Wild-type CYP2C9 Research Articles

Modeled Hepatic/Plasma Exposures of Fluvastatin Prescribed Alone in Subjects with Impaired Cytochrome P450 2C9*3 as One of Possible Determinant Factors Likely Associated with Hepatic Toxicity Reported in a Japanese Adverse Event Database.

Fluvastatin is a 3-hydroxy-3-methylglutaryl CoA reductase inhibitor that competitively inhibits human cytochrome P450 (P450) 2C9 in vitro. Drug interactions between a variety of P450 2C9 substrates/inhibitors and fluvastatin can increase the incidence of fluvastatin-related hepatic or skeletal muscle toxicity in vivo. In this survey, the prescribed dosage of fluvastatin was reduced or discontinued in 133 of 164 patients receiving fluvastatin alone, as recorded in the Japanese Adverse Drug Event Report database of spontaneously reported events. The median days to onset of fluvastatin-related disorders were in the range 30-35 d in the 87 patients. Therefore, we aimed to focus on fluvastatin and, using the pharmacokinetic modeling technique, estimated the virtual plasma and hepatic exposures in subjects harboring the impaired CYP2C9*3 allele. The plasma concentrations of fluvastatin modeled after a virtual oral 20-mg dose increased in homozygotes with CYP2C9*3; the area under the plasma concentration curve was 4.9-fold higher than that in Japanese homozygotes for wild-type CYP2C9*1. The modeled hepatic concentrations of fluvastatin in patients with CYP2C9*3/*3 after virtual daily 20-mg doses for 7 d were 31-fold higher than those in subjects with CYP2C9*1/*1. However, heterozygous Chinese patients with CYP2C9*1/*3 reportedly have a limited elevation (1.2-fold) in plasma maximum concentrations. Virtual hepatic/plasma exposures in subjects harboring the impaired CYP2C9*3 allele estimated using pharmacokinetic modeling indicate that such exposure could be a causal factor for hepatic disorders induced by fluvastatin prescribed alone in a manner similar to that for interactions with a variety of co-administered drugs.

Metabolism of testosterone and progesterone by cytochrome P450 2C19 allelic variants.

CYP2C19 is a member of the human microsomal cytochrome P450 (CYP). Significant variation in CYP2C19 levels and activity can be attributed to polymorphisms in this gene. Wildtype CYP2C19 and 13 mutants (CYP2C19.1B, CYP2C19.5A, CYP2C19.5B, CYP2C19.6, CYP2C19.8, CYP2C19.9, CYP2C19.10, CYP2C19.11, CYP2C19.13, CYP2C19.16, CYP2C19.19, CYP2C19.23, CYP2C19.30, and CYP2C19.33) were coexpressed with NADPH-cytochrome P450 reductase in Escherichia coli. Hydroxylase activity toward testosterone and progesterone was also examined. Ten CYP2C19 variants showed Soret peaks (450nm) typical of P450 in the reduced CO-difference spectra. CYP2C19.11 and CYP2C19.23 showed higher testosterone 11α, 16α-/17- and progesterone 6β-,21-,16α-/17α-hydroxylase activities than CYP2C19.1B. CYP2C19.6, CYP2C19.16, CYP2C19.19, and CYP2C19.30 showed lower activity than CYP2C19.1B. CYP2C19.9, CYP2C19.10. CYP2C19.13, and CYP2C19.33 showed different hydroxylation activities than CYP2C19.1B. These results indicated that CYP2C19 variants have very different substrate specificities for testosterone and progesterone.

PREDICTION OF THE EFFECT OF SINGLE NUCLEOTIDE POLYMORPHISMS (SNPS) IN THE CYP2C9 ON WARFARIN METABOLISM BY IN SILICO STUDY

Objective: This study aimed to predict the effect of SNPs CYP2C9 s on the metabolic activity of S-warfarin in the body.
 Methods: Molecular modeling was performed to obtain SNPs CYP2C9 and molecular docking was performed to predict the effect of SNPs CYP2C9 on the metabolic activity of S-warfarin.
 Results: The results showed that wild-type CYP2C9 had the strongest binding affinity (∆G: -9.76 kcal/mol), indicating that wild-type CYP2C9 had the best metabolic activity compared to SNPs CYP2C9. There was a decrease in hydrogen bond formation in SNPs CYP2C9 and an increase in the distance between C7 S-warfarin and Fe-Heme in CYP2C9 SNPs when compared to wild-type CYP2C9
 Conclusion: The decrease in binding affinity, decrease in hydrogen bond formation, and an increase in the distance between C7 S-warfarin and Fe-Heme on SNPs CYP2C9 indicated that SNPs CYP2C9 had decreased metabolic activity against S-warfarin which led to an increased risk of bleeding.

