Genetic Variation In CYP2C9 Research Articles

Evidence for sex differences in the impact of cytochrome P450 genotypes on early subjective effects of cannabis

Early positive subjective effects of cannabis predict the development of cannabis use disorder (CUD). Genetic factors, such as the presence of cytochrome P450 genetic variants that are associated with reduced Δ9-tetrahydrocannabinol (THC) metabolism, may contribute to individual differences in subjective effects of cannabis. Young adults (N = 54) with CUD or a non-CUD substance use disorder (control) provided a blood sample for DNA analysis and self-reported their early (i.e., effects upon initial uses) and past-year positive and negative subjective cannabis effects. Participants were classified as slow metabolizers if they had at least one CYP2C9 or CYP3A4 allele associated with reduced activity. Though the CUD group and control group did not differ in terms of metabolizer status, slow metabolizer status was more prevalent among females in the CUD group than females in the control group. Slow metabolizers reported greater past year negative THC effects compared to normal metabolizers; however, slow metabolizer status did not predict early subjective cannabis effects (positive or negative) or past year positive effects. Post-hoc analyses suggested males who were slow metabolizers reported more negative early subjective effects of cannabis than female slow metabolizers. Other sex-by-genotype interactions were not significant. These initial findings suggest that genetic variation in CYP2C9 and CYP3A4 may have sex-specific associations with cannabis-related outcomes. Slow metabolizer genes may serve as a risk factor for CUD for females independent of subjective effects. Male slow metabolizers may instead be particularly susceptible to the negative subjective effects of cannabis.

Effects of pharmacogenetic profiles on pediatric pain relief and adverse events with ibuprofen and oxycodone.

Individual genetic variation may influence clinical effects for pain medications. Effects of CYP2C9, CYP3A4, and CYP2D6 polymorphisms on clinical effectiveness and safety for ibuprofen and oxycodone were studied. Primary objectives were to AU2 evaluate if allelic variations would affect clinical effectiveness and adverse events (AEs) occurrence. This pragmatic prospective, observational cohort included children aged 4 to 16 years who were seen in a pediatric emergency department with an acute fracture and prescribed ibuprofen or oxycodone for at-home pain management. Saliva samples were obtained for genotyping of allelic variants, and daily telephone follow-up was conducted for 3 days. Pain was measured using the Faces Pain Scale-Revised. We included 210 children (n = 140 ibuprofen and n = 70 oxycodone); mean age was 11.1 (±SD 3.5) years, 33.8% were female. Median pain reduction on day 1 was similar between groups [ibuprofen 4 (IQR 2,4) and oxycodone 4 (IQR 2,6), P = 0.69]. Over the 3 days, the oxycodone group experienced more AE than the ibuprofen group (78.3% vs 53.2%, P < 0.001). Those with a CYP2C9*2 reduced function allele experienced less adverse events with ibuprofen compared with those with a normal functioning allele CYP2C9*1 (P = 0.003). Neither CYP3A4 variants nor CYP2D6 phenotype classification affected clinical effect or AE. Although pain relief was similar, children receiving oxycodone experienced more AE, overall, than those receiving ibuprofen. For children receiving ibuprofen or oxycodone, pain relief was not affected by genetic variations in CYP2C9 or CYP3A4/CYP2D6, respectively. For children receiving ibuprofen, the presence of CYP2C9*2 was associated with less adverse events.

Effect of CYP2C9 rs2860905 Polymorphism on the Efficacy of Losartan in Pakistani Hypertensive Patients

Hypertension is a multifactorial disease characterized by high blood pressure in blood vessels. It is caused by the dysregulation of renin angiotensin aldosterone system (RAAS). It is a major risk factor for other metabolic diseases including cardiovascular diseases, diabetes, and others. Various RAAS targeting drugs such as losartan are prescribed as the first line therapy to treat hypertension. However, their efficacy varies among individuals owing to genetic variations in drug binding substrates or drug metabolizing enzymes, which convert the prodrug to active drug. CYP2C9 gene encodes for an enzyme which metabolizes losartan. Various studies have concluded that genetic variations in CYP2C9 affect the response of losartan due to the variation in its metabolism. Thus, the current study aimed to check the effect of CYP2C9 rs2860905 G&gt;A polymorphism on the efficacy of losartan. For this purpose, a total of 48 subjects were selected and genotyped for rs2860905 polymorphism using in-house developed tetra-ARMS-PCR. The subjects were divided into responding (n=34) and non-responding (n=14) groups on the basis of their blood pressure after treatment with losartan. Statistical analysis demonstrated that rs2860905 GG genotype was more prevalent in the responding group as compared to the non-responding group (50% vs. 36%). Multinomial regression analysis showed that the carriers of GA or AA genotype did not respond to losartan treatment efficiently as compared to those of GG genotype. However, these results could not achieve statistical significance. To conclude, CYP2C9 rs2860905 G&gt;A polymorphism does not affect the efficacy of losartan in Pakistani hypertensive subjects.

