CYP2C9

Function

CYP2C9 is a crucial cytochrome P450 enzyme, which plays a significant role in the metabolism, by oxidation, of both xenobiotic and endogenous compounds. CYP2C9 makes up about 18% of the cytochrome P450 protein in liver microsomes. The protein is mainly expressed in the liver, duodenum, and small intestine. About 100 therapeutic drugs are metabolized by CYP2C9, including drugs with a narrow therapeutic index such as warfarin and phenytoin, and other routinely prescribed drugs such as acenocoumarol, tolbutamide, losartan, glipizide, and some nonsteroidal anti-inflammatory drugs. By contrast, the known extrahepatic CYP2C9 often metabolizes important endogenous compounds such as serotonin and, owing to its epoxygenase activity, various polyunsaturated fatty acids, converting these fatty acids to a wide range of biologically active products.

In particular, CYP2C9 metabolizes arachidonic acid to the following eicosatrienoic acid epoxide (EETs) stereoisomer sets: 5R,6S-epoxy-8Z,11Z,14Z-eicosatetraenoic and 5S,6R-epoxy-8Z,11Z,14Z-eicosatetraenoic acids; 11R,12S-epoxy-8Z,11Z,14Z-eicosatetraenoic and 11S,12R-epoxy-5Z,8Z,14Z-eicosatetraenoic acids; and 14R,15S-epoxy-5Z,8Z,11Z-eicosatetraenoic and 14S,15R-epoxy-5Z,8Z,11Z-eicosatetraenoic acids. It likewise metabolizes docosahexaenoic acid to epoxydocosapentaenoic acids (EDPs; primarily 19,20-epoxy-eicosapentaenoic acid isomers [i.e. 10,11-EDPs]) and eicosapentaenoic acid to epoxyeicosatetraenoic acids (EEQs, primarily 17,18-EEQ and 14,15-EEQ isomers). Animal models and a limited number of human studies implicate these epoxides in reducing hypertension; protecting against myocardial infarction and other insults to the heart; promoting the growth and metastasis of certain cancers; inhibiting inflammation; stimulating blood vessel formation; and possessing a variety of actions on neural tissues including modulating neurohormone release and blocking pain perception (see epoxyeicosatrienoic acid and epoxygenase).

In vitro studies on human and animal cells and tissues and in vivo animal model studies indicate that certain EDPs and EEQs (16,17-EDPs, 19,20-EDPs, 17,18-EEQs have been most often examined) have actions which often oppose those of another product of CYP450 enzymes (e.g. CYP4A1, CYP4A11, CYP4F2, CYP4F3A, and CYP4F3B) viz., 20-Hydroxyeicosatetraenoic acid (20-HETE), principally in the areas of blood pressure regulation, blood vessel thrombosis, and cancer growth (see 20-Hydroxyeicosatetraenoic acid, epoxyeicosatetraenoic acid, and epoxydocosapentaenoic acid sections on activities and clinical significance). Such studies also indicate that the eicosapentaenoic acids and EEQs are: 1) more potent than EETs in decreasing hypertension and pain perception; 2) more potent than or equal in potency to the EETs in suppressing inflammation; and 3) act oppositely from the EETs in that they inhibit angiogenesis, endothelial cell migration, endothelial cell proliferation, and the growth and metastasis of human breast and prostate cancer cell lines whereas EETs have stimulatory effects in each of these systems. Consumption of omega-3 fatty acid-rich diets dramatically raises the serum and tissue levels of EDPs and EEQs in animals as well as humans, and in humans is by far the most prominent change in the profile of polyunsaturated fatty acids metabolites caused by dietary omega-3 fatty acids.

CYP2C9 may also metabolize linoleic acid to the potentially very toxic products, coronaric acid (also termed leukotoxin) and vernolic acid (also termed isoleukotoxin); these linoleic acid epoxides cause multiple organ failure and acute respiratory distress in animal models and may contribute to these syndromes in humans.