Identification and drug metabolic characterization of four new CYP2C9 variants CYP2C9*72-*75 in the Chinese Han population.

Cytochrome 2C9 (CYP2C9), one of the most important drug metabolic enzymes in the human hepatic P450 superfamily, is required for the metabolism of 15% of clinical drugs. Similar to other CYP2C family members, CYP2C9 gene has a high genetic polymorphism which can cause significant racial and inter-individual differences in drug metabolic activity. To better understand the genetic distribution pattern of CYP2C9 in the Chinese Han population, 931 individuals were recruited and used for the genotyping in this study. As a result, seven synonymous and 14 non-synonymous variations were identified, of which 4 missense variants were designated as new alleles CYP2C9*72, *73, *74 and *75, resulting in the amino acid substitutions of A149V, R150C, Q214H and N418T, respectively. When expressed in insect cell microsomes, all four variants exhibited comparable protein expression levels to that of the wild-type CYP2C9 enzyme. However, drug metabolic activity analysis revealed that these variants exhibited significantly decreased catalytic activities toward three CYP2C9 specific probe drugs, as compared with that of the wild-type enzyme. These data indicate that the amino acid substitution in newly designated variants can cause reduced function of the enzyme and its clinical significance still needs further investigation in the future.

Impact of <i>CYP2C19</i> gene polymorphisms on clinical outcomes in patients with myocardial infarction during 12-month follow-up

Highlights. CYP2C19 gene polymorphisms in patients with acute myocardial infarction are common in clinical practice. The article assesses the role of genetic predisposition in the development of ischemic and hemorrhagic events during dual antiplatelet therapy (aspirin and clopidogrel) within the first 12 months after revascularization for acute myocardial infarction.Aim. To evaluate the impact of CYP2C19 gene *1, *2, *3, *17 alleles polymorphism on 12-month clinical outcomes in patients who underwent coronary revascularization due to acute myocardial infarction and took clopidogrel.Methods. 363 patients with acute myocardial infarction undergoing percutaneous coronary intervention were enrolled in the prospectively study in 2010–2012. CYP2C19 gene *1, *2, *3, *17 alleles polymorphism analysis was performed in all study participants. Dual antiplatelet therapy, consisting of aspirin and clopidogrel, was prescribed for 12 months. The follow-up period was 12 months, the incidence of cardiovascular death, non-fatal myocardial infarction, stroke and bleeding was assessed.Results. 12 months after inclusion in the study, the incidence of composite endpoint (defined as cardiovascular death, non-fatal myocardial infarction and stroke) was observed in 18 patients (7% [5%; 11%]; 95% CI) with wild-type CYP2C19 gene and in 12 patients (11% [6%; 18%]; 95% CI) with lost-of-function *2+*3 alleles, with no statistical difference (OR = 1.6 [0.7; 3.6], 95% CI; p = 0.301). Presence of any LOF-alleles did not predict composite endpoint events (OR = 1.56 [0.71; 3.34], 95% CI, p<0.253). Multivariable logistic regression analysis revealed that CYP2C19*2 homozygotes have higher risk of composite endpoint (OR = 6.34, 95% CI [1.57; 22.23], p<0.005) and myocardial infarction (OR = 5.45, 95% CI [1.14; 19.97], p<0.016) compared to *2 heterozygotes and wild-type carriers. 14 patients had major bleedings, required blood transfusion or hospitalization. Patient’s age, increase in creatinine level and gain-of-function (GOF) CYP2C19*17 homozygotic carriage were identified as the predictors of major bleeding during follow-up period.Conclusion. In this study CYP2C19 LOF alleles polymorphism except the CYP2C19*2 homozygotic carriage demonstrated no impact on the incidence of ischemic events during 12-month follow-up in patients with acute MI who underwent successful revascularization. CYP2C19*17 homozygotes demonstrated increased risk of major bleeding only in young individuals with elevated blood creatinine levels.

