Aim: Human cytochrome P450 3A4 is the most abundant isoform of P450 enzyme in the liver. It plays an important role in the metabolism of wide variety of xenobiotic and endogenous substrates. So far, there are few reports about the functional characterization of CYP3A4  variants in terms of specific substrates. The aim of this study was to systematically investigate the genetic polymorphisms of 23 CYP3A4  alleles and evaluate their catalytic activities on the metabolism of lidocaine in vitro.
Methods and results: The wild-type and 22 CYP3A4  variants were expressed in Spodoptera frugiperda 21 insect cells. Then the insect microsomes were incubated with the CYP3A4-specific substrate lidocaine. Reactions were performed with 50–3,000 µM for 60 min at 37°C. Lidocaine and its metabolite monoethylglycinexylidide were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry system. Of the 23 CYP3A4  allelic variants tested, 2 variants (CYP3A4 *17  and CYP3A4 *30 ) had no detectable enzyme activity; and 5 variants (CYP3A4 *2 , CYP3A4 *5 , CYP3A4 *9 , CYP3A4 *16  and CYP3A4 *24 ) showed significantly decreased intrinsic clearance values compared with wild-type CYP3A4* 1.
Conclusion: As the first study of all these CYP3A4  alleles for lidocaine metabolism, our results in vitro assessment may provide novel insights into the allele-specific and substrate-specific activity of CYP3A4  and may also offer a reference to the personalized treatment of lidocaine in a clinical setting.
Keywords: CYP3A4 , genetic polymorphism, drug metabolism, lidocaine, personalized treatment