Pharmacogenomics

The CYP2C9 gene is highly polymorphic. At least 20 single nucleotide polymorphisms (SNPs) have been reported to have functional evidence of altered enzyme activity. In fact, adverse drug reactions (ADRs) often result from unanticipated changes in CYP2C9 enzyme activity secondary to genetic polymorphisms. Especially for CYP2C9 substrates such as warfarin and phenytoin, diminished metabolic capacity because of genetic polymorphisms or drug-drug interactions can lead to toxicity at normal therapeutic doses. Information about how human genetic variation of CYP2C9 affects response to medications can be found in databases such PharmGKB, Clinical Pharmacogenetics Implementation Consortium (CPIC).

The label CYP2C91 is assigned by the Pharmacogene Variation Consortium (PharmVar) to the most commonly observed human gene variant. Other relevant variants are cataloged by PharmVar under consecutive numbers, which are written after an asterisk (star) character to form an allele label. The two most well-characterized variant alleles are CYP2C92 (NM_000771.3:c.430CT, p.Arg144Cys, rs1799853) and CYP2C9*3 (NM_000771.3:c.1075AC, p. Ile359Leu, rs1057910), causing reductions in enzyme activity of 30% and 80%, respectively.

Metabolizer phenotypes

On the basis of their ability to metabolize CYP2C9 substrates, individuals can be categorized by groups. The carriers of homozygous CYP2C9*1 variant, i.e. of the 1/1 genotype, are designated extensive metabolizers (EM), or normal metabolizers. The carriers of the CYP2C92 or CYP2C93 alleles in a heterozygous state, i.e. just one of these alleles (*1/*2, *1/*3) are designated intermediate metabolizers (IM), and those carrying two of these alleles, i.e. homozygous (*2/*3, *2/*2 or *3/*3) – poor metabolizers (PM). As a result, the metabolic ratio – the ratio of unchanged drug to metabolite – is higher in PMs.

A study of the ability to metabolize warfarin among the carriers of the most well-characterized CYP2C9 genotypes (*1, *2 and *3), expressed as a percentage of the mean dose in patients with wild-type alleles (*1/*1), concluded that the mean warfarin maintenance dose was 92% in *1/*2, 74% in *1/*3, 63% in *2/*3, 61% in *2/*2 and 34% in 3/*3.

CYP2C93 reflects an Ile359-Leu (I359L) change in the amino acid sequence, and also has reduced catalytic activity compared with the wild type (CYP2C91) for substrates other than warfarin. Its prevalence varies with race as:

Test panels of variant alleles

The Association for Molecular Pathology Pharmacogenomics (PGx) Working Group in 2019 has recommended a minimum panel of variant alleles (Tier 1) and an extended panel of variant alleles (Tier 2) to be included in assays for CYP2C9 testing.

CYP2C9 variant alleles recommended as Tier 1 by the PGx Working Group include CYP2C9 *2, *3, *5, *6, *8, and *11. This recommendation was based on their well-established functional effects on CYP2C9 activity and drug response availability of reference materials, and their appreciable allele frequencies in major ethnic groups.

The following CYP2C9 alleles are recommended for inclusion in tier 2: CYP2C9*12, *13, and *15.

CYP2C913 is defined by a missense variant in exon 2 (NM_000771.3:c.269TC, p. Leu90Pro, rs72558187). CYP2C913 prevalence is approximately 1% in the Asian population, but in Caucasians this variant prevalence is almost zero. This variant is caused by a T269C mutation in the CYP2C9 gene which in turn results in the substitution of leucine at position-90 with proline (L90P) at the product enzyme protein. This residue is near the access point for substrates and the L90P mutation causes lower affinity and hence slower metabolism of several drugs that are metabolized CYP2C9 by such as diclofenac and flurbiprofen. However, this variant is not included in the tier 1 recommendations of the PGx Working Group because of its very low multiethnic minor allele frequency and a lack of currently available reference materials. the evidence level for CYP2C9*13 in the PharmVar database is limited, comparing to the tier 1 alleles, for which the evidence level is definitive.