Association Between Cytochrome P450 2C9 Gene Polymorphisms and Blood Pressure in Response to Losartan

To identify the genetic contribution to the variation in blood pressure (BP) response to angiotensin receptor blockers (ARBs), single-nucleotide polymorphisms (SNPs) in the cytochrome P450 (CYP) 2C9 gene were evaluated for their association with BP response to Losartan in Pakistani patients with hypertension. We selected 100 hypertensive patients and genotyped them for CYP2C9*1, *2, and *3. Our results show that 40% of patients were responsive to antihypertensive treatment as per the defined criteria (a reduction of at least 10mm systolic & 5mm diastolic). More than 63% of patients who had wild-type CYP2C9 genotype did not respond to antihypertensive therapy, the rest did respond to the antihypertensive therapy. Similarly, more than 46% of patients having one of the polymorphic genotypes did not respond to therapy while the rest did. However, there was no statistically significant difference between the two groups and hence polymorphism in the CYP2C9 gene in our hypertensive cohort had no association with the antihypertensive therapy including Losartan. Since our study has a relatively low sample size, we encourage larger studies to replicate and confirm these findings.

Effects of CYP2C19 variants on the metabolism of tapentadol in vitro.

Objective(s):This study aims to evaluate the catalytic activities of 31 CYP2C19 alleles and their effects on the metabolism of tapentadol in vitro. Materials and Methods:Insect microsomes expressing the CYP2C19 alleles were incubated with 50–1250 μM tapentadol for 40 min at 37 °C and terminated by cooling to -80 °C, immediately. Tapentadol and N-desmethyl tapentadol were analyzed by a UPLC-MS/MS system. The kinetic parameters Km, Vmax, and intrinsic clearance (Vmax/Km) of N-desmethyl tapentadol were determined. Results:As a result, the intrinsic clearance (Vmax/Km) values of most variants were significantly altered, while CYP2C19.3 and 35FS had no detectable enzyme activity. Only one variant, N277K, showed no significant difference from CYP2C19.1B. Two variants CYP2C19.29 and L16F displayed markedly increased intrinsic clearance values of 302.22% and 199.97%, respectively; whereas 24 variants exhibited significantly decreased relative clearance ranging from 0.32% to 79.15% of CYP2C19.1B. Especially, CYP2C19.2G, 2H, R124Q, and R261W exhibited a drastic decrease in clearance (>80%) compared with wild-type CYP2C19.1B. Conclusion:As the first study of all aforementioned alleles for tapentadol metabolism, the comprehensive data in vitro may provide novel insights into the allele-specific and substrate-specific activity of CYP2C19.

Functional Measurement of CYP2C9 and CYP3A4 Allelic Polymorphism on Sildenafil Metabolism.

AimWe aimed to systematically examine the effects of enzymatic activity of 38 human CYP2C9 alleles and 21 human CYP3A4 alleles, including wild-type CYP2C9.1 and CYP3A4.1, which contain the 24 CYP2C9 novel alleles (*36–*60) and 6 CYP3A4 novel alleles (*28–*34) newly found in the Chinese population, on sildenafil metabolism through in vitro experiment.MethodsThe recombinant cytochrome P450 alleles protein of CYP2C9 and CYP3A4 expressed in insect baculovirus expression system were reacted with 10–500 µM sildenafil for 30 minutes at 37°C, and the reaction was terminated by cooling to −80°C immediately. Next, we used ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection system to detect sildenafil and its active metabolite N-desmethyl sildenafil.ResultsThe intrinsic clearance (Vmax/Km) values of most CYP2C9 variants were significantly altered when compared with the wild-type CYP2C9*1, with most of these variants exhibiting either reduced Vmax and/or increased Km values. Four alleles (CYP2C9*11, *14, *31, *49) exhibited no markedly decreased relative clearance (1-fold). The relative clearance of the remaining thirty-three variants exhibited decrease in different levels, ranging from 1.81% to 88.42%. For the CYP3A4 metabolic pathway, when compared with the wild-type CYP3A4*1, the relative clearance values of four variants (CYP3A4*3, *10, *14 and *I335T) showed significantly higher relative clearance (130.7–134.9%), while five variants (CYP3A4*2, *5, *24, *L22V and *F113I) exhibited sharply reduced relative clearance values (1.80–74.25%), and the remaining nine allelic variants showed no statistical difference. In addition, the kinetic parameters of two CYP3A4 variants (CYP3A4*17 and CYP3A4*30) could not be detected, due to the defect of the CYP3A4 gene.ConclusionThese findings were the first evaluation of all these infrequent CYP2C9 and CYP3A4 alleles for sildenafil metabolism; when treating people who carry these CYP2C9 and CYP3A4 variants, there should be more focus on the relation of dose intensity, side effects and therapeutic efficacy when administering sildenafil. The study will provide fundamental data on effect of CYP2C9 and CYP3A4 allelic variation on sildenafil metabolism for further clinical research.

