CYP2C19 activity comparison between Swedes and Koreans: effect of genotype, sex, oral contraceptive use, and smoking

The frequencies of CYP2C19*2, *3, and *17 alleles and their impact on the clinical efficacy of doubled maintenance dose of clopidogrel in Syrian patients with coronary artery disease

BACKGROUND

Genetic variations in the CYP2C19 gene, which encodes the major enzyme responsible for activating clopidogrel, may influence response to Clopidogrel antiplatelet therapy. This study aimed to assess the prevalence of CYP2C19 variants in Syrian patients with coronary artery disease (CAD) and evaluate the impact of these variants on the clinical efficacy of a doubled maintenance dose of clopidogrel following percutaneous coronary intervention (PCI).

METHODS

This study included 50 Syrian CAD patients on dual antiplatelet therapy (DAPT) with a doubled maintenance dose of clopidogrel. CYP2C19 genotypes were determined by PCR, followed by Sanger sequencing. Clinical outcomes, including major acute cardiovascular events (MACE) and bleeding events, were monitored over 18-24 months.

RESULTS

The allele frequencies were 8% for CYP2C19*2, 0% for CYP2C19*3, and 17% for CYP2C19*17. The distribution of our study population by CYP2C19 genotype-predicted metabolizer phenotypes was 56% for normal metabolizers (NMs), 26% for intermediate metabolizers (IMs), 12% for rapid metabolizers (RMs), and 2% for ultra-rapid metabolizers (UMs). No association was found between the CYP2C19*2 allele and recurrent ischemic events or between the CYP2C19*17 allele and bleeding complications in patients treated with a doubled maintenance dose of clopidogrel.

CONCLUSIONS

In Syrian patients undergoing PCI, a doubled maintenance dose of clopidogrel (150 mg/day) may help mitigate variability in response due to CYP2C19*2 carrier status, offering potential benefits in optimizing antiplatelet therapy. However, given the study's limited sample size, these findings should be interpreted with caution, and larger studies are needed to confirm this potential benefit.

Real-World Experience of Mavacamten for Patients With Obstructive Hypertrophic Cardiomyopathy in South Korea: A Prospective Multi-Center Observational Study

BACKGROUND AND OBJECTIVES

Mavacamten has shown promise in obstructive hypertrophic cardiomyopathy (oHCM); however, real-world evidence is limited in Asians. We aimed to provide the first multicenter, real-world analysis of mavacamten use in Korea.

METHODS

This prospective observational study included symptomatic oHCM patients treated at 7 tertiary hospitals in Korea. Changes in key parameters, including left ventricular outflow tract (LVOT) gradients, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and New York Heart Association functional class (NYHA Fc), were serially assessed. Adverse events, including death, arrhythmia, and heart failure hospitalizations were documented.

RESULTS

Forty-six patients were followed for a median of 147 days (interquartile range 56-205). There was one sudden cardiac death and one non-cardiac death. Resting and Valsalva LVOT gradients significantly decreased from 58.4±46.4 mmHg and 92.6±46.8 mmHg to 17.5±21.3 mmHg and 25.7±27.1 mmHg, respectively (both p<0.001). NT-proBNP levels also decreased significantly, strongly correlating with LVOT gradient reductions. Among the 44 survivors, 25 (58.1%) had at least one NYHA Fc improvement. Moreover, left atrial volume and maximal left ventricular (LV) wall thickness significantly decreased. However, mean reduction in LV ejection fraction (LVEF) was -3.4% with one patient experiencing LVEF <50%. We observed 2 newly-detected atrial fibrillations and 2 ischemic strokes.

CONCLUSIONS

This first real-world experience of mavacamten in Korean patients with oHCM demonstrates its efficacy and safety, aligning with previous pivotal trials. With the implementation of national insurance coverage, mavacamten will be more accessible to broader oHCM population, offering a non-invasive and effective therapeutic option aside from invasive septal reduction therapies.

The influence of female sex and estrogens on drug pharmacokinetics: what is the evidence?

INTRODUCTION

Pharmacological research has traditionally been skewed toward male subjects, leading to uniform treatment guidelines for both men and women that assume similar drug pharmacokinetics across sexes. This oversight contributes to women experiencing adverse drug reactions on average twice as often as men. More recent studies have revealed significant pharmacokinetic differences between the sexes, partly due to different sex hormone levels. Additionally, intraindividual differences in women have been observed due to fluctuating estrogen levels, impacting important aspects of drug pharmacokinetics.

AREAS COVERED

This review highlights key sex differences in drug pharmacokinetics, focusing on absorption, distribution, metabolism, and excretion. A particular emphasis is placed on the role of cytochrome P450 (CYP) and uridine diphosphate-glucuronosyltransferase (UGT) enzymes in drug metabolism, and on the role of P-glycoprotein (P-gp). The impact of estrogens is reviewed by exploring how drug pharmacokinetics change over the menstrual cycle, before and after menopause, and with estrogen-containing medications.

EXPERT OPINION

Personalized dosing based on sex and estrogen levels is important for improving treatment outcomes in female drug users. Clinical trials of drugs likely affected by these factors should incorporate pharmacokinetic studies that distinguish between sexes and evaluate the impact of estrogens, aiming to develop optimized dosing regimens.

Impact of fresh grape juice on the pharmacokinetics of omeprazole: results of a food-drug interaction study

Grapes have been widely used for dietary ailments due to their attributed pharmacological activities. Resveratrol, the chief constituent of grapes, is responsible for their pharmacological benefits. However, apart from their beneficial effects, grapes have also recently been considered in drug interaction studies. This study investigated the pharmacokinetic profile of omeprazole administered alone compared to omeprazole administered with grape juice, with a prior intake of grape juice, for 1 continuous week. The study was conducted on two groups of healthy male volunteers [n = 12]. One group was orally administered 40 mg of omeprazole alone, while the other group was administered omeprazole with grape juice. Blood samples were analyzed for omeprazole concentration by a reverse-phase HPLC method. Co-administration of 40 mg omeprazole with grape juice significantly decreased the AUC0-t and Cmax by 32% and 34%, respectively, suggesting a role being played by grapes in the activation of P-glycoprotein and omeprazole metabolizing enzymes, including CYP3A4 and CYP2C19. In conclusion, the addition of grapes as a dietary supplement in patients taking omeprazole for the management of peptic ulcer symptoms may lead to a higher required dose of omeprazole.

A web-based scoping review assessing the influence of smoking and smoking cessation on antidiabetic drug meabolism: implications for medication efficacy

Currently 1.3 billion individuals globally engage in smoking, leading to significant morbidity and mortality, particularly among diabetic patients. There is urgent need for a better understanding of how smoking influences antidiabetic treatment efficacy. The review underscores the role of cigarette smoke, particularly polycyclic aromatic hydrocarbons (PAHs), in modulating the metabolic pathways of antidiabetic drugs, primarily through the induction of cytochrome P450 (CYP450) enzymes and uridine diphosphate (UDP)-glucuronosyltransferases (UGTs), thus impacting drug pharmacokinetics and therapeutic outcomes. Furthermore, the review addresses the relatively uncharted territory of how smoking cessation influences diabetes treatment, noting that cessation can lead to significant changes in drug metabolism, necessitating dosage adjustments. Special attention is given to the interaction between smoking cessation aids and antidiabetic medications, a critical area for patient safety and effective diabetes management. This scoping review aims to provide healthcare professionals with the knowledge to better support diabetic patients who smoke or are attempting to quit, ensuring tailored and effective treatment strategies. It also identifies gaps in current research, advocating for more studies to fill these voids, thereby enhancing patient care and treatment outcomes for this at-risk population.

