Oxidative bioactivation and toxicity of leflunomide in immortalized human hepatocytes and kinetics of the non-enzymatic conversion to its major metabolite, A77 1726.
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.
Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Quee Ming
QM
Seah
Lee-Sun
LS
New
Eric C Y
EC
Chan
Urs A
UA
Boelsterli
D000814:Aniline Compounds / Q000008:administration & dosage / Q000378:metabolism* / Q000633:toxicity; D018501:Antirheumatic Agents / Q000008:administration & dosage / Q000378:metabolism* / Q000633:toxicity; D002478:Cells, Cultured; D002853:Chromatography, Liquid; D003437:Crotonates; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006207:Half-Life; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006885:Hydroxybutyrates / Q000008:administration & dosage / Q000378:metabolism* / Q000633:toxicity; D007555:Isoxazoles / Q000008:administration & dosage / Q000378:metabolism* / Q000633:toxicity; D007770:L-Lactate Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D000077339:Leflunomide; D009570:Nitriles; D010084:Oxidation-Reduction; D053719:Tandem Mass Spectrometry; D013997:Time Factors; D014052:Toluidines; D018675:Toxicity Tests
D000814:Aniline Compounds; D018501:Antirheumatic Agents; D003437:Crotonates; D006885:Hydroxybutyrates; D007555:Isoxazoles; D009570:Nitriles; D014052:Toluidines; C527525:teriflunomide; D003577:Cytochrome P-450 Enzyme System; D007770:L-Lactate Dehydrogenase; D000077339:Leflunomide