Oxidative bioactivation and toxicity of leflunomide in immortalized human hepatocytes and kinetics of the non-enzymatic conversion to its major metabolite, A77 1726

Drug Metab Lett. 2008 Aug;2(3):153-7. doi: 10.2174/187231208785425791.

Abstract

We used immortalized human hepatocytes to study the bioactivation of leflunomide and the metabolic degradation to its major metabolite, A77 1726. Both leflunomide and A77 1726 caused a time- and concentration-dependent increase in LDH release. The cytotoxicity of leflunomide, but not that of A77 1726, was prevented by the pan-CYP inhibitor, 1-aminobenzotriazole, indicating that an oxidative metabolite(s) was responsible for the cell injury. LC/MS/MS analysis revealed that leflunomide was rapidly degraded in hepatocytes biphasically (t((1/2))(a) = 1.5 h, t((1/2)) >24 h), but much slower in cell-free medium (t((1/2)) >24 h). In contrast, the generation of A77 1726 occurred at a similar rate in cells and cell-free systems. In conclusion, leflunomide was rapidly metabolized in human hepatocytes to A77 1726, but its toxicity was dependent on other, CYP-dependent intermediates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aniline Compounds / administration & dosage
  • Aniline Compounds / metabolism*
  • Aniline Compounds / toxicity
  • Antirheumatic Agents / administration & dosage
  • Antirheumatic Agents / metabolism*
  • Antirheumatic Agents / toxicity
  • Cells, Cultured
  • Chromatography, Liquid
  • Crotonates
  • Cytochrome P-450 Enzyme System / metabolism*
  • Dose-Response Relationship, Drug
  • Half-Life
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • Humans
  • Hydroxybutyrates / administration & dosage
  • Hydroxybutyrates / metabolism*
  • Hydroxybutyrates / toxicity
  • Isoxazoles / administration & dosage
  • Isoxazoles / metabolism*
  • Isoxazoles / toxicity
  • L-Lactate Dehydrogenase / drug effects
  • L-Lactate Dehydrogenase / metabolism
  • Leflunomide
  • Nitriles
  • Oxidation-Reduction
  • Tandem Mass Spectrometry
  • Time Factors
  • Toluidines
  • Toxicity Tests

Substances

  • Aniline Compounds
  • Antirheumatic Agents
  • Crotonates
  • Hydroxybutyrates
  • Isoxazoles
  • Nitriles
  • Toluidines
  • teriflunomide
  • Cytochrome P-450 Enzyme System
  • L-Lactate Dehydrogenase
  • Leflunomide