Pharmacodynamics, pharmacokinetics, and safety of the oral reversible P2Y12 antagonist AZD6140 with aspirin in patients with atherosclerosis: a double-blind comparison to clopidogrel with aspirin.

AIMS: This double-blind, parallel-group study was conducted to assess the pharmacodynamics, pharmacokinetics, and safety of AZD6140, the first oral, reversible adenosine diphosphate (ADP) receptor antagonist. METHODS AND RESULTS: Patients (n = 200) with atherosclerosis were randomized to receive AZD6140 50, 100, or 200 mg twice daily (bid) or 400 mg daily (qd) or clopidogrel 75 mg qd for 28 days. All groups received aspirin 75-100 mg qd. AZD6140 (100 and 200 mg bid, 400 mg qd) rapidly and nearly completely inhibited ADP-induced platelet aggregation after initial dosing (day 1) and at day 28. On day 1, peak final-extent inhibition of platelet aggregation (IPA) was observed 2-4 h post-dose with AZD6140, whereas clopidogrel minimally inhibited platelet aggregation (mean percentage IPA < 20%, all time points). Four hour post-dose at steady state, the three higher doses of AZD6140 produced comparable final-extent mean percentage IPA (approximately 90-95%), which exceeded that with AZD6140 50 mg bid or clopidogrel (approximately 60%). AZD6140 was generally well tolerated. All bleeding events, except one in a patient receiving 400 mg qd, were minor and of mild-to-moderate severity. CONCLUSION: AZD6140 100 and 200 mg bid were well tolerated and were superior to AZD6140 50 mg bid and clopidogrel 75 mg qd with regard to antiplatelet efficacy.     

Safety, tolerability, and initial efficacy of AZD6140, the first reversible oral adenosine diphosphate receptor antagonist, compared with clopidogrel, in patients with non-ST-segment elevation acute coronary syndrome: primary results of the DISPERSE-2 trial.

OBJECTIVES: Our goal was to compare the safety and initial efficacy of AZD6140, the first reversible oral adenosine diphosphate receptor antagonist, with clopidogrel in patients with non-ST-segment elevation acute coronary syndromes (NSTE-ACS). BACKGROUND: AZD6140 achieves higher mean levels of platelet inhibition than clopidogrel in patients with stable coronary artery disease. METHODS: A total of 990 patients with NSTE-ACS, treated with aspirin and standard therapy for ACS, were randomized in a 1:1:1 double-blind fashion to receive either twice-daily AZD6140 90 mg, AZD6140 180 mg, or clopidogrel 300-mg loading dose plus 75 mg once daily for up to 12 weeks. RESULTS: The primary end point, the Kaplan-Meier rate of major or minor bleeding through 4 weeks, was 8.1% in the clopidogrel group, 9.8% in the AZD6140 90-mg group, and 8.0% in the AZD6140 180-mg group (p = 0.43 and p = 0.96, respectively, vs. clopidogrel); the major bleeding rates were 6.9%, 7.1%, and 5.1%, respectively (p = 0.91 and p = 0.35, respectively, vs. clopidogrel). Although not statistically significant, favorable trends were seen in the Kaplan-Meier rates of myocardial infarction (MI) over the entire study period (MI: 5.6%, 3.8%, and 2.5%, respectively; p = 0.41 and p = 0.06, respectively, vs. clopidogrel). In a post-hoc analysis of continuous electrocardiograms, mostly asymptomatic ventricular pauses >2.5 s were more common, especially in the AZD6140 180-mg group (4.3%, 5.5%, and 9.9%, respectively; p = 0.58 and p = 0.01, respectively, vs. clopidogrel). CONCLUSIONS: This initial experience with AZD6140 in patients with ACS showed no difference in major bleeding but an increase in minor bleeding at the higher dose with encouraging results on the secondary end point of MI. This agent is currently being studied in a large outcomes trial in 18,000 patients with ACS.     