Impact of single nucleotide polymorphisms (R132Q and W120R) on the binding affinity and metabolic activity of CYP2C19 toward some therapeutically important substrates

Although CYP2C19 is minor human liver enzyme, it is responsible for the metabolism of many clinically important drugs. In this work, CYP2C19 wild type and its SNP mutants (R132Q and W120R) were prepared using over-expression system in E. coli, purified by column chromatography and their biological activities were compared. The enzyme activity toward certain drugs (amitriptyline, imipramine, lansoprazole and omeprazole) was investigated. Resonance Raman and UV–VIS spectroscopies revealed a minimal effect of SNP mutations on the heme structure. However, the mutation greatly affected the drug metabolism activities of CYP2C19. The degree of these effects was dependent on both the mutation and the chemical structure of the substrate. Surprisingly, the affected amino acid residue is located remotely from the heme center. Therefore, the direct effect of the mutation on the metabolic center is excluded. Alternatively, the significant impairment in the drug metabolism of these mutants could be attributed to a decrease in the electron flow to the iron center. Accordingly, understanding the effect of SNPs of CYP2C19, and the extents in which they participate in the drug metabolism, are important pillars that can enhance the therapeutic drugs efficacy and improve the patient outcomes toward the development of patient’s tailored medicine.

Heterologous Expression and Functional Characterization of Novel CYP2C9 Variants Identified in the Alaska Native People.

CYP2C9 is a major form of human liver cytochrome P450 that is responsible for the oxidative metabolism of several widely used low-therapeutic index drugs, including (S)-warfarin and phenytoin. In a cohort of Alaska Native people, ultrarare or novel CYP2C9 protein variants, M1L (rs114071557), N218I (rs780801862), and P279T (rs182132442, CYP2C9*29), are expressed with higher frequencies than the well characterized CYP2C9*2 and CYP2C9*3 alleles. We report here on their relative expression in lentivirus-infected HepG2 cells and the functional characterization of purified reconstituted enzyme variants expressed in Escherichia coli toward (S)-warfarin, phenytoin, flurbiprofen, and (S)-naproxen. In the infected HepG2 cells, robust mRNA and protein expression were obtained for wild-type, N218I, and P279T variants, but as expected, the M1L variant protein was not translated in this liver-derived cell line. His-tagged wild-type protein and the N218I and P279T variants, but not M1L, expressed well in E. coli and were highly purified after affinity chromatography. Upon reconstitution with cytochrome P450 oxidoreductase and cytochrome b5, the N218I and P279T protein variants metabolized (S)-warfarin, phenytoin, flurbiprofen, and (S)-naproxen to the expected monohydroxylated or O-demethylated metabolites. Steady-state kinetic analyses revealed that the relative catalytic efficiency ratios of (S)-warfarin metabolism by the P279T and N218I variants were 87% and 24%, respectively, of wild-type CYP2C9 protein. A similar rank ordering was observed for metabolism of phenytoin, flurbiprofen, and (S)-naproxen. We conclude that carriers of the variant N218I and, especially, the M1L alleles would be at risk of exacerbated therapeutic effects from drugs that rely on CYP2C9 for their metabolic clearance. SIGNIFICANCE STATEMENT: Novel gene variants of CYP2C9-M1L, and N218I, along with P279T (CYP2C9*29)-are expressed in Alaska Native people at relatively high frequencies. In vitro characterization of their functional effects revealed that each variant confers reduced catalytic efficiency toward several substrates, including the low-therapeutic index drugs (S)-warfarin and phenytoin. These data provide the first functional information for new, common CYP2C9 variants in this understudied population. The data may help guide dose adjustments in allele carriers, thus mitigating potential healthcare disparities.

Effects of CYP2C9 and VKORC1 genetic polymorphisms in Chinese Han population on maintenance dosage of warfarin

