Investigating CYP2C19 loss-of-function allele statuses and their association with stroke of different etiologies in a Taiwanese population.

BACKGROUND: CYP2C19 loss-of-function single-nucleotide polymorphisms (SNPs) are associated with poor responses of clopidogrel in secondary prevention of ischemic stroke (IS). It is still unclear whether these SNPs, which may result in poor cytochrome P450 2C19 (CYP2C19) enzymatic activity, affect the occurrence of IS and its subtypes. The present study evaluated the relationship between the CYP2C19 loss-of-function alleles and IS. METHODS: Eight hundred sixty-eight patients with IS and 557 nonstroke (NS) control individuals were prospectively recruited. Stroke etiologies, including large-artery atherosclerosis (LAA), cardioembolism (CE), and small-vessel occlusion (SVO), were determined. The two most common CYP2C19 loss-of-function alleles worldwide, CYP2C19*2 and CYP2C19*3, were investigated by genotyping. Patients with two loss-of-function alleles of the CYP2C19 genes were classified as poor metabolizers. RESULTS: Our population has a high frequency of CYP2C19 loss-of-function alleles, mostly contributed by CYP2C19*2, being present in 51.3% to 57.5% of patients with IS of different etiologies and 53.1% of NS individuals. The proportions of CYP2C19 poor metabolizers within NS group and each IS group with disparate etiology are similar (NS 73 [13.1%]; LAA 44 [14.2%], p = 0.623; CE 26 [14.0%], p = 0.541; SVO 38 [13.3%], p = 0.443). Nevertheless, the frequencies of CYP2C19*3 allele were different among the NS and different IS subgroups. Multivariate analyses adjusting for age, sex, and vascular risk factors revealed that CYP2C19*3 allele was a protective factor for SVO (odds ratio [OR] = 0.5, 95% confidence interval [CI] = 0.3 to 0.9, p = 0.015 [vs NS], OR = 0.5, 95% CI = 0.3 to 0.8, p = 0.010 [vs LAA and CE]). CONCLUSION: The CYP2C19 poor metabolizer is not associated with IS and its subtypes. Furthermore, CYP2C19*3 may be a protective factor for SVO and its mechanism warrants further investigation.

Metabolic activity testing can underestimate acute drug cytotoxicity as revealed by HepG2 cell clones overexpressing cytochrome P450 2C19 and 3A4.

Preclinical drug safety assessment includes in vitro studies with physiologically relevant cell cultures. As an in vitro system for hepatic toxicology testing, we have been generating cell clones of human hepatoblastoma cell line HepG2 by lentiviral transduction of phase I cytochrome P450 (CYP) enzymes. Here, we present a stable CYP2C19-overexpressing HepG2 cell clone (HepG2-2C19 C1) showing an enzyme activity of approximately 82 pmol x min-1 x mg-1 total cellular protein. The phenotypic stability over several passages of HepG2-2C19 C1 renders them to be a suitable reference cell clone for benchmarking CYP2C19 enzyme activity. In addition, we were interested to analyze acute cytotoxicity of the model drug cyclophosphamide (CPA) metabolized by HepG2-2C19 C1 and by a previously generated CYP3A4-overexpressing HepG2 cell clone. Upon 10 mM CPA exposure, we were able to detect its metabolites 4-hydroxy-cyclophosphamide and acrolein in CYP3A4- and CYP2C19-expressing cell clones, but not in parental HepG2 cell line. XTT and ATP assays showed a modest reduction of cell viability of not more than 50% with high dose (10 mM) CPA treatment. By contrast, dramatic acute cytotoxic effects of CPA were evident by the formation of nuclear γH2AX foci and by increased cell death events. These effects were paralleled by substantial decreases of cell membrane integrity as measured by the trypan blue exclusion test. Our data on CYP enzyme overexpressing HepG2 cell clones clearly show that cytotoxicity of CPA is dramatically underestimated by standard metabolic activity tests. Thus, additional tests to quantitate DNA damage formation and cell death induction might be required to realistically assess cytotoxicity of such compounds.

The influence of combination use of CYP450 inducers on the pharmacokinetics of voriconazole: a systematic review.