Evolving pattern of platelet P2Y12 inhibition in patients with acute coronary syndromes

Abstract

Dual antiplatelet therapy consisting of clopidogrel in addition to aspirin has previously been the standard of care for patients with acute coronary syndromes (ACS) but international guidelines have been evolving over the last 4 years with the introduction of prasugrel and ticagrelor. In October 2009, prasugrel was approved in the UK by the National Institute of Health and Clinical Excellence (NICE) for use in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI), diabetic patients with non-ST-elevation (NSTE) ACS undergoing PCI and patients with stent thrombosis while other ACS patients were to continue receiving clopidogrel. Ticagrelor was approved in October 2011 by NICE for use in patients with moderate-to-high risk NSTE ACS and STEMI undergoing primary PCI and was recommended in preference to clopidogrel in European guidelines. These recommendations were adopted in our region, constituting a population of 1.8 million. We studied the effect of changing patterns of P2Y₁₂ inhibitor usage on levels of platelet inhibition during maintenance therapy. Patients admitted to Northern General Hospital, Sheffield, with NSTE ACS or STEMI managed with primary PCI were enrolled over two periods of time: May 2010 to November 2011 (T1); and October 2012 to February 2013 (T2). Venous blood samples were obtained at 1 month after the onset of ACS. Light transmittance aggregometry (LTA) was performed and maximum aggregation response to ADP 20?μM was determined. A total of 116 patients were enrolled in T1 of whom 82 were receiving clopidogrel and 34 were receiving prasugrel. Twenty-nine patients were enrolled in T2, all of whom were receiving ticagrelor. Mean LTA results according to treatment with clopidogrel, prasugrel and ticagrelor were 57?±?18%, 41?±?20%, and 31?±?12%, respectively. Prasugrel was associated with significantly lower platelet aggregation responses than clopidogrel (p?<?0.001) and ticagrelor was associated with significantly lower platelet aggregation responses than both prasugrel (p?=?0.015) and clopidogrel (p?<?0.001). We conclude that international guidelines and NICE approval have led to increasing levels of P2Y₁₂ inhibition in ACS patients in this UK centre between May 2010 and February 2013. Ticagrelor was associated with significantly greater P2Y₁₂ inhibition than both clopidogrel and prasugrel during maintenance therapy.     

P2Y12, a new platelet ADP receptor, target of clopidogrel

Clopidogrel is a potent antithrombotic drug that inhibits ADP-induced platelet aggregation. The results of large clinical trials have demonstrated an overall benefit of clopidogrel over aspirin in the prevention of vascular ischemic events (myocardial infarction, stroke, vascular death) in patients with a history of symptomatic atherosclerotic disease. The antiaggregating effect of clopidogrel is attributed to an irreversible inhibition of ADP binding to a purinergic receptor present at the platelet surface. Clopidogrel is not active in vitro and can be considered a precursor of an active metabolite formed in the liver. The chemical structure of this active metabolite and its biological activity have been described recently. Several purinergic receptors have been described on platelets; P2X (1), a calcium channel, and P2Y1 a Gq-coupled seven-transmembrane domain receptor, have been found not to be antagonized by clopidogrel. Another Gi (2)-coupled receptor (named P2Y12) has been recently cloned and stably expressed in CHO cells. These cells displayed a strong affinity for (33)P-2MeS-ADP, a stable analogue of ADP, the binding characteristics of which corresponded in all points to those observed on platelets. The binding of (33)P-2MeS-ADP to these cells was strongly inhibited by the active metabolite of clopidogrel with a potency that was consistent with that observed for this compound on platelets. In these transfected CHO cells, as in platelets, ADP and 2MeS-ADP induced adenylyl cyclase downregulation, an effect that was inhibited by the active metabolite of clopidogrel. These results demonstrate that this receptor corresponds to the previously called "P2t" platelet receptor and show that the active metabolite of clopidogrel binds in a covalent manner to this receptor, thus explaining how it blocks the aggregating effect of ADP on platelets.     

