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Influence of CYP2C9 genotypes on the formation of a hepatotoxic metabolite of valproic acid in human liver microsomes

The Pharmacogenomics Journal volume 3, pages 335–342 (2003)Cite this article

ABSTRACT

The present study investigated the effect of cytochrome P450 2C9 (CYP2C9) genetic polymorphism on the biotransformation of valproic acid (VPA) to its hepatotoxic metabolite, 4-ene-VPA, and compared that to the formation of the inactive 4-OH-VPA and 5-OH-VPA. cDNA-expressed CYP2C9*2 and CYP2C9*3 variants were less efficient than the CYP2C9*1 wild type in catalyzing the formation of these metabolites, as assessed by the ratio of Vmax and apparent Km (in vitro intrinsic clearance). The reduced efficiency by CYP2C9*2 was due to a reduced Vmax, whereas, in the case of CYP2C9*3, it was the result of increased apparent Km. The formation rates of 4-ene-VPA, 4-OH-VPA, and 5-OH-VPA in human liver microsomes were reduced by 29, 28, and 31%, respectively, in samples with one mutated CYP2C9 allele, and by 61, 73, and 58%, respectively, in samples with two mutated CYP2C9 alleles. Overall, the homozygote and heterozygote CYP2C9*2 and CYP2C9*3 genotypes may compromise hepatic VPA biotransformation.

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Acknowledgements

We thank Vincent Tong for his assistance. This research was supported by Grant MOP-13744 (to FSA and TKHC) from the Canadian Institutes of Health Research. TKHC received a Research Career Award in the Health Sciences from the Canadian Institutes of Health Research and the Rx&D Health Research Foundation.

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Authors and Affiliations

  1. Faculty of Pharmaceutical Sciences, The University of British Columbia, British Columbia, Canada

    P C Ho, F S Abbott & T K H Chang

  2. Dr Margarete Fischer-Bosch Institut fur Klinische Pharmakologie, Stuttgart, Germany

    U M Zanger

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  1. P C Ho
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  2. F S Abbott
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  3. U M Zanger
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  4. T K H Chang
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Correspondence to T K H Chang.

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Ho, P., Abbott, F., Zanger, U. et al. Influence of CYP2C9 genotypes on the formation of a hepatotoxic metabolite of valproic acid in human liver microsomes. Pharmacogenomics J 3, 335–342 (2003). https://doi.org/10.1038/sj.tpj.6500210

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