Aspirin-free antiplatelet strategies after percutaneous coronary interventions

Dual antiplatelet therapy (DAPT) with aspirin and a platelet P2Y12 receptor inhibitor is the standard antithrombotic treatment after percutaneous coronary interventions (PCI). Several trials have challenged guideline-recommended DAPT after PCI by testing the relative clinical effect of an aspirin-free antiplatelet approach-consisting of P2Y12 inhibitor monotherapy after a short course (mostly 1-3 months) of DAPT-among patients undergoing PCI without a concomitant indication for oral anticoagulation (OAC). Overall, these studies have shown P2Y12 inhibitor monotherapy after short DAPT to be associated with a significant reduction in the risk of bleeding without an increase in thrombotic or ischaemic events compared with continued DAPT. Moreover, the effects of the P2Y12 inhibitor monotherapy without prior DAPT or following a very short course of DAPT after PCI are being investigated in emerging studies, of which one has recently reported unfavourable efficacy results associated with the aspirin-free approach compared with conventional DAPT. Finally, P2Y12 inhibitor alone has been compared with aspirin alone as chronic therapy after DAPT discontinuation, thus challenging the historical role of aspirin as a standard of care for secondary prevention following PCI. A thorough understanding of study designs, populations, treatments, results, and limitations of trials testing P2Y12 inhibitor monotherapy vs. DAPT or vs. aspirin is required to consider adopting this treatment in clinical practice. This review addresses the use of aspirin-free antiplatelet strategies among patients undergoing PCI without a concomitant indication for OAC, providing an overview of clinical evidence, guideline indications, practical implications, ongoing issues, and future perspectives.

Prediction of Omeprazole Pharmacokinetics and its Inhibition on Gastric Acid Secretion in Humans Using Physiologically Based Pharmacokinetic-Pharmacodynamic Model Characterizing CYP2C19 Polymorphisms

PURPOSE

To develop a whole physiologically based pharmacokinetic-pharmacodynamic (PBPK-PD) model to describe the pharmacokinetics and anti-gastric acid secretion of omeprazole in CYP2C19 extensive metabolizers (EMs), intermediate metabolizers (IMs), poor metabolizers (PMs) and ultrarapid metabolizers (UMs) following oral or intravenous administration.

METHODS

A PBPK/PD model was built using Phoenix WinNolin software. Omeprazole was mainly metabolized by CYP2C19 and CYP3A4 and the CYP2C19 polymorphism was incorporated using in vitro data. We described the PD by using a turn-over model with parameter estimates from dogs and the effect of a meal on the acid secretion was also implemented. The model predictions were compared to 53 sets of clinical data.

RESULTS

Predictions of omeprazole plasma concentration (72.2%) and 24 h stomach pH after administration (85%) were within 0.5-2.0-fold of the observed values, indicating that the PBPK-PD model was successfully developed. Sensitivity analysis demonstrated that the contributions of the tested factors to the plasma concentration of omeprazole were Vmax,2C19 ≈ Papp > Vmax,3A4 > Kti, and contributions to its pharmacodynamic were Vmax,2C19 > kome > kms > Papp > Vmax,3A4. The simulations showed that while the initial omeprazole dose in UMs, EMs, and IMs increased 7.5-, 3- and 1.25-fold compared to those of PMs, the therapeutic effect was similar.

CONCLUSIONS

The successful establishment of this PBPK-PD model highlights that pharmacokinetic and pharmacodynamic profiles of drugs can be predicted using preclinical data. The PBPK-PD model also provided a feasible alternative to empirical guidance for the recommended doses of omeprazole.

Pharmacokinetics and bioequivalence evaluation of omeprazole and sodium bicarbonate dry suspensions in healthy Chinese volunteers

Omeprazole and sodium bicarbonate dry suspension are effective treatments for acid-related disorders. This study compared the bioequivalence and safety of the two formulations of omeprazole and sodium bicarbonate powder and assessed how CYP2C19 gene polymorphisms affect pharmacokinetics (PK). A single-center, randomized, single-dose, 2-sequence and 2-period crossover method was performed in forty healthy Chinese subjects. Blood samples were collected after a single dose for PK (AUC0-∞, AUC0-t, and Cmax) analysis. The concentrations of Omeprazole in human plasma were determined by HPLC-MS/MS. Besides, the gene polymorphisms of CYP2C19 were assessed by Sanger sequencing. The geometric mean ratios (90% confidence interval) [GMR (95% CI)] of Test/Reference preparation for Cmax: 95.2% (88.48%, 102.43%), AUC0-t: 97.47% (94.4%, 101.02%), AUC0-∞: 97.68% (94.27%, 101.21%) were within the range of 80.00-125.00%. The non-parametric test showed no statistical difference in Tmax between the two groups (p > 0.05). All drugs were well tolerated, no severe adverse reactions occurred, and no significant differences in adverse events between the two drugs. For CYP2C19 gene polymorphisms, the results showed that of 40 subjects, 12 subjects were extensive metabolizers, 24 were intermediate metabolizers, and 4 were poor metabolizers, the frequency of metabolic genotypes were 30%, 60%, and 10%. And the allele distributions for CYP2C19 were *1, *2, and *3 at 60%, 38.75%, and 1.25%. Both the CYP2C19 alleles and metabolic genotypes were consistent with other studies in Chinese. The results of PK parameters showed that different genotypes of CYP2C19 lead to significant differences in t1/2, AUC0-t, AUC0-∞ and Cmax, but no significant differences in Tmax in each group. At the same time, we confirmed that the PK parameters of the test and reference had no differences between the males and females. This study has shown that the pharmacokinetic parameters of the two formulations are not significantly different, which showed bioequivalence and exemplary safety. CYP2C19 gene polymorphism significantly differed in the PK parameters of omeprazole sodium bicarbonate powder.

Antipsychotic medication for women with schizophrenia spectrum disorders

There are significant differences between men and women in the efficacy and tolerability of antipsychotic drugs. Here, we provide a comprehensive overview of what is currently known about the pharmacokinetics and pharmacodynamics of antipsychotics in women with schizophrenia spectrum disorders (SSDs) and translate these insights into considerations for clinical practice. Slower drug absorption, metabolism and excretion in women all lead to higher plasma levels, which increase the risk for side-effects. Moreover, women reach higher dopamine receptor occupancy compared to men at similar serum levels, since oestrogens increase dopamine sensitivity. As current treatment guidelines are based on studies predominantly conducted in men, women are likely to be overmedicated by default. The risk of overmedicating generally increases when sex hormone levels are high (e.g. during ovulation and gestation), whereas higher doses may be required during low-hormonal phases (e.g. during menstruation and menopause). For premenopausal women, with the exceptions of quetiapine and lurasidone, doses of antipsychotics should be lower with largest adjustments required for olanzapine. Clinicians should be wary of side-effects that are particularly harmful in women, such as hyperprolactinaemia which can cause oestrogen deficiency and metabolic symptoms that may cause cardiovascular diseases. Given the protective effects of oestrogens on the course of SSD, oestrogen replacement therapy should be considered for postmenopausal patients, who are more vulnerable to side-effects and yet require higher dosages of most antipsychotics to reach similar efficacy. In conclusion, there is a need for tailored, female-specific prescription guidelines, which take into account adjustments required across different phases of life.

