Molecular cloning and functional analysis of HnSaratin from Hirudo nipponia.

In order to finish a bloodmeal successfully, hematophagous organisms often stored a variety of anticoagulant proteins in their salivary glands, such as proteins that inhibit platelet aggregation. When they ingest a bloodmeal, these proteins are injected into the host to prevent the blood from clotting. As one of the origins of leeches used in traditional Chinese medicine, H. nipponia was proved to be clinically effective in treatment of cardiovascular and cerebrovascular diseases. This study cloned the sequence of HnSaratin cDNA derived from salivary glands of H. nipponia. The sequence contains an open reading frame of 387 bp, encoding a protein of 128 amino acids containing a signal peptide of 21 amino acids. After removal of the signal peptide, the molecular mass of mature HnSaratin was 12.37 kDa, with a theoretical isoelectric point (pI) of 3.89. The N-terminal of mature HnSaratin was folded into a globular structure, in which 3 disulfide bonds, a ßßαßßß topology and 2 Glu residues that binds collagenous Lys2 were located, and the C-terminal formed a flexible region. The fusion HnSaratin protein was obtained by a prokaryotic expression system. The protein showed anti-platelet aggregation activity, and was observed to prevent blood clotting in rats. The significant high expression of HnSaratin mRNA in salivary glands was induced by bloodmeal ingestion of H. nipponia. Briefly, our work provides theoretical basis for further development and utilization of H. nipponia.

Identification of Potential Biological Factors Affecting the Treatment of Ticagrelor After Percutaneous Coronary Intervention in the Chinese Population.

BACKGROUND: Generally, many individual factors can affect the clinical application of drugs, of which genetic factors contribute more than 20%. Ticagrelor is a new class of receptor inhibitors receptor antagonist of P2Y12 and is used as an antiplatelet agents. But it is not affected by the influence of CYP2C19 polymorphism. With lack of predicted biomarkers, especially the research data of Chinese, it has the important significance in studying individual differences of ticagrelor in the antiplatelet efficacy and safety, through pharmacogenomics research. METHODS: Whole-exome sequencing (WES) was performed in 100 patients after PCI with ticagrelor treatment. Clinical characteristics and WES of patients were used to performed genome-wide association analysis (GWAS), region-based tests of rare DNA variant to find the influencing factors of antiplatelet effect to ticagrelor and bleeding events. Co-expression, protein-protein interaction (PPI) network and pathway enrichment analysis were then used to find possible genetic mechanisms. Atlas of GWAS (https://atlas.ctglab.nl/) were used for external data validation. RESULTS: DNAH17, PGS1 and ABCA1 as the potential variant genes are associated with the expected antiplatelet effect to ticagrelor. The affected pathways may include the synthesis and metabolism of lipoprotein cholesterol and the catabolic process of pyrimidine-containing compound (GO:0072529). Age, sex and PLT were found may be potential factors for ticagrelor bleeding events. CONCLUSION: We systematically identified new genetic variants and some risk factors for reduced efficacy of ticagrelor and highlighted related genes that may be involved in antiplatelet effects and bleeding event of ticagrelor. Our results enhance the understanding of the absorption and metabolic mechanisms that influence antiplatelet response to ticagrelor treatment. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03161002. First Posted: May 19, 2017. https://clinicaltrials.gov/ct2/show/study/NCT03161002.

Efficacy and safety of different ticagrelor regimens versus clopidogrel in patients with coronary artery disease: a retrospective multicenter study (SUPERIOR).

Current guidelines favor dual anti-platelet therapy with ticagrelor 90 mg BID (T90BID) over clopidogrel 75 mg QD (C75QD) in addition to aspirin for acute coronary syndrome. However, an increased risk of ticagrelor-related adverse events prompted the evaluation of low-dose regimens. This study (NCT03381742) retrospectively analyzed the data from 11 hospitals on 3,043 patients with coronary artery disease, who received C75QD, T90BID, ticagrelor 45 mg BID (T45BID), or ticagrelor 90 mg QD (T90QD). Compared with C75QD, both T45BID and T90QD showed significantly higher inhibition of platelet aggregation (P < .0001) and lower platelet-fibrin clot strength (P < .0001) induced by adenosine diphosphate. Furthermore, compared with T90BID, two low-dose regimens had a much lower minor bleeding rate and a significantly higher proportion of patients within the therapeutic window for P2Y12 receptor reactivity. There were no significant differences between T45BID and T90QD in the trough plasma concentrations of ticagrelor and its active metabolite. Similar efficacy and safety outcomes were observed in the propensity score-matched analysis. In conclusion, the low-dose ticagrelor regimen, either T45BID or T90QD, may provide a more attractive benefit-risk profile than C75QD or T90BID.

