Selective blockade of P2Y12 receptors by prasugrel inhibits myocardial infarction induced by thrombotic coronary artery occlusion in rats

We evaluated the effects of prasugrel, a third-generation thienopyridyl prodrug, on P2Y12 receptors, adenosine 5'-diphosphate (ADP)-induced platelet aggregation, and myocardial infarction (MI) in rats. Oral administration of prasugrel (0.3-3 mg/kg) resulted in the dose-related inhibition of washed platelet aggregation induced by ADP (1-10 μM). Ex vivo [H]-2-MeS-ADP binding to platelet P2Y12 receptors was also inhibited by prasugrel in a similar dose range. The antiaggregatory effects of prasugrel correlated strongly with P2Y12 blockade with correlation coefficients of 0.85-0.92, suggesting that the antiaggregatory activity of prasugrel largely reflected P2Y12 blockade achieved in vivo. We further examined the effects of the in vivo P2Y12 inhibition by prasugrel (1-10 mg/kg, po) on MI induced by thrombotic coronary artery occlusion in rats. In surviving rats, infarct size at 24 hours after photoirradiation was evaluated. In the vehicle group, necrosis area/total left ventricular area was 37.9% ± 6.8% (mean ± SE, n = 7). At all prasugrel doses tested (n = 7 for each dose), necrosis area/total left ventricular area was significantly smaller than that in the vehicle group: 14.4% ± 4.0% for 1 mg/kg (P < 0.01), 19.8% ± 4.5% for 3 mg/kg (P < 0.05), and 14.8% ± 3.6% for 10 mg/kg (P < 0.01). At the highest administered dose of prasugrel (10 mg/kg), blood pressure and heart rate were unchanged. Arrhythmia was observed in 5 of 7 animals in the vehicle group at 24 hours after irradiation; in contrast, no arrhythmia was found in the group treated with prasugrel (10 mg/kg). Taken together, these results demonstrate that prasugrel is a selective P2Y12 inhibitor in vivo, providing effective inhibition of platelet aggregation and MI in rats.     

A multiple dose study of prasugrel (CS-747), a novel thienopyridine P2Y12 inhibitor, compared with clopidogrel in healthy humans

AIMS: This double-blind, placebo-controlled trial was designed to evaluate the pharmacodynamics, pharmacokinetics, safety, and tolerability of prasugrel (CS-747, LY640315), a novel thienopyridine P2Y(12) ADP receptor antagonist compared with clopidogrel, during multiple oral dosing in healthy subjects. METHODS: Thirty subjects received placebo, prasugrel 5 mg, 10 mg, or 20 mg, or clopidogrel 75 mg orally, daily for 10 days. Platelet aggregation, bleeding time, and prasugrel metabolites were measured and adverse events were recorded. RESULTS: Inhibition of ADP-induced platelet aggregation reached steady state by day 3 following prasugrel 10 and 20 mg compared with 5 days for clopidogrel 75 mg or prasugrel 5 mg. Compared with placebo, at 24 h after the last dose of study drug, inhibition of platelet aggregation using (20 microm) ADP was significantly higher in the prasugrel 10 mg group (58.2 +/- 4.9% vs. 9.2 +/- 4.0%, P < 0.001) with no difference in the clopidogrel group (15.7 +/- 6.8% vs. 9.2 +/- 4.0%, P = 0.78). With 5 microm ADP, inhibition of platelet aggregation with prasugrel 10 mg and clopidogrel 75 mg was significantly higher than with placebo (prasugrel 10 mg, 70.5 +/- 4.7%; clopidogrel 75 mg, 36.5 +/- 9.0%; vs. placebo, 11.3 +/- 5.1%; P < 0.0001 and P = 0.02). On day 10 at 4 h postdose, bleeding time was prolonged with prasugrel 10 mg (prasugrel 10 mg, 706 +/- 252 s vs. placebo, 221 +/- 38 s, P = 0.05) but not with clopidogrel (283 +/- 56 s, P = 0.98). There were no clinically significant bleeding events, serious adverse events, or discontinuations of the study drug. CONCLUSIONS: Compared with clopidogrel 75 mg, prasugrel 10 mg and 20 mg daily for 10 days resulted in more rapid, more consistent, and higher levels of platelet inhibition.     

