CYP2C9 Alleles Research Articles

The prevalence of VKORC1 1639 G>A and CYP2C9*2*3 genotypes in patients that requiring anticoagulant therapy in Turkish population

The aim was to investigate the prevalence of VKORC1 and CYP2C9 genotypes in patients requiring anticoagulant therapy in two different region's populations of Turkey. The recent cohort included 292 patients that needed anticoagulant therapy, and who had a history of deep vein thrombosis and/or pulmonary artery thromboembolism. Genomic DNA was isolated from peripheral blood samples and the StripAssay reverse hybridization or Real Time PCR technique was used for genotype analysis. Genotypes for CYP2C9 were detected as follows: 165 (56.5 %) for CYP2C9*1/*1, 67 (23.0 %) for CYP2C9*1/*2, 25 (8.6 %) for CYP2C9*1/*3, 9 (3.0 %) for CYP2C9*2/*2, 21 (7.2 %) for CYP2C9*2/*3, 5(1.7 %) for CYP2C9*3/*3 for CYP2C9 and the allele frequencies were: 0.723 for allele*1, 0.182 for allele*2 and 0.095 for allele*3 respectively. Genotypes for VKORC1 were detected as follows: 64 (21.9 %) for GG, 220 (75.4 %) for GA and 8 (2.7 %) for AA alleles. The G allele frequency was detected as 0.596, and the A allele frequency was 0.404. The VKORC1 1639 G>A and CYP2C9 mutation prevalence and allele frequency of the current results from two different populations (Sivas and Canakkale) showed similarly very variable profiles when compared to the other results from the Turkish population.

Lack of association between clopidogrel responsiveness tested using point-of-care assay and prognosis of patients with coronary artery disease

Dual antiplatelet therapy is important treatment modality across the spectrum of coronary artery disease manifestations. However, a significant number of patients do not have a completely effective response to clopidogrel. This study assessed the impact of response after clopidogrel with Verify Now device on prognosis on patients undergoing coronary interventions. Consecutive patients following percutaneous coronary intervention were prospectively enrolled. A loading dose of 600mg of clopidogrel was administered before or during PCI. Blood samples were drawn within 24h after clopidogrel administration. The effect of clopidogrel was measured using VerifyNow. All patients were evaluated at 6months. The primary end-point was the combination of death, MI and stroke. 378 patients (69.3% men and 30.7% women) were enrolled. The mean age was 67.2±12.8years, BMI 28.9±17.7, and 116 patients had diabetes (30.7%). During the 6-months follow-up 30 patients (7.94%) experienced a monitored end-point: 12 patients (3.17%) had MI; five patients (1.32%) strokes and 15 patients (3.97%) died. The remaining 248 patients (71.26%) were end-point free. Factors associated with a poor prognosis were: leukocytes (OR 1.7 [1.2-2.4], p<0.01), creatinine (OR 1.4 [1.1-2.5], p<0.05) and at a borderline level the presence of AA allele of gene CYP2C19*2 (OR 2.5 [0.99-4.1], p=0.052). The results using VerifyNow were similar between both groups (Group End-point: 208.5±85.5, group No end-point 203.1±91.3) and failed to show any prognostic value (OR 1.00 [0.992-1.007], p=0.9). The measurement of clopidogrel efficacy using VerifyNow had no prognostic value for our unselected cohort of patients after PCI.

RESEARCH CYP2C19*2 GENE POLYMORPHISM WITH ACUTE CORONARY SYNDROME

ObjectivesCytochrome P450 (cytochrome P450 or CYP450, hereinafter referred to as CYP) is a group of ferroheme enzymes. CYP2C19 enzyme is very important metabolic enzyme in this enzyme system. CYP2C19 gene...

Clinical pharmacogenomics and concept of personalized medicine / Klinička farmakogenomika i koncept personalizovane medicine

