title: Influence of anti-infliximab antibodies and residual infliximab concentrations on the occurrence of acquired drug resistance to infliximab in rheumatoid arthritis patients.
abstract: BACKGROUND
  Infliximab (IFX) can be immunogenic for humans and lead to the formation of antibodies against IFX (anti-IFX Ab), which could induce acquired IFX resistance.
  
  
  OBJECTIVE
  To test whether the presence of anti-IFX Ab and residual circulating IFX levels are associated with acquired IFX resistance in RA.
  
  
  METHODS
  A multivariate logistic regression was used to analyze the relationship between anti-IFX Ab, residual IFX concentrations, and acquired IFX resistance in a nested cohort within the Swiss RA registry (SCQM-RA).
  
  
  RESULTS
  Sixty-four RA patients on longstanding IFX therapy were included; 24 with an acquired therapeutic resistance to IFX and 40 with continuous good response to IFX. The two groups had similar disease characteristics, but patients with acquired IFX resistance required significantly higher dosage of IFX (5.4 mg/kg versus 4.3 mg/kg, p=0.02) and shorter infusion intervals (7.1 versus 8.7 weeks, p=0.01) than long-term good responders. The presence of residual IFX tended to be associated with a decreased risk of acquired therapeutic resistance (OR 0.4 [95% CI: 0.1-1.5]), while the presence of anti-IFX Ab tended to be associated with an increased risk of acquired therapeutic resistance (OR: 1.8 [95% CI: 0.4 - 9.0]). The presence of either high anti-IFX Ab levels or low residual IFX concentrations was strongly associated with acquired therapeutic resistance to IFX (OR 5.9, 95% CI 1.3 - 26.6). However, just 42% of patients with acquired IFX resistance had either low IFX or high anti-IFX Ab levels.
  
  
  CONCLUSIONS
  These results suggest that the assessment of anti-IFX Ab and residual IFX levels is of limited value for individual patients in routine clinical care.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University Hospital of Geneva, 26, avenue Beau-Sejour, 1211 Geneva, Switzerland. axel.finckh@hcuge.ch
authors.forename: Axel
authors.initials: A
authors.lastname: Finckh
authors.forename: Jean
authors.initials: J
authors.lastname: Dudler
authors.forename: Felix
authors.initials: F
authors.lastname: Wermelinger
authors.forename: Adrian
authors.initials: A
authors.lastname: Ciurea
authors.forename: Diego
authors.initials: D
authors.lastname: Kyburz
authors.forename: Cem
authors.initials: C
authors.lastname: Gabay
authors.forename: Sylvette
authors.initials: S
authors.lastname: Bas
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D000911:Antibodies, Monoclonal / Q000097:blood* / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005260:Female; D006801:Humans; D000069285:Infliximab; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D015415:Biomarkers; D000069285:Infliximab