Polymorphic Variants (CYP2C9*3 and CYP2C9*5) and the F114L Active Site Mutation of CYP2C9: Effect on Atypical Kinetic Metabolism Profiles

Abstract

This article is available online at http://dmd.aspetjournals.org ABSTRACT:CYP2C9 wild-type protein has been shown to exhibit atypical kinetic profiles of metabolism that may affect in vitro-in vivo predictions made during the drug development process. Previous work suggests a substrate-dependent effect of polymorphic variants of CYP2C9 on the rate of metabolism; however, it is hypothesized that these active site amino acid changes will affect the kinetic profile of a drug's metabolism as well. To this end, the kinetic profiles of three model CYP2C9 substrates (flurbiprofen, naproxen, and piroxicam) were studied using purified CYP2C9*1 (wild-type) and variants involving active site amino acid changes, including the naturally occurring variants CYP2C9*3 (Leu359) and CYP2C9*5 (Glu360) and the man-made mutant CYP2C9 F114L. CYP2C9*1 (wild-type) metabolized each of the three compounds with a distinctive profile reflective of typical hyperbolic (flurbiprofen), biphasic (naproxen), and substrate inhibition (piroxicam) kinetics. CYP2C9*3 metabolism was again hyperbolic for flurbiprofen, of a linear form for naproxen (no saturation noted), and exhibited substrate inhibition with piroxicam. CYP2C9*5-mediated metabolism was hyperbolic for flurbiprofen and piroxicam but linear with respect to naproxen turnover. The F114L mutant exhibited a hyperbolic kinetic profile for flurbiprofen metabolism, a linear profile for naproxen metabolism, and a substrate inhibition kinetic profile for piroxicam metabolism. In all cases except F114L-mediated piroxicam metabolism, turnover decreased and the K m generally increased for each allelic variant compared with wild-type enzyme. It seems that the kinetic profile of CYP2C9-mediated metabolism is dependent on both substrate and the CYP2C9 allelic variant, thus having potential ramifications on drug disposition predictions made during the development process.

Pharmacogenetics of nonsteroidal anti-inflammatory drugs

“…This may affect some of the pharmacokinetic data that have been gathered for diclofenac. 18 Indomethacin Indomethacin can be used for closure of patent ductus arteriosus in premature infants. 22 Indomethacin is metabolized by CYP2C9 and carboxy esterase (minor pathway).…”

“…3 Flurbiprofen Flurbiprofen is an organic acid 43 that is metabolized by CYP2C9 forming 4 0 -hydroxiflurbiprofen. 18 Interestingly, flurbiprofen is a medication that is used in the assessment of CYP2C9 variations and pharmacokinetic ramifications. 43 A typical hyperbolic profile metabolism is displayed for CYP2C9*3 and CYP2C9*5, in addition to the wild-type CYP2C9*1.…”

“…25 Like flurbiprofen, the CYP2C9*3 and CYP2C9*5 alleles show a lower clearance when compared with the wild-type CYP2C9*1. 18 However, another study assessed the role of CYP2C9 in the overall clearance of naproxen and concluded that CYP2C9 played a minor role in naproxen clearance, suggesting that pharmacogenetic differences would not be clinically significant if compromised CYP2C9 activity was possessed by a patient taking this medication. 40 Furthermore, there was no significant difference between the C max and AUC for naproxen in patients experiencing gastrointestinal bleeding compared with those without bleeding from two studies.…”

“…As the result, the investigators concluded that a single change in amino acid was correlated to a significant change in metabolism of piroxicam. 18 Tenoxicam Tenoxicam is primarily metabolized by CYP2C9. 58 The in vivo clearance of tenoxicam for the CYP2C9 Ile359 to Leu359 variant allele represents o10% of that of the wild-type allele.…”

“…CYP2C9*2 and CYP2C9*3, two of the more common variant alleles, have been extensively studied. [16][17][18][19] Genetic testing for these specific variances in alleles would aid in determining if a medication will be a valid pharmacotherapeutic option for a specific patient. For example, there appears to be a demarcation in the enzymatic function because of the fact that *1*1 genotype exists in 96% of the Chinese and Japanese populations, whereas heterozygous CYP2C9*1/*3 boasts 4% of these two populations.…”