A Safety Study of JNJ-56021927 in Participants With Metastatic Castration-Resistant Prostate Cancer

The purpose of this study is to evaluate the safety and tolerability of JNJ-56021927 in Japanese participants with metastatic castration-resistant prostate cancer (mCRPC- prostate cancer that is resistant to medical \[for example. hormonal\] or surgical treatments).

This is a Phase 1, multicenter, open-label (participants will know the identity of study drug received) study in participants with Metastatic Castration-Resistant Prostate Cancer (mCRPC). The study consists of 4 parts: Screening (28 days before study commences on Day 1), pharmacokinetic week (PK), Continuous daily dosing, Extension and Safety follow-up period. In PK week participants will receive a single oral capsule of JNJ-56021927 at a dose of 240 milligram (mg) on Day 1 and will be monitored for 1 week. After Week 1, in continuous daily dosing period, participants will receive continuous daily therapy at the same dose for 4 weeks (Cycle 1). After Cycle 1 participants, who will not meet the criteria for discontinuation listed such as progressive disease (PD) or unacceptable toxicity, will continue in safety follow-up period and will receive continuous daily therapy at the same dose up to cycle 13. Primarily dose limiting toxicity (DLT) will be evaluated. Participants' safety will be monitored throughout.

Eligibility Criteria:
Inclusion Criteria:

* Histologically or cytologically confirmed adenocarcinoma of the prostate without neuroendocrine differentiation or small cell features, with metastatic disease
* Castration-resistant prostate cancer (CRPC) demonstrated during continuous androgen deprivation therapy (ADT)/post orchiectomy
* Maintain castrate levels of testosterone (less than \[\<\] 50 nanogram per deciliter (ng/dL) \[1.72 nanomol per liter {nmol/L}\]) within 4 weeks before enrollment
* Prostate-specific antigen (PSA) evidence for progressive prostate cancer consists of a PSA level of at least greater than or equal to (\>=) 2 nanogram per milliliter (ng/mL) within 2 weeks before enrollment which has risen on at least 2 successive occasions, at least 1 week apart. If the confirmatory PSA value is less than the last PSA value, then an additional test for rising PSA will be required to document progression
* Participants who received a first generation anti-androgen \[for example, bicalutamide, flutamide, nilutamide (not approved in Japan)\] as part of an initial combined androgen blockade therapy or as second-line hormonal therapy must show continuing disease progression off the anti-androgen for at least 4 weeks prior to the first dose of study drug

Exclusion Criteria:

* History of, or current metastases in the brain or untreated spinal cord compression
* Participants with progressive epidural disease
* Participants has a history of another malignancy within 5 years before screening
* Prior treatment with second generation anti-androgens ( for example, enzalutamide) or Cytochrome P450 17 (CYP 17) inhibitors \[for example, abiraterone acetate, orteronel, galeterone, systemic ketoconazole (not approved in Japan, respectively)\]
* Participants had used radiopharmaceutical agents (for example, Strontium-89) or investigational immunotherapy (for example, sipuleucel-T) within 12 weeks before the first dose of study drug