A Study of CDP870 as Add-on Meditation to Methotrexate (MTX) in Patients With Rheumatoid Arthritis

Inclusion Criteria: * Adult-onset RA of at least 6 months but not longer than 15 years in duration as defined by the 1987 American College of Rheumatology classification criteria * Active RA disease as defined by at least 9 tender joints and 9 swollen joints, ESR of 30 mm/hour or CRP of 1.5 mg/dL * MTX (with or without folic acid) for at least 24 weeks prior to the Baseline visit, The dose of MTX and route of administration must have been stable for at least 8 weeks prior to the baseline visit. The minimum stable dose of MTX allowed is 10 mg weekly. Exclusion Criteria: * Any other inflammatory arthritis (e.g., psoriatic arthritis, ankylosing spondylitis or reactive arthritis) * Secondary, non-inflammatory type of arthritis (eg, osteoarthritis, fibromyalgia) * NYHA (New York Heart Association) Class III or IV congestive heart failure * current or history of, tuberculosis * history of chronic infection, recent serious or life-threatening infection (within 24 weeks , including herpes zoster), or any current sign or symptom that may indicate an infection (e.g., fever, cough) * High risk of infection * Have received any experimental non-biological therapy, within or outside a clinical trial in the 12 weeks prior to Baseline * Have received previous B-cell therapy (eg. Rituximab) * Have received any other biological therapy for RA within 24 weeks prior to Baseline visit, except for etanercept where a three month washout prior to baseline visit is acceptable * Have received previous treatment with a biological therapy for RA that resulted in a severe hypersensitivity reaction or an anaphylactic reaction * Failed to respond to previous treatment with an anti-TNF drug * Female breast feeding, pregnant or plan to become pregnant during the trial or for 12 weeks following the last dose of study drug