title: Anti-infliximab antibodies in patients with rheumatoid arthritis who require higher doses of infliximab to achieve or maintain a clinical response.
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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Rheumatology, Centre Hospitalier de l'Université de Montréal, and Groupe de recherche des maladies rhumatismales du Québec, Montréal, Quebec, Canada. boulos.haraoui@ssss.gouv.qc.ca
authors.forename: Boulos
authors.initials: B
authors.lastname: Haraoui
authors.forename: Louise
authors.initials: L
authors.lastname: Cameron
authors.forename: Michèle
authors.initials: M
authors.lastname: Ouellet
authors.forename: Barbara
authors.initials: B
authors.lastname: White
mesh_terms: D000906:Antibodies / Q000097:blood; D000911:Antibodies, Monoclonal / Q000008:administration & dosage* / Q000276:immunology*; D018501:Antirheumatic Agents / Q000008:administration & dosage* / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000276:immunology* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D005260:Female; D006304:Health Status; D006801:Humans; D000069285:Infliximab; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D000069285:Infliximab