Antiplatelet effect of ticagrelor with aspirin in acute minor stroke and transient ischemic attack stratified by CYP2C19 metabolizer status: subgroup analysis of the PRINCE trial.

Studies on antiplatelet effect of ticagrelor/aspirin and clopidogrel/aspirin in patients with acute minor stroke and transient ischemic attack (TIA) stratified by CYP2C19 metabolizer status is limited. We gained data from the Platelet Reactivity In Non-disabling Cerebrovascular Events study. Platelet reactivity was tested at baseline, 2 hours, 24 hours, 7 days and 90 days after initial dose, including high on-treatment platelet reactivity (HOPR), which was defined as P2Y12 reaction unit >208, and percentage inhibition of platelet aggregation (IPA). A total of 365 patients were included. There were 199 (54.5%) individuals classified as carriers of CYP2C19 loss-of-function alleles. For carriers and non-carriers, the proportions of HOPR were significantly lower in those with ticagrelor/aspirin compared with those with clopidogrel/aspirin at 2 hours, 24 hours, 7 days, respectively (all p<0.05). IPA was higher at all time points except at baseline in patients with ticagrelor/aspirin compared with those with clopidogrel/aspirin in both carriers and non-carriers of CYP2C19 lose-of-function alleles (all p<0.05). Our findings showed that ticagrelor/aspirin therapy possessed greater platelet inhibition and more rapid onset in platelet inhibition compared with clopidogrel/aspirin therapy both in carriers and non-carriers of CYP2C19 lose-of-function alleles with acute minor stroke or TIA.

Pharmacodynamic assessment of prasugrel and clopidogrel in patients with non-cardioembolic stroke: a multicenter, randomized, active-control clinical trial.

Prasugrel, a novel P2Y12 receptor antagonist, has been shown to be more effective than clopidogrel for preventing cardiovascular events in patients with acute coronary syndromes undergoing percutaneous coronary intervention. We investigated the dose-response antiplatelet effects of prasugrel compared with clopidogrel in Japanese patients with non-cardioembolic stroke. The influence of cytochrome P450 (CYP) polymorphisms on the antiplatelet effects of both drugs was also compared. In this multicenter randomized active-control comparative study, patients were randomized to receive prasugrel 2.5 mg, 5 mg, or 7.5 mg (double blind) or clopidogrel 75 mg (open label) once daily for 14 days. The primary endpoint was inhibition of platelet aggregation (IPA) in response to adenosine diphosphate 20 µM within 8 h of study drug administration on day 14. Of the 66 patients randomized, data from 63 (prasugrel 2.5 mg, 5 mg, and 7.5 mg groups, n = 14, 16, and 18, respectively; clopidogrel group, n = 15) were used in the pharmacodynamic assessment. IPA (arithmetic mean ± SD) after prasugrel administration increased dose-dependently (33 ± 9%, 44 ± 11%, and 53 ± 14%, at 2.5 mg, 5 mg, and 7.5 mg, respectively) and was higher in these groups than after clopidogrel (23 ± 16%). In a subgroup of CYP2C19 intermediate metabolizers, IPA was higher in the prasugrel 5 mg and 7.5 mg groups than in the clopidogrel group. No death or serious adverse events were reported. Prasugrel was well tolerated at doses up to 7.5 mg/day and had antiplatelet effects higher than those of clopidogrel 75 mg/day. CYP2C19 polymorphisms may have reduced clopidogrel-induced IPA.

Prediction of Ticagrelor and its Active Metabolite in Liver Cirrhosis Populations Using a Physiologically Based Pharmacokinetic Model Involving Pharmacodynamics.