Summary The term »personalized medicine« (PM) was coined in the late 1990s, but was not introduced to general US public until about a decade later, through Genomics and Personalized Medicine Act. According to this act, PM is defined as any clinical practice model that utilizes genomic and family history information to customize diagnostic and therapeutic interventions and improve health outcomes. One of the emerging disciplines essential for implementation of PM is clinical pharmacogenomics (PGx), where patient’s genetic information is utilized to personalize drug therapy. PGx testing includes mostly detection of small DNA variations, such single nucleotide polymorphisms (SNPs), insertions, and deletions in the genes encoding the drug transporters, receptors and metabolizing enzymes. By providing the right drug at the optimal dose to each patient, PGx promises to significantly improve drug efficacy and prevent adverse drug reactions. In the early 2000s, the US Food and Drug Administration joined scientists and laboratorians in their efforts to translate recent genetic advances into clinical practice by requiring the drug manufacturers to include genetic information on their product labels. To date several drugs including irinotecan, warfarin, abacavir and clopidogrel are labeled with the information relating different enzymatic polymorphisms with the adverse drug effects or the impaired drug efficacy. The majority of PGx testing involves SNP detection within the family of Cytochrome (CYP) P450 enzymes responsible for metabolism of most drugs, such as anti-depressants (e.g. CYP2D6) and anticoagulants (e.g. CYP2C9, 2C19) to name a few. PGx tests are still very low volume tests and it is not clear how and to what extent genotyping information is being utilized in the clinical practice, mostly due to the lack of outcome studies demonstrating the clinical utility of PGx testing. For instance, it is well known that approximately 30% of Caucasian population carries a polymorphic CYP2C9 allele that predisposes them to higher warfarin sensitivity and thus to increased bleeding risk. How - ever, there are no large, randomized outcome studies that conclusively demonstrate reduction of bleeding events or decrease in hospitalization rates in population dosed based on genotype information. The clinicians are thus reluctant to incorporate warfarin genotyping into their practice. Despite the attention PGx has received in recent years, the adoption of PGx into routine clinical testing is still far from being commonplace. The barriers to wider adoption and implementation of PGx include lack of education and understanding by prescribing physicians regarding the available tests, lack of consensus guidelines on interpretation and use of genotype results and scarcity of randomized controlled trials demonstrating the clinical utility of PGx testing. However, as ge netic testing is becoming increasingly patient driven thought di - rect-to-consumer testing, clinicians and laboratorians must continue to work toward full implementation of PGx testing into routine clinical practice.

Pharmacogenetics of Clopidogrel

Clopidogrel used in conjunction with aspirin has a central role in the treatment of patients with an acute coronary syndrome (ACS) and/or undergoing percutaneous coronary intervention (PCI). The pharmacokinetic and pharmacodynamic responses to this drug are highly variable leaving up to one third of patients with inadequate platelet inhibition or high on-treatment platelet reactivity (HPR), and subsequent increased ischemic cardiovascular events. Genetic variability in drug absorption and metabolism is a key factor responsible for the inefficient generation of the active drug metabolite. The two-step hepatic cytochrome P450 (CYP)-dependant oxidative metabolism of the prodrug appears to be of particular importance. Pharmacogenomic analyses have identified loss-of-function variant alleles of CYP 2C19 and specifically the 2C19*2 allele, to be the predominant genetic mediators of the antiplatelet effect of clopidogrel. Carriers were have been shown to have lower active metabolite levels of clopidogrel, higher platelet reactivity and associated poorer outcomes. Rapid and accurate point-of-care genetic tests to identify these alleles are currently in development but several questions about the role of such testing remain such as patient selection and whether personalized treatment based on genotype has a positive impact on clinical outcome. At present, genetic testing cannot be recommended in routine clinical practice due to insufficient prospective data. However, the significant body of research published to date suggests a likely role when used in combination with platelet function analysis in ACS patients undergoing stenting who have other known risk factors for recurrent ischemic events.

Influence of CYP2C19 loss-of-function variants on the antiplatelet effects and cardiovascular events in clopidogrel-treated Chinese patients undergoing percutaneous coronary intervention

A large number of clinical studies have well demonstrated that the loss-of-function variant allele CYP2C19 2 is associated with attenuated response to clopidogrel and increased risk of developing stent thrombosis (ST) in white or black patients with stenting. However, similar association studies on the effect of the CYP2C19 2 and 3 variants on maximum platelet aggregation (MPA) and the risk of cardiovascular events are currently unavailable for the Chinese patients. This work was aimed at assessing the impact of the CYP2C19 2 and 3 variants on the antiplatelet effects and adverse cardiovascular events in clopidogrel-treated Chinese patients undergoing percutaneous coronary intervention (PCI). The study population consisted of 617 patients undergoing PCI. Genotypes were determined using MALDI/TOF-MS. MPA was measured by light transmittance aggregometry. The clinical end-point was the 1-year incidence of adverse cardiovascular events, including ST. Carriers of CYP2C19 heterozygous (1/2, or 1/3; n = 278) and mutant homozygous (2/2, 2/3, or 3/3, n = 80) genotypes had significantly higher MPA values than noncarriers (1/1; n = 259; P = 0.036 and 0.007 respectively). Moreover, the presence of the CYP2C19 2 or 3 mutant allele was significantly associated with an increased risk of developing ST, with the higher risk of ST being seen in patients homozygous for the CYP2C19 2 or 3 variant allele than in noncarriers (OR, 13.58; 95% CI, 1.49-123.31; P = 0.012). Furthermore, multivariate analysis revealed an independent association of the presence of CYP2C19*2 and/or 3 variant alleles with greater MPA values (P = 0.001) and increased risk of ST (OR, 11.67; 95% CI, 1.21-78.83; P = 0.022). However, there was no significant influence of CYP2C19 2 and 3 on the risk of developing other adverse cardiovascular events. Carriage of the loss-of-function genetic variants CYP2C19 2 and 3 is significantly associated with attenuated platelet response to clopidogrel and an increased risk of ST in Chinese patients treated with stenting.