Profiling of warfarin pharmacokinetics‐associated genetic variants: Black Africans portray unique genetic markers important for an African specific warfarin pharmacogenetics‐dosing algorithm

BackgroundWarfarin dose variability observed in patients is attributed to variation in genes involved in the warfarin metabolic pathway. Genetic variation in CYP2C9 and VKORC1 has been the traditional focus in evaluating warfarin dose variability, with little focus on other genes. ObjectiveWe set out to evaluate 27 single nucleotide polymorphisms (SNPs) in the CYP2C cluster loci and 8 genes (VKORC1, ABCB1, CYP2C9, CYP2C19, CYP2C8, CYP1A2, CYP3A4, and CYP3A5) involved in pharmacokinetics of warfarin. Patients/Methods503 participants were recruited among black Africans and Mixed Ancestry population groups, from South Africa and Zimbabwe, and a blood sample taken for DNA. Clinical parameters were obtained from patient medical records, and these were correlated with genetic variation. ResultsAmong black Africans, the SNPs CYP2C rs12777823G>A, CYP2C9 c.449G>A (*8), CYP2C9 c.1003C>T (*11) and CYP2C8 c.805A>T (*2) were significantly associated with warfarin maintenance dose. Conversely, CYP2C9 c.430C>T (*2), CYP2C8 c.792C>G (*4) and VKORC1 g.‐1639G>A were significantly associated with maintenance dose among the Mixed Ancestry. The presence of CYP2C8*2 and CYP3A5*6 alleles was associated with increased mean warfarin maintenance dose, whereas CYP2C9*8 allele was associated with reduced warfarin maintenance dose. ConclusionAfrican populations present with a diversity of variants that are important in predicting pharmacogenetics‐based warfarin dosing in addition to those reported in CYP2C9 and VKORC1. It is therefore important, to include African populations in pharmacogenomics studies to be able to identify all possible biomarkers that are potential predictors for drug response.

Structure of Cytochrome P450 2C9*2 in Complex with Losartan: Insights into the Effect of Genetic Polymorphism.

The human CYP2C9 plays a crucial role in the metabolic clearance of a wide range of clinical therapeutics. The *2 allele is a prevalent genetic variation in CYP2C9 that is found in various populations. A marked reduction of catalytic activity toward many important drug substrates has been demonstrated by CYP2C9*2, which represents an amino acid variation at position 144 from arginine to cysteine. The crystal structure of CYP2C9*2 in complex with an antihypertensive drug losartan was solved using X-ray crystallography at 3.1-Å resolution. The Arg144Cys variation in the *2 complex disrupts the hydrogen-bonding interactions that were observed between the side chain of arginine and neighboring residues in the losartan complex of CYP2C9 and the wild-type (WT) ligand-free structure. The conformation of several secondary structural elements is affected, thereby altering the binding and orientation of drug and important amino acid side chains in the distal active site cavity. The new structure revealed distinct interactions of losartan in the compact active site of CYP2C9*2 and differed in occupancy at the other binding sites previously identified in the WT-losartan complex. Furthermore, the binding studies in solution using losartan illustrated lower activity of the CYP2C9*2 compared with the WT. Together, the findings yield valuable insights into the decreased hydroxylation activity of losartan in patients carrying CYP2C9*2 allele and provide a useful framework to investigate the effect of a single-nucleotide polymorphism that leads to altered metabolism of diverse drug substrates. SIGNIFICANCE STATEMENT: The *2 allele of the human drug-metabolizing enzyme CYP2C9 is found in different populations and results in significantly reduced activity toward various drug substrates. How the CYP2C9*2 variant induces altered drug metabolism is poorly understood given that the Arg144Cys variation is located far away from the active site. This work yield insight into the effect of distal variation using multitude of techniques that include X-ray crystallography, isothermal titration calorimetry, enzymatic characterization, and computational studies.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2C9 and HLA-B Genotypes and Phenytoin Dosing: 2020 Update.

