title: Formation of antibodies against infliximab and adalimumab strongly correlates with functional drug levels and clinical responses in rheumatoid arthritis.
abstract: BACKGROUND
  Tumour necrosis factor alpha (TNFalpha) neutralising antibody constructs are increasingly being used to treat rheumatoid arthritis (RA).
  
  
  OBJECTIVE
  To determine potential differences in clinical responses, soluble drug levels and antibody formation between patients with RA receiving infliximab and adalimumab.
  
  
  METHODS
  69 patients with RA fulfilling the 1987 American College of Rheumatology criteria and about to start treatment with infliximab or adalimumab, were enrolled consecutively. All patients had active disease (28-joint count Disease Activity Score >3.2). Infliximab was given intravenously at 3 mg/kg at baseline and after 2, 6 and 14 weeks. Adalimumab was administered as 40 mg biweekly subcutaneously. Concomitant drug treatment was monitored and continued at constant dosage during the study. All serum samples were tested for infliximab/adalimumab levels and anti-infliximab/anti-adalimumab antibodies.
  
  
  RESULTS
  35 patients received infliximab, 34 received adalimumab. At 6 months, 15 (43%), 6 (17%) and 14 (40%) of the infliximab-treated patients fulfilled the EULAR criteria for good, moderate and non-responders, respectively, whereas the corresponding figures for adalimumab-treated patients were 16 (47%), 8 (24%) and 10 (29%). Clinical responses correlated with the levels of S-infliximab/adalimumab and the formation of anti-infliximab/anti-adalimumab antibodies.
  
  
  CONCLUSIONS
  The clinical response to two anti-TNFalpha biological agents closely follows the trough drug levels and the presence of antibodies directed against the drugs. Further studies that focus on the underlying pathways leading to antibody formation are warranted to predict immunogenicity of these expensive biological agents and treatment outcomes.
authors.affiliation: Department of Rheumatology, Radboud University Nijmegen Medical Centre, Geert Grooteplein 8, 6500 HB Nijmegen, The Netherlands. T.Radstake@reuma.umcn.nl
authors.forename: T R D J
authors.initials: TR
authors.lastname: Radstake
authors.forename: M
authors.initials: M
authors.lastname: Svenson
authors.forename: A M
authors.initials: AM
authors.lastname: Eijsbouts
authors.forename: F H J
authors.initials: FH
authors.lastname: van den Hoogen
authors.forename: C
authors.initials: C
authors.lastname: Enevold
authors.forename: P L C M
authors.initials: PL
authors.lastname: van Riel
authors.forename: K
authors.initials: K
authors.lastname: Bendtzen
mesh_terms: D000068879:Adalimumab; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000096:biosynthesis* / Q000097:blood; D000911:Antibodies, Monoclonal / Q000097:blood / Q000276:immunology* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy / Q000276:immunology; D005260:Female; D006801:Humans; D000069285:Infliximab; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011863:Radioimmunoassay / Q000379:methods; D012720:Severity of Illness Index; D016896:Treatment Outcome; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D000068879:Adalimumab