The impact of catha edulis (vahl) forssk. ex endl. (celestraceae) (khat) on pharmacokinetics of clinically used drugs

INTRODUCTION

Catha edulis (Vahl) Forssk. ex Endl. (Celestraceae) is used as a recreational drug on daily basis for its euphoric and psychostimulant effects. It is also chewed by individuals who are on medications, raising the possibility of drug-khat interaction. However, limited data are available in the literature, although clinically significant interactions are expected, as khat contains a complex mixture of pharmacologically active constituents.

AREAS COVERED

It provides an overview of the phytochemistry, pharmacokinetics, pharmacodynamics, and pharmacogenetics of khat based on the literature mined from PubMed, Google Scholar, and Cochrane databases. It also presents a detailed account of drug-khat interactions with specific examples and their clinical significance. The interactions mainly occur at the pharmacokinetics level and particular attention is paid for the phases of absorption and cytochrome P450 enzyme-mediated metabolism.

EXPERT OPINION

Despite the increasing trend of khat chewing with medications among the populace and the potential risk for the occurrence of clinically significant interactions, there is paucity of data in the literature demonstrating the magnitude of the risk. The available data, however, clearly demonstrate that the consequence of drug-khat interaction is dependent on genotype. Genotyping, where feasible, could be used to improve clinical outcome and minimize adverse reactions.

Exploring pharmacogenetic difference using adverse event database: an example of clopidogrel and cardiovascular events

Background: Poor clopidogrel metabolizers, carrying a cytochrome P450 2C19 loss-of-function allele, are more frequent among East Asians than Caucasians/White. Materials & methods: The Korea adverse event reporting system database and a case/noncase study design were used to examine the disproportionality of cardiovascular events following clopidogrel use. The US FDA's adverse event reporting system database was also analyzed for comparison. Results: In the Korea adverse event reporting system data, the clopidogrel reporting odds ratio for cardiovascular events was 7.34, more than double that of ticagrelor. In the FDA's adverse event reporting system data, the clopidogrel reporting odds ratio was 4.69, lower than that of ticagrelor. Adjustment for covariates did not change the trend. Conclusion: Considering the prevalence of poor clopidogrel metabolizers and the reported cardiovascular events among Koreans, rigorous clinical management is required for clopidogrel users.

Relationships between CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 metabolic phenotypes and genotypes in a Nicaraguan Mestizo population

Interethnic variability in the drug-metabolizing capacity of CYP450 enzymes may lead to discrepancies in the relationship between genotypes and phenotypes worldwide. The present study was aimed to analyze for the first time whether there is a relationship between clinically relevant CYP450 genetic polymorphisms and their drug oxidation capacity (metabolic phenotype) in a population of healthy Nicaraguan volunteers. Two hundred and twelve participants were genotyped for CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, and their actual metabolic phenotype (evaluated by the Metabolic Ratio, MR) was analyzed by using the CEIBA cocktail approach. The results showed the wide interindividual variability in all the studied enzymes and a significant difference (p < 0.004) in the activity of CYP1A2 between male and female subjects. The number of CYP2C19 (p < 0.0001) and CYP2D6 (p < 0.0001) active alleles were shown inversely correlated with their corresponding MR, although there were marked genotype-phenotype discrepancies. There was an actual enzyme capacity overlapping (MR) between genotypically Poor (gPMs) and Extensive Metabolizers (gEMs) of 3.14% subjects for CYP2D6 and 0.94% for CYP2C9. Similarly, there was an overlapping for metabolic phenotypes of 11.48% of genotypically ultrarapid metabolizers (gUMs) for CYP2C19 and 2.09% for CYP2D6 and gEMs. Therefore, the current approach for metabolic phenotype prediction based just on genotype does not predict properly for all individuals within this Nicaraguan Mestizo population, thus representing a potential barrier for the clinical implementation of personalized medicine in this region. However, it is necessary to improve the prediction of phenotype from genotype in order to improve the pharmacogenetic implementation in populations with specific ethnic backgrounds.

Efficacy and safety of combination antifungal therapy in Korean haematological patients with invasive aspergillosis

This randomised, double‐blind, placebo‐controlled trial assessed the efficacy, safety and tolerability of voriconazole+anidulafungin (combination) or voriconazole+placebo (monotherapy) for invasive aspergillosis (IA; NCT00531479). We present a post hoc analysis of Korean and non‐Korean patients with IA (including baseline positive serum galactomannan [GM]). Immunocompromised patients ≥ 16 years with IA were randomised 1:1, combination or monotherapy, for ≥ 2 weeks’ treatment. The primary endpoint was 6‐ and 12‐week all‐cause mortality (Korean modified intent‐to‐treat [mITT] population). Overall, 454 patients enrolled (Koreans: 56 [combination: 28, monotherapy: 28], non‐Koreans: 398 [combination: 200, monotherapy: 198]). The mITT population comprised 40 Koreans (combination: 23; monotherapy: 17) and 237 non‐Koreans (combination: 112; monotherapy: 125). Week 6 treatment difference in mortality rate between combination and monotherapy was −6.4% in non‐Koreans. This reduction was more marked in Koreans (−22.4%). Week 12 difference in all‐cause mortality between combination and monotherapy was −17.7% (Koreans) and −20.2% at Week 6 (Koreans; positive baseline GM). Week 6 mortality (Koreans [mITT]; baseline GM >0.5‐2.0) was 0/13 (combination) and 2/6 (monotherapy). Serious adverse events were numerically higher for combination than monotherapy (Koreans: 57.1%, 46.4%; non‐Koreans: 49.5%, 46.0%). In Koreans, combination therapy was associated with marginally better outcomes than monotherapy and more so than in non‐Koreans.

Inconsistency in race and ethnic classification in pharmacogenetics studies and its potential clinical implications

Introduction

Racial and ethnic categories are frequently used in pharmacogenetics literature to stratify patients; however, these categories can be inconsistent across different studies. To address the ongoing debate on the applicability of traditional concepts of race and ethnicity in the context of precision medicine, we aimed to review the application of current racial and ethnic categories in pharmacogenetics and its potential impact on clinical care.

Methods

One hundred and three total pharmacogenetics papers involving the CYP2C9, CYP2C19, and CYP2D6 genes were analyzed for their country of origin, racial, and ethnic categories used, and allele frequency data. Correspondence between the major continental racial categories promulgated by National Institutes of Health (NIH) and those reported by the pharmacogenetics papers was evaluated.

Results

The racial and ethnic categories used in the papers we analyzed were highly heterogeneous. In total, we found 66 different racial and ethnic categories used which fall under the NIH race category “White”, 47 different racial and ethnic categories for “Asian”, and 62 different categories for “Black”. The number of categories used varied widely based on country of origin: Japan used the highest number of different categories for “White” with 17, Malaysia used the highest number for “Asian” with 24, and the US used the highest number for “Black” with 28. Significant variation in allele frequency between different ethnic subgroups was identified within 3 major continental racial categories.

