A Phase 3, Multi-Site, Randomized, Mixed-Blind, Parallel-Group Treatment Withdrawal And Re-Treatment Study Of The Efficacy And Safety Of 2 Oral Doses Of CP-690,550 In Subjects With Moderate To Severe Chronic Plaque Psoriasis

The primary objectives of the study are to 1) compare the efficacy responses of CP 690,550 (5 mg BID and 10 mg BID) versus placebo following 24 weeks of CP 690,550 treatment and subsequent withdrawal of active treatment at various timepoints during the 16 week double blind active or placebo treatment period; 2) evaluate the regain of efficacy responses of CP 690,550 (5 mg BID and 10 mg BID) following 4 -16 weeks of CP 690,550 treatment withdrawal and subsequent re treatment; and 3) evaluate the safety and tolerability of CP 690,550 (5 mg BID and 10 mg BID) in subjects with moderate to severe chronic plaque psoriasis who are candidates for systemic therapy or phototherapy.