P2Y receptor antagonists in thrombosis

The dual role of P2Y1 and P2Y12 receptors in platelet aggregation by ADP has been firmly established, based on the action of selective inhibitors, gene targeting in mice and human genetic evidence. Both of these receptor subtypes constitute targets for antithrombotic agents, and compounds with a dual action might also be of interest. However, the agents currently on the market (ticlopidine and clopidogrel), or known to be in development (cangrelor, AZD-6140 and prasugrel), all target the P2Y12 receptor. The thienopyridines (ticlopidine, clopidogrel and prasugrel) irreversibly inactivate the P2Y12 receptor via the covalent binding of an active metabolite generated in the liver, while the other compounds are competitive antagonists. Cangrelor, an ATP derivative, is suitable for intravenous perfusion, whereas AZD-6140 is in clinical development as an orally active agent.     

Repeat oral dosing of prasugrel, a novel P2Y12 receptor inhibitor, results in cumulative and potent antiplatelet and antithrombotic activity in several animal species

Antiplatelet and antithrombotic activity of multiple oral dosing of prasugrel were evaluated in several animal species. Prasugrel's active metabolite concentration-relatedly inhibited in vitro ADP-induced aggregation of rat, rabbit, dog, monkey and human platelets. Oral administration of prasugrel to dogs (0.03-0.3 mg/kg/day) and monkeys (0.1 and 0.3 mg/kg/day) once a day for 14 days resulted in potent, dose-related and cumulative inhibition of ADP-induced platelet aggregation. The inhibitory effects reached a plateau on days 3 to 5 and thereafter were maintained during dosing. Inhibition decreased gradually after cessation of dosing with near full recovery by 7 days after last dose. Antiplatelet and antithrombotic activity of prasugrel and clopidogrel were further examined in rats. Multiple oral dosing of prasugrel (0.3-3 mg/kg/day) to rats resulted in more potent inhibition of platelet aggregation compared to clopidogrel (3-30 mg/kg/day) and ticlopidine (30-300 mg/kg/day). Separate experiments confirmed that platelet inhibition was associated with inhibition of [(3)H]-2-methylthio-ADP binding to rat platelets. In a rat model of electrically-induced arterial thrombosis, prasugrel (0.1-1 mg/kg/day, p.o.) significantly prolonged the time to arterial occlusion and increased the duration of arterial patency. The inhibition of platelet aggregation of prasugrel was about 10 and 300 times more potent than clopidogrel and ticlopidine, respectively. Overall these results show that in several species multiple oral administration of prasugrel results in more potent inhibition of platelet aggregation and thrombus formation than clopidogrel and ticlopidine, and that these effects are mediated by inhibition of platelet ADP receptors.     

新型血小板P2Y12受体拮抗药

抑制ADP诱导的血小板聚集的药物(如氯吡格雷)已成为目前心血管领域内最重要的抗血小板药物。但氯吡格雷起效较慢,抗血小板作用相对较弱,尚有一定的低反应者和无反应者。普拉格雷是一个较新的血小板P2Y12受体拮抗药。TRITON-TIMI 38研究表明普拉格雷可使主要终点发生率(心血管死亡、非致死性心肌梗死、非致死性卒中)降低19%,但使出血并发症增加。坎格雷洛,替格雷洛,依诺格雷是更新的血小板P2Y12受体拮抗药。     

Assessment of VerifyNow P2Y12 assay accuracy in evaluating clopidogrel-induced platelet inhibition

