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Methotrexate polyglutamates in erythrocytes are associated with lower disease activity in juvenile idiopathic

Maja Bulatović Ćalasan1, Ethan den Boer2, Maurits C F J de Rotte2

  • 1Department of Paediatric Immunology, University Medical Centre Utrecht, Wilhelmina Children's Hospital, Utrecht, The Netherlands.

Annals of the Rheumatic Diseases
|November 30, 2013
PubMed
Abstract

Insights

Higher levels of long-chain methotrexate polyglutamates (MTX-PGs) in red blood cells correlate with reduced disease activity in juvenile idiopathic arthritis (JIA) patients treated with methotrexate. MTX-PGs may aid in monitoring methotrexate effectiveness in JIA.

Area of Science:

  • Pharmacology
  • Immunology
  • Pediatrics

Background:

  • Juvenile idiopathic arthritis (JIA) is a chronic autoimmune disease affecting children.
  • Methotrexate (MTX) is a common disease-modifying antirheumatic drug (DMARD) used in JIA management.
  • Erythrocyte methotrexate polyglutamates (MTX-PGs) are active metabolites of MTX, but their role in JIA is not fully understood.

Purpose of the Study:

  • To investigate the association between erythrocyte MTX-PG levels and disease activity in JIA patients.
  • To explore the relationship between MTX-PGs and adverse effects during MTX treatment in JIA.
  • To assess the potential of MTX-PGs as a biomarker for MTX therapy in JIA.

Main Methods:

  • A prospective cohort of 113 JIA patients initiating MTX therapy was studied for 12 months.
  • Erythrocyte MTX-PGs (1-5 glutamate residues) were quantified at 3 months using tandem mass spectrometry.
  • Disease activity was assessed using the Juvenile Arthritis Disease Activity Score (JADAS)-27; adverse effects were also recorded.

Main Results:

  • Higher concentrations of MTX-PG3, MTX-PG4, MTX-PG5, and combined MTX-PG3-5 were significantly associated with lower JADAS-27 scores at 3 months.
  • These associations persisted over the 12-month treatment period, indicating sustained lower disease activity.
  • No significant association was found between MTX-PG levels and the occurrence of adverse effects.

Conclusions:

  • Long-chain MTX-PGs are linked to reduced disease activity in JIA patients treated with methotrexate.
  • Erythrocyte MTX-PG levels show promise as a biomarker for therapeutic drug monitoring of MTX in JIA.
  • Further research can validate MTX-PGs for optimizing MTX dosing and treatment outcomes in pediatric rheumatology.
Keywords:
DMARDs (synthetic)Disease ActivityJuvenile Idiopathic ArthritisMethotrexateTreatment

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