CYP3A4 and CYP2C19 genetic polymorphisms and zolpidem metabolism in the Chinese Han population: A pilot study

Zolpidem (ZPD) is an imidazopyridine hypnotic and little is known about the pharmacogenetics of ZPD. Our objective was to evaluate inter-individual genetic variation in conjunction with metabolic ratios of ZPD found in a toxicological analysis. Healthy individuals (n=300) were genotyped for CYP2D6, CYP2C19, CYP2C9, CYP3A4 and CYP1A2 by allele-specific primer extension followed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-four Chinese volunteers were chosen and divided into the following four groups (n=6/group): group 1: CYP3A4*18 (wild-type, W), CYP2C19*2 (W); group 2: CYP3A4*18 (mutant, M), CYP2C19*2 (W); group 3: CYP3A4*18 (W), CYP2C19*2 (M); and group 4: CYP3A4*18 (M), CYP2C19*2 (M). ZPD and its major metabolites zolpidem 6-carboxylic acid (ZCA) and zolpidem phenyl-4-carboxylic acid (ZPCA) were determined after oral administration of ZPD (10mg), using an UPLC–MS/MS method. Positive correlations between CYP3A4 and CYP2C19 alleles and ZPD metabolism were found. The results of this study show that CYP3A4*18 increases CYP3A4 activity while CYP2C19*2 reduces CYP2C19 activity; the latter mutation is associated with the poor metabolism of ZPD in the Chinese Han population. The results also suggest that genetic factors play a major role in the metabolism of individual drugs with implications for both forensic science and clinical pharmacogenetics.

Distribution of CYP2D6 and CYP2C19 Polymorphisms Associated with Poor Metabolizer Phenotype in Five Amerindian Groups and Western Mestizos from Mexico

The distribution of polymorphisms in the CYP2D6 and CYP2C19 genes allows inferring the potential risk for specific adverse drug reactions and lack of therapeutic effects in humans. This variability shows differences among human populations. The aim of this study was to analyze single-nucleotide polymorphisms related to a poor metabolizer (PM) phenotype in nonpreviously studied Amerindian groups and Mestizos (general admixed population) from Mexico. We detected by SNaPshot(®) different polymorphisms located in CYP2D6 (*3, *4, *6, *7, and *8) and CYP2C19 (*2, *3, *4 and *5) in western Mestizos (n=145) and five Amerindian groups from Mexico: Tarahumaras from the North (n=88); Purépechas from the Center (n=101); and Tojolabales (n=68), Tzotziles (n=88), and Tzeltales (n=20) from the Southeast. Genotypes were observed by capillary electrophoresis. The genetic relationships among these populations were estimated based on these genes. The wild-type allele (*1) of both genes was predominant in the Mexican populations studied. The most widely observed alleles were CYP2C19*2 (range, 0%-31%) and CYP2D6*4 (range, 1.2%-7.3%), whereas CYP2D6*3 was exclusively detected in Mestizos. Conversely, CYP2C19*4 and *5, as well as CYP2D6*3, *6, *7, and *8, were not observed in the majority of the Mexican populations. The Tarahumaras presented a high frequency of the allele CYP2C19*2 (31%) and of homozygotes *2/*2 (10.7%), which represent a high frequency of potentially PM phenotypes in this Amerindian group. The genetic distances showed high differentiation of Tarahumaras (principally for CYP2C19 gene). In general, a relative proximity was observed between most of the Amerindian, Mexican-Mestizo, and Latin-American populations. In general, the wild-type allele (*1) predominates in Mexican populations, outlining a relatively homogeneous distribution for CYP2C19 and CYP2D6. The exception is the Tarahumara group that displays a potentially increased risk for adverse reactions to CYP2C19-metabolized drugs.

Development of primer-special TaqMan PCR: a novel SNP detection method to detect CYP2C9 3 in South Chinese.