Additional variants

Not all clinically significant genetic variant alleles have been registered by PharmVar. For example, in a 2017 study, the variant rs2860905 showed stronger association with warfarin sensitivity (

Ligands

Most inhibitors of CYP2C9 are competitive inhibitors. Noncompetitive inhibitors of CYP2C9 include nifedipine, phenethyl isothiocyanate, medroxyprogesterone acetate and 6-hydroxyflavone. It was indicated that the noncompetitive binding site of 6-hydroxyflavone is the reported allosteric binding site of the CYP2C9 enzyme.

Following is a table of selected substrates, inducers and inhibitors of CYP2C9. Where classes of agents are listed, there may be exceptions within the class.

Inhibitors of CYP2C9 can be classified by their potency, such as:

• Strong being one that causes at least a 5-fold increase in the plasma AUC values, or more than 80% decrease in clearance.
• Moderate being one that causes at least a 2-fold increase in the plasma AUC values, or a 50–80% decrease in clearance.
• Weak being one that causes at least a 1.25-fold but less than 2-fold increase in the plasma AUC values, or 20–50% decrease in clearance.

Epoxygenase activity

CYP2C9 attacks various long-chain polyunsaturated fatty acids at their double (i.e. alkene) bonds to form epoxide products that act as signaling molecules. It along with CYP2C8, CYP2C19, CYP2J2, and possibly CYP2S1 are the principle enzymes which metabolizes 1) arachidonic acid to various epoxyeicosatrienoic acids (also termed EETs); 2) linoleic acid to 9,10-epoxy-octadecenoic acids (also termed coronaric acid, linoleic acid 9,10-oxide, or leukotoxin) and 12,13-epoxy-octadecenoic acids (also termed vernolic acid, linoleic acid 12,13-oxide, or isoleukotoxin); 3) docosahexaenoic acid to various epoxydocosapentaenoic acids (also termed EDPs); and 4) eicosapentaenoic acid to various epoxyeicosatetraenoic acids (also termed EEQs). Animal model studies implicate these epoxides in regulating: hypertension, myocardial infarction and other insults to the heart, the growth of various cancers, inflammation, blood vessel formation, and pain perception; limited studies suggest but have not proven that these epoxides may function similarly in humans (see Epoxyeicosatrienoic acid and Epoxygenase). Since the consumption of omega-3 fatty acid-rich diets dramatically raises the serum and tissue levels of the EDP and EEQ metabolites of the omega-3 fatty acid, i.e. docosahexaenoic and eicosapentaenoic acids, in animals and humans and in humans is the most prominent change in the profile of polyunsaturated fatty acids metabolites caused by dietary omega-3 fatty acids, eicosapentaenoic acids and EEQs may be responsible for at least some of the beneficial effects ascribed to dietary omega-3 fatty acids.