The emergence of point-of-care assays enabling bedside testing such as the VerifyNow P2Y12 system might prove useful in clinical settings. The aim of this study was to evaluate the ability of the VerifyNow P2Y12 assay to estimate the inhibition of platelet aggregation provided by clopidogrel in the absence of baseline off-drug aggregation data. Sixty-eight patients with coronary artery disease scheduled to initiate clopidogrel therapy underwent platelet aggregation testing by VerifyNow P2Y12 at baseline and after clopidogrel administration. The inhibition reported by the VerifyNow assay (relative to thrombin receptor activating peptide-induced platelet aggregation, serving as baseline) was compared with that calculated with the actual adenosine diphosphate-induced baseline obtained with the same methodology. The postclopidogrel thrombin receptor activating peptide-induced aggregation showed a great discordance with that induced by adenosine diphosphate before clopidogrel with a bias of 24 units (95% limits of agreement from -142 to 190 units). Moreover, the inhibition reported by the assay overestimated the standard before-and-after testing data by an average of 8% (95% limits of agreement from -49% to 65%), making its use without a true baseline comparator unsatisfactory. The VerifyNow P2Y12 assay fails to accurately quantify platelet inhibition achieved by clopidogrel compared with before-and-after testing. Further studies are required to establish the clinical usefulness of the VerifyNow P2Y12 assay to accurately predict the occurrence of major adverse cardiovascular events in patients with reduced clopidogrel efficacy before it can be implemented in clinical practice. At present, the use of this assay in clinical care cannot be recommended for monitoring clopidogrel therapy.     

Ticagrelor: a P2Y12 antagonist for use in acute coronary syndromes

Agents that inhibit platelet function are used routinely in the treatment and prevention of acute coronary syndromes. The main antiplatelet treatments used combine aspirin with one of the thienopyridine P2Y(12) antagonists, either clopidogrel or prasugrel. By blocking the synthesis of thromboxane A(2) in platelets and by blocking the effects of ADP, respectively, these agents reduce platelet activity, platelet aggregation and thrombus formation. Ticagrelor (marketed by AstraZeneca as Brilinta? in the USA, and as Brilique(?) or Possia(?) in Europe) is a cyclopentyl-triazolo-pyrimidine, a new chemical class of P2Y(12) antagonist that is now approved for use in the wide spectrum of acute coronary syndromes. In this article we provide an overview of ticagrelor. We discuss the differences in mode of action compared with other P2Y(12) antagonists, examine its pharmacodynamic, pharmacokinetic and safety profile, and summarize the various clinical trials that have provided information on its efficacy in combination with aspirin. Ticagrelor appears to overcome some of the difficulties that have been encountered with other antiplatelet treatments, clopidogrel in particular.     

Optimizing platelet P2Y12 inhibition for patients undergoing PCI

Guidelines recommend that dual antiplatelet therapy using aspirin and clopidogrel should be administered to the majority of patients with acute coronary syndromes, including those undergoing percutaneous coronary intervention (PCI). However, the results of a large randomized, placebo-controlled study suggest that a 300-mg loading dose of clopidogrel must be administered at least 15 h prior to PCI in order to achieve a significant reduction in peri-PCI thrombotic events. Other data suggest that 2 h of pretreatment may be sufficient if a 600-mg loading dose is used. Since it is often difficult to achieve an adequate pretreatment goal with clopidogrel in clinical practice, more rapid achievement of platelet P2Y(12) inhibition may improve patient outcomes. Prasugrel, [6-[2-(3,4-diflurophenyl) cyclopropyl1-1-y1] amino-2-propylthio-9-D-ribofuranosyl-9H-purine (AZD6140), and cangrelor are platelet P2Y(12) receptor antagonists currently in development that offer faster acting inhibition of adenosine diphosphate (ADP)--induced platelet aggregation. These agents act upon the same platelet receptor as clopidogrel, but are distinguished by their routes of administration, reversibility, and pharmacodynamic properties. Prasugrel is an orally administered agent that provides faster, higher, and more consistent inhibition of platelet aggregation than clopidogrel. The results of Phase II testing suggest that the risk of bleeding is similar in prasugrel- and clopidogrel-treated patients. AZD6140 is another orally administered platelet inhibitor with rapid and reversible action. Again, Phase II testing suggests similar bleeding risk for clopidogrel. Preliminary evidence suggests that clinical outcomes may be better in prasugrel- and AZD6140-treated patients than in clopidogrel-treated patients. Cangrelor is an intravenously administered, reversible, short-acting agent with a rapid onset of activity. Bleeding risk and clinical outcomes data are similar in cangrelor- and abciximab-treated patients. The results of ongoing Phase III clinical trials involving more than 40,000 patients will demonstrate whether these agents fulfill their potential to improve outcomes in PCI-treated patients by providing faster, higher, and more consistent inhibition of platelet aggregation.     

