title: Evidence for differential acquired drug resistance to anti-tumour necrosis factor agents in rheumatoid arthritis.
abstract: BACKGROUND
  Acquired drug resistance or gradual drug failure has been described with most disease modifying antirheumatic drugs (DMARDs) and is also starting to be recognised with anti-tumour necrosis factor (anti-TNF) agents.
  
  
  OBJECTIVE
  To study acquired drug resistance to anti-TNF agents in rheumatoid arthritis (RA).
  
  
  METHODS
  Swiss health authorities requested continuous monitoring of patients receiving biological agents. Intensification of co-therapy with traditional DMARDs, gradual dose escalation, and drug discontinuation rates in all patients receiving infliximab, etanercept, or adalimumab, adjusting for potential confounders, were analysed. Intensification of DMARD co-therapy and time to discontinuation of the three anti-TNF agents were analysed using a proportional hazards models. Dose escalation and evolution of RA disease activity (DAS28) were analysed using a longitudinal regression model.
  
  
  RESULTS
  1198 patients contributing 1450 patient-years of anti-TNF treatment met the inclusion criteria. The rate of intensification of traditional DMARD co-therapy over time was significantly higher with infliximab (hazards ratio = 1.73 (99% confidence interval (CI) 1.19 to 2.51)) than with the two other agents. Infliximab also showed significant dose escalation over time, with an average dose increase of +12% (99% CI 8% to 16%) after 1 year, and +18% (99% CI 11% to 25%) after 2 years. No significant differences in discontinuation rates were seen between the three anti-TNF agents (ANOVA, p = 0.67). Evolution of disease activity over time indicated a lower therapeutic response to infliximab (DAS28, p<0.001) compared with etanercept, after 6 months' treatment.
  
  
  CONCLUSIONS
  In this population, infliximab was associated with a higher risk of requiring intensification of DMARD co-therapy than the other anti-TNF agents and a significant dose escalation over time. Analysis of RA disease activity indicated a reduced therapeutic response to infliximab after the first 6 months of treatment, suggestive of acquired drug resistance.
authors.affiliation: Department of Medicine, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Harvard Medical School, Boston, USA. afinckh@post.harvard.edu
authors.forename: A
authors.initials: A
authors.lastname: Finckh
authors.forename: J F
authors.initials: JF
authors.lastname: Simard
authors.forename: C
authors.initials: C
authors.lastname: Gabay
authors.forename: P-A
authors.initials: PA
authors.lastname: Guerne
mesh_terms: D000068879:Adalimumab; D000704:Analysis of Variance; D000911:Antibodies, Monoclonal / Q000009:adverse effects / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D018501:Antirheumatic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D003625:Data Collection; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004351:Drug Resistance; D000068800:Etanercept; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000009:adverse effects / Q000627:therapeutic use; D000069285:Infliximab; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use; D013997:Time Factors; D016896:Treatment Outcome; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018501:Antirheumatic Agents; D007074:Immunoglobulin G; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D000068879:Adalimumab; D000068800:Etanercept