Rheumatology Advance Access originally published online on December 7, 2004
Rheumatology 2005 44(3):323-331; doi:10.1093/rheumatology/keh491
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Rheumatology Vol. 44 No. 3 © British Society for Rheumatology 2004; all rights reserved
TNF-
neutralization in cytokine-driven diseases: a mathematical model to account for therapeutic success in rheumatoid arthritis but therapeutic failure in systemic inflammatory response syndrome
Department of Mathematics and 1 Cellular Microbiology Research Group, Eastman Dental Institute, University College London, London and 2 European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK.
Correspondence to: R. M. Seymour, Department of Mathematics, University College London, Gower Street, London WC1E 6BT, UK. E-mail: rms{at}math.ucl.ac.uk
Objectives. Neutralization of TNF-
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-
has little clinical benefit in the majority of patients with systemic inflammatory response syndrome (SIRS) in spite of the identification of TNF-
as a key factor in its pathology. It is not clear why there is such a significant difference in the responses to TNF-
neutralization in these two conditions. Here we use mathematical modelling to investigate this discrepancy.
Methods. Using the known pharmacokinetic and pharmacodynamic properties of TNF-
-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-
levels in RA, which we propose is a condition in which TNF-
production and inhibition are in equilibrium. However, when free TNF-
drops to a low level, as can occur in SIRS, which we propose is a non-equilibrium condition, the sequestered TNF-
can act as a slow-release reservoir, thereby sabotaging its effectiveness.
Conclusions. These results may explain the effectiveness of TNF-
blockade in the equilibrium condition RA and the ineffectiveness in the non-equilibrium condition SIRS.
KEY WORDS: Rheumatoid arthritis, SIRS, TNF-
, Enbrel, Remicade, Cytokine networks, Mathematical modelling