Inhibitory effects of P2Y12 receptor antagonists on TRAP-induced platelet aggregation,procoagulant activity,microparticle formation and intracellular calcium responses in patients with acute coronary syndromes

Thrombin induces platelet aggregation and membrane rearrangements leading to enhanced procoagulant activity and microparticle production, all of which are thought to contribute to thrombus formation in patients with acute coronary syndromes (ACS). Clopidogrel, an adenosine diphosphate (ADP) receptor antagonist acting at the P2Y₁₂ receptor, has been shown to provide clinical benefit in ACS. We aimed to investigate the effects of clopidogrel ex vivo and another ADP-antagonist, AR-C69931MX in vitro on thrombin receptor activating peptide (TRAP)-induced platelet aggregation, procoagulant activity, microparticle formation and [Ca²⁺]_i responses in patients with ACS. Measurements were performed in platelet-rich plasma using aggregometry and flow cytometry (n?=?12). Clopidogrel (300?mg loading dose plus 75?mg daily) significantly inhibited TRAP-induced aggregation, procoagulant activity (annexin V binding) and microparticle production (all P?<?0.05) but not as extensively as AR-C69931MX (400?nmol/l). [Ca²⁺]_i responses induced by a combination of TRAP and ADP designed to mimic the physiological effects of released ADP showed that clopidogrel partially and AR-C69931MX completely removed the ADP component of the [Ca²⁺]_i responses (n?=?6). The results provide new information on the mechanisms involved in the beneficial effects of P2Y₁₂ antagonists in patients with ACS.     

Inhibitory effects of P2Y12 receptor antagonists on TRAP-induced platelet aggregation, procoagulant activity, microparticle formation and intracellular calcium responses in patients with acute coronary syndromes

Thrombin induces platelet aggregation and membrane rearrangements leading to enhanced procoagulant activity and microparticle production, all of which are thought to contribute to thrombus formation in patients with acute coronary syndromes (ACS). Clopidogrel, an adenosine diphosphate (ADP) receptor antagonist acting at the P2Y(12) receptor, has been shown to provide clinical benefit in ACS. We aimed to investigate the effects of clopidogrel ex vivo and another ADP-antagonist, AR-C69931MX in vitro on thrombin receptor activating peptide (TRAP)-induced platelet aggregation, procoagulant activity, microparticle formation and [Ca(2+)]i responses in patients with ACS. Measurements were performed in platelet-rich plasma using aggregometry and flow cytometry (n = 12). Clopidogrel (300 mg loading dose plus 75 mg daily) significantly inhibited TRAP-induced aggregation, procoagulant activity (annexin V binding) and microparticle production (all P < 0.05) but not as extensively as AR-C69931MX (400 nmol/l). [Ca(2+)]i responses induced by a combination of TRAP and ADP designed to mimic the physiological effects of released ADP showed that clopidogrel partially and AR-C69931MX completely removed the ADP component of the [Ca(2+)]i responses (n = 6). The results provide new information on the mechanisms involved in the beneficial effects of P2Y(12) antagonists in patients with ACS.     

Rapid and reversible modulation of platelet function in man by a novel P2Y12 ADP-receptor antagonist,INS50589

