Safety and Efficacy of TAK-385 for Patients With Localized Prostate Cancer

The drug being tested in this study is called TAK-385. Men with prostate cancer benefit from receiving androgen deprivation therapy (ADT) to minimize testosterone levels before, during and after EBRT. This combination increases the potential success of treating their disease. This study will see if TAK-385 \[an oral gonadotropin-releasing hormone (GnRH) antagonist\] brings testosterone levels down sufficiently, with the convenience and comfort of taking a pill. It will look at the time it takes to restore testosterone levels after radiation therapy as well. One hundred participants will be assigned by chance (like flipping a coin) to a treatment group: 60 to TAK-385, and 40 to degarelix. Those assigned to TAK-385 will take a daily pill. Those assigned to degarelix will receive an injection under the skin once every four weeks at the clinic. They will start radiation therapy when testosterone is low enough, after at least 12 weeks of treatment. This trial will be conducted at clinics in the United States (US) and United Kingdom (UK). Participants will visit the clinic up to 14 times over 37 weeks for physical exams and blood tests, and might receive one follow-up telephone call.