Phenytoin is an antiepileptic drug with a narrow therapeutic index and large interpatient pharmacokinetic variability, partly due to genetic variation in CYP2C9. Furthermore, the variant allele HLA-B*15:02 is associated with an increased risk of Stevens-Johnson syndrome and toxic epidermal necrolysis in response to phenytoin treatment. We summarize evidence from the published literature supporting these associations and provide therapeutic recommendations for the use of phenytoin based on CYP2C9 and/or HLA-B genotypes (updates on cpicpgx.org).

Insights into the Effect of Genetic Variation in CYP2C9 (*11) on Drug Binding.

Cytochrome P450s (CYP) are a family of membrane associated heme‐containing enzymes involved in xenobiotic metabolism with recent relevance in pharmacogenomics. The human CYP2C9 enzyme metabolizes up to 15–20% of drugs that include warfarin, losartan, ibuprofen, and tolbutamide. It is highly polymorphic with several genetic variations associated with significantly altered activity of the enzyme. The CYP2C9*11 allele occurs predominantly in African Americans but also in Caucasian and other ethnic populations with a frequency of around 0.05. The *11 genetic variation represents a substitution of amino acid residue at 335 from arginine to tryptophan (R335W) that has demonstrated decreased catalytic activity towards various substrates including S‐warfarin. The R335W was created in CYP2C9 wild‐type (WT) construct using site‐directed mutagenesis and co‐expressed in E. Coli alongside chaperone proteins (GroEL/ES). Generation of purified CYP2C9*11 protein enabled catalytic studies and crystallization in complex with the drug substrate losartan. The enzymatic assays revealed marked reduction in losartan turn‐over by CYP2C9*11 compared to the WT enzyme. Additionally, comparison of the amino acid sequence revealed that R335 is conserved across the CYP2C subfamily of enzymes. The R335 is located on the distal J‐J’ loop and interacts with multiple amino acid side chains on the J and J’ helices. The computational analysis suggests that the substitution with hydrophobic and bulkier tryptophan located on the surface region may result in destabilizing interactions with several helices including those located near the active site heme, affecting protein stability and function. Overall, these observations establish the effect of distal variation prompting further evaluation by structural and biophysical studies.Support or Funding InformationThe research was funded by the start‐up funds from the Albany College of Pharmacy and Health Sciences.

Crystal Structure of CYP2C9*2 Genetic Variant in Complex with an Angiotensin II Receptor Blocker Drug Losartan

Cytochrome P450 (CYP)‐dependent monooxygenases are a superfamily of heme‐containing enzymes involved in the metabolism of various xenobiotics. The drug metabolizing CYP2C9 enzyme metabolizes up to 20% of the clinical drugs that include losartan, warfarin, ibuprofen, tolbutamide, and glimepiride. The CYP2C9*2 and *3 are the two prevalent genetic variants that demonstrate significant reduction of the catalytic activity compared to the wild‐type (WT) enzyme for many important CYP2C9 substrates. Despite the abundant structural information available regarding various CYPs, the structural information about the effect of genetic polymorphisms on drug binding has remained scant. The CYP2C9*2 variant represents an amino acid change from arginine to cysteine at position 144, also referred to as R144C. To understand how genetic variation in CYP2C9 affects drug binding and oxidation, we solved the crystal structure of CYP2C9*2 in complex with the antihypertensive drug losartan using X‐ray crystallography. The prodrug losartan is an angiotensin II receptor antagonist that is predominantly metabolized by CYP2C9 and CYP3A4. The overall structure of the CYP2C9*2‐losartan complex illustrate remarkable differences compared to the WT complex. These include altered conformation of important secondary structural elements and residue side chains previously shown to be responsible for binding interactions with different substrates. Furthermore, the new structure revealed significant changes in binding of losartan compared to the previously solved losartan complexes of the CYP2C9 WT, *3 and *30. The structure highlights how single nucleotide polymorphism affects drug binding and yield insights into altered metabolism. Overall, the structural complex provides a useful framework to study, computationally as well as biophysically, the binding of different substrates to genetic variants of CYP2C9 and understand the effect of amino acid substitution in decreased hydroxylation activity of the enzyme.Support or Funding InformationThe authors are grateful to Albany College of Pharmacy and Health Sciences for funding.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of age and genetic variations in VKORC1, CYP2C9 and CYP3A4 on the phenprocoumon dose in pediatric patients.