Objective To analyze CYP2C9 and VKORC1 gene polymorphisms in Chinese Han population and their correlation with the maintenance dosage of warfarin. Methods From October 2017 to April 2018, 458 Chinese Han patients (213 males and 245 females, aged from 26 to 94 years old) who underwent coagulation analysis in Peking University People′s Hospital were included in this retrospective study. PCR-Fluorescent probe method was applied to detect CYP2C9*3 and VKORC1-1639A>G gene polymorphisms in 458 patients, and among them, 130 patients who took warfarin for anticoagulant therapy and reached the international standard ratio of prothrombin time (INR) within the range of 2.0-3.0 were recorded. The basic information, dosage of warfarin and INR were also recorded. The statistical analysis data were compared with the reference table of recommended dosage of warfarin for different genotypes of patients recommended by FDA and the formula of predicted dosage of warfarin was simply verified by SPSS. Results Among the 458 patients who took anticoagulant therapy, the genotype frequencies of CYP2C9*1/*1(AA), CYP2C9*1/*3(AC) and CYP2C9*3/*3(CC) were 90.8%, 8.5%, and 0.7%; the genotype frequencies of VKORC1-1639GG and VKORC1-1639AG were 0.9% and 14.2%; the genotype frequencies of VKORC1-1639AA was 84.9%. After INR was reached, the results showed that the variant CYP2C9*1/*3 and CYP2C9*3/*3 required lower daily maintain dosage [(2.92±1.29) mg] than wild-type CYP2C9*1/*1 patients did [(3.91±1.63) mg], with statistically significant difference (P=0.018). And variant VKORC1-AA required lower daily maintain dosage [(3.68±1.64) mg] than variant VKORC1-AG patients did [(4.54±1.29) mg], with statistically significant difference (P=0.001). The application dosage of warfarin in patients with different VKORC1+CYP2C9 genotypes was consistent with the recommended dosage of the FDA reference table. The prediction accuracy of miao 2007 formula was lower than that of IWPC formula, and 94.1% of patients′ dosages of warfarin were underestimated. Conclusion Patients with CYP2C9*3 or VKORC1-AA genotype required lower warfarin dosage. The CYP2C9 and VKORC1 gene polymorphisms had a certain correlation with maintenance dosage of warfarin. Key words: Warfarin; Polymorphism, genetic; Cytochrome P-450 CYP2C9; Vitamin K epoxide reductases; Dose-respanse relationship,drug

Effect of Drug Combination on Omeprazole Metabolism by Cytochrome P450 2C19 in Helicobacter pylori Eradication Therapy.

Helicobacter pylori (H. pylori) infection is common and can result in gastric and duodenal ulcers, and in some cases, gastric lymphoma and cancer. Omeprazole (OMP)-in combination with clarithromycin (CLR), amoxicillin (AMX), tinidazole (TND), or metronidazole (MET)-is used in double or triple combination therapy for eradication of H. pylori. However, the roles of the drugs other than OMP are not clearly understood. Therefore, in the present study, we aimed to investigate any effects of these drugs on OMP metabolism by wild-type CYP2C19 using spectroscopy and enzyme kinetics. The dissociation constants (Kd) for CYP2C19 with OMP, CLR, AMX, TND, and MET were 8.6, 126, 156, 174, and 249 µM, respectively. The intrinsic clearance of OMP was determined to be 355 mL/min/µmol of CYP2C19. Metabolism of OMP was significantly inhibited by 69, 66, 28, and 40% in the presence of CLR, TND, AMX, and MET, respectively. Moreover, the combination of CLR and TND resulted in 76% inhibition of OMP metabolism, while the combination of AMX and MET resulted in 48% inhibition of OMP metabolism. Both combinations of drugs not only have antibacterial effects, but also enhance the effect of OMP by inhibiting its metabolism by CYP2C19. These results indicate that drug-drug interactions of co-administered drugs can cause complex effects, providing a basis for OMP dose adjustment when used in combination therapy for H. pylori eradication.

Both CYP2C19 and PON1 Q192R Genotypes Influence Platelet Response to Clopidogrel by Thrombelastography in Patients with Acute Coronary Syndrome.

Objective The objective of this study is to explore the relationships of the effects of CYP2C19 and PON1 Q192R polymorphism on the activity of clopidogrel and the risk of high platelet responsiveness (HPR) by thrombelastography in patients with acute coronary syndrome (ACS). Methods 459 ACS patients with aspirin and clopidogrel were enrolled in this observational case control study from July 13, 2015, to November 11, 2017. The patients with <30% platelet inhibition were defined as HPR group, while the others were defined as normal platelet responsiveness (NPR) group. The genotypes distribution between the groups was assessed, and the clinical impact of genetic variants was investigated by comparing the relationship between the risk of HPR and genotypes including CYP2C19⁎2, CYP2C19⁎3, CYP2C19⁎17, ABCB1, and PON1. Results Compared with CYP2C19⁎1/⁎1 wild type carriers, CYP2C19⁎2 and ⁎3 carriers showed a significant association with the lower platelet inhibition (P=0.048). The platelet inhibition in carriers of at least one CYP2C19 loss-of-function (LOF) alleles was obviously higher than noncarriers (P=0.031). The platelet inhibition of PON1 192R carriers was lower than PON1 192Q carriers (P=0.044). Patients with the CYP2C19⁎2 and ⁎3 alleles had a greater risk of HPR than CYP2C19 wild type carriers (adjusted P=0.018 and adjusted P=0.005). At least one PON1 192R carrier predicted a significantly higher risk of HPR than PON1 192Q carriers (adjusted P=0.021). Individual CYP2C19⁎17 and ABCB1 variants did not differ significantly between the two groups. Conclusions CYP2C19 and PON1 Q192R variants influence ADP-induced platelet inhibition by thrombelastography (TEG) in ACS patients with clopidogrel. In addition, both LOF CYP2C19 and PON1 192R variants are independent risk factors of HPR, which is measured by the relative platelet inhibition.