Conclusion

Our analysis showed that racial and ethnic classification is highly inconsistent across different papers as well as between different countries. Evidence-based consensus is necessary for optimal use of self-identified race as well as geographical ancestry in pharmacogenetics. Common taxonomy of geographical ancestry which reflects specifics of particular countries and is accepted by the entire scientific community can facilitate reproducible pharmacogenetic research and clinical implementation of its results.

Effects of Cytochrome P450 (CYP) 2C19 Genotypes on Steady-State Plasma Concentrations of Escitalopram and its Desmethyl Metabolite in Japanese Patients With Depression

Background:

Plasma concentrations of the S-enantiomer of citalopram were different between extensive and poor CYP2C19 metabolizers in healthy subjects and depressed patients. However, most studies applied dose-corrected concentrations. Thus, we studied the effects of polymorphisms of the CYP2C19 gene on raw plasma drug concentrations in Japanese patients with depression.

Methods:

Subjects in this study consisted of 412 depressed patients receiving 5, 10, 15, or 20 mg of escitalopram once a day. Plasma concentrations of escitalopram and desmethylescitalopram were quantified using HPLC. CYP2C19 genotypes were identified using polymerase chain reaction methods.

Results:

There were no differences in the steady-state plasma concentrations of escitalopram or desmethylescitalopram in each dose group (5, 10, 15, or 20 mg of escitalopram) among CYP2C19 genotype groups. However, 1-way analysis of variance showed significant effects of CYP2C19 genotypes on the dose-adjusted plasma concentration of escitalopram but not in the dose-adjusted plasma concentration of desmethylescitalopram. Analysis of covariance including age, sex, and body weight showed significant effects of CYP2C19 genotypes on the dose-adjusted plasma concentration of escitalopram and the ratio of desmethylescitalopram to escitalopram.

Conclusions:

These findings suggest that the CYP2C19 variants are associated with steady-state plasma concentrations of escitalopram to some extent but are not associated with desmethylescitalopram.

Prevalence of the CYP2C19*2 (681 G>A), *3 (636 G>A) and *17 (‑806 C>T) alleles among an Iranian population of different ethnicities

Polymorphisms in the cytochrome P (CYP) 450 family may cause adverse drug responses in individuals. Cytochrome P450 2C19 (CYP2C19) is a member of the CYP family, where the presence of the 681 G>A, 636 G>A and 806 C>T polymorphisms result in the CYP2C19*2, CYP2C19*3 and CYP2C19*17 alleles, respectively. In the current study, the frequency of the CYP2C19*2, CYP2C19*3 and CYP2C19*17 alleles in an Iranian population cohort of different ethnicities were examined and then compared with previously published frequencies within other populations. Allelic and genotypic frequencies of the CYP2C19 alleles (*2, *3 and *17) were detected using polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis, PCR-single-strand conformation polymorphism analysis and DNA sequencing from blood samples of 1,229 unrelated healthy individuals from different ethnicities within the Iranian population. The CYP2C19 allele frequencies among the Iranian population were 21.4, 1.7, and 27.1% for the CYP2C19*2, CYP2C19*3 and CYP2C19*17 alleles, respectively. The frequency of the homozygous A/A variant of the CYP2C19*2 allele was significantly high and low in the Lur (P<0.001) and Caspian (P<0.001) ethnicities, respectively. However, the frequency of the homozygous A/A variant of the CYP2C19*3 allele was not detected in the Iranian cohort in the current study. The frequency of the heterozygous G/A variant of the CYP2C19*3 allele had the significantly highest and lowest frequency in the Fars (P<0.001) and Lur (P<0.001) groups, respectively. The allele frequency of the homozygous T/T variant of the CYP2C19*17 allele was significantly high in the Caspian (P<0.001) and low in the Kurd (P<0.05) groups. The frequency of the CYP2C19 alleles involved in drug metabolism, may improve the clinical understanding of the ethnic differences in drug responses, resulting in the advancement of the personalized medicine among the different ethnicities within the Iranian population.

Analysis of the CYP2C19 genotype associated with bleeding in Serbian STEMI patients who have undergone primary PCI and treatment with clopidogrel

PURPOSE

Bleeding is one of the possible adverse events during clopidogrel therapy. The CYP2C19 gene is the most significant genetic factor which influences response to clopidogrel treatment. We aimed to examine the contribution of the CYP2C19 gene to bleeding occurrence during clopidogrel therapy in Serbian patients with ST segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

METHODS

This case-control study included 53 patients who experienced bleeding and 55 patients without bleeding. Bleeding events were defined and classified using the Bleeding Academic Research Consortium (BARC) criteria. All patients were prescribed daily doses of clopidogrel during the 1-year follow-up after PCI. The CYP2C19*17 (c.-806C>T, rs12248560), rs11568732 (c.-889T>G, CYP2C19*20), CYP2C19*2 (c.681G>A; rs4244285) and CYP2C19*3 (c.636G>A; rs4986893) variants were analysed in all 108 patients. Additionally, sequencing of all nine exons, 5'UTR and 3'UTR in the rs11568732 carriers was performed.

RESULTS

Association between bleeding (BARC type ≥ 2) and the CYP2C19*17 variant was not observed [odds ratio (OR), 0.53; 95% confidence interval (CI), 0.2-1.1; p = 0.107). The rs11568732 variant showed significant association with bleeding (OR, 3.7; 95% CI, 1.12-12.44; p = 0.025). Also, we found that the rs11568732 variant appears independently of haplotype CYP2C19*3B, which is contrary to the previous findings.

CONCLUSIONS

Our results indicate the absence of CYP2C19*17 influence and turn the attention to the potential significance of the rs11568732 variant in terms of adverse effects of clopidogrel. However, it is necessary to conduct an independent conformation study in order to verify this finding. Also, an analysis of the functional implication of the rs11568732 variant is necessary in order to confirm the significance of this variant, both in relation to its influence on gene expression and in relation to its medical significance.

En route to precision medicine through the integration of biological sex into pharmacogenomics

Frequently, pharmacomechanisms are not fully elucidated. Therefore, drug use is linked to an elevated interindividual diversity of effects, whether therapeutic or adverse, and the role of biological sex has as yet unrecognized and underestimated consequences. A pharmacogenomic approach could contribute towards the development of an adapted therapy for each male and female patient, considering also other fundamental features, such as age and ethnicity. This would represent a crucial step towards precision medicine and could be translated into clinical routine. In the present review, we consider recent results from pharmacogenomics and the role of sex in studies that are relevant to cardiovascular therapy. We focus on genome-wide analyses, because they have obvious advantages compared with targeted single-candidate gene studies. For instance, genome-wide approaches do not necessarily depend on prior knowledge of precise molecular mechanisms of drug action. Such studies can lead to findings that can be classified into three categories: first, effects occurring in the pharmacokinetic properties of the drug, e.g. through metabolic and transporter differences; second, a pharmacodynamic or drug target-related effect; and last diverse adverse effects. We conclude that the interaction of sex with genetic determinants of drug response has barely been tested in large, unbiased, pharmacogenomic studies. We put forward the theory that, to contribute towards the realization of precision medicine, it will be necessary to incorporate sex into pharmacogenomics.

Potent acid inhibition by vonoprazan in comparison with esomeprazole, with reference to CYP2C19 genotype

BACKGROUND

Acid inhibitory effects of proton pump inhibitors (PPIs) are influenced by CYP2C19 genotype. In contrast, the potent acid inhibition of vonoprazan is not influenced by CYP2C19 genotype.

