A Multi-center, Randomized, Double-blind, Placebo-controlled Study to Evaluate the Efficacy and Safety of Certolizumab Pegol in Combination With Methotrexate in the Treatment of Disease Modifying Antirheumatic Drugs (DMARD)-naïve Adults With Early Active Rheumatoid Arthritis

This study is intended to evaluate the efficacy and safety of Certolizumab Pegol (CZP) in combination with Methotrexate (MTX) for sustaining clinical response achieved in study RA0055 Period 1 \[NCT01519791\]. Subjects entering this study RA0055 Period 2 achieved sustained Low Disease Activity at Week 52 in study RA0055 Period 1.