A PHASE 3, MULTICENTER, RANDOMIZED, DOUBLE-BLIND, PARALLEL-GROUP, PLACEBO- AND ACTIVE-CONTROLLED STUDY FOLLOWED BY A PLACEBO-CONTROLLED MAINTENANCE PERIOD AND OPEN-LABEL FOLLOW-UP TO EVALUATE THE EFFICACY AND SAFETY OF CERTOLIZUMAB PEGOL IN SUBJECTS WITH MODERATE TO SEVERE CHRONIC PLAQUE PSORIASIS