To study the effects of clinical and genetic factors on the phenprocoumon dose requirement in pediatric patients and to develop a dosing algorithm. Pediatric patients who used phenprocoumon were invited to participate in a retrospective follow-up study. Clinical information and genotypes of genetic variations in CYP2C9, VKORC1, CYP4F2, CYP2C18 and CYP3A4 were collected and tested with linear regression for association with phenprocoumon dose requirement. Of the 41 patients included in the analysis, age, VKORC1, CYP2C9*2/*3 and CYP3A4*1B were statistically significantly associated with dose requirement, and together explained 80.4% of the variability in phenprocoumon dose requirement. Our study reveals that age and genetic variations explain a significant part of the variability in phenprocoumon dose requirement in pediatric patients.

Polymorphic analysis of CYP2C9 gene in Vietnamese population.

Genetic variations in CYP2C9 are associated to inter-individual variability of drugs metabolism and response. The only report has been done previously mainly focusing on the common variant alleles of CYP2C9 in Vietnamese Kinh subjects. However, little is known about the complete spectrum of this gene polymorphism in different ethnic groups of Vietnam. We sequenced the promoter region and all exons of CYP2C9 in 100 healthy unrelated Vietnamese Kinh subjects. Additionally, common CYP2C9 variants, *2 and *3, were also analyzed by RFLP-PCR in extra 194 Kinh subjects and 279 of other four ethnic groups in Vietnam. The results of these common variants observed from five ethnic groups were compared with other populations in the world. Seven previously reported alleles and two genotypes were determined in Kinh subjects. The percentage of CYP2C9*1 and CYP2C9*3 alleles are 96.5 and 3.5%, respectively. We found one novel non-synonymous variant in exon 7 leading to amino acid change at 363 position from proline to histidine. Functional analysis by SIFT and Polyphen-2 indicated that this mutation is intolerant and probably damaging. Prevalence of CYP2C9*2 observed in Vietnamese population was significantly lower compared with that of other populations in the South and West of Asia as well as in Europe. This study provides information of genetic distribution pattern of CYP2C9 in Vietnamese, which would be useful for optimizing drug therapies in Vietnam.

Putting pharmacogenomics into practice

Putting pharmacogenomics into practice

Prediction of Warfarin Dose: Why, When and How?

Prediction models are the key to individualized drug therapy. Warfarin is a typical example of where pharmacogenetics could help the individual patient by modeling the dose, based on clinical factors and genetic variation in CYP2C9 and VKORC1. Clinical studies aiming to show whether pharmacogenetic warfarin dose predictions are superior to conventional initiation of warfarin are now underway. This review provides a broad view over the field of warfarin pharmacogenetics from basic knowledge about the drug, how it is monitored, factors affecting dose requirement, prediction models in general and different types of prediction models for warfarin dosing.

Pharmacogenomics: a key component of personalized therapy

Pharmacogenomics: a key component of personalized therapy

CYP2C9 genotype does not affect risk of tobacco-related cancer in the general population

Background: CYP2C9 enzymes are important in the metabolism of procarcinogenic chemicals such as polycyclic aromatic hydrocarbons (PAHs) found in tobacco smoke. Two functional variants in the CYP2C9 gene (CYP2C9*2 and CYP2C9*3) are known to be associated with decreased enzyme activity towards tolbutamide and warfarin, while this has not been investigated for PAHs. We hypothesised that these two variants in the CYP2C9 gene influence risk of tobacco-related cancer. Methods: In a prospective study of the general population ( n = 10 392) with 60 years of follow-up, the Copenhagen City Heart Study, we associated two variants of CYP2C9 (CYP2C9*2 and CYP2C9*3) with risk of tobacco-related cancer and all cancer. All results were re-tested in a cross-sectional study of the general population ( n = 36 856), the Copenhagen General Population Study. Results: We found no association between any of the CYP2C9 genotypes and risk of tobacco-related cancer, individual tobacco-related cancers, or all cancer. For the combined carriers (any CYP2C9*2 or CYP2C9*3 heterozygotes or homozygotes) vs. non-carriers we had 90% statistical power to exclude measures of relative risks below/above 0.8/1.2 and 0.9/1.1 in the Copenhagen City Heart Study and below/above 0.8/1.3 and 0.9/1.1 in the Copenhagen General Population Study for tobacco-related cancer and all cancer, respectively. Conclusion: Genetic variations in CYP2C9 do not affect risk of tobacco-related cancers.

