 At the Week 18 visit, subjects who were ACR20 American College of Rheumatology 20 Improvement responders at Week 16 will be randomized in a double-blinded way to receive either 400 mg CZP given every 4 weeks and placebo given every 4 weeks given as two injections alternating CZP and placebo every two weeks plus MTX, 200 mg CZP and placebo administered every 2 weeks one injection of each plus MTX, or Placebo administered as two injections every 2 weeks plus MTX. Non-responders will be withdrawn from the study. 