Minimal Physiologically Based Pharmacokinetic Model of Intravenously and Orally Administered Delta-9-Tetrahydrocannabinol in Healthy Volunteers.

Lack of information on the pharmacokinetics of the active moiety of Cannabis or the metabolites of delta-9-tetrahydrocannabinol (THC) does not seem to be discouraging medical or recreational use. Cytochrome P450 (CYP)2C9, the primary enzyme responsible for THC metabolism, has two single nucleotide polymorphisms-Arg144Cys (*2) and Ile359Leu (*3). In the Caucasian population, allelic frequency is between 0.08 and 0.14 for CYP2C9*2 and between 0.04 and 0.16 for CYP2C9*3. In vitro data suggest that metabolic capacity for the variants CYP2C9*2 and CYP2C9*3 is about one-third compared to wild-type CYP2C9. Previous work has suggested exposure to the terminal metabolite is genetically determined. We therefore sought to characterize the pharmacokinetics of THC and its major metabolites 11-hydroxy-delta-9-tetrahydrocannabinol (THC-OH) and 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH) in healthy volunteers with known CYP2C9 status by non-compartmental analysis (NCA), compartmental modeling (CM) and minimal physiologically based pharmacokinetic (mPBPK) modeling. Blood samples drawn for THC, THC-OH and THC-COOH after a single intravenous (IV) bolus of 0.1mg/kg (0.32μM/kg) THC were analyzed using a validated LC-MS/MS method. NCA generated initial estimates and CM and the mPBPK model were then fit to plasma concentration data using non-linear mixed-effects modeling. Blood samples from orally dosed (10, 25 and 50mg) THC brownies were added to validate the model. THC can be described as a high hepatic extraction ratio drug with blood flow-dependent metabolism not restricted by protein binding. THC hepatic clearance is dependent on the CYP2C9 genetic variant in the population. High extraction drugs display route-dependent metabolism. When administered via the IV or inhalation routes, induction or inhibition of CYP2C9 should be non-contributory as the elimination of THC is dependent only on liver blood flow. THC-OH is also a high extraction ratio drug, but its hepatic clearance is significantly impacted by the hepatic diffusional barrier that impedes its access to hepatic CYP2C9. THC-COOH is glucuronidated and renally cleared; subjects homozygous for CYP2C9*3 have reduced exposure to this metabolite as a result of the polymorphism reducing THC production, the hepatic diffusional barrier impeding egress from the hepatocyte, and increased renal clearance. It has recently been reported that the terminal metabolite THC-COOH is active, implying the exposure difference in individuals homozygous for CYP2C9*3 may become therapeutically relevant. Defining the metabolism of THC in humans is important, as it is increasingly being used as a drug to treat various diseases and its recreational use is also rising. We have used NCA, CM, and mPBPK modeling of THC and its metabolites to partially disentangle the complexity of cannabis disposition in humans.

Влияние цитофлавина на апоптоз лейкоцитов крови пациентов с ишемической болезнью сердца в зависимости от носительства полиморфизма гена цитохрома CYP2C9 в условиях &lt;i&gt;in vitro&lt;/i&gt;

