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Eflornithine and Testosterone Followed by Enzalutamide for the Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer, APEX Trial

Trial Status: active

This phase II trial tests how well eflornithine and testosterone cypionate followed by enzalutamide works in treating patients with prostate cancer that has spread from where it first started (primary site) to other places in the body (metastatic) and that grows and continues to spread despite treatment to lower testosterone in the blood (castration-resistant). Eflornithine inhibits an enzyme required for tumor cell formation and proliferation and it has been shown to cause death in some types of tumor cells. Testosterone cypionate is a synthetic form of testosterone. It can be used to increase testosterone levels in men who do not make enough testosterone on their own. Enzalutamide blocks testosterone in prostate tumor cells by inhibiting the activity of androgen receptors on the cells. This may lead to a reduction in prostate tumor cell proliferation and a reduction in the serum prostate specific antigen level. Research has shown that castration-resistant prostate cancer cells can be killed by high levels of testosterone followed by a rapid drop to low testosterone levels. This is called bipolar androgen therapy. After bipolar androgen therapy, many patients show improved response to treatment with enzalutamide. Giving eflornithine and testosterone cypionate together may be more effective in blocking prostate tumor growth than either drug alone and may make castration-resistant prostate tumor cells more sensitive to treatment with enzalutamide.