Maintaining Suppression of Testosterone With Transdermal Estradiol Gel

This is a multi-center, randomized, double-blind, placebo-controlled, dose finding study in men with advanced androgen-sensitive prostate cancer. Patients who give informed consent will have screening evaluations, and if fulfilling the entry criteria, will be randomized to one of 4 treatment groups: 1mL, 2mL or 3mL of 0.36% BHR-200 (transdermal estradiol gel) or Placebo. Study drug will be initiated on the day they were scheduled to receive next depot GnRH agonist injection. Patients will be offered low-dose radiation to aid in the prevention of gynecomastia. Patients will apply the study drug once per day. The first dose of study gel will be applied under the supervision of the PI/designee. Subsequent doses will be self-administered daily by the patient until he is no longer chemically castrated (testosterone levels increase above 50 ng/dL), a rise over baseline PSA of \> 0.5 ng/mL is observed, or he has completed 52 weeks of study drug administration. At the conclusion of study participation, patients will be advised to resume standard of care treatment under the supervision of their healthcare provider. While on treatment, patients will be evaluated at Day 1 and every 2 weeks, for the first 24 weeks and every 4 weeks thereafter with a final post-treatment follow-up visit 2 weeks (+/- 1 week) post last dose administration.