancer.

222 Background: Men with advanced prostate cancer are being treated with androgen deprivation therapy (ADT) for longer periods of time. The use of ADT can be limited by estrogen deficiency side effects, including a loss of bone and a higher incidence of fractures. GTx-758 is an ERα agonist that lowers serum free testosterone greater than an LHRH agonist. Herein we compare the effects of GTx-758 and leuprolide on markers of bone turnover, C-terminal telopeptides and bone specific alkaline phosphatase, in men with advanced prostate cancer treated with ADT. Methods: In a Phase II study (G200705), men with advanced prostate cancer (n=159) received 1000 mg or 2000 mg of GTx-758 daily or leuprolide. Serum samples were collected and analyzed by a reference laboratory. C-terminal telopeptides (pg/ml) and bone specific alkaline phosphatase (U/L) were measured as indicators of bone turnover. All p values describe the comparison of the GTx-758 treatment groups to the leuprolide treated men at day 120. Results: Men r...