CYP2C9 3 (1075A/C) is an inherited single nuclear polymorphism (SNP) of cytochrome P450 (CYP) 2C9, which affects the activity of the enzyme. In vitro studies with several drugs have indicated that the CYP2C9 3 variant has an impaired capacity for drug metabolism. Therefore an efficient detection assay for this mutation may be important for clinical dose adjustment. The aim of this work was to develop an appropriate tool for detection of the CYP2C9 3 polymorphism in the clinical laboratory. The previously described TaqMan mismatch amplification mutation assay (TaqMAMA) was modified to a primer-special (PS)-TaqMan PCR to satisfy the high-throughput requirements of a clinical laboratory. 404 genomic DNA samples from South Chinese individuals were genotyped to test the detection system. The results were checked by bi-directional sequencing. PS-TaqMan PCR could correctly genotype the CYP2C9 allele from a genomic template at a concentration of 1 x 104 to 1 x 1011 copies/PCR. Among the 404 genomic DNA samples, 24 heterozygotes and 380 wild-type homozygotes were detected and confirmed by bi-directional sequencing. PS-TaqMan PCR was successfully developed for CYP2C9 3 detection. This efficient, reliable, high-throughput tool could satisfy the requirements of a clinical laboratory test.

Significance of CYP2C9 genetic polymorphism in inhibitory effect of Δ9-tetrahydrocannabinol on CYP2C9 activity

We recently reported that Δ9-tetrahydrocannabinol (Δ9-THC), the primary psychoactive constituent in marijuana, potently inhibits the catalytic activity of cytochrome P450 (CYP) 2C9.1, a wild-type variant. However, effects of CYP2C9 genetic polymorphisms on the inhibitory potency of Δ9-THC have not been investigated. In this study, in vitro inhibitory effects of Δ9-THC on catalytic activities of two major allelic variants, CYP2C9.2 and CYP2C9.3, were examined with the recombinant enzymes. Δ9-THC inhibited S-warfarin 7-hydroxylation, diclofenac 4′-hydroxylation, and tolbutamide 4-hydroxylation by CYP2C9.2 and CYP2C9.3 in a concentration-dependent manner. The IC50 values for the catalytic activities toward S-warfarin, diclofenac, and tolbutamide were 2.39, 1.04, and 1.12 μM, respectively, for CYP2C9.2, and 2.91, 1.38, and 1.09 μM, respectively, for CYP2C9.3. The inhibitory potencies against these mutant variants were similar to those against the wild-type variant. In contrast, Δ9-THC inhibited 7-methoxy-4-(trifluoromethyl)coumarin O-demethylase activity of CYP2C9.1, CYP2C9.2, and CYP2C9.3 to various extents, showing the IC50 values of 1.02, 4.20 and >10 μM, respectively. Our recent study showed that a preincubation of Δ9-THC in the presence of NADPH decreased the inhibitory effect on CYP2C9.1 activity. Then the effect of preincubation on Δ9-THC-mediated inhibition of S-warfarin 7-hydroxylation was investigated with CYP2C9.2 and CYP2C9.3. The preincubation of Δ9-THC with CYP2C9.2 attenuated the inhibitory effect of the phytocannabinoid, whereas preincubation with CYP2C9.3 did not. These results indicate that the inhibitory effects of Δ9-THC on CYP2C9 variants depend on the substrates used and the preincubation time.

Pharmacogenetic tests could be helpful in predicting of VKA maintenance dose in elderly patients at treatment initiation

Several studies have linked mutations in the genes encoding cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex 1 (VKORC1) to a reduced VKA dose requirement and an increased risk of bleeding. Nevertheless, implementation of genotyping as a routine practice is still controversial. Our study was conducted in order to investigate the impact of genetic factors, presence of VKORC1-c.1639A, CYP2C*2 and CYP2C*3 among outpatients referred to Anticoagulation Service due to extremely unstable anticoagulant therapy. From 2008 to 2011, 68 patients, mean age 65.9, were included in the study. They were referred from primary care physicians due to inability to sustain the therapeutic range in the period of initiation of anticoagulant therapy. Genotyping results showed that 17 (25%) of them were carriers of both CYP2C9 and VKORC1 variant alleles, 38 (55.9%) were carriers of VKORC1 c.1639AA, 6 (8.8%) were carriers of CYP2C9 variant alleles, while 7 (10.3%) of them were carriers of wild type alleles. INR control upon admission showed that 34 (50%) of them were over-anticoagulated, while 12 (17.6%) of them had subsequent bleeding complications. Among over-anticoagulated patients, 32 were carriers of mutated alleles in both CYP2C9 and VKORC1 gene or VKORC1 alone, while 2 of patients carried wild type alleles. In addition to presence of CYP2C9 or VKORC 1 alleles, older age was an important factor related to a lower dose and risk for over-anticoagulation. Genotype (CYP2C9/VKORC1) and age are the most important factors that could predispose an extreme response and subsequent bleeding complications during the initiation of VKA.