AIM

To compare the acid inhibitory effects of vonoprazan and esomeprazole in relation to CYP2C19 genotype.

METHODS

Twenty-eight healthy Japanese volunteers [7 CYP2C19 poor metabolisers (PMs), 11 intermediate metabolisers (IMs) and 10 rapid metabolisers (RMs)] received four different regimens in a randomised crossover manner: (i) vonoprazan 20 mg twice daily (b.d.), (ii) vonoprazan 20 mg daily, (iii) esomeprazole 20 mg b.d. and (iv) esomeprazole 20 mg daily. The timing of each dosing was 1 h before a meal. Twenty-four-hour intragastric pH monitoring was performed on day 7 on each regimen.

RESULTS

In the overall genotype group, pH ≥4 holding time ratios (pH 4 HTRs) with vonoprazan b.d., vonoprazan daily, esomeprazole b.d. and esomeprazole daily were 100%, 95%, 91%, and 68% respectively. pH 5 HTRs were 99%, 91%, 84% and 54% respectively. Vonoprazan b.d. potently suppressed acid for 24 h, and was significantly superior to other regimens irrespective of CYP2C19 genotype. Vonoprazan daily was equivalent to esomeprazole b.d. in IMs and PMs, but superior in RMs. CYP2C19 genotype-dependent differences were observed in esomeprazole daily but not in vonoprazan b.d. or daily.

CONCLUSION

Vonoprazan 20 mg b.d. inhibits acid irrespective of CYP2C19 genotype, more potently than esomeprazole 20 mg b.d., pH 4 and 5 holding time ratios reached 100% and 99%, respectively.

One-day front-loading with four doses of rabeprazole followed by a standard twice-daily regimen provides sufficient acid inhibition in extensive metabolizers of CYP2C19

BACKGROUND

Four times daily dosing (qid) with a proton pump inhibitor can cause rapid increase in intragastric pH. We investigated the efficacy of the front-loading with rabeprazole 10 mg qid on a subsequent regimen with rabeprazole 10 mg twice daily (bid) for 7 days in extensive metabolizers (EMs) of CYP2C19.

METHODS

Five EMs received three different 1-week regimens in a crossover manner as follows: (1) rabeprazole 10 mg bid for 7 days; (2) a front-loading regimen of rabeprazole (rabeprazole 10 mg qid on day 0 and bid on days 1 to 7); and (3) rabeprazole 10 mg qid for 7 days. Five intermediate metabolizers (IMs) and four poor metabolizers (PMs) received rabeprazole 10 mg bid regimen only. Twenty-four-hour intragastric pH-monitorings were performed on days 1, 4, and 7. Area under the intragastric pH-time curves (AUCs) from days 1 to 7 was calculated using 24-h median intragastric pHs on days 1, 4, and 7.

RESULTS

Twenty-four-hour intragastric pHs in the front-loading group on days 1, 4, and 7 were 5.1, 4.9, and 5.1, respectively. The median AUC with front-loading in EMs (34.4, pH·day) was significantly higher than that in EMs with rabeprazole 10 mg bid (30.74, p = 0.043). No statistically significant differences in median AUCs were noted among front-loading in EMs, rabeprazole 10 mg qid in EMs (37.2), rabeprazole 10 mg bid in IMs (37.3), and PMs (39.4).

CONCLUSIONS

The one-day front-loading regimen of rabeprazole 10 mg qid provided sufficient acid inhibition for 7 days, even in CYP2C19 EMs.

Interethnic variation of CYP2C19 alleles, 'predicted' phenotypes and 'measured' metabolic phenotypes across world populations

The present study evaluates the worldwide frequency distribution of CYP2C19 alleles and CYP2C19 metabolic phenotypes ('predicted' from genotypes and 'measured' with a probe drug) among healthy volunteers from different ethnic groups and geographic regions, as well as the relationship between the 'predicted' and 'measured' CYP2C19 metabolic phenotypes. A total of 52 181 healthy volunteers were studied within 138 selected original research papers. CYP2C19*17 was 42- and 24-fold more frequent in Mediterranean-South Europeans and Middle Easterns than in East Asians (P<0.001, in both cases). Contrarily, CYP2C19*2 and CYP2C19*3 alleles were more frequent in East Asians (30.26% and 6.89%, respectively), and even a twofold higher frequency of these alleles was found in Native populations from Oceania (61.30% and 14.42%, respectively; P<0.001, in all cases), which may be a consequence of genetic drift process in the Pacific Islands. Regarding CYP2C19 metabolic phenotype, poor metabolizers (PMs) were more frequent among Asians than in Europeans, contrarily to the phenomenon reported for CYP2D6. A correlation has been found between the frequencies of CYP2C19 poor metabolism 'predicted' from CYP2C19 genotypes (gPMs) and the poor metabolic phenotype 'measured' with a probe drug (mPMs) when subjects are either classified by ethnicity (r=0.94, P<0.001) or geographic region (r=0.99, P=0.002). Nevertheless, further research is needed in African and Asian populations, which are under-represented, and additional CYP2C19 variants and the 'measured' phenotype should be studied.

The impact of CYP2C19 polymorphisms on citalopram metabolism in patients with major depressive disorder

WHAT IS KNOWN AND OBJECTIVE

Genetic variations in drug-metabolizing enzyme genes change drug pharmacokinetics and response. CYP2C19 is a clinically important enzyme that metabolizes citalopram (CIT). The objective of this study was to determine CYP2C19 genetic polymorphisms and to evaluate the impact of these polymorphisms on the metabolism of citalopram in a sample of the Turkish population. We also assessed *17 polymorphism in healthy subjects in this population.

METHODS

The CYP2C19 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism method (209 healthy individuals and 50 patients for CIT metabolism), and the plasma concentrations of CIT and demethylcitalopram (DCIT) were quantified by high-performance liquid chromatography.

RESULTS AND DISCUSSION

The CYP2C19*1 and *17 allele frequencies for the patient group and the healthy group were 71·0%, 18·0% and 81·1%, 18·9%, respectively. There was no significant difference between the two groups (P > 0·05). The mean plasma concentrations and the mean dose-corrected (C/D) plasma levels of DCIT were significantly higher in patients with the CYP2C19*1/*1 genotype compared to patients with CYP2C19*1/*2 and CYP2C19*2/*2 genotypes (P < 0·05). Furthermore, the mean metabolic ratio (MR, CIT/DCIT) was also significantly higher in the CYP2C19*1/*2 + CYP2C19*2/*2 genotypes (P < 0·05). On the other hand, plasma CIT, DCIT concentrations and M/R value in the CYP2C19*1/*1 genotypes were no different to those of the CYP2C19*1/*17 genotypes (P > 0·05).

WHAT IS NEW AND CONCLUSION

Our data suggest that CYP2C19*17 polymorphism does not have a significant effect on CIT metabolism. In contrast CYP2C19*2 polymorphism has a prominent role and is likely to contribute to interindividual variability in CIT metabolism in vivo at therapeutic doses.

Evaluation of predictive CYP2C19 genotyping assays relative to measured phenotype in a South African cohort

AIM

To align predicted and measured CYP2C19 phenotype in a South African cohort.

