Abstract: Anti-Infliximab Antibodies in Patients with Rheumatoid Arthritis Who Require Higher Doses of Infliximab to Achieve or Maintain a Clinical Response

Anti-Infliximab Antibodies in Patients with Rheumatoid Arthritis Who Require Higher Doses of Infliximab to Achieve or Maintain a Clinical Response

BOULOS HARAOUI, LOUISE CAMERON, MICHÈLE OUELLET, and BARBARA WHITE

ABSTRACT.

Objective. To determine whether the need to use doses of infliximab greater than 3 mg/kg every 8 weeks to achieve or maintain clinical response in patients with rheumatoid arthritis (RA) is associated with differences in baseline clinical characteristics or anti-infliximab antibodies.

Methods. Baseline clinical characteristics and anti-infliximab levels were evaluated retrospectively in a cohort of 51 consecutive patients with RA treated with infliximab at a single center. Patients were divided into 2 groups for comparison: Group 1 patients achieved and maintained clinical responses with infliximab 3 mg/kg every 8 weeks; Group 2 patients required higher doses.

Results. Thirty-two (63%) patients required infliximab dose escalation (Group 2). There were no statistically significant differences in baseline or clinical characteristics between Group 1 and Group 2 patients. Anti-infliximab antibodies occurred in 47% of Group 2 versus 27% of Group 1 patients, with higher anti-infliximab antibody concentrations in Group 2 patients (mean ± SD: 18.3 ± 8.9 g/ml vs 7.5 ± 4.8 g/ml; p = 0.02). Patients who developed anti-infliximab antibodies were younger and receiving less prednisone at the time of infliximab initiation than patients who did not.

Conclusion. Finding higher anti-infliximab antibody concentrations in patients who needed dose escalation of infliximab to achieve or maintain clinical responses with lower serum trough levels of infliximab suggests that development of anti-infliximab antibodies may reduce clinical efficacy of infliximab in some patients with RA. (J Rheumatol 2006;33:31-6)

Key Indexing Terms:

RHEUMATOID ARTHRITIS
INFLIXIMAB
ANTI-INFLIXIMAB ANTIBODIES
DOSE ESCALATION
CLINICAL RESPONSE

From the Department of Rheumatology, Centre Hospitalier de l'Université de Montréal, and Groupe de recherche des maladies rhumatismales du Québec, Montréal, Quebec, Canada; and Amgen Inc., Thousand Oaks, California, USA.

Supported by a grant from Immunex Corporation, a wholly owned subsidiary of Amgen Inc., and by Wyeth Research.

B. Haraoui, MD, FRCPC, Clinical Associate Professor of Medicine, Centre Hospitalier de l'Université de Montréal; L. Cameron, RN; M. Ouellet, RN, Groupe de recherche des maladies rhumatismales du Québec; B. White, MD, Medical Affairs, Amgen Inc.

Address reprint requests to Dr. B. Haraoui, Centre Hospitalier de l'Université de Montréal, 1560 Sherbrooke Est, Montréal, PQ, H2L 4M1. E-mail: boulos.haraoui@ssss.gouv.qc.ca

Accepted for publication August 15, 2005.