WHAT IS KNOWN AND OBJECTIVES: Voriconazole is a triazole antifungal agent and is extensively metabolized via cytochrome P450 (CYP450); therefore, special precautions need to be taken when co-administered with a known CYP450 inducer, which may lead to treatment failure. The influence of some CYP450 inducers on the pharmacokinetics of voriconazole has been described in previous studies, but a systematic review was lacking. In this study, we carried out a systematic review to assess the influence of CYP450 inducers on the pharmacokinetic (PK) parameters of voriconazole. METHODS: Pubmed, Embase, Cochrane Library, Clinicaltrials.gov and three Chinese databases (CNKI, CBM and WanFang) were searched through January 2016. Interventional and observational studies comparing the PK parameters of voriconazole used alone or with CYP450 inducers in healthy volunteers and patients were included. The outcomes included were the area under the plasma concentration-time curve (AUC), peak plasma concentrations (Cmax ) and trough plasma concentrations (Cmin ). The quality of the included studies was assessed using Cochrane's risk of bias tool, Newcastle-Ottawa Scale (NOS) and a modified risk of bias tool for pharmacokinetic before-and-after studies. RESULTS AND DISCUSSION: Sixteen studies were included in this review: three randomized controlled trials (RCTs), five single-arm before-after studies (SBAs), six cohort studies and two case reports. All studies except case reports had moderate to high quality. Of the 11 inducers reviewed, efavirenz, ritonavir (chronic use), phenytoin, rifampin and rifabutin significantly decreased mean AUC and Cmax of voriconazole; St John's wort significantly decreased only mean AUC; rifampin, rifabutin, phenobarbital and carbamazepine significantly decreased mean Cmin . Etravirine and Ginkgo biloba did not reveal any such influence. The influence of glucocorticoids may depend on its type and dose. WHAT IS NEW AND CONCLUSIONS: To conclude, the combination use of high-dose efavirenz, high-dose ritonavir, St John's wort, rifampin, phenobarbital, or carbamazepine with voriconazole is contraindicated as instructed in the drug label. Low-dose efavirenz, low-dose ritonavir, rifabutin and phenytoin may be used together with voriconazole provided TDM and dose adjustment of voriconazole. Moreover, this study shows there is low risk of drug-drug interactions when voriconazole is co-administered with etravirine or G. biloba; however, whether the use of glucocorticoids has a clinically significant effect on voriconazole still requires more evidence. This study also highlights the lack of clinical studies and future high-quality studies assessing the influence of CYP450 inducers on voriconazole. PK parameters and dosing optimization should be designed to provide a more definitive answer regarding the necessity of TDM and the recommendations for dose adjustment of voriconazole.

The Impact of CYP2C19 Loss-of-Function Polymorphisms, Clinical, and Demographic Variables on Platelet Response to Clopidogrel Evaluated Using Impedance Aggregometry.

INTRODUCTION: Clopidogrel is an antiplatelet drug widely used in patients with acute coronary syndromes or stroke. Despite adequate antiplatelet therapy, some patients develop acute ischemic events. This is partly attributed to the fact that they have poor inhibition of platelet reactivity, despite treatment. This study aimed to assess the impact of clinical and demographic variables and of cytochrome P450 2C19 (CYP2C19) loss-of-function polymorphisms on platelet response to clopidogrel evaluated using impedance aggregometry in an East European population. METHODS: The study included 189 clopidogrel-treated patients with acute coronary syndromes and noncardiogenic ischemic stroke. Platelet aggregation was evaluated by impedance aggregometry. CYP2C19 loss-of-function polymorphisms were detected using the polymerase chain reaction restriction fragment length polymorphism technique. Various clinical and demographic data were also recorded. RESULTS: In our data set, 81% of the patients were responders and 19% nonresponders to clopidogrel therapy. The distribution of CYP2C19 polymorphisms was as follows: 61.1% of patients were CYP2C19 wild-type homozygotes, 27.7% of patients were CYP2C19*2 heterozygotes, 1.1% of patients were CYP2C19*3 heterozygotes, and 10% of patients were CYP2C19*2 homozygotes. The highest level of association with clopidogrel response status was found for CYP2C19 polymorphisms, concomitant aspirin treatment, leukocyte and platelet count, history of myocardial infarction, arterial hypertension, and ward where patients were admitted. CONCLUSION: The prevalence of clopidogrel resistance in our East European population was in line with that reported for Western populations. Clopidogrel response was significantly influenced by the presence of CYP2C19 polymorphisms. Interestingly, the concomitant use of aspirin had a significant impact on platelet response to clopidogrel, indicating a synergic interaction between these drugs.

