The purpose of this study is to assess the safety and tolerability of CNTO 1959 following a single subcutaneous (SC, under the skin) dose administered to Japanese participants with moderate to severe plaque psoriasis.

This is a randomized (participants are assigned to treatment groups by chance), double-blind (participants and study personnel know what study agents are given), placebo-controlled (a placebo is a treatment identical in appearance to CNTO 1959 but does not contain active drug), single-dose study. The study will include 24 participants: 4 groups of at least 6 participants each. If it is decided that additional data are needed to define the safety and tolerability of CNTO 1959, an additional group may be enrolled. A given dose level may be repeated in newly enrolled participants, or a lower or intermediate dose may be administered based on preliminary data. The total duration of participation will be approximately 30 weeks, which includes a screening period of up to 6 weeks before the administration of study agent. Participant safety will be monitored. Ascending doses of 10, 30, 100, and 300 mg dose of CNTO 1959 and placebo will be administered as single SC injections; however, 2 SC injections may be required for the 300 mg dose level. Dosing will be performed for 24 weeks.

Inclusion Criteria:

• Diagnosis of plaque-type psoriasis at least 6 months prior to screening (participants with concurrent psoriatic arthritis may be enrolled)
• Having plaque-type psoriasis covering at least 10% of total body surface area (BSA) at baseline
• Has a Psoriasis Area and Severity Index (PASI) score of 12 or greater at baseline
• Is a candidate for systemic phototherapy or systemic treatment of psoriasis (either new to treatment or having had previous treatment)
• Has at least 2 plaques suitable for repeat biopsy (Only participants who consent separately to participate in this assessment. Refusal to give consent for this component does not exclude an individual from participation in the clinical study).

Exclusion Criteria:

• Currently has non-plaque forms of psoriasis (eg, erythrodermic, guttate, or pustular)
• Has current drug-induced psoriasis (e.g., a new onset of psoriasis or an exacerbation of psoriasis from beta blockers, calcium channel blockers, or lithium)
• Has a history of chronic or recurrent infectious disease, including but not limited to chronic renal infection, chronic chest infection (e.g., secondary infection occurred on bronchiectasis), recurrent urinary tract infection (recurrent pyelonephritis or chronic nonremitting cystitis), or open, draining, or infected skin wounds or ulcers
• Has a history of latent, or active or opportunistic systemic infection with pathogens including, but not limited to, Klebsiella pneumoniae, Cryptococcus neoformans, Candida albicans, Toxoplasma gondii, and Pneumocystis jiroveci prior to screening
• Has or has had a serious infection (e.g., sepsis, pneumonia or pyelonephritis), or have been hospitalized or received intravenous antibiotics for an infection during the 2 months prior to screening