Functional Characterization of CYP2B6 Allelic Variants in Demethylation of Antimalarial Artemether

• Published in: Drug metabolism and disposition Vol. 39; no. 10; pp. 1860 - 1865
• Main Authors: Honda, Masashi, Muroi, Yuka, Tamaki, Yuichiro, Saigusa, Daisuke, Suzuki, Naoto, Tomioka, Yoshihisa, Matsubara, Yoichi, Oda, Akifumi, Hirasawa, Noriyasu, Hiratsuka, Masahiro
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.10.2011; American Society for Pharmacology and Experimental Therapeutics
• Subjects: Alleles; Animals; Antimalarials - metabolism; Artemether; Artemisinins - metabolism; Aryl Hydrocarbon Hydroxylases - genetics; Aryl Hydrocarbon Hydroxylases - metabolism; Biological and medical sciences; Chlorocebus aethiops; COS Cells; Cytochrome P-450 CYP2B6; Cytochrome P-450 CYP3A - metabolism; Genetic Variation; Half-Life; Humans; Kinetics; Medical sciences; Methylation; Microsomes, Liver - enzymology; Microsomes, Liver - metabolism; Oxidoreductases, N-Demethylating - genetics; Oxidoreductases, N-Demethylating - metabolism; Pharmacology. Drug treatments; Protein Isoforms; P450; ART; AM; DHA; MS/MS; LC; Antimalarial; Genetic variability; Enzyme; Isozyme; Cytochrome P450; Genotype; Metabolism; Characterization; Variant; Demethylation; Parasiticide; Artemether; Pharmacokinetics; Cytochrome P450 2B6
• ISSN: 0090-9556; 1521-009X; 1521-009X
• DOI: 10.1124/dmd.111.040352

Artemether (AM) is one of the most effective antimalarial drugs. The elimination half-life of AM is very short, and it shows large interindividual variability in pharmacokinetic parameters. The aim of this study was to identify cytochrome P450 (P450) isozymes responsible for the demethylation of AM and to evaluate functional differences between 26 CYP2B6 allelic variants in vitro. Of 14 recombinant P450s examined in this study, CYP2B6 and CYP3A4 were primarily responsible for production of the desmethyl metabolite dihydroartemisinin. The intrinsic clearance (Vmax/Km) of CYP2B6 was 6-fold higher than that of CYP3A4. AM demethylation activity was correlated with CYP2B6 protein levels (P = 0.004); however, it was not correlated with CYP3A4 protein levels (P = 0.27) in human liver microsomes. Wild-type CYP2B6.1 and 25 CYP2B6 allelic variants (CYP2B6.2-CYP2B6.21 and CYP2B6.23-CYP2B6.27) were heterologously expressed in COS-7 cells. In vitro analysis revealed no enzymatic activity in 5 variants (CYP2B6.8, CYP2B6.12, CYP2B6.18, CYP2B6.21, and CYP2B6.24), lower activity in 7 variants (CYP2B6.10, CYP2B6.11, CYP2B6.14, CYP2B6.15, CYP2B6.16, CYP2B6.20, and CYP2B6.27), and higher activity in 4 variants (CYP2B6.2, CYP2B6.4, CYP2B6.6, and CYP2B6.19), compared with that of wild-type CYP2B6.1. In kinetic analysis, 3 variants (CYP2B6.2, CYP2B6.4, and CYP2B6.6) exhibited significantly higher Vmax, and 3 variants (CYP2B6.14, CYP2B6.20 and CYP2B6.27) exhibited significantly lower Vmax compared with that of CYP2B6.1. This functional analysis of CYP2B6 variants could provide useful information for individualization of antimalarial drug therapy.