Comparative Pharmacokinetics and Pharmacodynamics of Platelet Adenosine Diphosphate Receptor Antagonists and their Clinical Implications

Over the last two decades or more, anti-platelet therapy has become established as a cornerstone in the treatment of patients with ischaemic cardiovascular disease, since such drugs effectively reduce arterial thrombotic events. The original agent used in this context was aspirin (acetylsalicylic acid) but, with the advent of adenosine diphosphate (ADP) receptor antagonists, the use of dual anti-platelet therapy has resulted in further improvement in cardiovascular outcomes when compared with aspirin alone. The first group of platelet ADP receptor antagonists to be developed was the thienopyridine class, which comprise inactive pro-drugs that require in vivo metabolism to their active metabolites before exerting their inhibitory effect on the P2Y(12) receptor. Clopidogrel has been the principal ADP receptor antagonist in use over the past decade, but is limited by variability in its in vivo inhibition of platelet aggregation (IPA). The pharmacokinetics of clopidogrel are unpredictable due to their vulnerability to multiple independent factors including genetic polymorphisms. Expression of the 3435T/T genetic variant encoding the MDR1 gene for the P-glycoprotein efflux transporter results in a significantly reduced maximum drug concentration and area under the plasma concentration-time curve as intestinal absorption of clopidogrel is reduced; and the expression of the mutant *2 allele of CYP2C19 results in similar pharmacokinetic effects as the two cytochrome P450 (CYP)-mediated steps required for the production of the active metabolite of clopidogrel are impaired. These variable pharmacokinetics lead to erratic pharmacodynamics and cannot reliably be overcome with increased dosing. Both prasugrel, a third-generation thienopyridine, and ticagrelor, a cyto-pentyl-triazolo-pyrimidine, have more predictable pharmacokinetics and enhanced pharmacodynamics than clopidogrel. Neither appears to be affected by the same genetic polymorphisms as clopidogrel; prasugrel requires only a single CYP-mediated step to produce its active metabolite and ticagrelor is not a pro-drug. Enhanced IPA by both prasugrel and ticagrelor is achieved at the expense of increased major bleeding, although this is partially mitigated in the case of ticagrelor due to its reversible IPA. However, the reversible binding of ticagrelor to the P2Y(12) receptor requires a twice-daily dosing regimen. Due to limited data from clinical studies, the use of prasugrel is currently restricted to individuals undergoing percutaneous coronary intervention who are ≤75 years old and have a body weight ≥60 kg. The clinical data for ticagrelor are more comprehensive and this drug therefore has a place in the management of patients with acute coronary syndrome at moderate-to-high risk of ischaemic events, irrespective of treatment strategy. Here we review in detail the pharmacokinetics and pharmacodynamics of clopidogrel, prasugrel and ticagrelor, and explore the implications of the differences in these parameters for their clinical use.

Allele and genotype frequencies of the polymorphic cytochrome P450 genes (CYP1A1, CYP3A4, CYP3A5, CYP2C9 and CYP2C19) in the Jordanian population

Drug metabolizing enzymes participate in the neutralizing of xenobiotics and biotransformation of drugs. Human cytochrome P450, particularly CYP1A1, CYP2C9, CYP2C19, CYP3A4 and CYP3A5, play an important role in drug metabolism. The genes encoding the CYP enzymes are polymorphic, and extensive data have shown that certain alleles confer reduced enzymatic function. The goal of this study was to determine the frequencies of important allelic variants of CYP1A1, CYP2C9, CYP2C19, CYP3A4 and CYP3A5 in the Jordanian population and compare them with the frequency in other ethnic groups. Genotyping of CYP1A1(m1 and m2), CYP2C9 (2 and 3), CYP2C19 (2 and 3), CYP3A4 5, CYP3A5 (3 and 6), was carried out on Jordanian subjects. Different variants allele were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). CYP1A1 allele frequencies in 290 subjects were 0.764 for CYP1A1 1, 0.165 for CYP1A1 2A and 0.071 for CYP1A1 2C. CYP2C9 allele frequencies in 263 subjects were 0.797 for CYP2C9 1, 0.135 for CYP2C9 2 and 0.068 for CYP2C9 3. For CYP2C19, the frequencies of the wild type (CYP2C19 1) and the nonfunctional (2 and 3) alleles were 0.877, 0.123 and 0, respectively. Five subjects (3.16 %) were homozygous for 2/2. Regarding CYP3A4 1B, only 12 subjects out of 173 subjects (6.9 %) were heterozygote with none were mutant for this polymorphism. With respect to CYP3A5, 229 were analyzed, frequencies of CYP3A5 1, 3 and 6 were 0.071, 0.925 and 0.0022, respectively. Comparing our data with that obtained in several Caucasian, African-American and Asian populations, Jordanians are most similar to Caucasians with regard to allelic frequencies of the tested variants of CYP1A1, CYP2C9, CYP2C19, CYP3A4 and CYP3A5.