Ticagrelor, a P2Y12 receptor antagonist, has been highly recommended for use in acute coronary syndrome. The major active metabolite (AM) is similar to the parent drug, which exhibits antiplatelet activity. The inhibition of platelet aggregation (IPA) is used as an assay to demonstrate the anticoagulant efficacy of ticagrelor. In this study, we developed a physiologically based pharmacokinetic (PBPK) model to predict the pharmacokinetics of ticagrelor and its AM and combined this model with a pharmacodynamics model to reflect potential pharmacodynamic alterations in liver cirrhosis populations. The simulated results obtained using the PBPK model were validated by fold error values, which were all smaller than 2. Comparisons of exposure in different classifications of liver cirrhosis indicated that exposure to ticagrelor increased significantly with an increase in the degree of cirrhosis severity, whereas exposure to AM was decreased. The total concentration of ticagrelor and AM was related to the IPA included in the Sigmoid Emax model. The PBPK model of ticagrelor and AM could predict the pharmacokinetics of all populations, and a combination of PD models was used to extrapolate for predicting unknown scenarios. Liver cirrhosis may result in prolonged IPA, depending on the severity degree of this disease. The combined PBPK model including IPA can reveal changes in pharmacokinetics and pharmacodynamics in populations affected by liver cirrhosis and indicate the risk potential.

Clinical Pharmacology of the Reversible and Potent P2Y12 Receptor Antagonist ACT-246475 After Single Subcutaneous Administration in Healthy Male Subjects.

ACT-246475 is a selective and reversible P2Y12 receptor antagonist inducing inhibition of platelet aggregation (IPA). A randomized, double-blind, placebo-controlled, parallel-design study was performed to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of escalating single subcutaneous doses of ACT-246475 (1, 2, 4, 8, 16, or 32 mg) in healthy male subjects (N = 8 per dose, 3:1 active:placebo ratio). Pharmacodynamic effects were assessed based on maximum platelet aggregation and P2Y12 reaction units using light transmission aggregometry and VerifyNow® assays, respectively. ACT-246475 was safe and well tolerated up to 32 mg based on adverse event data and absence of clinically relevant changes in hematology, biochemistry, vital signs, and electrocardiogram variables. Median time to reach maximum plasma concentration was 0.5-0.75 hours, and geometric mean terminal half-life ranged from 1.3 to 9.2 hours across the tested dose range. Exposure to ACT-246475 was dose proportional across all dose groups. The maximal %IPA was reached within 30 minutes after subcutaneous administration of ACT-246475. A dose-dependent duration and extent of effect were observed based on area under the effect curve and maximum effect data. Similar results were observed for maximum platelet aggregation and P2Y12 reaction units. The %IPA was ≥85% at doses ≥2 mg. This level of %IPA was extended to at least 12 hours in the 32-mg dose group. The safety and pharmacokinetic/pharmacokinetic profile with quick onset and adequate duration of IPA support further investigation in patients with coronary artery disease.

Pharmacokinetic-pharmacodynamic modelling of platelet response to ticagrelor in stable coronary artery disease and prior myocardial infarction patients.

AIMS: To characterize ticagrelor exposure-response relationship for platelet inhibition in patients with stable coronary artery disease (CAD) and a history of myocardial infarction (MI), using nonlinear mixed effects modelling and simulation. METHODS: Platelet function data were integrated with plasma concentration data of ticagrelor and its active metabolite AR-C1249010XX in a population pharmacokinetic (PK) and pharmacodynamic (PD) model, based on two clinical studies. In the ONSET/OFFSET study, PK and platelet function were assessed in 123 CAD patients receiving placebo, ticagrelor (180 mg followed by 90 mg twice daily) or clopidogrel (600 mg followed by 75 mg once daily). In the PEGASUS-TIMI 54 platelet function substudy, PK and platelet function were assessed during maintenance dosing in 180 prior MI patients receiving placebo, ticagrelor 60 mg or ticagrelor 90 mg twice daily. RESULTS: Platelet inhibition by ticagrelor was described by a sigmoidal Emax model. On average, half maximal inhibition was reached at ticagrelor concentrations of 116 (RSE: 5.3%) nmol l-1 . Simulations showed that near maximal platelet inhibition is achieved with both ticagrelor 60 and 90 mg twice daily. At simulated lower doses, platelet inhibition is overall reduced, more variable between patients, and show greater peak-to-trough variability. Ticagrelor antiplatelet response was similar between the studied patient populations. CONCLUSIONS: In patients with stable CAD or a history of MI, near maximal platelet inhibition is achieved with both ticagrelor 60 and 90 mg twice daily. At modelled doses <60 mg, the response is reduced overall, more variable between patients, and patients will display greater peak-to-trough variability.