P2Y₁₂ receptors participate in ADP-induced activation and aggregation of human platelets. INS50589, a selective P2Y₁₂ receptor antagonist, is being developed for use where controlled, reversible modulation of the platelet hemostatic function is needed. The tolerability, pharmacokinetics, and pharmacodynamics of INS50589 were tested in healthy human volunteers. Thirty-six subjects received intravenous infusions of placebo or INS50589 at 0.1–3?mg/kg/h for four hours. Platelet function, clotting parameters, bleeding time, safety assessments, and plasma concentrations of INS50589 and its major metabolite were monitored for 24 hours. Near-steady state plasma concentrations of INS50589 and effects on platelet function were achieved rapidly. The average maximal plasma concentration of INS50589 was linearly related to the dose administered. Intravenous INS50589 produced dose-dependent inhibition of platelet activation and aggregation in response to ADP in vitro until nearly full inhibition was achieved at the higher doses. Bleeding time was correspondingly increased, without any effect on activated clotting time, prothrombin time, or activated partial thromboplastin time. Platelet response to ADP had returned to at least 75% of the baseline value within 0.25–4?h after cessation of the intravenous infusion of INS50589, depending upon the dose and ADP challenge concentration. Infusions were well tolerated up to the highest dose tested. There was no evidence that the principal metabolite (INS51088) contributed to these effects. INS50589 is a well-tolerated, reversible, competitive antagonist of ADP at the P2Y₁₂ human platelet receptor, and its potential therapeutic utility in various cardiovascular settings is discussed.     

P2Y12 receptor in platelet activation

ADP plays an important role in hemostasis and thrombosis. The P2Y12 receptor, activated by ADP, plays a central role in platelet activation and thrombus formation. Thus, the P2Y12 receptor has been an effective target for antithrombotic drugs.     

P2Y12 receptor in platelet activation

ADP plays an important role in hemostasis and thrombosis. The P2Y12 receptor, activated by ADP, plays a central role in platelet activation and thrombus formation. Thus, the P2Y12 receptor has been an effective target for antithrombotic drugs.     

Follow-up of hemorheological parameters and platelet aggregation in patients with acute coronary syndromes

Pathologic hemorheological parameters and increased platelet aggregation in association with other risk factors significantly increase the possibility of the development of myocardial ischemia. Hemorheological parameters and platelet aggregation were investigated in 157 patients (mean age: 65+/-12 years) with acute coronary syndromes and in 68 healthy subjects (mean age: 36+/-6 years). Plasma fibrinogen, plasma and whole blood viscosity, red blood cell aggregation and filterability and platelet aggregation were measured in the hospital phase (after admission, on 2nd and 6th days) and monitored after discharge (at 1, 6 and 12 months). After admission all these parameters were significantly higher in patients than in control subjects (p<0.01) and almost all of them remained in the pathologic range at discharge. Some of the rheologic parameters showed a slight improvement after 1 month, but hematocrit and whole blood viscosity were higher than those after admission and of control subjects (p<0.05). After 6 and 12 months these parameters showed a small, but significant increase. Pathologically altered hemorheological parameters could be observed in patients with classical cardiovascular risk factors and significant improvement was found after elimination of them. Antiplatelet therapy was efficient in about half of the treated patients after admission; and despite a significant improvement, the proportion of ineffectively treated patients was still considerable during the follow-up. Our results support the role of abnormal hemorheological parameters in the development of myocardial ischemia and draw attention to the rheologic risk of these patients. The results of platelet aggregation measurements show the insufficiency of antiplatelet therapy at some cases and confirm the importance of guided secondary prevention.     

Rapid and reversible modulation of platelet function in man by a novel P2Y(12) ADP-receptor antagonist, INS50589

P2Y(12) receptors participate in ADP-induced activation and aggregation of human platelets. INS50589, a selective P2Y(12) receptor antagonist, is being developed for use where controlled, reversible modulation of the platelet hemostatic function is needed. The tolerability, pharmacokinetics, and pharmacodynamics of INS50589 were tested in healthy human volunteers. Thirty-six subjects received intravenous infusions of placebo or INS50589 at 0.1-3 mg/kg/h for four hours. Platelet function, clotting parameters, bleeding time, safety assessments, and plasma concentrations of INS50589 and its major metabolite were monitored for 24 hours. Near-steady state plasma concentrations of INS50589 and effects on platelet function were achieved rapidly. The average maximal plasma concentration of INS50589 was linearly related to the dose administered. Intravenous INS50589 produced dose-dependent inhibition of platelet activation and aggregation in response to ADP in vitro until nearly full inhibition was achieved at the higher doses. Bleeding time was correspondingly increased, without any effect on activated clotting time, prothrombin time, or activated partial thromboplastin time. Platelet response to ADP had returned to at least 75% of the baseline value within 0.25-4 h after cessation of the intravenous infusion of INS50589, depending upon the dose and ADP challenge concentration. Infusions were well tolerated up to the highest dose tested. There was no evidence that the principal metabolite (INS51088) contributed to these effects. INS50589 is a well-tolerated, reversible, competitive antagonist of ADP at the P2Y(12) human platelet receptor, and its potential therapeutic utility in various cardiovascular settings is discussed.     