Association of cytochrome P450 genetic polymorphisms with neoadjuvant chemotherapy efficacy in breast cancer patients

BackgroundThe enzymes of the cytochrome P450 family (CYPs) play an important role in the metabolism of a great variety of anticancer agents; therefore, polymorphisms in genes encoding for metabolizing enzymes and drugs transporters can affect drug efficacy and toxicity.MethodsThe genetic polymorphisms of cytochrome P450 were studied in 395 patients with breast cancer by RLFP analysis.ResultsHere, we studied the association of functionally significant variant alleles of CYP3A4, CYP3A5, CYP2B6, CYP2C8, CYP2C9 and CYP2C19 with the clinical response to neoadjuvant chemotherapy in breast cancer patients. A significant correlation was observed between the CYP2C9*2 polymorphism and chemotherapy resistance (OR = 4.64; CI 95% = 1.01 – 20.91), as well as between CYP2C9*2 heterozygotes and chemotherapy resistance in women with nodal forms of breast cancer and a cancer hereditary load (OR = 15.50; CI 95% = 1.08 – 826.12) when the potential combined effects were examined. No significant association between chemotherapy resistance and the other examined genotypes and the potential combined clinical and tumour-related parameters were discovered.ConclusionIn conclusion, CYP2C9*2 was associated with neoadjuvant chemotherapy resistance (OR = 4.64; CI 95% = 1.01 – 20.91) in the population of interest.

Relationship between cytochrome P450 2C19*17 genotype distribution platelet aggregation and bleeding risk in patients with blood stasis syndrome of coronary artery disease treated with clopidogrel

To assess the impact of cytochrome P450 (CYP) 2C19*17 allelic variant on platelet aggregation and bleeding risk in Chinese patients with blood stasis syndrome undergoing percutaneous coronary intervention (PCI) and treated with clopidogrel. A total of 520 patients with blood stasis syndrome undergoing PCI after pretreatment with 300 mg clopidogrel and aspirin were studied from July 2009 to April 2011 in Fujian Provincial Institute of Cardiovascular Diseases. CYP2C19*17 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism. Platelet aggregation induced by 5μmol/L of adenosine diphosphate (ADP) was analyzed with platelet-rich plasma and platelet-poor plasma by turbidimetry method before and after 10 d of treatment with clopidogrel. Bleeding events were observed in 5.96% of patients after thrombolysis for myocardial infarction, and the ratio of patients with CYP2C19*17 allele was 7.98%. The bleeding rate in patients carrying CYP2C19*17 allele, heterozygous (wt/*17) and homozygous (*17/*17), was higher than that in patients with wild-type homozygotes (wt/wt) (P<0.01). At baseline, ADP-induced light transmission at maximal aggregation, 5-min aggregation and disaggregation showed no significant difference among patients with the three different CYP2C19*17 genotypes. However, after 10-day administration of clopidogrel, values of ADP-induced platelet aggregation in *17/*17 and wt/*17 carriers were significantly decreased compared with the wild-type homozygotes (P<0.05, P<0.01); the inhibition rate of platelet aggregation was higher in patients carrying *17/*17 and wt/*17 than those only carrying wt/wt, and the same result was found in disaggregation of platelet after 10-day treatment (P<0.05, P<0.01). Patients with wt/*17 and *17/*17 allele of CYP2C19 showed a higher risk of bleeding than those with wild-type allele (P<0.01), and the occurrence of bleeding was highest in patients with CYP2C19*17 homozygotes. CYP2C19*17 allele is associated with enhanced response to clopidogrel and an increased risk of bleeding in patients with blood stasis syndrome of coronary artery disease treated by clopidogrel.