MATERIALS & METHODS

Genotyping of CYP2C19*2, *3, *9, *15, *17, *27 and *28 was performed using PCR-RFLP, and an activity score (AS) system was used to predict phenotype. True phenotype was measured using plasma concentrations of omeprazole and its metabolite 5'-hydroxyomperazole.

RESULTS

Partial genotype-phenotype discrepancies were reported, and an adapted AS system was developed, which showed a marked improvement in phenotype prediction. Results highlight the need for a more comprehensive CYP2C19 genotyping approach to improve prediction of omeprazole metabolism.

CONCLUSION

Evidence for the utility of a CYP2C19 AS system is provided, for which the accuracy can be further improved by means of comprehensive genotyping and substrate-specific modification.

Frequency of CYP450 enzyme gene polymorphisms in the Greek population: review of the literature, original findings and clinical significance

The cytochrome P450 (CYP450) enzyme family is involved in the oxidative metabolism of many therapeutic drugs and various endogenous substrates. These enzymes are highly polymorphic. Prevalence of CYP450 enzyme gene polymorphisms vary among different populations and substantial inter- and intra-ethnic variability in frequency of CYP450 enzyme gene polymorphisms has been reported. This paper provides an overview and investigation of CYP450 genotypic and phenotypic reports published in the Greek population.

Hydroxylation index of omeprazole in relation to CYP2C19 polymorphism and sex in a healthy Iranian population

BACKGROUND

Polymorphism of CYP2C19 gene is one of the important factors in pharmacokinetics of CYP2C19 substrates. Omeprazole is a proton pump inhibitor which is mainly metabolized by cytochrome P450 2C19 (CYP2C19). The aim of present study was to assess omeprazole hydroxylation index as a measure of CYP2C19 activity considering new variant allele (CYP2C19*17) in Iranian population and also to see if this activity is sex dependent.

METHODS

One hundred and eighty healthy unrelated Iranian individuals attended in this study. Blood samples for genotyping and phenotyping were collected 3 hours after administration of 20 mg omeprazole orally. Genotyping of 2C19 variant alleles *2, *3 and *17 was performed by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and semi-nested PCR methods. Plasma concentrations of omeprazole and hydroxyomeprazole were determined by high performance liquid chromatography (HPLC) technique and hydxroxylation index (HI) (omeprazole/ hydroxyomeprazole) was calculated.

RESULTS

The CYP2C19*17 was the most common variant allele in the studied population (21.6%). Genotype frequencies of CYP2C19*17*17, *1*17, and *2*17 were 5.5%, 28.8% and 3.3% respectively. The lowest and the highest median omeprazole HI was observed in *17*17 and *2*2 genotypes respectively (0.36 vs. 13.09). The median HI of omeprazole in subjects homozygous for CYP2C19*1 was 2.16-fold higher than individuals homozygous for CYP2C19*17 (P < 0.001) and the median HI of CYP2C19*1*17 genotype was 1.98-fold higher than CYP2C19 *17*17 subjects (P < 0.001). However, subjects with CYP2C19*2*17 (median HI: 1.74) and CYP2C19*1*2 (median HI: 1.98) genotypes and also CYP2C19*1*17 (median HI: 0.71) and CYP2C19*1*1 (mean HI: 0.78) did not show any significantly different enzyme activity. In addition, no statistically significant difference was found between women and men in distribution of CYP2C19 genotypes. Furthermore, the hydroxylation index of Omeprazole was not different between women and men in the studied population.

CONCLUSION

Our data point out the importance of CYP2C19*2 and CYP2C19*17 variant alleles in metabolism of omeprazole and therefore CYP2C19 activity. Regarding the high frequency of CYP2C19*17 in Iranian population, the importance of this new variant allele in metabolism of CYP2C19 substrates shall be considered.

Pharmacodynamic effects of cilostazol versus clopidogrel in stented patients under proton pump inhibitor co-administration: the ACCEL-PARAZOL study

AIM

Proton pump inhibitor (PPI) therapy has been shown to attenuate the antiplatelet effects of clopidogrel. The aim of this study was to compare the antiplatelet effects of cilostazol versus clopidogrel in patients co-administered a PPI.

METHODS

We enrolled PPI-naïve stented patients treated with standard clopidogrel and aspirin therapy for at least six months (n=100). The patients were randomly assigned to receive either cilostazol at a dose of 100mg twice daily (CILO group) or clopidogrel at a dose of 75mg daily (CLPD group) in addition to lansoprazole (30mg daily). The platelet aggregation (PA) determined using light transmittance aggregometry and the platelet reactivity index (PRI) obtained using a vasodilator-stimulated phosphoprotein phosphorylation assay were measured before randomization and at the 14-day follow-up visit. The primary endpoint was the PRI value at follow-up.

RESULTS

At follow-up, the CLPD group showed similar values of PRI as the CILO group (66.9±14.0% vs. 63.1±14.1%; mean difference: 3.9%; 95% confidence interval of difference: -1.7% to 9.4%; p=0.174). However, the 6μg/mL collagen- and 0.5mg/mL arachidonic acid-induced PA values in the CLPD group were higher than those observed in the CILO group (mean differences: 9.8% to 11.1%; all p values ＜0.001). CYP2C19 loss-of-function allele carriage was the major contributing factor associated with the PRI level in the absence of lansoprazole treatment (with a gene-dose effect); this association was not observed in the subjects receiving lansoprazole co-administration in the CLPD group.

CONCLUSIONS

During lansoprazole co-administration, cilostazol treatment achieves a more favorable platelet function profile than clopidogrel therapy. The use of combination treatment with cilostazol and aspirin deserves further attention with respect to the management of stable stented patients requiring PPI co-administration.

Towards the clinical implementation of pharmacogenetics in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a psychiatric illness defined by pathological alterations between the mood states of mania and depression, causing disability, imposing healthcare costs and elevating the risk of suicide. Although effective treatments for BD exist, variability in outcomes leads to a large number of treatment failures, typically followed by a trial and error process of medication switches that can take years. Pharmacogenetic testing (PGT), by tailoring drug choice to an individual, may personalize and expedite treatment so as to identify more rapidly medications well suited to individual BD patients.

DISCUSSION

A number of associations have been made in BD between medication response phenotypes and specific genetic markers. However, to date clinical adoption of PGT has been limited, often citing questions that must be answered before it can be widely utilized. These include: What are the requirements of supporting evidence? How large is a clinically relevant effect? What degree of specificity and sensitivity are required? Does a given marker influence decision making and have clinical utility? In many cases, the answers to these questions remain unknown, and ultimately, the question of whether PGT is valid and useful must be determined empirically. Towards this aim, we have reviewed the literature and selected drug-genotype associations with the strongest evidence for utility in BD.

SUMMARY

Based upon these findings, we propose a preliminary panel for use in PGT, and a method by which the results of a PGT panel can be integrated for clinical interpretation. Finally, we argue that based on the sufficiency of accumulated evidence, PGT implementation studies are now warranted. We propose and discuss the design for a randomized clinical trial to test the use of PGT in the treatment of BD.

Clinical Impact of Cytochrome P450 2C19 Genotype on the Treatment of Invasive Aspergillosis under Routine Therapeutic Drug Monitoring of Voriconazole in a Korean Population

Background

Genetic polymorphisms of cytochrome P450 enzymes, especially CYP2C19 influence voriconazole pharmacokinetics. However, the impact of CYP2C19 genetic polymorphisms on the therapeutic efficacy and toxicity of voriconazole therapy are not well established.