С целью определения характера влияния цитофлавина на апоптоз лейкоцитов крови пациентов с ишемической болезнью сердца (ИБС) в зависимости от наличия полиморфизма гена цитохрома CYP2C9*2 C430T были обследованы 90 пациентов с ИБС: стабильной стенокардией напряжения. Методом полимеразной цепной реакции определяли генные полиморфизмы цитохрома CYP2C9*2 C430T. Методом ДНК-комет, который позволяет оценить уровень апоптоза белых клеток крови, по разработанному авторами способу в тестах in vitro оценивали влияние цитофлавина в терапевтической концентрации на ДНК лейкоцитов крови больных. При частотном анализе гена CYP2C9*2 C430T среди пациентов было установлено, что 75 человек (83 %) гомозиготны по дикому аллелю (генотип СС), 15 человек (17 %) — гетерозиготны (генотип СТ), гомозиготных лиц по полиморфному аллелю (генотип ТТ) в выборке не обнаружено. У носителей полиморфного гена цитохрома CYP2C9*2 С430Т (генотипа СТ) наблюдали более сильное повреждение ДНК в исходном статусе (11,00 ± 3,21) % повреждённых клеток в сравнении с (3,43 ± 1,13) % у пациентов с генотипом СС (р = 0,02). При введении цитофлавина в терапевтической концентрации in vitro обнаружили тенденцию разнонаправленного изменения состояния ДНК лейкоцитов в зависимости от наличия полиморфизма гена CYP2C9*2 С430Т. Так, у пациентов с диким геном CYP2C9*2 С430Т при введении цитофлавина in vitro обнаружили незначительное недостоверное увеличение количества апоптотических лейкоцитов крови, в то время как у пациентов с полиморфным геном CYP2C9*2 С430Т (генотипом СТ) обнаружили чёткую тенденцию снижения количества апоптотических клеток практически до нулевых значений показателя (p = 0,087), что позволяет выдвинуть гипотезу о возможной способности цитофлавина модулировать стабильность ДНК в зависимости от состояния генома и о необходимости разработки персонализированных подходов к использованию цитофлавина у пациентов с ИБС в клинической практике.

SA79 - FUNCTIONAL CHARACTERIZATION OF HUMAN CYP2C9 ALLELIC VARIANTS IN COS-7 CELLS

Background Variability in activity of CYP2C9, which is involved in the metabolism of approximately 15% of current therapeutic drugs, is an important contributor to interindividual differences in drug response. Methods To evaluate the functional alternations of CYP2C9(⁎)2, CYP2C9(⁎)3, CYP2C9(⁎)8, CYP2C9(⁎)11 and CYP2C9(⁎)31, identified in our previous study in Chinese Han population, allelic variants as well as the wild-type CYP2C9 were transiently expressed in COS-7 cells. Kinetic parameters (Km, Vmax, and Clint) for S-warfarin 7-hydroxylation by these recombinant CYP2C9s were determined. Results Relative to CYP2C9.1, recombinant CYP2C9.3 and CYP2C9.11 exhibited significantly higher Km values, and all allelic variants showed significantly decreased Vmax and Clint values. Among all allelic variants, catalytic activity of CYP2C9.3 and CYP2C9.11 reduced the most (8.2% and 9.8% of Clint ratio, respectively; P Discussion These findings should be useful for predicting the phenotype profiles of CYP2C9 in Chinese Han population, comparing the functional results of these alleles accurately, and finally optimizing pharmacotherapy of drug treatment.

Metabolism of steroids by cytochrome P450 2C9 variants.

CYP2C9 is a human microsomal cytochrome P450c (CYP). Much variation in CYP2C9 levels and activity can be attributed to polymorphisms of this gene. Wild-type CYP2C9 and ten mutants were co-expressed with NADPH-cytochrome P450 reductase in Escherichia coli. The hydroxylase activities toward steroids were examined. CYP2C9.2, CYP2C9.3, CYP2C9.4, CYP2C9.16, CYP2C9.28, CYP2C9.48 and CYP2C9.52 had higher testosterone 6β-hydroxylation than CYP2C9.1. CYP2C9.4 showed higher progesterone 6β-hydroxylation activity than CYP2C9.1. CYP2C9.28 and CYP2C9.48 showed higher progesterone 11α-hydroxylation activity than CYP2C9.1. CYP2C9.48 showed higher progesterone 16α-hydroxylation activity than CYP2C9.1. CYP2C9.2, CYP2C9.3, CYP2C9.16 and CYP2C9.30 had higher estrone 16α-hydroxylation activity than CYP2C9.1. CYP2C9.3 had higher estrone 11α-hydroxylation activity than CYP2C9.1. CYP2C9.39 and CYP2C9.57 showed similar activities to CYP2C9.1. These results indicate that the substrate specificity of CYP2C9.39 and CYP2C9.57 was not changed, but CYP2C9.2, CYP2C9.3, CYP2C9.4, CYP2C9.16, CYP2C9.28, CYP2C9.30, CYP2C9.48 and CYP2C9.52 showed different hydroxylation activities toward steroids compared with CYP2C9.1.

The Cytochrome P450 Slow Metabolizers CYP2C9*2 and CYP2C9*3 Directly Regulate Tumorigenesis via Reduced Epoxyeicosatrienoic Acid Production.