不同氯吡格雷代谢型急性心肌梗死患者的血小板聚集率变化

目的观察不同氯吡格雷代谢型急性心肌梗死患者使用氯吡格雷后血小板聚集功能的被抑制情况。方法入选2013年3—8月急性心肌梗死患者48例,经过基因检测分为氯吡格雷慢代谢型6例、快代谢型17例和中间代谢型25例。患者均于入病房前服用负荷剂量阿司匹林300 mg和氯吡格雷300 mg,之后阿司匹林100 mg/d和氯吡格雷75 mg/d连续服用,于服药后第6天检测血小板聚集率、血细胞计数、纤维蛋白原含量和肝肾功能。结果所有患者服用氯吡格雷后第6天的血小板聚集率明显下降,二磷酸腺苷、肾上腺素诱导的抑制率分别为74%和84%。氯吡格雷快代谢型、中间代谢型和慢代谢型3组急性心肌梗死患者的二磷酸腺苷诱导的血小板聚集率分别为22.2%±13.4%、32.1%±20.1%和18.6%±13.9%(P>0.05),3组血小板抑制率分别为87%、78%和82%。结论本研究中不同氯吡格雷代谢型急性心肌梗死患者的血小板聚集功能的抑制情况无明显差异。     

Effects of P2Y 1 and P2Y 12 receptor antagonists on platelet aggregation induced by different agonists in human whole blood

ADP plays a major role in the amplification of platelet aggregation induced by other platelet agonists. ADP initiates platelet activation via the P2Y 1 receptor and amplifies platelet activation via the P2Y 12 receptor. Using the selective P2Y 1 receptor antagonist A2P5P and the selective P2Y 12 receptor antagonist AR-C69931MX, we assessed the relative contributions of P2Y 1 receptor and P2Y 12 receptor activation to platelet aggregation in hirudin-anticoagulated whole blood induced by PAF, 5HT, epinephrine, TRAP, streptokinase, U46619 and collagen. The effects of aspirin were assessed concurrently. A2P5P and AR-C69931MX variably inhibited aggregation induced by most of the agonists studied, whereas aspirin only inhibited aggregation induced by streptokinase and collagen. In some experiments, A2P5P and AR-C69931MX yielded additive inhibition of aggregation. All three antagonists interacted synergistically to inhibit collagen-induced aggregation. These studies demonstrate that P2Y 1 receptor activation plays a significant role in amplifying aggregation induced by agonists other than ADP, in addition to the established roles of P2Y 12 receptor activation and thromboxane A 2 synthesis.     

Clopidogrel affects leukocyte dependent platelet aggregation by P2Y12 expressing leukocytes

