RT Journal Article SR Electronic T1 Decreased Susceptibility of the Cytochrome P450 2B6 Variant K262R to Inhibition by Several Clinically Important Drugs JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 644 OP 650 DO 10.1124/dmd.108.023655 VO 37 IS 3 A1 Jyothi C. Talakad A1 Santosh Kumar A1 James R. Halpert YR 2009 UL http://dmd.aspetjournals.org/content/37/3/644.abstract AB Cytochrome P450 (P450) 2B6 metabolizes a number of clinically relevant drugs and is one of the most highly polymorphic human P450 enzymes, with the Lys262→Arg substitution being especially common in several genetic variants. Therefore, K262R (2B6*4) was created in the CYP2B6dH background (N-terminal-modified and C-terminal His-tagged) and expressed in Escherichia coli. The recombinant CYP2B6dH and K262R were purified and studied to investigate the effect of the Lys262→Arg substitution with six of the most potent drug inhibitors of CYP2B6, namely, clopidogrel, clotrimazole, itraconazole, raloxifene, sertraline, and ticlopidine. K262R showed a >3-fold increase in the Ki values with clopidogrel, itraconazole, and raloxifene and ∼6-fold increase in Ki with sertraline compared with CYP2B6dH. Likewise, K262R showed 2-, 4-, and >20-fold higher Ks values than CYP2B6dH with clopidogrel, sertraline, and itraconazole, respectively. In contrast, when tested with several known type II inhibitors of CYP2B enzymes, K262R showed a 10-fold lower IC50 with 4-(phenyl)pyridine and ∼2-fold lower IC50 with 4-(4-nitrobenzyl)pyridine or 1-(4-phenyl)benzylimidazole than CYP2B6dH. Subsequent analysis predicted possible in vivo drug-drug interactions between the CYP2B6 substrate efavirenz and drug inhibitors clopidogrel, clotrimazole, itraconazole, sertraline, and ticlopidine. Furthermore, Q172H/K262R (2B6*6), which is the most common genetic variant of CYP2B6 harboring K262R, was created in CYP2B6dH, expressed, purified, and characterized for inhibition. Q172H/K262R showed a >6-fold increase in Ki with sertraline and clopidogrel compared with CYP2B6dH. The results suggest that individuals, especially homozygotes, with the 2B6*4 or 2B6*6 allele might be less susceptible to drug interactions resulting from P450 inhibition. The American Society for Pharmacology and Experimental Therapeutics