A Study to Assess the Effect of Ustekinumab (Stelara®) and Etanercept (Enbrel®) in Participants With Moderate to Severe Psoriasis (MK-0000-206)

Exclusion Criteria

• •Has nonplaque forms of psoriasis specifically erythrodermic psoriasis, predominantly pustular psoriasis, medication-induced or medication-exacerbated psoriasis, or new onset guttate psoriasis - Parts 1 and 2
• •Women of childbearing potential who are pregnant, intend to become pregnant (within 6 months of completing the trial), or are lactating - Parts 1 and 2
• •Has a history of neoplastic disease or concurrent malignancy - Part 2
• •Requires oral or injectable corticosteroids during the trial - Part 2
• •Have any infection requiring treatment with antibiotics within 2 weeks prior to screening or serious infection requiring hospitalization or treatment with IV antibiotics within 8 weeks prior to screening - Part 2
• •Has a positive human immunodeficiency virus (HIV) test result, hepatitis B surface antigen, or hepatitis C test result - Part 2
• •Has received live virus vaccination within 4 weeks prior to screening or who intends to receive live virus vaccination during the trial - Part 2
• •Has previous exposure to any agents targeting IL-12 and/or IL-23 (e.g. ustekinumab) - Part 2
• •Has prior exposure tumor necrosis factor (TNF) antagonists (e.g. infliximab, etanercept, golimumab, adalimumab) and discontinued due to lack of efficacy or for adverse effects - Part 2
• •Has been treated with any medications that are associated with Progressive Multifocal Leukoencephalopathy (PML), such as efalizumab (Raptiva) or natalizumab (Tysabri) - Part 2
• •Has taken any immunosuppressive agents (e.g. corticosteroids, methotrexate, azathioprine, cyclosporine) for treatment of conditions other than for Psoriasis within 4 weeks of screening - Part 2
• •Is currently taking any of the prohibited medications and is unwilling to washout of the medication(s) for the indicated timeframe prior to screening and for the duration of the study - Part 2