title: Development of an ELISA-Based Competitive Binding Assay for the Analysis of Drug Concentration and Antidrug Antibody Levels in Patients Receiving Adalimumab or Infliximab.
abstract: BACKGROUND
  There is increasing interest in measuring both drug and antidrug antibody (ADA) levels in patients receiving anti-tumor necrosis factor treatment as part of algorithms for guiding therapeutic strategies. Many of the current assays for ADA detection have limitations with respect to specificity, sensitivity, and/or laboratory requirements. Specific identification of ADA based on their inhibitory activity in a simple competitive binding assay remains problematic. The development of an enzyme-linked immunosorbent assay (ELISA)-based method for detection of both drug and ADA in patients receiving either adalimumab or infliximab would widen availability of monitoring for these patients.
  
  
  METHODS
  An ELISA for the specific detection of adalimumab and infliximab using widely available reagents was developed. A simple modification for the detection of ADA capable of competitively inhibiting the in vitro binding of drug to solid phase tumor necrosis factor was also developed. Drug and ADA levels were analyzed in patients with rheumatoid arthritis and inflammatory bowel disease.
  
  
  RESULTS
  The ELISA specifically detected drug concentrations in patient sera with no evidence of positive or negative interference by rheumatoid factor positive control sera. A subset of those patients with low drug concentrations had detectable levels of ADA with inhibitory activity in a competitive binding assay. Spiking with both drugs confirmed the specificity of the ADA detected.
  
  
  CONCLUSIONS
  A modified ELISA protocol can be used to for the detection of both drug concentrations and ADA in patients receiving either adalimumab or infliximab. The ELISA incorporates those features identified in the literature as important for the accurate analysis of these antibodies and uses laboratory facilities and reagents that are widely available. It therefore provides a relatively simple and low cost assay for therapeutic drug monitoring of inpatients receiving adalimumab or infliximab.
authors.affiliation: *Haematology Research Group, Christchurch Hospital; †Department of Medicine, University of Otago; ‡Department of Rheumatology, Immunology and Allergy, Christchurch Hospital; §Immunology Section, Canterbury Health Laboratories; and ¶Department of Clinical Pharmacology, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: Barry D
authors.initials: BD
authors.lastname: Hock
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Stamp
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Hayman
authors.forename: Paula E
authors.initials: PE
authors.lastname: Keating
authors.forename: Esther T J
authors.initials: ET
authors.lastname: Helms
authors.forename: Murray L
authors.initials: ML
authors.lastname: Barclay
mesh_terms: D000068879:Adalimumab / Q000008:administration & dosage* / Q000276:immunology / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000276:immunology / Q000627:therapeutic use; D000906:Antibodies / Q000097:blood; D018501:Antirheumatic Agents / Q000008:administration & dosage* / Q000276:immunology / Q000493:pharmacokinetics; D001172:Arthritis, Rheumatoid / Q000188:drug therapy; D001667:Binding, Competitive; D016903:Drug Monitoring / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D005765:Gastrointestinal Agents / Q000008:administration & dosage / Q000276:immunology / Q000627:therapeutic use; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy; D000069285:Infliximab / Q000008:administration & dosage* / Q000276:immunology / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors; D055815:Young Adult
chemical_list: D000893:Anti-Inflammatory Agents; D000906:Antibodies; D018501:Antirheumatic Agents; D005765:Gastrointestinal Agents; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D000068879:Adalimumab