Determinants of gefitinib pharmacokinetics in healthy Chinese male subjects: A pharmacogenomic study of cytochrome p450 enzymes and transporters.

Abstract

Gefitinib, an inhibitor of the epidermal growth factor receptor tyrosine kinase, exhibited a wide interindividual variability in pharmacokinetics. In the present study, we aimed to evaluate the impact of single-nucleotide polymorphisms in the metabolizing enzymes and transporters on gefitinib disposition in healthy Chinese subjects. Fourteen single-nucleotide polymorphisms, including polymorphisms of ATP-binding cassette (ABC) transporters and cytochrome P450 enzymes, were genotyped by Sanger sequencing, and the concentration of gefitinib was measured by ultrafast liquid chromatography-tandem mass spectrometry. The association between the pharmacokinetic parameters (peak plasma concentration [Cmax ], time to reach Cmax , plasma half-life, area under the concentration-time curve from 0 to 168hours [AUC(0-168h) ], AUC(0-∞) and plasma clearance [CL/F]) and genotypes was evaluated using unpaired t test or Mann-Whitney U test. A stepwise multiple linear regression analysis was applied to assess the relationships between multiple factors and gefitinib pharmacokinetics. Thirty-nine healthy Chinese male subjects were enrolled in the pharmacokinetic study. Subjects carrying an ABCG2 A allele (c.421CA+c.421AA genotypes) exhibited 33 and 37% increases in the mean gefitinib AUC(0-168h) and AUC(0-∞) values (P<.05), respectively, compared to that of subjects carrying wild-type ABCG2 (c.421CC). Additionally, the mean CL/F of the c.421A allele carriers was 32% less than that of the c.421CC carriers (P<.05). No associations were found between polymorphisms in other metabolic enzymes or ABC transporters and gefitinib pharmacokinetics. Our results suggested that a single-nucleotide polymorphism in ABCG2 (c.421C>A) significantly affected the pharmacokinetics of gefitinib. Further studies are required to evaluate the effects of single-nucleotide polymorphism on the pharmacokinetics, pharmacodynamics and toxicity of gefitinib.