Genetic polymorphisms in metabolic and cellular transport pathway of methotrexate impact clinical outcome of methotrexate monotherapy in Japanese patients with rheumatoid arthritis

Methotrexate pharmacogenetics in rheumatoid arthritis: a status report

Methotrexate (MTX), an antifolate drug, is the first-line disease-modifying agent for the treatment of rheumatoid arthritis (RA) worldwide. MTX has excellent long-term efficacy, tolerability and safety. Early initiation of MTX in patients with RA controls joint destruction and slows progression of disease. However, the clinical response to MTX and frequency of adverse effects from the drug exhibit marked interpatient variability. Over the past decade, there has been a quest to identify genetic markers that reliably predict MTX efficacy and toxicity and help optimize MTX therapy in RA; that is, the field of MTX pharmacogenetics. This review will summarize key pharmacogenetic studies examining SNPs in the genes encoding enzymes in the MTX cellular pathway and their association with MTX response in RA. As evident from this review, MTX pharmacogenetics in RA remains a muddled field, mostly due to inconsistent results from several small underpowered studies.

Pharmacogenetics of disease-modifying antirheumatic drugs in rheumatoid arthritis: towards personalized medicine

Rheumatoid arthritis is a disease showing considerable heterogeneity in all its aspects, including response to therapy. The efficacy of disease-modifying antirheumatic drugs (DMARDs), with or without biological activity, has been unambiguously established. DMARDs improve the symptoms associated with the disease, and, even more importantly, are capable of stagnating the joint damage associated with the disease. Nonetheless, a considerable proportion of patients fail to achieve an adequate response and/or experience toxicity. This variability in treatment response between individuals has given rise to an extensive search for prognostic markers in order to personalize and optimize therapy in rheumatoid arthritis patients. Pharmacogenetics, the study of genetic variation underlying differential responses to drugs, is a rapidly progressing field in rheumatology that might enable personalized therapy in rheumatic diseases. This review will summarize the pharmacogenetics of commonly used synthetic and biological DMARDs.

Old drugs, old problems: where do we stand in prediction of rheumatoid arthritis responsiveness to methotrexate and other synthetic DMARDs?

Methotrexate (MTX) is the central drug in the management of rheumatoid arthritis (RA) and other immune mediated inflammatory diseases. It is widely used either in monotherapy or in association with other synthetic and biologic disease modifying anti-rheumatic drugs (DMARDs). Although comprehensive clinical experience exists for MTX and synthetic DMARDs, to date it has not been possible to preview correctly whether or not a patient will respond to treatment with these drugs. Predicting response to MTX and other DMARDs would allow the selection of patients based on their likelihood of response, thus enabling individualized therapy and avoiding unnecessary adverse effects and elevated costs. However, studies analyzing this issue have struggled to obtain consistent, replicable results and no factor has yet been recognized to individually distinguish responders from nonresponders at treatment start. Variables possibly influencing drug effectiveness may be disease-, patient- or treatment-related, clinical or biological (genetic and nongenetic). In this review we summarize current evidence on predictors of response to MTX and other synthetic DMARDs, discuss possible causes for the heterogeneity observed and address its translation into daily clinical practice.

Genetic polymorphisms in key methotrexate pathway genes are associated with response to treatment in rheumatoid arthritis patients

We investigated the effect of Single Nucleotide Polymorphisms (SNPs) spanning 10 methotrexate (MTX) pathway genes, namely AMPD1, ATIC, DHFR, FPGS, GGH, ITPA, MTHFD1, SHMT1, SLC19A1 (RFC) and TYMS on the outcome of MTX treatment in a UK rheumatoid arthritis (RA) patient cohort. Tagging SNPs were selected and genotyping performed in 309 patients with predefined outcomes to MTX treatment. Of the 129 SNPs tested, 11 associations were detected with efficacy (p-trend ≤ 0.05) including four SNPs in the ATIC gene (rs12995526, rs3821353, rs7563206 and rs16853834), 6 SNPs in the SLC19A1 gene region (rs11702425, rs2838956, rs7499, rs2274808, rs9977268, rs7279445) and a single SNP within the GGH gene (rs12681874). Five SNPs were significantly associated with adverse events; three in the DHFR gene (rs12517451, rs10072026, and rs1643657) and two of borderline significance in the FPGS gene. The results suggest that genetic variations in several key MTX pathway genes may influence response to MTX in RA patients. Further studies will be required to validate these findings and if confirmed these results could contribute towards a better understanding of and ability to predict MTX response in RA.