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This article is part of the supplement: 25th European Workshop for Rheumatology Research

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Inhibition of tumour necrosis factor alpha production by activated T cells of rheumatoid arthritis patients by novel anti-folate drugs: an ex vivo pilot study

JW van der Heijden1, AH Gerards2, R Oerlemans1, WF Lems1, RJ Scheper3, LA Aarden4, BAC Dijkmans1 and G Jansen1

Author Affiliations

1 Department of Rheumatology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands

2 Vlietland Hospital, Schiedam, The Netherlands

3 Department of Pathology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands

4 Department of Immunopathology, Sanquin-Research, Amsterdam, The Netherlands

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Arthritis Research & Therapy 2005, 7(Suppl 1):P84  doi:10.1186/ar1605

The electronic version of this article is the complete one and can be found online at:

Received:11 January 2005
Published:17 February 2005

© 2005 BioMed Central Ltd


The folate antagonist methotrexate (MTX) is the 'anchor-drug' in the treatment of patients with rheumatoid arthritis (RA) [1]. The main target of MTX in intracellular folate metabolism is dihydrofolate reductase (DHFR) but several other targets have been described (e.g. thymidylate synthase [TS] and 5-amino-imidazole-4-carboxamide ribonucleotide [AICAR]). At present the exact mechanism of action of MTX in RA still remains elusive [1]. Despite the potent anti-rheumatic capacity of MTX many patients (at least 50%) become resistant to MTX during long-lasting therapy. However, little is known about the mechanisms of resistance against MTX in RA patients [2].

From the field of oncology, where MTX is used against haematological malignancies, new anti-folate drugs were developed to circumvent MTX resistance [3]. These new folate antagonists have the following characteristics: are better transported through the reduced folate carrier, are retained intracellular more efficiently by polyglutamylation via folylpolyglutamate synthetase, and/or have other targets in the folate pathway besides DHFR (e.g. TS).


To investigate whether two new-generation anti-folate drugs, PT523 (DHFR-inhibitor) and ZD1694 (TS-inhibitor), have equal or better anti-inflammatory capacity compared with MTX based on their capacity to inhibit tumour necrosis factor alpha (TNF-α) production by activated T cells.


Whole blood from 11 RA patients and six healthy volunteers was incubated ex vivo with MTX, PT523, ZD1694 and, as a control, the DMARD sulphasalazine (SSZ) after T-cell stimulation with α-CD3/CD28. Inhibition of TNF-α production was measured after 72 hours by ELISA [4].

The IC-50 values (defined as the drug concentration exerting 50% inhibition of TNF-α production) are used as a value for the anti-inflammatory capacity of the drug (Table 1).

Table 1. Characteristics of drugs and mean IC-50 values (± standard deviation)


Both PT523 and D1694 turned out to inhibit TNF-α production by activated T cells much more efficiently than MTX (5–15 times). For comparison, the DMARD SSZ is effective at much higher concentration (μM range). The inhibition of TNF-α production by the anti-folate drugs does not seem to be a result of (apoptotic) cell death of T cells whereas SSZ induces apoptosis of T cells (data not shown).


In an ex vivo setting, two novel anti-folate drugs designed to circumvent MTX resistance proved to be very effective in inhibiting TNF-α production by activated T cells from RA patients and healthy volunteers. Future experiments are designed to evaluate ex vivo anti-folate sensitivity profiles for 'MTX-responders' and 'MTX-non-responders' to investigate whether these novel generation of antifolate drugs can be useful in cases of clinical failure on MTX.


This study is supported by the Dutch Arthritis Association (Grant NRF-03-I-40).


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