Functional Outcome and Safety of Intracranial Thrombectomy After Emergent Extracranial Stenting in Acute Ischemic Stroke Due to Tandem Occlusions.

Background and Purpose: Various endovascular approaches to treat acute ischemic stroke caused by extra- intracranial tandem occlusions (TO) exist: percutaneous transluminal angioplasty with or without emergent extracranial carotid stenting (ECS) due to high-grade stenosis preceded or followed by intracranial mechanical and/or aspiration thrombectomy (MT). Which treatment strategy to use is still a matter of debate. Methods: From our ongoing prospective stroke registry we retrospectively analyzed 1,071 patients with anterior circulation stroke getting endovascular treatment within 6 h of symptom onset. ECS prior to intracranial MT for TO (n = 222) was compared to MT as standard of care (control group; acute intracranial vessel occlusion without concomitant ipsilateral ICA-occlusion or high-grade stenosis [C; n = 849]). Good functional outcome (mRS ≤ 2 at 3 months), mortality rates, frequencies of symptomatic intracranial hemorrhage (sICH) and successful recanalization (Thrombolysis in Cerebral Infarction Score [TICI] 2b or 3) were assessed. In subgroup analyses we tried to detect possible influences of stroke etiology, dual inhibition of platelet aggregation (IPA; clopidogrel [CLO]: n = 83; ticagrelor [TIC]: n = 137; in combination with Aspirin) and intravenous thrombolysis (IVT). Results: Functional outcome was superior in TO (mRS 0-2: 44.6%) when compared with controls (36.0%; OR [95% CI]: 3.49 [1.59-7.67]; p = 0.002). There was no difference in all-cause mortality at 3 months (TO: 21.6%; C: 27.7%; 0.78 [0.47-1.29]; p = 0.324), in-hospital mortality (0.76 [0.45-1.30]; p = 0.324), sICH (TO: 3.2%; C: 5.0%; 0.70 [0.30-1.59]; p = 0.389), and TICI 2b/3 (TO: 89.1%; C: 88.3%; p = 0.813). In subgroup-analysis, TIC and CLO did not differ in functional outcome (TIC: 45.3%; CLO: 44.6%; 1.04 [0.51-2.09]; p = 0.920) and mortality rates (all-cause mortality: TIC: 23.4%; CLO: 16.9%; 0.75 [0.27-2.13]; p = 0.594). sICH was more frequent in TIC (n = 7 [5.1%]) vs. CLO (n = 0; p = 0.048). Conclusion: In our pre-selected cohort, ECS prior to intracranial MT in TO allowed for a good functional outcome that was superior compared to a control population. Mortality rates did not differ. Despite a dual IPA in TO, there was no increase in sICH. CLO and TIC for dual IPA did not differ in terms out outcome and mortality rates. A significant increase in sICH was observed after initial loading with TIC.

Ticagrelor and Eptifibatide Bolus Versus Ticagrelor and Eptifibatide Bolus With 2-Hour Infusion in High-Risk Acute Coronary Syndromes Patients Undergoing Early Percutaneous Coronary Intervention.

BACKGROUND: In patients with non-ST-segment elevation acute coronary syndromes, inhibition of platelet aggregation (IPA) with a potent P2Y12 inhibitor, ticagrelor, was inferior to tirofiban infusion at 2 hours, indicating that glycoprotein IIb/IIIa inhibitors are still needed. Ticagrelor and eptifibatide bolus only may maximally inhibit platelet aggregation and decrease bleeding, but IPA with ticagrelor and eptifibatide bolus versus 2-hour infusion is unknown. METHODS AND RESULTS: A total of 70 P2Y12-naïve patients, with high-risk non-ST-segment elevation acute coronary syndromes, were randomized to ticagrelor and eptifibatide bolus (group 1) versus ticagrelor and eptifibatide bolus with 2-hour infusion (group 2). Levels of IPA with ADP, thrombin receptor-activating peptide, collagen, and high on-treatment platelet reactivity were measured by light transmission aggregometry at baseline and at 2, 6, and 24 hours after percutaneous coronary intervention in both groups. The primary end point, IPA with ADP 20 µmol/L at 2 hours, was 99.59±0.43% in group 1 versus 99.88±1.0% in group 2 (P<0.001 for noninferiority). High on-treatment platelet reactivity with ADP was zero at 2, 6, and 24 hours in both groups. IPA levels with ADP, thrombin receptor-activating peptide, and collagen were significantly higher at 2 and 6 hours than at 24 hours in both groups. Periprocedural myocardial infarction was not significantly different between the groups. Hemoglobin level was significantly less at 24 hours versus baseline in group 2 (13.35±1.8 versus 12.38±1.8 g/dL, respectively; P<0.01). CONCLUSIONS: Ticagrelor and eptifibatide bolus maximally inhibited platelet aggregation at 2 hours, which was associated with no significant hemoglobin drop after percutaneous coronary intervention. This obviates the need for eptifibatide 2-hour infusion and might decrease bleeding complications. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01919723.