Up to 30% of all patients who are treated with a coronary stent do not respond sufficiently to antiplatelet therapy. This condition results in an increased risk for thrombotic complications such as stent thrombosis and myocardial infarction. The aim of the study was to determine clinical parameters modulating ASA and clopidogrel responsiveness. Patients were enrolled into three groups: (A) Patients with coronary artery disease without recent PCI treated with 100 mg/day ASA (n = 67). (B) Patients who underwent coronary stent implantation taking 100 mg/day ASA and 75 mg/day clopidogrel (n = 87). (C) Patients in whom CAD was excluded by angiography and who were not treated with anti-platelet medication served as controls (n = 32). Platelet aggregation was determined by impedance aggregometry using the Multiplate^® point of care device. Drug response was differentiated by stimulation of whole blood with arachidonic acid (AA, ASA responsiveness) or adenosine diphosphate (ADP, clopidogrel responsiveness). P2Y₁₂ receptor expression was determined by RT-PCR. ADP induced platelet aggregation correlated with the leukocyte count (r = 0.61, p < 0.001) suggesting that platelets and leukocytes interact functionally. Clopidogrel treatment abolished the influence of leukocytes on platelets and caused decreased leukocyte activation. We detected the expression of the clopidogrel target P2Y₁₂ on leukocytes suggesting that clopidogrel may act directly on these cells and not only on platelets. In contrast to ASA responsiveness, clopidogrel response correlated with body mass index (r = 0.34; p = 0.001). In conclusion, (1) leukocytes influence ADP induced platelet aggregation most likely by expression of the P2Y₁₂ receptor. This interaction is abolished by clopidogrel. Therefore, clopidogrel may act directly on leukocytes via the P2Y₁₂ receptor. (2) Clopidogrel may be under dosed in obese patients.     

血小板ADP-P2Y12受体拮抗剂研究进展

血小板在动脉粥样硬化斑块破裂后血栓形成发病机制中发挥关键作用,因而针对血小板激活途径的药物成为抗栓治疗的主要手段。循证医学表明,抗血小板治疗可以有效地预防动脉粥样硬化疾病患者发生严重的心血管事件。已经成为防治急性冠脉综合征的主要方法。     

P2Y12基因多态性与冠心病患者氯吡格雷抵抗的相关性研究

目的探讨冠心病患者血小板二磷酸腺苷(ADP)受体亚基12(P2Y12)基因多态性位点rs6798347的分布特征及其与氯吡格雷抵抗的相关性。方法入选91例经冠状动脉造影或CT冠状动脉造影确诊的冠心病患者。给予充分的氯吡格雷治疗后,运用富血小板血浆光学法来测定患者服药后最大血小板聚集率。根据最大血小板聚集率将患者分成氯吡格雷抵抗组(CR)30例和非氯吡格雷抵抗组(NCR)61例。应用Mass ARRAY时间飞行质谱技术对患者P2Y12基因单核苷酸多态性位点rs6798347进行基因分型,比较两组患者基因型的分布情况以及不同基因型之间血小板聚集率的差异。结果 91例患者rs6798347成功分型90例,其中CR组(29例)的GG、AA、AG基因型分别有14例(48.28%)、5例(17.24%)、10例(34.48%);NCR组(61例)的GG、AA、AG基因型分别有33例(54.10%)、5例(8.20%)、23例(37.70%)。两组基因型分布差异无统计学意义(均为P>0.05),携带突变型等位基因A的患者服氯吡格雷后最大血小板聚集率有升高趋势(45.21%±16.67%比51.63%±16.18%,P=0.068);部分CR的患者服用氯吡格雷后最大血小板聚集率高于其未服药时的基线值(68.70%±13.59%比58.90%±4.93%,P=0.046);各基因型之间冠状动脉病变支数的差异无统计学意义(均为P>0.05)。CR组与NCR组之间总胆固醇[(4.11±1.12)mmol/L比(4.81±1.34)mmol/L,P=0.015]和低密度脂蛋白胆固醇[(2.18±0.81)mmol/L比(2.57±0.89)mmol/L,P=0.049]水平差异均有统计学意义;但两组患者其余临床资料差异无统计学意义(均为P>0.05)。结论 (1)血小板膜P2Y12受体基因多态性位点rs6798347与冠心病患者CR的发生无明显关系;(2)血小板膜P2Y12受体基因多态性位点rs6798347的突变型等位基因可能影响氯吡格雷抗血小板聚集的能力。