A Multiplex Assay for Detecting Genetic Variations in CYP2C9, VKORC1, and GGCX Involved in Warfarin Metabolism

A Multiplex Assay for Detecting Genetic Variations in CYP2C9, VKORC1, and GGCX Involved in Warfarin Metabolism

A Multiplex Assay for Detecting Genetic Variations in CYP2C9, VKORC1, and GGCX Involved in Warfarin Metabolism

Patients differ in responses to warfarin, which is commonly prescribed to treat thromboembolic events. Genetic variations in the cytochrome P450, family 2, subfamily C, polypeptide 9 (CYP2C9), vitamin K epoxide reductase complex, subunit 1 (VKORC1), and gamma-glutamyl carboxylase (GGCX) genes have been shown to contribute to impaired metabolism of warfarin. We designed a custom multiplex single-nucleotide polymorphism (SNP) panel to interrogate the CYP2C9 *2, *3, VKORC1 (-1639G-->A), and GGCX (1181T-->G) alleles simultaneously in a single sample by use of single-base extension and capillary electrophoresis after genomic DNA extraction and PCR amplification. Our assay successfully detected various genotypes from known controls and 24 unknown samples. It was found to be 100% concordant with sequencing results. Our multiplexed SNP panel can be successfully used in genotyping of patient blood samples. Results can be combined with other clinical parameters in an algorithm for warfarin dosing. These data provide a proof-in-principle of multiplexed SNP analysis using rapid single-base extension and capillary electrophoresis, and warrant additional validation using a larger cohort of patient samples.

Personalizing Health Care—Is This the Right Time for Warfarin?

Personalizing Health Care—Is This the Right Time for Warfarin?

臨床応用可能なＰＧｘ ３．ＷａｒｆａｒｉｎとＣＹＰ２Ｃ９，ＶＫＯＲＣ１遺伝子多型

Warfarin is the mainstay of anticoagulation therapy, worldwide. Its clinical use, however, is complicated by the fact that it has a narrow therapeutic index with potential bleeding complications. The dosage requirement of warfarin to produce therapeutic anticoagulation varies widely among patients. Recently genetic factors such as the CYP2C9 and VKORC1 genes have been demonstrated to be determinants of warfarin response. CYP2C9 is the enzyme primarily responsible for the metabolic clearance of the S-enantiomer of warfarin. VKOR is the target protein of warfarin which recycles the reduced form of vitamin K, an essential cofactor in the formation of the vitamin K-dependent clotting factors. There is strong evidence to support an association between these genetic variants and therapeutic doses of warfarin. On the basis of these observations, the Food and Drug Administration (FDA) approved a labeling change for warfarin that includes the genetic information of VKORC1 and CYP2C9 as factors influencing inter-individual variability in warfarin dosing. The package insert as of August 2007 states that “lower initiation doses should be considered for patients with certain genetic variations in CYP2C9 and VKORC1 enzymes.” The FDA also approved clinical tests for these genetic variants. However, at present, a validated dosing algorithm, evidence of the clinical utility of genotyping and a reliable economic analysis are not availabie to recommend routine CYP2C9 and VKORC1 testing in every patient before the initiation of warfarin. The results of several randomized prospective controlled trials conducted to test the impact of genotype-guided warfarin dosing in Caucasian and Asian patients are shown in this review.

The use of mechanistic DM‐PK‐PD modelling to assess the power of pharmacogenetic studies –CYP2C9 and warfarin as an example

To assess the power of in vivo studies needed to discern the effect of genotype on pharmacokinetics (PK) and pharmacodynamics (PD) using CYP2C9 and (S)-warfarin as an example. Information on the in vitro metabolism of (S)-warfarin and genetic variation in CYP2C9 was incorporated into a mechanistic population-based PK-PD model. The influence of study design on the ability to detect significant differences in PK (AUC(0-12 h)) and PD (AUEC(0-12 h) INR) between CYP2C9 genotypes was investigated. A study size of 90 (based on the natural abundance of genotypes and uniform dosage) was required to achieve 80% power to discriminate the PK of (S)-warfarin between wild type (*1/*1) and the combination of all other genotypes. About 250 subjects were needed to detect a difference in anticoagulant response. The power to detect differences between specific genotypes was much lower. Analysis of experimental comparisons of the PK or PD between wild-type and other individual genotypes indicated that only 21% of cases (20 of 95 comparisons within 11 PD and four PK-PD studies) reported statistically significant differences. This was similar to the percentage expected from our simulations (20%, chi(2) test, P = 0.80). Simulations of studies enriched with specific genotypes indicated that only three and five subjects were required to detect differences in PK and PD between wild type and the *3/*3 genotype, respectively. The utilization of prior information (including in vivo enzymology) in clinical trial simulations can guide the design of subsequent in vivo studies of the impact of genetic polymorphisms, and may help to avoid costly, inconclusive outcomes.