BACKGROUND: Inflammatory cytokines such as tumor necrosis factor (TNF) have been implicated in the pathogenesis of psoriasis. We evaluated the safety and efficacy of etanercept, a TNF antagonist, for the treatment of plaque psoriasis. METHODS: In this 24-week, double-blind study, 672 patients underwent randomization and 652 either received placebo or received etanercept subcutaneously at a low dose (25 mg once weekly), a medium dose (25 mg twice weekly), or a high dose (50 mg twice weekly). After 12 weeks, patients in the placebo group began twice-weekly treatment with 25 mg of etanercept. The primary measure of clinical response was the psoriasis area-and-severity index. RESULTS: At week 12, there was an improvement from base line of 75 percent or more in the psoriasis area-and-severity index in 4 percent of the patients in the placebo group, as compared with 14 percent of those in the low-dose--etanercept group, 34 percent in the medium-dose--etanercept group, and 49 percent in the high-dose-etanercept group (P<0.001 for all three comparisons with the placebo group). The clinical responses continued to improve with longer treatment. At week 24, there was at least a 75 percent improvement in the psoriasis area-and-severity index in 25 percent of the patients in the low-dose group, 44 percent of those in the medium-dose group, and 59 percent in the high-dose group. The responses as measured by improvements in the psoriasis area-and-severity index were paralleled by improvements in global assessments by physicians and the patients and in quality-of-life measures. Etanercept was generally well tolerated. CONCLUSIONS: The treatment of psoriasis with etanercept led to a significant reduction in the severity of disease over a period of 24 weeks. Copyright 2003 Massachusetts Medical Society