Prostate cancer drug interaction study aims to improve safety

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) performance status score of 0, 1, or 2 * Adenocarcinoma of the prostate * Participants with non-metastatic castration-resistant prostate cancer (NM-CRPC) or metastatic castration-resistant prostate cancer (mCRPC), who in the opinion of the investigator may benefit from treatment with JNJ-56021927 * Surgically or medically castrated, with testosterone levels of \<50 nanogram per deciliter (ng/dL) * If the participant is being treated with a gonadotropin-releasing hormone (GnRHa) (ie, participant who has not undergone bilateral orchiectomy), then this therapy must have been initiated at least 4 weeks prior to the Cycle 1 Day 1 visit and must be continued throughout the study * Adequate bone marrow and organ function defined as: Hemoglobin (\>=9.0 g/dL, independent of transfusion or growth factor support within the prior 7 days); Absolute neutrophil count (\>=1000/mm\^3 independent of growth factor support within the prior 7 days); Platelet count (\>=75,000/mm\^3 independent of transfusion or growth factor support within the prior 7 days); Serum albumin (\>=3.0 g/dL); Serum creatinine (\<=1.5\*upper limit of normal (ULN) or calculated creatinine clearance \>=50 mL/min/1.73m\^2); Total bilirubin \[\<1.5\*ULN (participants with Gilbert's Syndrome may be enrolled if the total bilirubin is \<4 mg/dL with predominance of indirect bilirubin \>=80% of total bilirubin\]); Aspartate aminotransferase or alanine aminotransferase (\<=3.0\*ULN); Prothrombin time (PT) or partial thromboplastin time (PTT) or international normalized ratio (INR) (PT \<=15 sec or INR \<=1.2 PTT \<=40 sec). Exclusion Criteria: * Known brain metastases * Chemotherapy or immunotherapy for the treatment of prostate cancer within 4 weeks of the Study Day 15 (Cycle 1 Day 1) visit * Prior treatment with enzalutamide within 8 weeks before first dose of drug probes * Therapies that must be discontinued or substituted prior to study visit Day 1, or must be temporarily interrupted during the course of the study, include the following: a) Medications known to lower the seizure threshold within 4 weeks before Study Day 15 (Cycle 1 Day 1) and b) Medications known to induce or inhibit drug metabolizing enzymes (CYP3A4, CYP2C9, CYP2C19 and CYP2C8) or transporter proteins (P-gp, BRCP, OATP1B1, and OATPB3) * Participant has known allergies, hypersensitivity, or intolerance to any of the study drugs/drug probes or excipients * History of seizure or any condition that may predispose to seizure within 12 months prior to enrollment (Study Day 1); brain arteriovenous malformation; or intercranial masses such as schwannoma or meningioma that is causing edema or mass effect * Participants with poor metabolizer genotype for CYP2C9 (\*2, \*3), or CYP2C19 (\*2, \*3, \*4, \*8)