title: TNF-alpha neutralization in cytokine-driven diseases: a mathematical model to account for therapeutic success in rheumatoid arthritis but therapeutic failure in systemic inflammatory response syndrome.
abstract: OBJECTIVE
  Neutralization of TNF-alpha with either monoclonal antibodies or soluble receptors, although not curative, has significant clinical benefit in patients with rheumatoid arthritis (RA). In contrast, blockade of TNF-alpha has little clinical benefit in the majority of patients with systemic inflammatory response syndrome (SIRS) in spite of the identification of TNF-alpha as a key factor in its pathology. It is not clear why there is such a significant difference in the responses to TNF-alpha neutralization in these two conditions. Here we use mathematical modelling to investigate this discrepancy.
  
  
  METHODS
  Using the known pharmacokinetic and pharmacodynamic properties of TNF-alpha-blocking biological agents, we constructed a mathematical model of the biological actions of soluble(s) TNFR2, Etanercept and Infliximab.
  
  
  RESULTS
  Our model predicts that all three inhibitors, but especially Etanercept, are effective at controlling TNF-alpha levels in RA, which we propose is a condition in which TNF-alpha production and inhibition are in equilibrium. However, when free TNF-alpha drops to a low level, as can occur in SIRS, which we propose is a non-equilibrium condition, the sequestered TNF-alpha can act as a slow-release reservoir, thereby sabotaging its effectiveness.
  
  
  CONCLUSIONS
  These results may explain the effectiveness of TNF-alpha blockade in the equilibrium condition RA and the ineffectiveness in the non-equilibrium condition SIRS.
authors.affiliation: Department of Mathematics, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: M
authors.initials: M
authors.lastname: Jit
authors.forename: B
authors.initials: B
authors.lastname: Henderson
authors.forename: M
authors.initials: M
authors.lastname: Stevens
authors.forename: R M
authors.initials: RM
authors.lastname: Seymour
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000276:immunology; D000068800:Etanercept; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology / Q000627:therapeutic use; D007166:Immunosuppressive Agents / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use; D000069285:Infliximab; D008433:Mathematics; D008954:Models, Biological; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology / Q000627:therapeutic use; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000276:immunology / Q000627:therapeutic use; D018746:Systemic Inflammatory Response Syndrome / Q000188:drug therapy* / Q000276:immunology; D017211:Treatment Failure; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D018124:Receptors, Tumor Necrosis Factor; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D000068800:Etanercept