Pharmacogenetics of P2Y12 receptor inhibitors

Oral P2Y₁₂ inhibitors are commonly prescribed for cardiovascular disease and include clopidogrel, prasugrel, and ticagrelor. Each of these drugs has its strengths and weaknesses. Prasugrel and ticagrelor are more potent inhibitors of platelet aggregation and were shown to be superior to clopidogrel in preventing major adverse cardiovascular events after an acute coronary syndrome and percutaneous coronary intervention (PCI) in the absence of genotyping. However, both are associated with an increased risk for non-coronary artery bypass-related bleeding. Clopidogrel is a prodrug requiring bioactivation, primarily via the CYP2C19 enzyme. Approximately 30% of individuals have a CYP2C19 no function allele and decreased or no CYP2C19 enzyme activity. Clopidogrel-treated carriers of a CYP2C19 no function allele have decreased exposure to the clopidogrel active metabolite and lesser inhibition of platelet aggregation, which likely contributed to reduced clopidogrel efficacy in clinical trials. The pharmacogenetic data for clopidogrel are most robust in the setting of PCI, but evidence is accumulating for other indications. Guidance is available from expert consensus groups and regulatory agencies to assist with integrating genetic information into P2Y₁₂ inhibitor prescribing decisions, and CYP2C19 genotype-guided antiplatelet therapy after PCI is one of the most common examples of clinical pharmacogenetic implementation. Herein, we review the evidence for pharmacogenetic associations with clopidogrel response and outcomes with genotype-guided P2Y₁₂ inhibitor selection and describe guidance to assist with pharmacogenetic implementation. We also describe processes for applying genotype data for P2Y₁₂ inhibitor therapy selection and remaining gaps in the field. Ultimately, consideration of both clinical and genetic factors may guide selection of P2Y₁₂ inhibitor therapy that optimally balances the atherothrombotic and bleeding risks.     

Prasugrel: a novel thienopyridine antiplatelet agent. A review of preclinical and clinical studies and the mechanistic basis for its distinct antiplatelet profile

Prasugrel (CS-747, LY640315) is a novel member of the thienopyridine class of oral antiplatelet agents that includes ticlopidine and clopidogrel. Like other thienopyridines, prasugrel is a prodrug that is inactive in vitro. Prasugrel's distinct chemical structure permits efficient conversion to its active metabolite with a less rigorous dependence on specific cytochrome P-450 enzymes. Prasugrel is rapidly converted in vivo to an active metabolite (R-138727) that binds specifically and irreversibly to the platelet P2Y 12 purinergic receptor inhibiting ADP-mediated platelet activation and aggregation. Preclinical studies indicated that prasugrel is approximately 10- and 100-fold more potent at inhibiting ex vivo platelet aggregation and in vivo thrombus formation than clopidogrel and ticlopidine, respectively. Early clinical data in healthy subjects confirmed the greater platelet inhibition and consistency with prasugrel compared to clopidogrel. While the active metabolites of prasugrel and clopidogrel resulted in similar levels of platelet inhibition in vitro, the amount of each active metabolite generated in vivo was quite different-prasugrel (60 mg) resulting in an approximately 12-fold greater exposure to its active metabolite compared with clopidogrel (300 mg). This observation provides a mechanistic basis for the faster, greater, and more consistent inhibition of platelet aggregation observed with prasugrel. Clinical studies in patients with cardiovascular disease confirmed the potent antiplatelet effect of prasugrel compared with clopidogrel. Collectively, these phase 1/1b studies and a phase 2 study (JUMBO-TIMI 26) aided in dose selection for the recently completed phase 3 trial (TRITON-TIMI 38) in patients with acute coronary syndrome undergoing percutaneous coronary intervention.     