Chewing versus Swallowing Ticagrelor to Accelerate Platelet Inhibition in Acute Coronary Syndrome - the CHEERS study. For The PLATIS (Platelets and Thrombosis in Sheba) Study Group.

It was the study objective to evaluate whether chewing a 180 mg loading dose of ticagrelor versus an equal dose of traditional oral administration, enhances inhibition of platelet aggregation 1 hour (h) after administering a ticagrelor loading dose in non-ST elevation myocardial infarction (NSTEMI) patients. Dual anti-platelet therapy represents standard care for treating NSTEMI patients. Ticagrelor is a direct acting P2Y12 inhibitor and, unlike clopidogrel and prasugrel, does not require metabolic activation. Fifty NSTEMI patients were randomised to receive either a chewing loading dose of 180 mg ticagrelor or an equal standard oral dose of ticagrelor. Platelet reactivity was evaluated by VerifyNow at baseline, 1 and 4 h post-loading dose. Results are reported in P2Y12 reaction units. Patients then continued to receive standard 90 mg oral ticagrelor twice daily. Baseline characteristics did not differ between the two groups. P2Y12 reaction units in the chewing group compared with the standard group at 0, 1 and 4 h after ticagrelor loading dose were: 245 vs 239 (p=0.59), 45 vs 130 (p=0.001) and 39 vs 60 (p=0.12), respectively, corresponding to a relative inhibition of platelet aggregation of 83 % vs only 47 % at 1 h (p< 0.001), and 84 % vs 77 % (p=0.59) at 4 h. Major adverse cardiac and cardiovascular events at 30 days were low (2 %), occurring in only one patient in the standard group. In conclusion, chewing a 180 mg ticagrelor loading dose is feasible and facilitates both faster and improved early inhibition of platelet aggregation in NSTEMI patients, compared with a standard oral-loading dose.

Platelet Aggregation Inhibitory Effects and Pharmacokinetics of Prasugrel Used in Combination With Aspirin in Healthy Japanese Subjects.

We evaluated the pharmacokinetics and pharmacodynamics of prasugrel used in combination with aspirin in healthy Japanese subjects. All subjects received aspirin 100 mg/day. Subsequently, in the single-administration study, 23 subjects also received prasugrel 20 or 30 mg, and in the multiple-administration study, 20 subjects received a loading dose of prasugrel 20 or 30 mg on day 1, followed by a maintenance dose of prasugrel 5 or 7.5 mg/day, respectively, on days 2-5. In both studies, the plasma concentration of the active metabolite of prasugrel, R-138727, reached a maximum 0.5 hours after administration and rapidly decreased within 4 hours. In the single-administration study, the inhibitory effect on adenosine diphosphate-induced platelet aggregation was significantly higher in the prasugrel 20- and 30-mg groups than in the placebo group at all times (1-144 hours) after administration. In the multiple-administration study, a similar antiplatelet effect was found after both the loading dose and the maintenance dose and was maintained for 3-6 days after the last administration. There were study drug-related adverse events; however, all were mild, and none was clinically significant.