A case report of voriconazole therapy failure in a homozygous ultrarapid CYP2C19*17/*17 patient comedicated with carbamazepine

Recently this journal published an article in which the authors examined by literature search the clinical implication of the ultrarapid CYP2C19*17 variant allele [1]. The authors concluded that the CYP2C19*17 increased enzyme activity is unlikely to be clinically significant for voriconazole. However, a comment to this article [2] replied that in the case of voriconazole the variant allele CYP2C19*17 certainly is clinically relevant and that data have shown that in subjects carrying a single CYP2C19*17 allele, exposure may be reduced by up to 50% compared with normal metabolizers. The authors of the comment also mention that they are not aware of published studies of homozygous CYP2C19*17/*17 patients; and they assume that these subjects would display further reduced voriconazole exposure. In this case report we present a case of voriconazole therapy failure in a homozygous CYP2C19*17/*17 patient comedicated with carbamazepine. A 62-year-old Caucasian woman with acute myeloid leukemia was admitted to our hospital for myelosuppressive chemotherapy. Shortly after administration of the second cycle of cytostatic drugs she developed neutropenic fever which persisted despite of treatment with broad spectrum antibiotics. A high-resolution CT scan showed multiple lesions in the lungs, liver and spleen, suspect for a disseminated fungal infection. Because a zygomycosis was also considered, treatment with both voriconazole and liposomal amphotericin B was started. Oral voriconazole was started with a standard loading dose of 400 mg twice daily (1 day) and a maintenance dose of 200 mg twice daily. Because of the potential induction interaction with carbamazepine (200 mg twice daily orally, given at least since 2005 for treatment of a bipolar disorder), we performed therapeutic drug monitoring of voriconazole. No other drug−drug interactions for voriconazole were present. At day 5 after the start of voriconazole therapy, the voriconazole trough serum concentration was very low, i.e. <0.3 mg l−1 (therapeutic range 1–2 to 5 mg l−1) [3]. To achieve higher voriconazole concentrations, the administration route of voriconazole was switched to intravenous and the dose was raised substantially to a loading dose of 6 mg kg−1 (510 mg) and a maintenance dose of 5 mg kg−1 (425 mg) twice daily, a dosage regimen recommended for other inducers such as phenytoin and rifabutin [4]. We did not stop carbamazepine therapy since this would not result in a direct stop of the induction and therapy was highly desirable for this patient. Four days after the start of this raised dosage regimen measurement of the voriconazole concentration was repeated. Again the trough concentration was subtherapeutic, i.e. 0.5 mg l−1. Therefore, we stopped voriconazole therapy and switched to caspofungin. Liposomal amphotericin B had been discontinued when cultures confirmed infection with Candida tropicalis and not a zygomycete. Because of the extremely low voriconazole concentrations despite the high dosage regimen, we suspected CYP2C19 ultrarapid metabolism. CYP2C19 genotyping was performed and revealed a homozogous ultrarapid CYP2C19*17/17 genotype. The patient improved gradually and was discharged from the hospital. Antifungal therapy was switched from intravenous caspofungin to oral posaconazole. The prevalence of the homozygous CYP2C19*17/17 genotype is not known. For Caucasians, the prevalence of the heterozygous CYP2C19*17 is about 20% [1]. Theoretically, if the prevalence of heterozygous CYP2C19*17 is 20%, the prevalence of homozygous CYP2C19*17/*17 can be estimated at 4%. Voriconazole exposure in homozygous CYP2C19*17/*17 ultrarapid metabolizers has not yet been described. Recently an article has been published in which retrospective analysis of routine therapeutic drug monitoring for voriconazole samples showed that in a subgroup of low voriconazole concentrations of 0.2 mg l−1 or less the frequency of the genotype CYP2C19 ultrarapid metabolism (heterozygous CYP2C19*1/*17 or homozygous CYP2C19*17/*17) was significantly higher than in the reference group of healthy volunteers [5]. In a defined subgroup (without potential confounders such as inductive co-medication), 80% of the patients carried the *17 allele (heterozygous CYP2C19*1/*17 or homozygous CYP2C19*17/*17). However, the data of heterozygous CYP2C19*1/*17 and homozygous CYP2C19*17/*17 groups are combined and no individual data are presented for homozygous CYP2C19*17/*17 subject(s). In our patient voriconazole concentrations were extremely low due to a combination of homozygous ultrarapid CYP2C19*17/17 metabolism and metabolism induction by carbamazepine. The individual contributions of the genotype and co-medication cannot, however, be distinguished. Although not many patients will have this ‘unfortunate’ combination, because of the substantial prevalence of altered CYP2C19 metabolism, ultrarapid but also poor metabolizers, and the multiple potential drug–drug interactions, we recommend routine therapeutic drug monitoring of voriconazole therapy. In our hospital we have recently introduced this policy.

