The purpose of this study is to determine if infliximab (anti-TNF) is effective in the treatment of plaque psoriasis.

This is an experimental medical research study. The purpose of this study is to determine if infliximab is effective in the treatment of plaque psoriasis. A total of about 375 patients primarily in Europe will participate in this study. The time of participation in this study is about 17 months. Infliximab is the active drug in Remicade. Infliximab is currently approved for the treatment of Crohn's disease (an irritable bowel disease), and rheumatoid arthritis. The usefulness and safety of infliximab in those diseases has been proven in previous research studies, which included more than 1300 patients in North America and Europe. In a previous small study of infliximab in 33 patients with psoriasis, about 80% of patients treated with infliximab showed improvement in their psoriasis symptoms after the first 3 infusions, while 20% of patients who received placebo showed improvement.

Patients will be assigned to one of two treatment groups (Group 1 and Group 2). Group 1 will receive 5mg/kg infliximab infusions at wks 0, 2, 4, 6, 14, 22, 30, 38 and 46 with placebo infusions at wks 24 and 26. Group 2 will receive placebo infusions at wks 0, 2, 6, 10, 14, 22, with placebo infusions at wks 24, 26, 30, 38 and 46. All study medication is given though an intravenous (into the vein) line.

Safety evaluations will be performed at specified intervals throughout the study and will consist of laboratory tests, vital signs (such as blood pressure), physical examinations and the occurrence and severity of adverse events as well as other study specific procedures. There are 2 different treatment groups: Group 1 will receive 5mg/kg infliximab infusions at wks 0, 2, 4, 6, 14, 22, 30, 38 and 46 with placebo infusions at wks 24 and 26. Group 2 will receive placebo infusions at wks 0, 2, 6, 10, 14, 22, with placebo infusions at wks 24, 26, 30, 38 and 46. All study medication is given though an intravenous (into the vein) line.

Inclusion Criteria:

• Patients who have had a diagnosis of plaque-type psoriasis for at least 6 months
• Patients who have plaque-type psoriasis covering at least 10% of the body

Exclusion Criteria:

• Patients must not have nonplaque forms of psoriasis
• Patients must not have current drug-induced psoriasis
• Patients must not be pregnant, nursing, or planning pregnancy (both men and women) within 18 months of enrollment
• Patients must not have had any previous treatment with infliximab or any therapeutic agent targeted at reducing TNF