A Study to Evaluate Safety and Efficacy of Toreforant (JNJ-38518168) in Participants With Moderate to Severe Plaque-type Psoriasis

The purpose of this study is to evaluate the efficacy, safety and tolerability of JNJ-38518168 in participants with moderate to severe plaque-type psoriasis (common genetically determined, chronic, inflammatory skin disease characterized by rounded erythematous, dry, scaling patches).

This is a randomized (study medication assigned to participants by chance), double-blind (neither the researchers nor the participants know what treatment the participant is receiving), parallel-group, placebo-controlled (an inactive substance; a pretend treatment \[with no drug in it\] that is compared in a clinical trial with a drug to test if the drug has a real effect) study. The study consists of Screening Phase (maximum of 42 days prior to Week 0), Treatment Phase (Week 0-12) and Follow-up Phase (up to Week 16). Participants will be randomly assigned to receive JNJ-38518168 (3 milligram \[mg\] or 30 mg or 60 mg) or placebo once daily. The initial group of the participants will be randomized to either JNJ-38518168 30 mg or placebo. The dose assignments for the subsequent participants will depend on the results of up to 2 interim analyses. Efficacy will be primarily assessed by percentage of participants who achieve a Psoriasis Area and Severity Index (PASI) 75 response at Week 12. Participants' safety will be monitored throughout the study.

Eligibility Criteria:
Inclusion Criteria:

* Participant must have a diagnosis of plaque-type psoriasis (with or without psoriatic arthritis \[PsA\]) for at least 6 months before the first administration of study drug
* Participant must have a Psoriasis Area and Severity Index (PASI) Greater Than or equal to (\>=) 12 at screening and at baseline
* Participant must have an Investigator's Global Assessment (IGA) \>=3 at screening and at baseline
* A woman of childbearing potential must have a negative urine pregnancy test at screening and at Week 0
* A man who is sexually active with a woman of childbearing potential and has not had a vasectomy must agree to use a barrier method of birth control during the study and for 4 months after receiving the last administration of study drug. All men must also agree to not donate sperm during the study and for 4 months after receiving the last administration of study drug

Exclusion Criteria:

* Participant has a history or current signs or symptoms of severe, progressive, or uncontrolled renal, hepatic, hematologic, gastrointestinal, endocrine, pulmonary, cardiac, neurologic, cerebral, or psychiatric disease
* Participant has a current malignancy or history of malignancy within 5 years before screening (with the exception of a nonmelanoma skin cancer that has been adequately treated with no evidence of recurrence for at least 3 months before the first study drug administration, or cervical carcinoma in situ that has been treated with no evidence of recurrence for at least 1 year before the first study drug administration)
* Participant has a history of lymphoproliferative disease, including lymphoma; a history of monoclonal gammopathy of undetermined significance (MGUS); or signs and symptoms suggestive of possible lymphoproliferative disease, such as lymphadenopathy or splenomegaly
* Participant has a history of chronic or recurrent infectious disease, including but not limited to chronic renal infection, chronic chest infection (eg, bronchiectasis), recurrent urinary tract infection (recurrent pyelonephritis or chronic nonremitting cystitis), fungal infection (mucocutaneous candidiasis), or open, draining, or infected skin wounds or ulcers
* Participant has a history of an infected joint prosthesis, or has received antibiotics for a suspected infection of a joint prosthesis, if that prosthesis has not been removed or replaced
* Participant has ever received any previous biologic therapy for psoriasis or psoriatic arthritis