Using IPA rate to assess the high platelet reactivity of patient with coronary heart disease / 实用医学杂志

Objective Using IPA rate to assess platelet reactivity of coronary heart disease patients re-ceived the dual antiplatelet therapy after PCI. Methods CHD patients received the loading dose of clopidogrel (300 mg)on the first day of hospitalization or before PCI,then received clopidogrel(75 mg/d)and aspirin(100 mg/d) for one year. IPA was measured after administration of the loading dose of clopidogrel. The patients were divided into the HPR and LPR group according to the rate of IPA. Observe patients incidences of cardiovascular events were followed up for one year. Results A total of 102 patients were enrolled into this study ,including 77 males and 25 females with average age of 65.7 ± 10.9. Patients were divided into the HPR and LPR group with 69 and 33 patients,respectively. The average IPA value of HPR group was obvious lower than that of LPR group(P<0.01). The accumulative 12-month cardiovascular events incidence in the HPR and LPR group were 15.9% and 3.0% respectively ,with significant difference (P < 0.05). Conclusion IPA could be used to evaluate platelet reactivity,which suggests that clinicians can detect IPA to reduce or avoid the recurrence of cardiovascular events.

Using IPA rate to assess the high platelet reactivity of patient with coronary heart disease / 实用医学杂志

Objective Using IPA rate to assess platelet reactivity of coronary heart disease patients re-ceived the dual antiplatelet therapy after PCI. Methods CHD patients received the loading dose of clopidogrel (300 mg)on the first day of hospitalization or before PCI,then received clopidogrel(75 mg/d)and aspirin(100 mg/d) for one year. IPA was measured after administration of the loading dose of clopidogrel. The patients were divided into the HPR and LPR group according to the rate of IPA. Observe patients incidences of cardiovascular events were followed up for one year. Results A total of 102 patients were enrolled into this study ,including 77 males and 25 females with average age of 65.7 ± 10.9. Patients were divided into the HPR and LPR group with 69 and 33 patients,respectively. The average IPA value of HPR group was obvious lower than that of LPR group(P<0.01). The accumulative 12-month cardiovascular events incidence in the HPR and LPR group were 15.9% and 3.0% respectively ,with significant difference (P < 0.05). Conclusion IPA could be used to evaluate platelet reactivity,which suggests that clinicians can detect IPA to reduce or avoid the recurrence of cardiovascular events.

Pharmacokinetics and pharmacodynamics of prasugrel in healthy Japanese subjects.

This randomized double-blind and placebo-controlled study assessed the pharmacodynamics and pharmacokinetics of prasugrel in healthy adult Japanese male subjects after single (n = 50) and multiple (n = 40) oral administration. With a single administration of prasugrel (2-30 mg), the plasma concentration of the active metabolite increased rapidly, reached a maximum at 30 min after administration, and then decreased rapidly within 4 h. The 5 mg and higher doses prevented ADP-induced platelet aggregation in a dose-dependent manner. Further analyses showed that 30 mg prasugrel exhibited the peak inhibition, and 20 mg prasugrel showed a nearly equivalent effect. With multiple doses (2.5-10 mg), the pharmacokinetic parameters on Day 1 and Day 7 were similar, and no accumulation attributable to multiple dosing was observed. The inhibitory effect on ADP-induced platelet aggregation increased with doses from 2.5 to 7.5 mg, and reached the peak level at 7.5 mg. Regarding safety, all of the drug-related adverse events observed were mild, and there were no clinically significant bleeding-related adverse events. This study indicates that a single oral administration of prasugrel at a dose of up to 30 mg and a maintenance dose of up to 10 mg are tolerated in Japanese healthy subjects.

Comparison of half- and standard-dose ticagrelor in Chinese patients with NSTE-ACS.