Biology and pharmacology of the platelet P2Y12 receptor

Platelets possess two receptors for ADP, P2Y(1) and P2Y(12). ADP is released from platelet dense granules upon platelet activation by numerous agonists and thereby amplifies platelet responses regardless of the initial stimulus. The P2Y(1) receptor is one of many platelet receptors coupled to Gq and initiates ADP-induced activation. The P2Y(12) receptor on the other hand is linked to Gi and plays a special role in the amplification of platelet activation initiated by numerous other pathways. Platelet activation leads to a range of responses that play a critical role in arterial thrombosis and the inflammatory responses associated with this, including platelet aggregation, dense and alpha granule secretion and procoagulant activity. P2Y(12) receptor activation yields powerful amplification of these processes such that P2Y(12) receptor antagonists may have dramatic inhibitory effects on platelet function regardless of the activating stimuli. This phenomenon, coupled with the restricted distribution of the P2Y(12) receptor in humans, makes the receptor an ideal target for pharmaceutical therapy. This has already been established by the therapeutic success of clopidogrel, which acts, via an active metabolite, on this receptor. However, current therapeutic regimens of clopidogrel yield variable and incomplete P2Y(12) receptor blockade and more effective strategies to block P2Y(12) receptor activation offer the potential of greater clinical efficacy.     

Ticagrelor: a P2Y12 antagonist for use in acute coronary syndromes

Agents that inhibit platelet function are used routinely in the treatment and prevention of acute coronary syndromes. The main antiplatelet treatments used combine aspirin with one of the thienopyridine P2Y₁₂ antagonists, either clopidogrel or prasugrel. By blocking the synthesis of thromboxane A₂ in platelets and by blocking the effects of ADP, respectively, these agents reduce platelet activity, platelet aggregation and thrombus formation. Ticagrelor (marketed by AstraZeneca as Brilinta? in the USA, and as Brilique^® or Possia^® in Europe) is a cyclopentyl-triazolo-pyrimidine, a new chemical class of P2Y₁₂ antagonist that is now approved for use in the wide spectrum of acute coronary syndromes. In this article we provide an overview of ticagrelor. We discuss the differences in mode of action compared with other P2Y₁₂ antagonists, examine its pharmacodynamic, pharmacokinetic and safety profile, and summarize the various clinical trials that have provided information on its efficacy in combination with aspirin. Ticagrelor appears to overcome some of the difficulties that have been encountered with other antiplatelet treatments, clopidogrel in particular.     

P2Y12 receptor inhibitors: an evolution in drug design to prevent arterial thrombosis

Introduction: P2Y12 inhibitors are a critical component of dual antiplatelet therapy (DAPT), which is the superior strategy to prevent arterialthrombosis in patients with acute coronary syndromes (ACS) and undergoing stent implantation..

Areas covered: Basic science articles, clinical studies, and reviews from 1992–2017 were searched using Pubmed library to collet impactful literature. After an introduction to the purinergic receptor biology, this review summarizes current knowledge on P2Y12 receptor inhibitors. Furthermore, we describe the subsequent improvements of next-generation P2Y12 receptor inhibitors facing the ambivalent problem of bleeding events versus prevention of arterial thrombosis in a variety of clinical settings. Therefore, we summarize data from relevant preclinical and clinical trials of currently approved P2Y12 receptor inhibitors (clopidogrel, prasugrel, ticagrelor, cangrelor) and provide strategies of drug switching and management of bleeding events.

