Open-label, Pilot Protocol of Patients With Rheumatoid Arthritis Who Switch to Infliximab After Incomplete Response to Etanercept

The purpose of this study, in patients with rheumatoid arthritis who have had an incomplete
response to etanercept and methotrexate (MTX), are to evaluate: safety and evidence of
therapeutic benefit of infliximab and methotrexate, the levels (pharmacokinetics) of
etanercept and infliximab and antibodies (immunogenicity) to etanercept and infliximab in
patients blood, whether switching from etanercept to infliximab changes progression of
structural damage over the study period, and whether specific markers in the blood
(pharmacodynamics) correlate with therapeutic response or benefit.