Materials and Methods

In this prospective observational study, we analyzed all consecutive adult patients with hematologic diseases who were treated for invasive aspergillosis (IA) with voriconazole between January 2011 and June 2012. CYP2C19 genotype and routine therapeutic drug monitoring of voriconazole were performed. The target range for voriconazole trough levels was 1-5.5 mg/L.

Results

A total of 104 consecutive patients were enrolled, including 39 homozygous extensive metabolizers (EMs, 38%), 50 heterozygous extensive metabolizers (HEMs, 48%), and 15 poor metabolizers (PMs, 14%). The initial voriconazole trough levels were 1.8, 2.7, and 3.2 mg/L in EMs, HEMs, and PMs, respectively (P = 0.068). Out-of-range initial trough levels were most frequently observed in EMs (46%) followed by HEMs (26%) and PMs (0%) (P = 0.001). The frequency of initial trough levels < 1 mg/L but not > 5.5 mg/L differed significantly among the 3 groups (P = 0.005). However, treatment response, all-cause and IA-attributable mortality, and the occurrence of voriconazole-related adverse events did not differ significantly among the 3 groups (P = 0.399, P = 0.412, P = 0.317, and P = 0.518, respectively).

Conclusions

While none of the initial voriconazole trough levels in PMs was outside the target range, subtherapeutic initial trough levels were frequent in EMs. Although there was no significant relationship between CYP2C19 genotype and either the clinical outcomes of IA or toxicity of voriconazole, further large-scale multicenter studies using clinical data from homogeneous populations are required.

Clinical Application of CYP2C19 Pharmacogenetics Toward More Personalized Medicine

More than 30 years of genetic research on the CYP2C19 gene alone has identified approximately 2,000 reference single nucleotide polymorphisms (rsSNPs) containing 28 registered alleles in the P450 Allele Nomenclature Committee and the number continues to increase. However, knowledge of CYP2C19 SNPs remains limited with respect to biological functions. Functional information on the variant is essential for justifying its clinical use. Only common variants (minor allele frequency >5%) that represent CYP2C19*2, *3, *17, and others have been mostly studied. Discovery of new genetic variants is outstripping the generation of knowledge on the biological meanings of existing variants. Alternative strategies may be needed to fill this gap. The present study summarizes up-to-date knowledge on functional CYP2C19 variants discovered in phenotyped humans studied at the molecular level in vitro. Understanding the functional meanings of CYP2C19 variants is an essential step toward shifting the current medical paradigm to highly personalized therapeutic regimens.

CYP2C19 genetics in fatal carisoprodol intoxications

INTRODUCTION

Carisoprodol, a frequently used muscle relaxant, can cause potentially fatal intoxications. Conversion to its active metabolite meprobamate is almost solely mediated by cytochrome P450 2C19 (CYP2C19), and mutations in this enzyme could have significant effects on serum concentrations. The objective of this study was to investigate the role of CYP2C19 genetics in mortalities due to carisoprodol intoxication.

METHODS

The frequencies of CYP2C19 variant alleles were compared between the study group (n = 75) and two control groups, i.e. (1) deaths where carisoprodol was detected in the blood of the deceased, but intoxication was not the cause of death (control group A, n = 38), and (2) a healthy population not using carisoprodol (control group B, n = 185). In the study group and control A, the concentrations of carisoprodol and meprobamate were compared between the different genotype subgroups.

RESULTS

The variant allele frequencies of CYP2C19 did not differ significantly between the study group and control groups. Moreover, no statistically significant difference in the concentrations of carisoprodol and meprobamate between the different genotype subgroups was found.

CONCLUSIONS

This study finds no evidence for an important association between CYP2C19 genetics and mortality risk of carisoprodol. Other factors, such as co-administration with other drugs, likely play a more important role.

Does Gender have an Influence on Platelet Function and the Efficacy of Oral Antiplatelet Therapy?

The underlying pathophysiology of ischemic complications during acute coronary syndrome involves thrombus generation at sites of plaque rupture and endothelial erosion, in which platelet activation and aggregation play major roles. This review discusses whether there are intrinsic differences in thrombogenicity between genders. In trials of acute coronary syndromes with dual antiplatelet therapy strategies, women tend to experience more ischemic events. Controversy exists surrounding the protective role of estrogens in the premenopausal woman. In vitro studies support the attenuation of platelet function by estrogen. Sufficient data support the presence of gender differences in thrombogenicity to promote further investigation in this area.

Population differences in major functional polymorphisms of pharmacokinetics/pharmacodynamics-related genes in Eastern Asians and Europeans: implications in the clinical trials for novel drug development

Drug lag, recently discussed extensively in Japan, can be divided into two phases: clinical development time and application review time. The former factor is still an important problem that might be improved by promoting multi-regional clinical trials and considering the results from other similar populations with Japanese, such as Koreans and Chinese. In this review, we compare the allelic or genotype frequencies of 30 relatively common functional alleles mainly between Eastern Asians and Europeans as well as among 3 major populations in Eastern Asian countries, Japan, Korea, and China, in 12 pharmacokinetics (PK)/pharmacodynamics (PD)-related genes; CYP2C9 (*2 and *3), CYP2C19 (*2, *3 and *17), 13 CYP2D6 haplotypes including *4, *5 and *10, CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5, *6 and *7), GSTM1 and GSTT1 null genotypes, SLCO1B1 521T>C, ABCG2 421C>A, and HLA-A*31:01 and HLA-B*58:01. In this review, differences in allele frequencies (AFs) or genotype frequencies (GFs) less than 0.1 (in the cases of highest AF (GF) ≥0.1) or less than 0.05 (in the cases of lowest AF (GF) <0.1) were regarded as similar. Between Eastern Asians and Europeans, AFs (or GFs) are regarded as being different for many alleles such as CYP2C9 (*2), CYP2C19 (*2, *3 and *17), CYP2D6 (*4 and *10), CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5*7), GSTT1 null and ABCG2 421C>A. Among the 3 Eastern Asian populations, however, only AFs of CYP2C19*3, CYP2D6*10, HLA-A*31:01 and HLA-B*58:01 are regarded as dissimilar. For CYP2C19*3, the total functional impact on CYP2C19 could be small if the frequencies of the two null alleles CYP2C19*2 and *3 are combined. Regarding CYP2D6*10, frequency difference over 0.1 is observed only between Japanese and Chinese (0.147). Although environmental factors should be considered for PK/PD differences, we could propose that among Japan, Korea, and China, genetic differences are very small for the analyzed common PK-related gene polymorphisms. On the other hand, AFs of the two HLA alleles important for cutaneous adverse drug reactions are diverse even among Eastern Asians and thus should be taken into account.

Evaluation of lansoprazole as a probe for assessing cytochrome P450 2C19 activity and genotype-phenotype correlation in childhood

PURPOSE

Lansoprazole, a cytochrome P450 2C19 (CYP2C19) substrate, has been widely used in children to manage acid-related diseases. CYP2C19 exhibits marked genetic polymorphisms, and distribution of these polymorphisms varies among different ethnic groups. There is limited data regarding the use of probe drugs for determining CYP2C19 activity in children. The aim of this study was to evaluate lansoprazole as an in vivo phenotyping probe for assessing CYP2C19 activity in children.

