Red blood cell methotrexate polyglutamates emerge as a function of dosage intensity and route of administration

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Thierry Dervieux1, Rong Zablocki, Joel Kremer

  • 1Cypress Bioscience, Inc., San Diego, CA 92117, USA. tdervieux@denovodx.com

Rheumatology (Oxford, England)
|August 18, 2010
PubMed
Abstract

Insights

Methotrexate (MTX) therapy leads to the accumulation of MTX polyglutamates (MTXPGs) in rheumatoid arthritis patients. Switching to parenteral MTX increases long-chain MTXPGs, enhancing anti-arthritic effects.

Area of Science:

  • Pharmacology
  • Rheumatology
  • Biochemistry

Background:

  • Methotrexate (MTX) is a cornerstone therapy for rheumatoid arthritis (RA), exerting its anti-arthritic effects via intracellular activation to methotrexate polyglutamates (MTXPGs).
  • Understanding the pharmacokinetics and accumulation patterns of MTXPGs is crucial for optimizing MTX treatment efficacy in RA patients.

Purpose of the Study:

  • To characterize the pharmacokinetics of intracellular MTXPGs in adult RA patients receiving weekly MTX.
  • To identify factors influencing MTXPG accumulation during MTX therapy.

Main Methods:

  • Evaluated MTX pharmacokinetics in 47 MTX-naïve and 223 long-term MTX-treated RA patients.
  • Measured short-chain (MTXPG1-2), long-chain (MTXPG3), and very long-chain (MTXPG4-5) concentrations in red blood cells using liquid chromatography.
  • Employed non-linear mixed models, multivariate regression, and Wilcoxon signed-rank tests for statistical analysis.

Main Results:

  • MTXPG accumulation followed a sigmoidal pattern, reaching steady-state concentrations around 7 weeks.
  • Increased MTX exposure and dose escalation selectively favored longer-chain MTXPGs (MTXPG3-5) over shorter-chain forms.
  • Age, glomerular filtration rate, and MTX administration route were key predictors of MTXPG accumulation. Parenteral MTX significantly increased long-chain MTXPGs and reduced disease activity.

Conclusions:

  • The accumulation of long-chain MTXPGs is dependent on MTX dose, duration of exposure, and administration route.
  • Switching from oral to parenteral MTX enhances the accumulation of potent long-chain MTXPGs, which are more effective inhibitors of purine biosynthesis, leading to improved disease control in RA.

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