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The effect of genotype on methotrexate polyglutamate variability in juvenile idiopathic arthritis and association

Mara L Becker1, Roger Gaedigk, Leon van Haandel

  • 1Children's Mercy Hospitals and Clinics, Kansas City, Missouri 64108, USA. mlbecker@cmh.edu

Arthritis and Rheumatism
|October 19, 2010
PubMed
Abstract

Insights

Methotrexate polyglutamate (MTXGlu) levels predict outcomes in juvenile idiopathic arthritis (JIA). Genetic factors influence MTXGlu variability, impacting drug response and toxicity in JIA patients.

Area of Science:

  • Pharmacogenomics
  • Pediatric Rheumatology
  • Drug Metabolism

Background:

  • Methotrexate (MTX) response and toxicity are unpredictable in juvenile idiopathic arthritis (JIA).
  • Intracellular MTX polyglutamation (MTXGlu) is a potential predictor of MTX efficacy.
  • Understanding MTXGlu variability is crucial for optimizing JIA treatment.

Purpose of the Study:

  • Investigate genetic predictors of MTXGlu variability in JIA patients.
  • Examine the association between MTXGlu levels and MTX response/toxicity.
  • Identify factors influencing MTX biotransformation in pediatric arthritis.

Main Methods:

  • Cross-sectional study of 104 JIA patients on stable MTX doses.
  • Genotyping of 34 single-nucleotide polymorphisms (SNPs) in 18 MTX metabolic pathway genes.
  • Quantification of MTX polyglutamates (MTXGlu1-7) in red blood cells using mass spectrometry.

Main Results:

  • Three distinct MTXGlu polyglutamation patterns (clusters) were identified.
  • SNPs in purine, pyrimidine, and adenosine pathways associated with MTXGlu clusters.
  • High MTXGlu3-5 concentrations linked to elevated liver enzymes and gastrointestinal side effects.

Conclusions:

  • MTXGlu levels are a potentially valuable tool for predicting MTX treatment outcomes in JIA.
  • Genetic variations influencing MTXGlu variability may explain differential drug responses.
  • Further research into MTX biotransformation predictors can improve JIA management.

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