Study to Compare Capsule and Liquid Formulations of Enzalutamide After Single Dose Administration Under Fasting Conditions in Prostate Cancer

* INCLUSION CRITERIA:
* Patients must have histologically or cytologically confirmed prostate cancer.

Note: If histopathological documentation is unavailable, a clinical course consistent with prostate cancer is acceptable.

* Eastern Cooperative Oncology Group (ECOG) performance status 0 to 2
* Patients must have adequate organ and marrow function as defined below:

  * Hemoglobin greater than or equal to 9 g/dL
  * leukocytes greater than or equal to 3000/mcL
  * absolute neutrophil count greater than or equal to 1500/mcL
  * platelets greater than or equal to 150000/mcL
  * total bilirubin within normal institutional limits
  * Aspartate aminotransferase (AST) serum glutamic oxaloacetic transaminase (SGOT)/ alanine aminotransferase (ALT) serum glutamic pyruvic transaminase (SGPT) less than or equal to X institutional upper limit of normal
  * creatinine within normal institutional limits

OR

--creatinine clearance greater than or equal to 30 mL/min/1.73 m\^2 for patients with creatinine levels above institutional normal (calculated via Cockcroft-Gault equation)

* Patients must not have other concurrent malignancies (within the past 2 years with the exception of non-melanoma skin cancer and Rai Stage 0 chronic lymphocytic leukemia), in situ carcinoma of any site, or life threatening illnesses, including untreated infection (must be at least 1 week off intravenous antibiotic therapy before beginning enzalutamide).
* Ability of subject to understand and the willingness to sign a written informed consent document.
* Willingness to travel to National Institutes of Health (NIH) for follow-up visits.
* Men age greater than or equal to 18 years of age. Children are excluded because prostate cancer is not common in pediatric populations. Women are not eligible because this disease occurs only in men
* The effects of enzalutamide on the developing human fetus are unknown. For this reason men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) throughout the course of the study and for 3 months after the last dose. Should a woman become pregnant or suspect she is pregnant while her partner is participating in this study, she should inform her treating physician immediately.

EXCLUSION CRITERIA:

* Patients who are receiving any other investigational agents (in the past 28 days) or herbal medications (within 7 days).
* Patients must not be on enzalutamide within five half-lives before the first planned dose of the study drug or anticipating to start enzalutamide within the next 3 months of the first planned dose of study drug
* History of allergic reactions attributed to compounds of similar chemical or biologic composition to enzalutamide or other agents used in study.
* Clinically significant cardiac disease, e.g. New York Heart Association (NYHA) classes III-IV; uncontrolled angina, uncontrolled arrhythmia or uncontrolled hypertension, myocardial infarction in the previous 6 months as confirmed by an electrocardiogram (ECG).
* Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements
* Patients who are taking medications that may alter the metabolism of enzalutamide. This includes the following: strong or moderate cytochrome P450 family 2 subfamily C member 8 (CYP2C8) inhibitors or inducers; strong cytochrome P450 family 3 subfamily A member 4 (CYP3A4) inhibitors or inducers; or Cytochrome P450 2C9 (CYP2C9), 2C19 or 3A4 substrates with a narrow therapeutic index.
* History of seizure, including any febrile seizure, loss of consciousness, or transient ischemic attach, or any condition that may pre-dispose to seizure (e.g. prior stroke, brain arteriovenous malformation, head trauma with loss of consciousness requiring hospitalization).