ANTIBODIES AGAINST INFLIXIMAB IN PATIENTS WITH RHEUMATOID ARTHRITIS: HIGH PREVALENCE AND ASSOCIATION WITH REDUCED RESPONSE TO TREATMENT

Background: Treatment with infliximab, a chimeric monoclonal IgG1 antibody against tumor necrosis factor, can result in the formation of antibodies against infliximab.Objectives: To evaluate the clinical significance of anti-infliximab antibodies in patients with rheumatoid arthritis.Methods: We developed a radioimmunoassay for the detection of anti-infliximab antibodies in serum and used this assay for post hoc evaluation of the presence of anti-infliximab antibodies in sera, collected prior to each infliximab infusion, from 50 consecutive RA patients with a follow-up of one year. Patients had been treated according to the consensus statement on the initiation and continuation of TNF blocking therapies in rheumatoid arthritis. Infliximab had been given as a 3mg/kg infusion at 0, 2, 6 and every eight weeks thereafter. In patients with insufficient response the infliximab dosage had been increased to 7,5 mg/kg every eight weeks. 44 patients used concomitant MTX at a median dose of 15mg/week, 3 patients azathioprine and 1 patient cyclosporine.Results: Antibodies to infliximab were detected in 22 (44%) patients. From the 22 patients who developed anti-infliximab antibodies 13 (59%) received a higher dosage (8) or stopped treatment before the end of the first year (5). From the 28 patients without anti-infliximab antibodies only 6 (20%) needed a higher dosage (3) or stopped treatment before the end of the year (3).Conclusion: The results of this study suggest that the development of antibodies against infliximab in rheumatoid arthritis patients is associated with reduced response to therapy.Citation: , volume , supplement , year 2004, page Session: Rheumatoid arthritis – Treatment