References

References

1. (April 1991). "Cloning and expression of complementary DNAs for multiple members of the human cytochrome P450IIC subfamily". Biochemistry.
2. (September 1994). "Fluorescence in situ hybridization analysis of chromosomal localization of three human cytochrome P450 2C genes (CYP2C8, 2C9, and 2C10) at 10q24.1". The Japanese Journal of Human Genetics.
3. (29 March 2021). "CYP2C9". National Center for Biotechnology Information, U.S. National Library of Medicine.
4. (2005). "Clinical and toxicological relevance of CYP2C9: drug-drug interactions and pharmacogenetics". Annual Review of Pharmacology and Toxicology.
5. (November 2011). "CYP-eicosanoids – a new link between omega-3 fatty acids and cardiac disease?". Prostaglandins & Other Lipid Mediators.
6. (October 2014). "The pharmacology of the cytochrome P450 epoxygenase/soluble epoxide hydrolase axis in the vasculature and cardiovascular disease". Pharmacological Reviews.
7. (January 2014). "Stabilized epoxygenated fatty acids regulate inflammation, pain, angiogenesis and cancer". Progress in Lipid Research.
8. (May 2016). "Soluble epoxide hydrolase: A potential target for metabolic diseases". Journal of Diabetes.
9. (October 2014). "The role of long chain fatty acids and their epoxide metabolites in nociceptive signaling". Prostaglandins & Other Lipid Mediators.
10. (June 2014). "Dietary omega-3 fatty acids modulate the eicosanoid profile in man primarily via the CYP-epoxygenase pathway". Journal of Lipid Research.
11. (September 2019). "Recommendations for Clinical CYP2C9 Genotyping Allele Selection: A Joint Recommendation of the Association for Molecular Pathology and College of American Pathologists". The Journal of Molecular Diagnostics.
12. (2006). "Interethnic and intraethnic variability of CYP2C8 and CYP2C9 polymorphisms in healthy individuals". Molecular Diagnosis & Therapy.
13. (Jan 2007). "The pharmacogenetics of CYP2C9 and CYP2C19: ethnic variation and clinical significance". Current Clinical Pharmacology.
14. "PharmGKB".
15. "CYP2C9 CPIC guidelines".
16. (November 2019). "Structural variation at the CYP2C locus: Characterization of deletion and duplication alleles". Human Mutation.
17. (June 2020). "PharmVar GeneFocus: CYP2C19". Clinical Pharmacology and Therapeutics.
18. (August 1996). "The role of the CYP2C9-Leu359 allelic variant in the tolbutamide polymorphism". Pharmacogenetics.
19. (2018). "Pharmacogenetics". Academic Press.
20. (November 2014). "Clinical pharmacogenetics implementation consortium guidelines for CYP2C9 and HLA-B genotypes and phenytoin dosing". Clinical Pharmacology and Therapeutics.
21. (2017). "SLCO1B1 gene-polymorphism frequency in Russian and Nanai populations". Pharmacogenomics and Personalized Medicine.
22. (January 2004). "Association between the CYP2C9 polymorphism and the drug metabolism phenotype". Clinical Chemistry and Laboratory Medicine.
23. "CYP2C9 allele nomenclature".
24. (November 2010). "International Conference on Computational Systems – Biology and Bioinformatics". Springer.
25. "rs72558187 allele frequency". National Center for Biotechnology Information.
26. "PharmVar".
27. (2017). "Warfarin Anticoagulation Therapy in Caribbean Hispanics of Puerto Rico: A Candidate Gene Association Study". Frontiers in Pharmacology.
28. (March 2009). "A genome-wide association study confirms VKORC1, CYP2C9, and CYP4F2 as principal genetic determinants of warfarin dose". PLOS Genetics.
29. "PharmGKB".
30. (June 2015). "Novel single nucleotide polymorphism in CYP2C9 is associated with changes in warfarin clearance and CYP2C9 expression levels in African Americans". Translational Research.
31. (August 2014). "Relationship between the CYP2C9 IVS8-109A>T polymorphism and high losartan hydroxylation in healthy Ecuadorian volunteers". Pharmacogenomics.
32. (July 2012). "Search for the molecular basis of ultra-rapid CYP2C9-catalysed metabolism: relationship between SNP IVS8-109A>T and the losartan metabolism phenotype in Swedes". European Journal of Clinical Pharmacology.
33. (February 1999). "Role of cytochrome P-4502C9 in irbesartan oxidation by human liver microsomes". Drug Metabolism and Disposition.
34. (February 2004). "Inhibitory effects of the monoamine oxidase inhibitor tranylcypromine on the cytochrome P450 enzymes CYP2C19, CYP2C9, and CYP2D6". Cellular and Molecular Neurobiology.