Cytochrome P450 CYP 2C19*2 Associated with Adverse 1-Year Cardiovascular Events in Patients with Acute Coronary Syndrome.

BACKGROUND: The cytochrome P450 (CYP450) 2C19 681 genotypes affect the antiplatelet activity of clopidogrel. We investigated the correlation of CYP 2C19 681G > A mutation with clopidogrel resistance (CR). Additionally, we studied the effect of CR on clinical prognosis of patients with acute coronary syndrome (ACS). METHODS: One hundred ten ACS patients undergoing percutaneous coronary intervention, who were followed-up for 1 year, were included in the study. The patients were co-administered aspirin 100 mg/d and clopidogrel 75mg/d following a loading dose of 300 mg. CR was assessed on the basis of polymorphism observed in the CYP2C19 subgroup. RESULTS: Patients in GG genotype group exhibited greater inhibition of platelet aggregation than patients in GA and AA genotype groups (16.2 ± 10.1%; 10.2 ± 9.9%; 8.0 ± 5.9%, respectively, p < 0.01). CYP2C19 681GG genotype group was associated with lower CR than CYP2C19 681A allele (GA + AA) group (9/59 vs. (12+5)/51; p = 0.009). Over a follow-up of 12 months, the incidence of recurrent angina, acute myocardial infarction, and intra-stent thrombosis in CYP2C19 681 GG carriers was significantly lower than that in CYP2C19 681A allele (GA + AA) group (2/59 vs. 8/51, 1/59 vs. 6/51, 0 vs. 4/51, respectively, p < 0.05). CONCLUSION: CYP 2C19*2 is associated with reduced clopidogrel antiplatelet activity and might be an important marker for poor prognosis of ACS.

[Drug resistant epilepsy. Clinical and neurobiological concepts]. / Farmacorresistencia en epilepsia. Conceptos clínicos y neurobiológicos.

Drug-resistant epilepsy, is a condition defined by the International League Against Epilepsy as persistent seizures despite having used at least two appropriate and adequate antiepileptic drug treatments. Approximately 20-30% of patients with epilepsy are going to be resistant to antiepileptic drugs, with different patterns of clinical presentation, which are related to the biological basis of this disease (de novo resistance, relapsing-remitting and progressive). Drug resistant epilepsy, impacts negatively the quality of life and significantly increases the risk of premature death. From the neurobiological point of view, this medical condition is the result of the interaction of multiple variables related to the underlying disease, drug interactions and proper genetic aspects of each patient. Thanks to advances in pharmacogenetics and molecular biology research, currently some hypotheses may explain the cause of this condition and promote the study of new therapeutic options. Currently, overexpression of membrane transporters such as P-glycoprotein, appears to be one of the most important mechanisms in the development of drug resistant epilepsy. The objective of this review is to deepen the general aspects of this clinical condition, addressing the definition, epidemiology, differential diagnosis and the pathophysiological bases.

TITLE: Farmacorresistencia en epilepsia. Conceptos clinicos y neurobiologicos.La epilepsia farmacorresistente es una condicion definida por la Liga Internacional contra la Epilepsia como la persistencia de crisis epilepticas a pesar de haber utilizado al menos dos tratamientos con farmacos antiepilepticos apropiados y adecuados. Cerca de un 20-30% de los pacientes con epilepsia van a ser resistentes a los farmacos antiepilepticos, con diferentes patrones de presentacion clinica, los cuales estan en relacion con las bases biologicas de esta enfermedad (resistencia de novo, recaida-remision y progresiva). La farmacorresistencia en epilepsia impacta negativamente en la calidad de vida y aumenta significativamente el riesgo de muerte prematura. Desde el punto de vista neurobiologico, esta condicion clinica es el resultado de la interaccion de multiples variables relacionadas con la enfermedad de base, las interacciones medicamentosas y los aspectos geneticos propios de cada paciente. Gracias a los avances en la investigacion farmacogenetica y de biologia molecular, actualmente se plantean algunas hipotesis que podrian explicar la causa de esta condicion y que promueven el estudio de nuevas opciones terapeuticas. En la actualidad, la sobreexpresion de transportadores de membrana, como la glucoproteina P, parece ser uno de los mecanismos mas importantes en el desarrollo de la farmacorresistencia en epilepsia. El objetivo de esta revision es profundizar en los aspectos generales de esta condicion clinica, abordando la definicion, los aspectos epidemiologicos, los diagnosticos diferenciales y las bases fisiopatologicas.

