Multicenter, double-blind, randomized, parallel and placebo-controlled outpatient study. The study consists of 2 parts: part A is a 6-week double-blind treatment period and part B is a 6-week open-label treatment period. During part A of the study, subjects will be randomly assigned to 1 of 2 treatment regimens: 2 etanercept 25 mg or placebo once weekly, administered subcutaneously (SC). After the completion of part A, all subjects will receive 2 etanercept 25 mg once weekly. The use of placebo as a control in part A is necessary to allow a valid comparison and to provide a quantitative assessment of effect.