Ticagrelor is a novel direct-acting P2Y12 receptor antagonist used for preventing atherothrombotic events in patients with acute coronary syndromes (ACS). The current recommended dose is 90 mg bid, but a low dose of ticagrelor has not been previously studied in Chinese ACS patients. Therefore, we performed this study to observe the different effects of half- and standard-dose ticagrelor on platelet aggregation in Chinese patients with NSTE-ACS. Sixty-two NSTE-ACS subjects were assigned to half-dose ticagrelor (n = 20), standard-dose ticagrelor (n = 22) and clopidogrel (n = 20) groups. Five days after drug administration, VerifyNow P2Y12 assay was performed to test P2Y12 reaction units (PRU) and inhibition of platelet aggregation (IPA). High-platelet reactivity (HPR) was defined as a PRU > 208. The adverse events, including bleeding events and dyspnoea, were monitored throughout the study. PRU values in the half-dose (44.55 ± 32.88) and standard-dose (39.10 ± 40.02) ticagrelor were dramatically lower than those in the clopidogrel group (189.20 ± 65.22; P < 0.0001). The half-dose (84% ± 10%) and standard-dose (86% ± 13%) ticagrelor both showed greater IPA than clopidogrel (33% ± 20%; P < 0.0001). There were no significant differences in PRU and IPA between the two ticagrelor groups (P = 0.3085 and 0.4028, respectively). HPR rates were significantly lower in the two ticagrelor groups (0% for both) than those in the clopidogrel group (35%). In conclusion, half-dose ticagrelor had a similar inhibitory effect on platelet aggregation as standard-dose ticagrelor in Chinese patients with NSTE-ACS, which was significantly stronger than that of clopidogrel.

Double-blind, randomized, prospective comparison of loading doses of 600 mg clopidogrel versus 60 mg prasugrel in patients with acute ST-segment elevation myocardial infarction scheduled for primary percutaneous intervention: the ETAMI trial (early thienopyridine treatment to improve primary PCI in patients with acute myocardial infarction).

OBJECTIVES: This study compared the timing of onset of antiplatelet action after treatment with clopidogrel and prasugrel at first medical contact in patients with ST-segment elevation myocardial infarction (STEMI) scheduled for primary percutaneous coronary intervention (PPCI). BACKGROUND: Little is known about the timing of onset of antiplatelet action after a pre-percutaneous coronary intervention (PCI) loading dose of clopidogrel or prasugrel in patients with STEMI. METHODS: This double-blind, prospective study randomized 62 patients with STEMI scheduled for PPCI in the ambulance or the emergency department to 60 mg prasugrel (n = 31) or 600 mg clopidogrel (n = 31). The primary endpoint was the platelet reactivity index (PRI) measured with the vasodilator-stimulated phosphoprotein assay 2 h after intake of the study medication. Secondary endpoints were PRI after 4 h, TIMI (Thrombolysis In Myocardial Infarction) patency of the infarct-related artery before and after PCI, and clinical events until day 30. RESULTS: The PRI after 2 h (50.4 ± 32.7% vs. 66.3 ± 22.2%; p = 0.035) and after 4 h (39.1 ± 27.5% vs. 54.5 ± 49.3%; p = 0.038) were significantly lower with prasugrel compared with clopidogrel. In addition, the rate of patients with a PRI <50% tended to be higher with prasugrel compared with clopidogrel after 2 h (46.7% vs. 28.6%; p = 0.15) and after 4 h (63.0% vs. 38.9%; p = 0.06). There were no significant differences in TIMI 2/3 patency before PCI (39.2% vs. 31.0%; p = 0.43) and TIMI 3 patency after PCI (88.5% vs. 89.3%; p = 0.92). CONCLUSIONS: The pre-PCI administration of prasugrel in patients with STEMI undergoing PPCI was associated with a significant faster platelet inhibition compared with clopidogrel. Therefore, prasugrel should be preferred to clopidogrel in this setting. (ETAMI-Study: Early Thienopyridine Treatment to Improve Primary PCI in Patients With Acute Myocardial Infarction; NCT01327534).

Effects of rabeprazole on the antiplatelet effects and pharmacokinetics of clopidogrel in healthy volunteers.