METHODS

The CYP2C19*2, *3, and *17 variants were determined in 244 children. Three hours after a single oral dose of lansoprazole (n = 94) or omeprazole (n = 19), plasma lansoprazole and 5-hydroxy lansoprazole or omeprazole and 5-hydroxy omeprazole concentrations were analyzed by high-performance liquid chromatography.

RESULTS

The CYP2C19*17 was the most frequent variant allele (24.4%). The group of patients with CYP2C19*17*17 genotype had a 70% lower (p < 0.05) mean lansoprazole plasma concentration compared with the CYP2C19*1*1 genotype group, whereas the CYP2C19*2*2 group had 6.9-fold higher (p < 0.01) mean lansoprazole plasma concentration. Lansoprazole metabolic ratios (lansoprazole/5-hydroxy-lansoprazole) were found to be significantly lower in the *17*17 [mean ± standard deviation (SD); 2.8 ± 2.1] group and higher in the *2*2 group (63.5 ± 12.2) compared with that of the *1*1 genotype group (6.1 ± 4.5).

CONCLUSION

According to our results from a Turkish pediatric population, lansoprazole is a suitable probe drug for phenotyping CYP2C19. The CYP2C19*2 and *17 variants should be taken into consideration in predicting the clinical outcome of therapy with lansoprazole in the pediatric population.

Omeprazole limited sampling strategies to predict area under the concentration-time curve ratios: implications for cytochrome P450 2C19 and 3A phenotyping

PURPOSE

To develop a limited sampling strategy (LSS) to predict area under the concentration-time curve (AUC) ratios of omeprazole (AUC(OPZ)) to its metabolites 5-hydroxyomeprazole (AUC(5OH)) and omeprazole sulfone (AUC(SUL)) as phenotyping parameters for cytochrome P450 (CYP) 2C19 and 3A.

METHODS

Data were obtained from 37 (4 women) Caucasian, Chinese, and Korean healthy adults from three published studies. The AUC(OPZ), AUC(5OH), and AUC(SUL) were calculated via noncompartmental analysis. Observed AUC(OPZ, OBS)/AUC(5OH, OBS) and AUC(OPZ, OBS)/AUC(SUL, OBS) were determined. Plasma concentrations of omeprazole, 5-hydroxyomeprazole, and omeprazole sulfone at 1, 1.5, 2, 3, 4, 6, and 8 h post-dose were used to generate limited sampling strategy (LSS) models to predict AUC(OPZ,PRE)/AUC(5OH,PRE) and AUC(OPZ,PRE/)AUC(SUL,PRE). Bias and precision were assessed via percentage mean prediction error (%MPE) and percentage mean absolute error (%MAE), with acceptable limits being <15%.

RESULTS

For CYP2C19, the AUC(OPZ,OBS)/AUC(5OH,OBS) was [mean ± standard deviation (SD)] 2.10 ± 1.63. Five LSS models of AUC(OPZ,PRE)/AUC(5OH,PRE) were generated, but none met the bias or precision criteria. Upon stratification by CYP2C19 genotype and ethnicity, a three-timepoint (at 1, 2, and 4 h) LSS model accurately predicted AUC(OPZ)/AUC(5OH) in Caucasian CYP2C19*1/*1 subjects. For CYP3A, AUC(OPZ,OBS)/AUC(SUL,OBS) (mean ± SD) was 1.79 ± 0.67. All LSS models had unacceptable %MAE, even when stratified by CYP2C19 genotype and ethnicity.

CONCLUSIONS

A LSS model to predict AUC(OPZ)/AUC(5OH), and thus CYP2C19 activity, was generated for Caucasian CYP2C19*1/*1 subjects. However, additional model validation is needed prior to general use. LSS models to predict AUC(OPZ)/AUC(SUL), and thus CYP3A activity, were not possible, even upon stratification by CYP2C19 genotype and ethnicity.

CYP2C19 and ABCB1 gene polymorphisms are differently distributed according to ethnicity in the Brazilian general population

Background

Recent studies have reported the clinical importance of CYP2C19 and ABCB1 polymorphisms in an individualized approach to clopidogrel treatment. The aims of this study were to evaluate the frequencies of CYP2C19 and ABCB1 polymorphisms and to identify the clopidogrel-predicted metabolic phenotypes according to ethnic groups in a sample of individuals representative of a highly admixtured population.

Methods

One hundred and eighty-three Amerindians and 1,029 subjects of the general population of 4 regions of the country were included. Genotypes for the ABCB1c.C3435T (rs1045642), CYP2C19*2 (rs4244285), CYP2C19*3 (rs4986893), CYP2C19*4 (rs28399504), CYP2C19*5 (rs56337013), and CYP2C19*17 (rs12248560) polymorphisms were detected by polymerase chain reaction followed by high resolution melting analysis. The CYP2C19*3, CYP2C19*4 and CYP2C19*5 variants were genotyped in a subsample of subjects (300 samples randomly selected).

Results

The CYP2C19*3 and CYP2C19*5 variant alleles were not detected and the CYP2C19*4 variant allele presented a frequency of 0.3%. The allelic frequencies for the ABCB1c.C3435T, CYP2C19*2 and CYP2C19*17 polymorphisms were differently distributed according to ethnicity: Amerindian (51.4%, 10.4%, 15.8%); Caucasian descent (43.2%, 16.9%, 18.0%); Mulatto (35.9%, 16.5%, 21.3%); and African descent (32.8%, 20.2%, 26.3%) individuals, respectively. As a result, self-referred ethnicity was able to predict significantly different clopidogrel-predicted metabolic phenotypes prevalence even for a highly admixtured population.

Conclusion

Our findings indicate the existence of inter-ethnic differences in the ABCB1 and CYP2C19 variant allele frequencies in the Brazilian general population plus Amerindians. This information could help in stratifying individuals from this population regarding clopidogrel-predicted metabolic phenotypes and design more cost-effective programs towards individualization of clopidogrel therapy.

Linkage disequilibrium between the CYP2C19*17 allele and wildtype CYP2C8 and CYP2C9 alleles: identification of CYP2C haplotypes in healthy Nordic populations

PURPOSE

To determine the distribution of clinically important CYP2C genotypes and allele frequencies in healthy Nordic populations with special focus on linkage disequilibrium.

METHODS

A total of 896 healthy subjects from three Nordic populations (Danish, Faroese, and Norwegian) were genotyped for five frequent and clinically important CYP2C allelic variants: the defective CYP2C8*3, CYP2C9*2, CYP2C9*3, and CYP2C19*2 alleles, and the CYP2C19*17 allele that causes rapid drug metabolism. Linkage disequilibrium was evaluated and CYP2C haplotypes were inferred in the entire population.

RESULTS

Ten CYP2C haplotypes were inferred, the most frequent of which (49%) was the CYP2C wildtype haplotype carrying CYP2C8*1, CYP2C9*1, and CYP2C19*1. The second most frequent haplotype (19%) is composed of CYP2C19*17, CYP2C8*1, and CYP2C9*1. This predicted haplotype accounts for 99.7% of the CYP2C19*17 alleles found in the 896 subjects.

CONCLUSION

CYP2C19*17 is a frequent genetic variant in Nordic populations that exists in strong linkage disequilibrium with wildtype CYP2C8*1 and CYP2C9*1 alleles, which effectively makes it a determinant for a haplotype exhibiting an efficient CYP2C substrate metabolism.