Interaction of rocuronium with human liver cytochromes P450.

Rocuronium is a neuromuscular blocking agent acting as a competitive antagonist of acetylcholine. Results of an inhibition of eight individual liver microsomal cytochromes P450 (CYP) are presented. As the patients are routinely premedicated with diazepam, possible interaction of diazepam with rocuronium has been also studied. Results indicated that rocuronium interacts with human liver microsomal CYPs by binding to the substrate site. Next, concentration dependent inhibition of liver microsomal CYP3A4 down to 42% (at rocuronium concentration 189 µM) was found. This effect has been confirmed with two CYP3A4 substrates, testosterone (formation of 6ß-hydroxytestosterone) and diazepam (temazepam formation). CYP2C9 and CYP2C19 activities were inhibited down to 75-80% (at the same rocuronium concentration). Activities of other microsomal CYPs have not been inhibited by rocuronium. To prove the possibility of rocuronium interaction with other drugs (diazepam), the effect of rocuronium on formation of main diazepam metabolites, temazepam (by CYP3A4) and desmethyldiazepam, (also known as nordiazepam; formed by CYP2C19) in primary culture of human hepatocytes has been examined. Rocuronium has caused inhibition of both reactions by 20 and 15%, respectively. The results open a possibility that interactions of rocuronium with drugs metabolized by CYP3A4 (and possibly also CYP2C19) may be observed.

[Relevance of CYP2C19 2 regarding platelet reactivity in patients with acute coronary syndrome treated with clopidogrel]. / Impacto de CYP2C19 2 en la reactividad plaquetar en pacientes con síndrome coronario agudo tratados con clopidogrel.

BACKGROUND AND OBJECTIVE: Previous studies have shown that the metabolism of P2Y12 receptor blockers is influenced not only by CYP2C19 2 but also by PON1-Q192R alelles. We aimed to evaluate the impact of CYP2C19 2 and PON1-Q192R polymorphisms carriage in platelet reactivity and clinical outcome in patients with ischemic heart disease undergoing cardiac catheterization. PATIENTS AND METHOD: We recruited prospectively patients with acute coronary syndrome undergoing cardiac catheterization (n=247). We evaluated the genotype (CYP2C19 2, CYP2C19 17, PON1-Q192R) with TaqMan(®) assay and platelet aggregometry in all patients. We assessed both in and out-of-hospital events (unstable angina, periprocedural and spontaneous myocardial infarction, myocardial infarction, all-cause death, stent thrombosis and stroke) during follow-up. RESULTS: Carriers of CYP2C19 2 alleles showed a significant higher residual platelet reactivity (PRU, mean [SD], 252 [76] vs. 287 [74], P=.002). Carriers of PON1-Q192R CT(RQ) and TT(QQ) alleles and CYP2C19 17 did not present a different response to clopidogrel. In a multivariable setting for the prediction of platelet reactivity, the contribution of CYP2C19 2 was modest (Wald=7.5; odds ratio [OR] for ≥ 1 alelle 2=2,786, 95% confidence interval [95% CI] 1,337-5,808). Independent predictors were baseline hemoglobin levels (g/dL, OR .666, 95% CI .555-.801) and the use of statins (OR .376, 95% CI .162-.873). Body mass index was a risk factor (OR 1,074, CI 95% 1,005-1,148). Studied polymorphisms did not predict an adverse outcome. CONCLUSIONS: CYP2C19 2 polymorphism influenced moderately platelet reactivity but did not show an impact on clinical outcome in patients with acute coronary syndrome. Neither CYP2C19 17 nor PON1-Q192R polymorphisms showed an impact upon platelet reactivity or outcome.