Expert opinion: An enormous amount of pharmacologic and clinical data is available for the application of P2Y12 receptor inhibitors. Today prasugrel, ticagrelor and clopidogrel are the standard of care drugs during dual antiplatelet therapy for ACS patients, but have considerable rates of bleeding. Recent and future clinical trials will provide evidence for subsequent escalation and de-escalation strategies of P2Y12 receptor inhibition. These data may pave the way for an evidence-based, individualized P2Y12 receptor inhibitor therapy.     

Review of clopidogrel dose escalation in the current era of potent P2Y12 inhibitors

Dual anti-platelet therapy with aspirin and a P2Y12 inhibitor is the standard of care for patients with acute coronary syndromes (ACS) and for patients undergoing percutaneous coronary intervention (PCI). Clopidogrel is associated with increased risk of high on-treatment platelet reactivity (HTPR) compared to ticagrelor and prasugrel. Investigators have therefore sought to “escalate” clopidogrel dosing to overcome HTPR to reduce ischemic/thrombotic events. In this review, we will summarize the evidence for dose escalation in the context of genetic determinants of resistance and platelet function data. We will review contemporary clinical trials that have sought to improve delivery of dual antiplatelet therapy to patients with coronary artery disease and discuss the potential of clopidogrel dose escalation in specific populations.     

血小板P2Y12受体拮抗剂临床研究进展

P2Y12受体拮抗剂是一类作用于血小板P2Y12受体、抑制血小板聚集的药物,临床上主要用于预防和治疗心血管疾病的血栓事件。氯吡格雷是目前临床上首选的双重抗血小板药物之一,但其疗效受限于CYP2C19基因的多态性、与质子泵抑制剂(PPIs)的相互作用和起效缓慢等。目前,一些新型P2Y12受体拮抗剂类抗血小板药物(如普拉格雷、替卡格雷等)已经进入临床,几项大型临床试验对其疗效和安全性进行了评价。本文对比了新型P2Y12受体拮抗剂与氯吡格雷在药理学、药代动力学、有效性和安全性方面的差异,并探讨其临床应用,为临床合理用药提供参考。     

血栓弹力图法和VerifyNow P2Y12法评估CYP2C19基因多态性对氯吡格雷反应性的影响

目的：通过血栓弹力图法（TEG）和VerifyNow P2Y12法检测来评估CYP2C19基因多态性对急性冠脉综合征（ACS）患者服用氯吡格雷疗效的影响，并比较2种方法检测结果的差异。方法：入选2017年10月至2018年10月因ACS入院且服用氯吡格雷（75 mg·d^-1）和阿司匹林（100 mg·d^-1）的患者230例，使用焦磷酸测序检测其CYP2C19基因型，并在服用氯吡格雷7 d后，使用TEG法检测其二磷酸腺苷（ADP）诱导的血小板聚集抑制率和VerifyNow P2Y12法检测其血小板反应单位（PRU）。结果：TEG法结果显示CYP2C19快代谢型、中间代谢型和慢代谢型患者出现氯吡格雷抵抗的比例分别为8.9%、40.2%和59.4%。VerifyNow P2Y12法检测结果显示各代谢型患者出现氯吡格雷抵抗的比例分别为6.9%、29.9%和50.0%。慢代谢型及中间代谢型患者出现氯吡格雷抵抗的概率明显高于快代谢组（P<0.05）。2种方法氯吡格雷抵抗检出率差异无显著性（P>0.05），检测结果显著相关（r=-0.719，P<0.001）。结论：CYP2C19基因多态性显著影响ACS患者服用氯吡格雷的疗效。TEG法和VerifyNow P2Y12法检测抗血小板聚集结果具有相关性。     

