Ruxolitinib and Enzalutamide for the Treatment of Metastatic Castration-Resistant Prostate Cancer

Inclusion Criteria: * Written informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization for release of personal health information prior to registration * Males age ≥ 18 years with progressive metastatic, castration-resistant prostate cancer, previous adenocarcinoma histology confirmation required * Ability to understand a written informed consent document, as determined by the study physician or designee * Surgical castration or continuous medical castration ≥ 8 weeks prior to screening; serum testosterone \< 50 ng/dL * Have progressed on prior abiraterone treatment by Prostate Cancer Working Group 3 prostate specific antigen (PSA) criteria * PSA must rise on two measurements at least 1 week apart in order to be eligible. Refer to PCWG3 for clarification. * Most Recent absolute PSA must be \> 2.0 ng/mL * Patient meets definition of poor responder to abiraterone by one of the following: * Abiraterone started in hormone-sensitive prostate cancer (HSPC) disease setting (abiraterone started within 4 months of starting continuous androgen deprivation therapy \[ADT\]): \< 12 months duration on abiraterone * Abiraterone started in castration-resistant prostate cancer (CRPC) disease setting: \< 6 months duration on abiraterone due to progression or failure to achieve PSA50 response while on therapy * The patient's current or most recent treatment is ADT and abiraterone. Participants must sign consent within 30 days of discontinuing abi…