Influence of Genetic Polymorphisms on the Effect of High- and Standard-Dose Clopidogrel After Percutaneous Coronary Intervention: The GIFT (Genotype Information and Functional Testing) Study

This study sought to evaluate the influence of single nucleotide polymorphisms (SNPs) on the pharmacodynamic effect of high- or standard-dose clopidogrel after percutaneous coronary intervention (PCI). There is a lack of prospective, multicenter data regarding the effect of different genetic variants on clopidogrel pharmacodynamics over time in patients undergoing PCI. The GRAVITAS (Gauging Responsiveness with A VerifyNow assay-Impact on Thrombosis And Safety) trial screened patients with platelet function testing after PCI and randomly assigned those with high on-treatment reactivity (OTR) to either high- or standard-dose clopidogrel; a cohort of patients without high OTR were also followed. DNA samples obtained from 1,028 patients were genotyped for 41 SNPs in 17 genes related to platelet reactivity. After adjusting for clinical characteristics, the associations between the SNPs and OTR using linear regression were evaluated. CYP2C19*2 was significantly associated with OTR at 12 to 24 h (R(2) = 0.07, p = 2.2 × 10(-15)), 30 days (R(2) = 0.10, p = 1.3 × 10(-7)), and 6 months after PCI (R(2) = 0.07, p = 1.9 × 10(-11)), whereas PON1, ABCB1 3435 C→T, and other candidate SNPs were not. Carriers of 1 and 2 reduced-function CYP2C19 alleles were significantly more likely to display persistently high OTR at 30 days and 6 months, irrespective of treatment assignment. The portion of the risk of persistently high OTR at 30 days attributable to reduced-function CYP2C19 allele carriage was 5.2% in the patients randomly assigned to high-dose clopidogrel. CYP2C19, but not PON1 or ABCB1, is a significant determinant of the pharmacodynamic effects of clopidogrel, both early and late after PCI. In patients with high OTR identified by platelet function testing, the CYP2C19 genotype provides limited incremental information regarding the risk of persistently high reactivity with clopidogrel 150-mg maintenance dosing. (Genotype Information and Functional Testing Study [GIFT]; NCT00992420).

Cardiovascular Pharmacogenomics: Current Status and Future Directions—Report of a National Heart, Lung, and Blood Institute Working Group

The National Heart, Lung, and Blood Institute (NHLBI) convened a Working Group on January 7, 2011, at George Washington University in Washington, DC, to provide recommendations to the NHLBI that would guide informed decisions on research directions and priorities in the field of cardiovascular

Multi-ethnic distribution of clinically relevant CYP2C genotypes and haplotypes.

To determine CYP2C19 and CYP2C8 allele frequencies, 28 coding and/or functional variants were genotyped in 1250 African-American, Asian, Caucasian, Hispanic and Ashkenazi Jewish (AJ) individuals. The combined CYP2C19 variant allele frequencies ranged from ~0.30–0.41; however, the CYP2C8 frequencies were much lower (~0.04–0.13). After incorporating previously reported CYP2C9 genotyping results from these populations (36 total CYP2C variants), 16 multi-ethnic CYP2C haplotypes were inferred with frequencies >0.5%. Notably, the 2C19*17-2C9*1-2C8*2 haplotype was identified among African-Americans (8%) and Hispanics (2%), indicating that CYP2C19*17 does not always tag a CYP2C haplotype that encodes efficient CYP2C-substrate metabolism. The 2C19*1-2C9*2-2C8*3 haplotype was identified in all populations except African-Americans and additional novel haplotypes were identified in selected populations (e.g., 2C19*2-2C9*1-2C8*4, 2C19*4B-2C9*1-2C8*1), together indicating that both CYP2C19*17 and *2 can be linked with other CYP2C loss-of-function alleles. These results have important implications for pharmacogenomic association studies involving the CYP2C locus and are clinically relevant when administering CYP2C-substrate medications.

NSAIDs pharmacotherapy and CYP2C9 allele frequency in pediatric sickle cell disease patients

Nonsteroidal, anti-inflammatory drugs (NSAIDs) used to treat prodromal signs and early forms of vaso-occlusive (VOC) pain in pediatric sickle cell disease (SCD) patients are substrates of the polymorphic cytochrome P450 CYP2C9 enzyme. Ethnic variation in CYP2C9 allelic frequency and ontogeny are important considerations for NSAIDs efficacy and toxicity in pediatric patients. Understanding the association between CYP2C9 genotypes and phenotypes and using this information for clinical studies of NSAIDs metabolism could facilitate personalized analgesic therapy.