35. (August 2001). "Inhibition and inactivation of human cytochrome P450 isoforms by phenethyl isothiocyanate". Drug Metabolism and Disposition.
36. (July 2006). "Inhibitory effect of medroxyprogesterone acetate on human liver cytochrome P450 enzymes". European Journal of Clinical Pharmacology.
37. (March 2009). "Mechanism of CYP2C9 inhibition by flavones and flavonols". Drug Metabolism and Disposition.
38. (2007). "Drug Interactions: Cytochrome P450 Drug Interaction Table". [[Indiana University School of Medicine]].
39. "Drug Development and Drug Interactions: Table of Substrates, Inhibitors and Inducers".
40. (2013). "In silico metabolism studies of dietary flavonoids by CYP1A2 and CYP2C9". Food Research International.
41. (June 2005). "Role of CYP2C9 and its variants (CYP2C93 and CYP2C913) in the metabolism of lornoxicam in humans". Drug Metabolism and Disposition.
42. "ketoprofen | C16H14O3". PubChem.
43. (October 2005). "CYP2C-catalyzed delta9-tetrahydrocannabinol metabolism: kinetics, pharmacogenetics and interaction with phenytoin". Biochemical Pharmacology.
44. (April 2018). "Altered metabolism of synthetic cannabinoid JWH-018 by human cytochrome P450 2C9 and variants". Biochemical and Biophysical Research Communications.
45. (February 2014). "Exogenous cannabinoids as substrates, inhibitors, and inducers of human drug metabolizing enzymes: a systematic review". Drug Metabolism Reviews.
46. (May 2002). "Metabolism of (+)- and (-)-limonenes to respective carveols and perillyl alcohols by CYP2C9 and CYP2C19 in human liver microsomes". Drug Metabolism and Disposition.
47. (October 2001). "Effects of CYP3A4 inhibition by diltiazem on pharmacokinetics and dynamics of diazepam in relation to CYP2C19 genotype status". Drug Metabolism and Disposition.
48. (December 2013). "Stereoselective inhibition of CYP2C19 and CYP3A4 by fluoxetine and its metabolite: implications for risk assessment of multiple time-dependent inhibitor systems". American Society for Pharmacology & Experimental Therapeutics (ASPET).
49. "Verapamil: Drug information. Lexicomp".
50. (27 June 2017). "Candesartan Tablet".
51. (25 January 2018). "Edarbi – azilsartan kamedoxomil tablet".
52. (Jan 2010). "Inhibitory effects of polyphenols on human cytochrome P450 3A4 and 2C9 activity". Food and Chemical Toxicology.
53. (October 2005). "Amentoflavone and its derivatives as novel natural inhibitors of human Cathepsin B". Bioorganic & Medicinal Chemistry.
54. "Facts for prescribers (Fakta för förskrivare)". Swedish environmental classification of pharmaceuticals.
55. (26 May 2021). "Drug Development and Drug Interactions: Table of Substrates, Inhibitors and Inducers". FDA.
56. (May 2015). "Metronidazole reduces the expression of cytochrome P450 enzymes in HepaRG cells and cryopreserved human hepatocytes". Xenobiotica; the Fate of Foreign Compounds in Biological Systems.
57. (October 2010). "Potential CYP2C9-mediated drug-drug interactions in hospitalized type 2 diabetes mellitus patients treated with the sulphonylureas glibenclamide, glimepiride or glipizide". Journal of Internal Medicine.
58. (February 2002). "Inhibitory effects of H1-antihistamines on CYP2D6- and CYP2C9-mediated drug metabolic reactions in human liver microsomes". European Journal of Clinical Pharmacology.
59. (February 2024). "Bergaptol, a Major Furocoumarin in Citrus: Pharmacological Properties and Toxicity". Molecules.
60. (November 2003). "Chloramphenicol is a potent inhibitor of cytochrome P450 isoforms CYP2C19 and CYP3A4 in human liver microsomes". Antimicrobial Agents and Chemotherapy.
61. (June 2000). "In vitro inhibition and induction of human hepatic cytochrome P450 enzymes by modafinil". Drug Metabolism and Disposition.
62. (1 January 2012). "Comparison in the in vitro inhibitory effects of major phytocannabinoids and polycyclic aromatic hydrocarbons contained in marijuana smoke on cytochrome P450 2C9 activity". Drug Metabolism and Pharmacokinetics.
63. (December 2018). "Food Bioactive Compounds and Their Interference in Drug Pharmacokinetic/Pharmacodynamic Profiles". Pharmaceutics.
64. (September 2020). "Resveratrol stereoselectively affected (±)warfarin pharmacokinetics and enhanced the anticoagulation effect". Scientific Reports.
65. (April 2015). "Cytochrome P450 epoxygenase pathway of polyunsaturated fatty acid metabolism". Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids.