Review of pharmacoeconomic evaluation of genotype-guided antiplatelet therapy

Introduction: Clopidogrel is an antiplatelet agent widely prescribed for acute coronary syndrome (ACS), and it is activated by the CYP enzyme system to active metabolite. CYP2C19 loss-of-function (LOF) allele(s) affect the responsiveness of clopidogrel, but not the new antiplatelet agents (prasugrel and ticagrelor). We reviewed the pharmacoeconomic studies on genotype-guided use of new antiplatelet agents.

Areas covered: A literature search was conducted between the period of 2000 and 2014. Seven studies including cost-effectiveness and risk-benefit analyses of CYP2C19 genotype-guided antiplatelet therapy in ACS patients were reviewed. Genotype-guided prasugrel was found to be cost-effective when compared with universal antiplatelet therapy in four studies. Three studies showed genotype-guided ticagrelor to be cost-effective in ACS patients with percutaneous coronary intervention (PCI), and universal ticagrelor to be cost-effective in ACS patients. Drug cost of antiplatelet agents and relative risk of the new antiplatelet versus clopidogrel for clinical events were common influential factors of cost-effectiveness analyses.

Expert opinion: All studies in the present review focused on selecting antiplatelet agents for carriers of CYP2C19 LOF allele(s). Cost-effectiveness of genotype-guided use of antiplatelets was demonstrated in high-risk ACS patients.     

Genetics of platelet inhibitor treatment

Dual antiplatelet therapy with aspirin and a P2Y₁₂ receptor antagonist is the standard of care in patients undergoing percutaneous coronary intervention (PCI) and in patients with acute coronary syndromes (ACS) because this regimen has markedly decreased the rate of cardiovascular events. The substantial variability in pharmacodynamic response as well as the moderate antiplatelet efficacy of clopidogrel has raised major concerns, since high on-clopidogrel platelet reactivity has consistently been associated with increased risk for ischaemic events in PCI patients. Baseline demographic and clinical variables contributing to the observed variability have been identified. Besides this, research within the past decade has focused on the impact of genetic polymorphisms encoding transport systems or enzymes involved in the absorption and metabolism of these drugs. Loss-of-function polymorphisms in CYP2C19 are the strongest individual variables affecting pharmacokinetics and antiplatelet response to clopidogrel, but explain no more than 5 to 12% of the variability in adenosine diphosphate-induced platelet aggregation on clopidogrel. No genetic variables contributing to clinical outcomes of patients treated with the newer P2Y₁₂ receptor antagonists, prasugrel or ticagrelor, have been identified so far. This review aims to provide an update on the current status of genotype-based personalized therapy with clopidogrel.     

The CYP2C19*2 and CYP2C19*17 Polymorphisms play a Vital Role in Clopidogrel Responsiveness after Percutaneous Coronary Intervention: A Pharmacogenomics Study

Clopidogrel inhibits platelet activation and aggregation by blocking the P2Y₁₂ receptor. Dual antiplatelet therapy with clopidogrel and aspirin is recommended treatment by current guidelines for patients undergoing percutaneous interventions. Recurrent ischaemic cardiac events after this treatment showed lack of clopidogrel responsiveness. We aimed to investigate the most noticeable variants in the genes involved in clopidogrel pharmacokinetics and pharmacodynamics. A total of 347 Turkish patients who underwent percutaneous coronary interventions with stent implantation were included in our study. Platelet reactivity (PRU) and % inhibition were measured with VerifyNow P2Y₁₂ assay in blood samples collected from patients who took a standard dose of clopidogrel (75 mg/day) for at least 7 days. The variants in the CYP2C19, CYP3A4, CYP2B6, ABCB1, ITGB3 and PON1 genes were genotyped using the Sequenom MassARRAY system. When grouped, the patients with PRU values >208 as non‐responsiveness to clopidogrel therapy; 104 (30%) patients were non‐responders and 243 (70%) patients were responders. A significant association was found between the CYP2C19*2 (G636A) polymorphism and non‐responsiveness to clopidogrel therapy (p < 0.001). An allele frequency of this single nucleotide polymorphism was high in non‐responders; its odds ratio was 2.92 compared with G allele (p < 0.001). PRU values of CT genotypes were lower (p = 0.029) and % inhibition values of CT genotypes were higher (p = 0.008) compared with CC genotypes for the CYP2C19*17 (C806T) polymorphism. None of the other genetic variants were found to be statistically associated with non‐responsiveness to clopidogrel and antiplatelet activity. Our findings suggest that the CYP2C19*2 polymorphism is associated with non‐responsiveness to clopidogrel therapy and the CYP2C19*17 polymorphism enhances antiplatelet activity of clopidogrel. Depending on haplotypes of these two polymorphisms, clopidogrel‐treated patients can be protected or not from stent thrombosis and ischaemic events.     

Efficacy and safety analysis of new P2Y12 inhibitors versus clopidogrel in patients with percutaneous coronary intervention: a meta-analysis

Objective:

New P2Y₁₂ inhibitors, classified as oral (prasugrel and ticagrelor) and intravenous (cangrelor and elinogrel) drugs, have shown improved antithrombotic effects compared with clopidogrel in patients with acute coronary syndrome (ACS) or patients undergoing percutaneous coronary intervention (PCI) in landmark trials. The purpose of this study was to perform a meta-analysis of randomized trials that compared new P2Y₁₂ inhibitors with clopidogrel to determine their efficacy and safety in patients undergoing PCI.

Methods:

Randomized controlled trials of at least 4 weeks, comparing new P2Y₁₂ inhibitors with clopidogrel in PCI, were identified using the electronic databases Cochrane Central Register of Controlled Trials, Medline, PubMed, Web of Science, and Google Scholar from January 1, 1980, to July 31, 2014.

Main outcome measures:

The primary efficacy endpoints were all-cause death and major adverse cardiovascular events (MACEs). The primary safety endpoint was thrombolysis in myocardial infarction (TIMI) major bleeding.

Results:

Twelve studies including 71,097 patients met the inclusion criteria. New P2Y₁₂ inhibitors significantly reduced all-cause death (odds ratio [OR]: 0.81; 95% confidence interval [CI] 0.73–0.90, p?p?p?p?=?0.03) and cardiovascular death (OR 0.82; 95% CI 0.73–0.92, p?=?0.001) compared with clopidogrel. There were no significant differences between stroke (OR 0.87; 95% CI 0.72–1.05, p?=?0.14) and major bleeding events (OR 1.22; 95% CI 0.99–1.52, p?=?0.06) between the new P2Y₁₂ inhibitor and clopidogrel groups.

Conclusion:

New P2Y₁₂ inhibitors decreased death in patients undergoing PCI compared with clopidogrel with a considerable safety and tolerability profile; however, the risk/benefit ratio of ischemic and bleeding events should be further investigated.     

PCI术后患者抗血小板治疗方案的药物经济学评价

目的 从医疗保险角度,对经皮冠脉支架置入（percutaneous coronary intervention,PCI）术后3种抗血小板药物治疗方案进行经济学评价。方法 3种治疗方案为在使用阿司匹林基础上,经验性给予国产氯吡格雷,或经验性给予替格瑞洛,或根据CYP2C19基因型指导选择国产氯吡格雷或替格瑞洛,由此建立决策树模型并进行成本效果分析,预测该3种方案避免主要心血管事件的发生率以及成本,研究时间为1年。结果 经验性给予国产氯吡格雷联合阿司匹林治疗方案为成本最低方案,但直接给予替格瑞洛联合阿司匹林治疗方案的经济性最好。结论 对于PCI术后的患者,最推荐直接采用替格瑞洛联合阿司匹林的治疗方案。     

Ticagrelor for the treatment of arterial thrombosis

Importance of the field: High platelet reactivity has been linked to recurrent ischemic events in patients treated with conventional dual antiplatelet therapy, in patients with arterial diseases and particularly in patients treated with coronary artery stenting. The limitations of clopidogrel have served as a major rationale for the development of new P2Y₁₂ blockers that have superior pharmacodynamic profiles uninfluenced by concomitant therapies or specific genotypes. Ticagrelor is the first direct-acting reversibly binding oral P2Y₁₂ receptor antagonist. Extensive Phase II investigations have addressed the pharmacokinetic, pharmacodynamic and safety-related properties of ticagrelor compared with clopidogrel. The recently completed PLATO trial demonstrated promise for ticagrelor as a major treatment strategy for a wide spectrum of patients with acute coronary syndromes. Ticagrelor is now being reviewed by the FDA as a P2Y₁₂ receptor blocker to treat patients with coronary artery disease and, once accepted, will be in widespread use as an antiplatelet agent. Thus, it is both appropriate and timely to review available data and provide a comprehensive review of ticagrelor.

Areas covered in this review: We discuss the rationale for the development of ticagrelor, a reversible and potent P2Y₁₂ receptor blocker. The data regarding ticagrelor based on preclinical and clinical studies are examined. We researched articles about ‘AZD6140’ and ‘ticagrelor’ in PubMed from 2006 to 2010 and also reviewed data presented at recent cardiology meetings.

What the reader will gain: This is an updated and comprehensive review of ticagrelor. The advantages and disadvantages of ticagrelor and available P2Y₁₂ receptor blockers such as clopidogrel and prasugrel are discussed, thus providing a clear picture to readers.

Take home message: Ticagrelor has an important role as an antiplatelet agent in the settings of acute coronary syndrome and percutaneous coronary intervention and once accepted will be in widespread use.     

CYP2C19*17 increases clopidogrel‐mediated platelet inhibition but does not alter the pharmacokinetics of the active metabolite of clopidogrel

The aim of the present study was to determine the impact of CYP2C19*17 on the pharmacokinetics and pharmacodynamics of the active metabolite of clopidogrel and the pharmacokinetics of proguanil. Thus, we conducted an open‐label two‐phase cross‐over study in 31 healthy male volunteers (11 CYP2C19*1/*1, 11 CYP2C19*1/*17 and nine CYP2C19*17/*17). In Phase A, the pharmacokinetics of the derivatized active metabolite of clopidogrel (CAMD) and platelet function were determined after administration of a single oral dose of 600 mg clopidogrel (Plavix; Sanofi‐Avensis, Horsholm, Denmark). In Phase B, the pharmacokinetics of proguanil and its metabolites cycloguanil and 4‐chlorphenylbiguanide (4‐CPB) were determined in 29 of 31 subjects after a single oral dose of 200 mg proguanil given as the combination drug Malarone (GlaxoSmithKline Pharma, Brondby, Denmark). Significant correlations were found between the area under the time–concentration curve (AUC_0–∞) of CAMD and both the absolute ADP‐induced P2Y₁₂ receptor‐activated platelet aggregation (r = ?0.60, P = 0.0007) and the percentage inhibition of aggregation (r = 0.59, P = 0.0009). In addition, the CYP2C19*17/*17 and CYP2C19*1/*17 genotype groups had significantly higher percentage inhibition of platelet aggregation compared with the CYP2C19*1/*1 subjects (geometric mean percentage inhibition of 84%, 73% and 63%, respectively; P = 0.014). Neither the absolute ADP‐induced P2Y₁₂ receptor‐activated platelet aggregation, exposure to CAMD nor the pharmacokinetic parameters of proguanil, cycloguanil and 4‐CPB exhibited any significant differences among the genotype groups. In conclusion, carriers of CYP2C19*17 exhibit higher percentage inhibition of platelet aggregation, but do not have significantly lower absolute P2Y₁₂ receptor‐activated platelet aggregation or higher exposure to the active metabolite after a single oral administration of 600 mg clopidogrel.     

CYP2C19基因指导冠心病患者经皮冠状动脉介入术后抗血小板药合理应用

目的 探索CYP2C19基因指导冠心病患者经皮冠状动脉介入（PCI）术后抗血小板药物的合理使用。方法 利用医院管理信息系统,收集2015年12月至2016年12月在心内科住院的冠心病患者2 836例,从中选取符合标准的CYP2C19 IM和PM基因型患者480例,根据患者是否根据基因型改变治疗方案,将患者分为常规剂量氯吡格雷组（常规治疗组）、氯吡格雷剂量加倍组和替格瑞洛组,观察各组患者血小板聚集抑制率和1年内主要不良心血管（MACE）及出血事件发生率。结果 最终入选468例患者,替格瑞洛组和剂量加倍组的血小板聚集抑制率均高于常规治疗组（P<0.05）,且替格瑞洛组又明显高于剂量加倍组（P<0.05）。MACE事件发生率方面,各组患者均是再发心肌梗死发生率最高,且替格瑞洛组及剂量加倍组明显低于常规治疗组（P<0.017）,其余MACE各事件及出血发生率各组之间无差异性（P>0.017）。结论 CYP2C19基因指导下冠心病患者PCI术后抗血小板治疗临床效果较好,临床应根据患者基因特点进行个体化合理用药。     

The impact of genetic polymorphisms of P2Y12, CYP3A5 and CYP2C19 on clopidogrel response variability in Iranian patients

Clopidogrel is an inhibitor of platelet ADP P2Y12 receptors and currently used for prevention of stent thrombosis. Despite certain clinical benefit using this drug in patients undergoing percutaneous coronary intervention (PCI), some patients do not attain adequate antiplatelet effects. In this study, we investigated the role of three genetic factors (P2Y12, CYP3A5, CYP2C19), demographic characteristics, and pathologic condition on clopidogrel response variability in Iranian patients after PCI. Patients who were candidate for elective PCI were enrolled in this study. All patients had received aspirin 80-325 mg daily for ≥ 1 week before PCI. Blood samples were taken from patients at baseline, 2 h after taking a 600-mg loading dose of clopidogrel, 24h and 30 days after PCI. Platelet aggregation was measured by turbidimetric aggregation assay with two different concentrations of ADP (5 and 20 μM). CYP2C19*2(rs4244285), CYP2C19*3(rs4986893), CYP3A5 (A6986G), and P2Y12 (T744C) genotypings were performed by PCR-RFLP. One hundred and twelve patients were included in this study. Maximum clopidogrel non-responsiveness (25.90%) occurred at 2 h after taking 600 mg of the loading dose of clopidogrel. Although there were no significant associations between clopidogrel responsiveness and polymorphisms of CYP2C19, CYP3A5, and P2Y12 (P > 0.05), subjects who were CYP3A5 genotype expressor had a greater inhibition of platelet aggregation. No significant associations were observed between environmental factors and clopidogrel responsiveness (P > 0.05). Our results showed that P2Y12, CYP3A5, and CYP2C19 polymorphisms along with non-genetic factors were not responsible for the interindividual variability in response to clopidogrel in Iranian population.     

Prevalence of CYP2C19 alleles,pharmacokinetic and pharmacodynamic variation of clopidogrel and prasugrel in Bangladeshi population

The extent to which cytochrome P450 (CYP) 2C19 genotype influences the effectiveness of clopidogrel remains uncertain due to considerable heterogeneity between studies. We used the polymerase chain reaction restriction fragment length polymorphism (PCR‐RFLP) method for genotyping loss of function (LOF) allele, CYP2C19*2 and gain of function (GOF) allele, CYP2C19*17 in 163 patients undergoing PCI and 165 healthy volunteers from an ethnically distinctive Bangladeshi population. Thirty‐eight patients took prasugrel and 125 patients took clopidogrel among whom 30 patients had their clopidogrel active metabolites (CAM) determined by LC‐MS/MS 1–1.5 h after clopidogrel intake. All patients who underwent PCI had their P2Y12 per cent inhibition (PRI) measured by VerifyNow System. The impact of different genotypes on CAM and PRI were also determined. We did not find significant variation of CYP2C19*2 (P > 0.05) and CYP2C9*17 (P > 0.05) alleles among healthy volunteers and patients. CAM concentration as well as PRI by clopidogrel varied significantly (P < 0.05) based on genotypic variation of CYP2C19*2 and CYP2C19*17 individually. Such influence was not observed in case of prasugrel. Genotypic variation did not impact PRI but as a whole PRI by prasugrel was better than that of clopidogrel (P < 0.05). Due to presence of both of alleles the effect on PRI by clopidogrel could not be predicted, effectively indicating possible involvement of other factors. Genotype guided clopidogrel dose adjustment would be beneficial and therefore we propose mandatory genotyping before clopidogrel dosing. Prasugrel proved to be less affected by genotypic variability, but due to lack of sufficient long‐term toxicity data, caution would be adopted before substituting clopidogrel.     

Efficacy and safety of ticagrelor in patients with acute coronary syndrome: A meta‐analysis of randomized controlled trials

Acute coronary syndrome (ACS) is a dangerous and urgent clinical pattern of coronary artery disease. Aspirin and adenosine diphosphate P2Y₁₂ receptor antagonists are the standard dual anti‐platelet therapy for patients with ACS. Ticagrelor is a new oral antagonist of the adenosine diphosphate P2Y₁₂ receptor. Randomized controlled trials (RCTs) have evaluated the efficacy and safety of ticagrelor compared to clopidogrel or prasugrel in patients with ACS, obtaining conflicting results. Thus, we conducted a meta‐analysis of these RCTs to determine the efficacy and safety of ticagrelor in patients with ACS. Results of the meta‐analysis indicate that ticagrelor decreased the risk of major adverse cardiovascular events (MACE) and all‐cause death, but increased the risk of bleeding events. In Asiatic patients, analysis indicates that ticagrelor did not decrease the risk of MACE and all‐cause death, while increasing the risk of bleeding events. Together, this meta‐analysis suggests that ticagrelor was more effective, but less safe than clopidogrel and prasugrel in patients with ACS. Subgroup analysis indicates that ticagrelor was not more effective, although less safe than clopidogrel in Asiatic patients, thus more evidence is needed to further evaluate the efficacy and safety of ticagrelor in Asiatic patients.     

Dyspnea and Reversibility Profile of P2Y12 Antagonists: Systematic Review of New Antiplatelet Drugs

Background

Dyspnea has been consecutively reported in some trials evaluating new P2Y₁₂ inhibitors.

Objective

We aimed to review and quantify the global risk of dyspnea of recent P2Y₁₂ inhibitor drugs, and evaluate its association with the reversibility profile of P2Y₁₂ inhibitors.

Methods

A database search (March 2013) retrieved randomized controlled trials (RCTs) comparing new antiplatelet drugs (ticagrelor, prasugrel, cangrelor, elinogrel) with clopidogrel. The primary outcome was the incidence of dyspnea. Placebo-controlled trials were excluded. Meta-analysis was performed and estimates were expressed as risk ratio (RR) and 95 % confidence intervals (95 % CIs). Dyspnea incidence was evaluated according to the reversibility profile of P2Y₁₂ antagonists.

Results

We found eight RCTs including 41,289 patients. Prasugrel was not associated with an increased risk of dyspnea (RR 1.09, 95 % CI 0.93–1.27), whereas ticagrelor (RR 1.95, 95 % CI 1.37–2.77), cangrelor (RR 2.42, 95 % CI 1.36–4.33), and elinogrel (RR 3.25, 95 % CI 1.57–6.72) showed an increased risk of dyspnea. Reversible inhibitors significantly increased the risk of dyspnea compared with the irreversible inhibitor, prasugrel, through adjusted indirect comparison (RR 1.99, 95 % CI 1.40–2.82).

Conclusions

The reversible P2Y₁₂ antagonists ticagrelor, cangrelor, and elinogrel have an increased incidence of dyspnea in increasing order when compared with irreversible P2Y₁₂ inhibitors such as clopidogrel or prasugrel.     

Ticagrelor: Positive,negative and misunderstood properties as a new antiplatelet agent

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Clopidogrel‐associated genetic variants on inhibition of platelet activity and clinical outcome for acute coronary syndrome patients

Acute coronary syndrome (ACS) has become a vital disease with high mortality worldwide. A combined antiplatelet therapy (aspirin and a P2Y₁₂ antagonist) is commonly used to prevent re‐infarction in ACS patients who have undergone percutaneous coronary intervention (PCI). Clopidogrel, a P2Y₁₂ antagonist, plays an important role in the inhibition of platelet aggregation (IPA). However, it is a pro‐drug requiring biotransformation by cytochrome P450 (CYP450). The aim of this study is to unravel the effect of clopidogrel‐associated genetic variants on inhibition of platelet activity and clinical outcomes in ACS patients. In our study, a total of 196 patients with metabolic gene polymorphism of clopidogrel were enrolled, and their antiplatelet effect as well as their cardiovascular events were collected. Approximately 2 mL of venous blood samples were used for genotype detection and another 4 mL were collected for platelet reactivity with thrombelastography. The primary clinical end‐point was defined as a combination of cardiovascular mortality and revascularization for targeted vascular lesion. Based on the results of IPA, the prevalence of high on‐treatment platelet reactivity (HPR) was 17.3% and the majority of patients (82.7%) obtained normal on‐treatment platelet reactivity (NPR). The HPR group had significantly higher body mass index (BMI) and lower arachidonic acid (AA) induced IPA (P < 0.05). Therapy including Glycoprotein (GP) IIb/IIIa antagonist increased IPA (P < 0.05). ADP‐induced IPA effect was lower with the presence of CYP2C19*2, *3 and paraoxonase (PON)1 Q192R loss‐of‐function (LOF) alleles, respectively (P < 0.05). Multivariate logistic regression analysis demonstrated that aspirin resistance (AA‐induced IPA < 50%) had a greater risk of the occurrence of major adverse cardiovascular events (MACE) (OR = 3.817; 95% CI: 1.672‐8.700; P = 0.002). CYP2C19*2 LOF alleles were associated with high risk of MACE in 1‐year post PCI operations (OR = 2.571; 95% CI: 1.143‐5.780; P = 0.030). For the ACS patients, the presence of CYP2C19*2 and PON1 Q192R LOF alleles were the major drivers of HPR.     

Pharmacogenetic Selection of Volunteers Increases Stringency of Bioequivalence Studies; The Case of Clopidogrel

Clinical response to clopidogrel varies widely due to under-dosing, drug interactions and intrinsic interindividual differences resulting from genetic polymorphisms. Cytochrome P450-2C19 is the principal enzyme involved in the activation of the prodrug and loss-of-function alleles have been described. Upon expiration of the pharmaceutical patent of clopidogrel, generic manufacturers have started to subject interchangeable formulations to bioequivalence studies. The purpose of the current investigation was to study the effect of selection of volunteers homozygous for the CYP2C19*1 haplotype on the bioavailability of clopidogrel. A regular 2×2 bioequivalence study between two formulations of clopidogrel was performed in volunteers selected and unselected for relevant CYP2C19 haplotypes for the Mexican population. It was found that selection of volunteers homozygous for the CYP2C19*1 haplotype, increased the stringency of bioequivalence statistics and resulted in bioinequivalence of a generic clopidogrel compound that otherwise proved equivalent when tested in an open unselected population. Augmentation of bioequivalence strictness is expected to result from pharmacogenetic selection of volunteers.     

Clinical significance of residual platelet reactivity in patients treated with platelet P2Y12 inhibitors

Platelet P2Y₁₂ inhibitors have become an essential component of the treatment strategy for patients with acute coronary syndromes and patients undergoing percutaneous coronary intervention. It is now well-established that approximately 30% of patients treated with the P2Y₁₂ inhibitor clopidogrel display high residual platelet reactivity despite treatment. Patients with high on-treatment platelet reactivity have approximately 2–3-fold greater risk of adverse cardiovascular events and stent thrombosis than those without high platelet reactivity. Conversely, clopidogrel-treated patients with low platelet reactivity display approximately 1.7-fold increased risk of major bleeding. High platelet reactivity is uncommon during treatment with prasugrel and ticagrelor, which achieve a greater reduction in adverse cardiovascular events compared to clopidogrel in ACS patients treated with PCI. This is at the expense of an increase in spontaneous bleeding, however. Minor bleeding events, such as skin haematomas, are more common in prasugrel- and ticagrelor-treated patients that have particularly low platelet reactivity values. These minor bleeding events may occasionally prompt discontinuation of therapy, but their overall prognostic impact is uncertain. However, risk factors for bleeding tend to overlap with risk factors for adverse cardiovascular events. Therefore, patients with these minor bleeding events may also be at higher risk of adverse cardiovascular events, conferring a benefit from low platelet reactivity. Further work is needed to determine the optimal level of platelet reactivity in individuals by taking into account their risk of subsequent adverse cardiovascular events and bleeding.     

CYP2C19和ABCB1基因检测指导患者氯吡格雷个体化给药

目的利用CYP2C19和ABCB1基因检测结果指导患者氯吡格雷个体化用药。方法选取某院2018年8月~2019年6月30例使用氯吡格雷的患者,采用荧光原位杂交法检测患者氯吡格雷相关基因(CYP2C19*17、CYP2C19*3、CYP2C19*2和ABCB1)的基因型,根据检测结果为患者提供给药建议。另选取1例冠状动脉粥样硬化心脏病PCI术后患者,测定氯吡格雷相关基因型,为患者提供个体化给药建议。结果CYP2C19基因检测结果显示,30例患者中1例为超快代谢型,8例为快代谢型,18例为中间代谢型,3例为慢代谢型;ABCB1 CC野生型13例,CT突变杂合型14例,TT突变纯合型3例。1例冠状动脉粥样硬化心脏病患者PCI术后规律双联抗血小板治疗仍反复胸闷胸痛,CYP2C19基因检测为CYP2C19*1/*2中间代谢型,无ABCB1突变,药物代谢减慢,建议氯吡格雷更换为替格瑞洛。结论通过基因检测指导患者氯吡格雷个体化给药,促进临床合理用药。     

Comparison of mechanism-based inhibition of human cytochrome P450 2C19 by ticlopidine,clopidogrel, and prasugrel

1. Mechanism-based inhibition of CYP2C19 in human liver microsomes by the thienopyridine antiplatelet agents clopidogrel, prasugrel and their thiolactone metabolites was investigated by determining the time- and concentration-dependent inhibition of the activity of S-mephenytoin 4′-hydroxylase as typical CYP2C19 activity and compared with ticlopidine and its metabolite.

2. Clopidogrel was shown to be a mechanism-based inhibitor of CYP2C19 with the inactivation kinetic parameters, k_inact and K_I, equal to 0.0557?min^?1 and 14.3?μM, respectively, as well as ticlopidine (0.0739?min^?1 and 3.32?μM, respectively). The thiolactone metabolite of ticlopidine and clopidogrel inhibited CYP2C19 only in a concentration-dependent manner. In contrast, neither prasugrel nor its thiolactone metabolite inhibited CYP2C19 at concentrations up to 100?μM.

3. The oxidation of the thiophene moiety of clopidogrel to form their respective thiolactones was found to be the critical reaction that produces the chemically reactive metabolites which cause the mechanism-based inhibition of CYP2C19.

4. Estimation of in vivo drug–drug interaction using in vitro parameters predicted clinically observed data. For clopidogrel, there was no increase in the area under the curve (AUC) at its clinical dose level as predicted by the in vitro parameters, and for ticlopidine the prediction agreed with the clinically observed AUC increase.

5. In conclusion, clopidogrel is potent mechanism-based inhibitors of CYP2C19 as well as ticlopidine, whereas prasugrel did not inactivate CYP2C19. Administration of prasugrel would not cause a clinically relevant interaction with CYP2C19.

     

Clopidogrel

Dual antiplatelet therapy with acetylsalicylic acid (aspirin) and clopidogrel is a guideline-recommended standard of care for patients with acute coronary syndromes (ACS) and those who undergo percutaneous coronary intervention (PCI). Despite a large body of clinical evidence obtained from randomized clinical trials and patient registries supporting the efficacy and safety of aspirin plus clopidogrel therapy in these patients, questions concerning the optimal use of dual antiplatelet therapy remain. Widely debated topics pertaining to dual antiplatelet therapy in patients with ACS or undergoing PCI include (i) the appropriate clopidogrel loading dose; (ii) the optimal time to initiate the clopidogrel loading dose; (iii) the optimal duration of dual antiplatelet therapy following ACS or PCI; (iv) impact of variability of platelet response on patient outcomes; and (v) the role of other recommended and emerging P2Y₁₂ antagonists. This review discusses these ongoing controversies regarding the optimal use of dual antiplatelet therapy with aspirin and clopidogrel in patients with ACS or those undergoing PCI.