Increased expression of cytochrome P450 CYP2C9, together with elevated levels of its products epoxyeicosatrienoic acids (EET), is associated with aggressiveness in cancer. Cytochrome P450 variants CYP2C9*2 and CYP2C9*3 encode proteins with reduced enzymatic activity, and individuals carrying these variants metabolize drugs more slowly than individuals with wild-type CYP2C9*1, potentially affecting their response to drugs and altering their risk of disease. Although genetic differences in CYP2C9-dependent oxidation of arachidonic acid (AA) have been reported, the roles of CYP2C9*2 and CYP2C9*3 in EET biosynthesis and their relevance to disease are unknown. Here, we report that CYP2C9*2 and CYP2C9*3 metabolize AA less efficiently than CYP2C9*1 and that they play a role in the progression of non-small cell lung cancer (NSCLC) via impaired EET biosynthesis. When injected into mice, NSCLC cells expressing CYP2C9*2 and CYP2C9*3 produced lower levels of EETs and developed fewer, smaller, and less vascularized tumors than cells expressing CYP2C9*1. Moreover, endothelial cells expressing these two variants proliferated and migrated less than cells expressing CYP2C*1. Purified CYP2C9*2 and CYP2C9*3 exhibited attenuated catalytic efficiency in producing EETs, primarily due to impaired reduction of these two variants by NADPH-P450 reductase. Loss-of-function SNPs within CYP2C9*2 and CYP2C9*3 were associated with improved survival in female cases of NSCLC. Thus, decreased EET biosynthesis represents a novel mechanism whereby CYPC29*2 and CYP2C9*3 exert a direct protective role in NSCLC development.Significance: These findings report single nucleotide polymorphisms in the human CYP2C9 genes, CYP2C9*2 and CYP2C9*3, exert a direct protective role in tumorigenesis by impairing EET biosynthesis. Cancer Res; 78(17); 4865-77. ©2018 AACR.

Effects of polymorphic variation on the thermostability of heterogenous populations of CYP3A4 and CYP2C9 enzymes in solution

The effect of non-synonymous single nucleotide polymorphisms (SNPs) on cytochrome P450 (CYP450) drug metabolism is currently poorly understood due to the large number of polymorphisms, the diversity of potential substrates and the complexity of CYP450 function. Previously we carried out in silico studies to explore the effect of SNPs on CYP450 function, using in silico calculations to predict the effect of mutations on protein stability. Here we have determined the effect of eight CYP3A4 and seven CYP2C9 SNPs on the thermostability of proteins in solution to test these predictions. Thermostability assays revealed distinct CYP450 sub-populations with only 65–70% of wild-type CYP3A4 and CYP2C9 susceptible to rapid heat-induced P450 to P420 conversion. CYP3A4 mutations G56D, P218R, S222P, I223R, L373F and M445T and CYP2C9 mutations V76M, I359L and I359T were destabilising, increasing the proportion of protein sensitive to the rapid heat-induced P450 to P420 conversion and/or reducing the half-life of this conversion. CYP2C9 Q214L was the only stabilising mutation. These results corresponded well with the in silico protein stability calculations, confirming the value of these predictions and together suggest that the changes in thermostability result from destabilisation/stabilisation of the protein fold, changes in the haem-binding environment or effects on oligomer formation/conformation.

Physiologically-based pharmacokinetic modelling of a CYP2C19 substrate, BMS-823778, utilizing pharmacogenetic data.

Previous studies demonstrated direct correlation between CYP2C19 genotype and BMS-823778 clearance in healthy volunteers. The objective of the present study was to develop a physiologically-based pharmacokinetic (PBPK) model for BMS-823778 and use the model to predict PK and drug-drug interaction (DDI) in virtual populations with multiple polymorphic genes. The PBPK model was built and verified using existing clinical data. The verified model was simulated to predict PK of BMS-823778 and significance of DDI with a strong CYP3A4 inhibitor in subjects with various CYP2C19 and UGT1A4 genotypes. The verified PBPK model of BMS-823778 accurately recovered observed PK in different populations. In addition, the model was able to capture the exposure differences between subjects with different CYP2C19 genotypes. PK simulation indicated higher exposures of BMS-823778 in CYP2C19 poor metabolizers who were also devoid of UGT1A4 activity, compared to those with normal UGT1A4 functionality. Moderate DDI with itraconazole was predicted in subjects with wild-type CYP2C19 or UGT1A4. However, in subjects without CYP2C19 or UGT1A4 functionality, significant DDI was predicted when BMS-823778 was coadministered with itraconazole. A PBPK model was developed using clinical data that accurately predicted human PK in different population with various CYP2C19 phenotypes. Simulations with the verified PBPK model indicated that UGT1A4 was probably an important clearance pathway in CYP2C19 poor metabolizers. DDI with itraconazole is likely to be dependent on the genotypes of CYP2C19 and UGT1A4.