Dose-dependent inhibition of human platelet aggregation by prasugrel and its interaction with aspirin in healthy subjects

The aims of this open-label, randomized, dose-escalation pharmacodynamic study of prasugrel, an orally active antiplatelet agent, were to assess its interaction with aspirin (ASA, 325 mg) in healthy subjects after a loading dose (LD) and subsequent 5 days of once-daily maintenance doses (MD) of prasugrel or the active comparator, clopidogrel. We measured platelet aggregation induced by ADP, collagen, and TRAP and compared effects on maximal and residual platelet aggregation responses. On a background of ASA, subjects were randomly assigned to 1 of 4 prasugrel treatment groups (LD/MD in mg: 20/5, 30/7.5, 40/10, or 60/15; n = 8/group) or to clopidogrel 300 mg LD/75 mg MD (n = 11). Prasugrel dose-dependently inhibited ADP-induced platelet aggregation and exhibited higher levels of platelet inhibition than clopidogrel or ASA alone. Prasugrel plus ASA resulted in additive inhibition of collagen- and TRAP-induced platelet aggregation. Although inhibition of residual aggregation was greater than inhibition of maximal aggregation, values were highly correlated. The safety and tolerability of prasugrel plus ASA were also monitored. Within the limitations of the study, prasugrel was found to be well tolerated when dosed as LD followed by MD in the presence of ASA and provided greater platelet inhibition than ASA alone.     

Cangrelor: a novel P2Y12 receptor antagonist

Antiplatelet therapy is critical in the prevention of thrombotic complications of acute coronary syndrome and percutaneous coronary interventions. Current antiplatelet agents (aspirin, clopidogrel and glycoprotein IIb/IIIa antagonists) have demonstrated the capacity to reduce major adverse cardiac events. However, these agents have limitations that compromise their clinical utility. The platelet P2Y₁₂ receptor plays a central role in platelet function and is a focus in the development of antiplatelet therapies. Cangrelor is a potent, competitive inhibitor of the P2Y₁₂ receptor that is administered by intravenous infusion and rapidly achieves near complete inhibition of ADP-induced platelet aggregation. This investigational drug has been studied for use during coronary procedures and the management of patients experiencing acute coronary syndrome and is undergoing evaluation for use in the prevention of perioperative stent thrombosis.     

Effects of the proton pump inhibitor lansoprazole on the pharmacokinetics and pharmacodynamics of prasugrel and clopidogrel

Prasugrel and clopidogrel, thienopyridine prodrugs, are each metabolized to an active metabolite that inhibits the platelet P2Y(12) ADP receptor. In this open-label, 4-period crossover study, the effects of the proton pump inhibitor lansoprazole on the pharmacokinetics and pharmacodynamics of prasugrel and clopidogrel were assessed in healthy subjects given single doses of prasugrel 60 mg and clopidogrel 300 mg with and without concurrent lansoprazole 30 mg qd. C(max) and AUC(0-tlast) of prasugrel's active metabolite, R-138727, and clopidogrel's inactive carboxylic acid metabolite, SR26334, were assessed. Inhibition of platelet aggregation (IPA) was measured by turbidimetric aggregometry 4 to 24 hours after each treatment. Lansoprazole (1) decreased R-138727 AUC(0-tlast) and C(max) by 13% and 29%, respectively, but did not affect IPA after the prasugrel dose, and (2) did not affect SR62334 exposure but tended to lower IPA after a clopidogrel dose. A retrospective tertile analysis showed in subjects with high IPA after a clopidogrel dose alone that lansoprazole decreased IPA, whereas IPA was unaffected in these same subjects after a prasugrel dose. The overall data suggest that a prasugrel dose adjustment is not likely warranted in an individual taking prasugrel with a proton pump inhibitor such as lansoprazole.     

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.