BACKGROUND: Several studies have suggested that proton-pump inhibitors (PPIs), mostly omeprazole, interact with clopidogrel efficacy by inhibiting the formation of its active metabolite via CYP2C19 inhibition. Whether this occurs with all PPIs is a matter of debate. As rabeprazole is a less potent CYP2C19 inhibitor than other PPIs, we studied the interaction between rabeprazole and the antiplatelet actions and pharmacokinetics of clopidogrel. AIM: To demonstrate the non-inferiority of rabeprazole over placebo using change in platelet reactivity index (PRI; vasodilator-stimulated phosphoprotein [VASP] assay) in a predefined population of good clopidogrel responders. Omeprazole was used as the positive control. METHODS: In this randomized three-period crossover study in healthy volunteers, 36 healthy men received clopidogrel (75 mg/day for 7 days) with placebo, omeprazole (20mg/day) or rabeprazole (20mg/day). Clopidogrel antiplatelet effects and disposition kinetics were assessed on day 7 of combination therapy. Non-inferiority threshold was predefined as an upper limit of the 90% confidence interval for the difference in change in PRI between placebo and rabeprazole of<10% in good clopidogrel responders. RESULTS: In good clopidogrel responders (inhibition of VASP index>30%), the clopidogrel antiplatelet effect remained non-inferior to placebo during rabeprazole (difference 3.4% [-1.7; 8.5]) but not omeprazole (difference 7.5% [2.5; 12.6]) co-administration. The AUC0-24 and Cmax of active clopidogrel metabolite decreased with both omeprazole and rabeprazole, and conditions of bioequivalence were not met, except for AUC0-24 with rabeprazole. CONCLUSIONS: Rabeprazole does not interact with clopidogrel to the same extent as omeprazole. However, under our experimental conditions and proton-pump inhibitor doses, there was no significant pharmacodynamic interaction between rabeprazole or omeprazole and clopidogrel, despite a significant decrease in the formation of clopidogrel active metabolite.

Ticagrelor: The first approved reversible oral antiplatelet agent.

Platelet aggregation plays an important role in the pathophysiology of acute coronary syndrome (ACS). Aspirin is the most widely used antiplatelet agent and acts by inhibiting thromboxane A2-induced platelet activation. But it does not prevent platelets activation and aggregation by other signaling pathways like adenosine diphosphate (ADP) and Glycoprotein IIb/IIIa. Ticagrelor is the first oral reversible ADP (P2Y12) receptor antagonist. As compared to clopidogrel, ticagrelor has rapid onset as well as offset of action because of its reversible binding to P2Y12 receptor. It has potential to change the standard drug therapy of patient of ACS as shown in Platelet inhibition and patient outcomes (PLATO) trial, but long-term studies are required to further evaluate its efficacy and safety in these patients.

The influence of smoking status on the pharmacokinetics and pharmacodynamics of clopidogrel and prasugrel: the PARADOX study.

OBJECTIVES: The goal of this study was to evaluate the effect of smoking on the pharmacokinetics and pharmacodynamics (PD) of clopidogrel and prasugrel therapy. BACKGROUND: Major randomized trial data demonstrated that nonsmokers experience less or no benefit from clopidogrel treatment compared with smokers (i.e., the "smokers' paradox"). METHODS: PARADOX was a prospective, randomized, double-blind, double-dummy, placebo-controlled, crossover study of objectively assessed nonsmokers (n = 56) and smokers (n = 54) with stable coronary artery disease receiving aspirin therapy. Patients were randomized to receive clopidogrel (75 mg daily) or prasugrel (10 mg daily) for 10 days and crossed over after a 14-day washout. PD was assessed by using VerifyNow P2Y12 and vasodilator-stimulated phosphoprotein phosphorylation assays. Clopidogrel and prasugrel metabolite levels, cytochrome P450 1A2 activity, CYP2C19 genotype, and safety parameters were determined. RESULTS: During clopidogrel therapy, device-reported inhibition of platelet aggregation (IPA) trended lower in nonsmokers than smokers (least squares mean treatment difference ± SE: 7.7 ± 4.1%; p = 0.062). Device-reported IPA was significantly lower in clopidogrel-treated smokers than prasugrel-treated smokers (least squares mean treatment difference: 31.8 ± 3.4%; p < 0.0001). During clopidogrel therapy, calculated IPA was lower and P2Y12 reaction units and vasodilator-stimulated phosphoprotein phosphorylation and platelet reactivity index were higher in nonsmokers than in smokers (p = 0.043, p = 0.005, and p = 0.042, respectively). Greater antiplatelet effects were present after prasugrel treatment regardless of smoking status (p < 0.001 for all comparisons). CONCLUSIONS: PARADOX demonstrated lower clopidogrel active metabolite exposure and PD effects of clopidogrel in nonsmokers relative to smokers. Prasugrel was associated with greater active metabolite exposure and PD effects than clopidogrel regardless of smoking status. The poorer antiplatelet response in clopidogrel-treated nonsmokers may provide an explanation for the smokers' paradox. (The Influence of Smoking Status on Prasugrel and Clopidogrel Treated Subjects Taking Aspirin and Having Stable Coronary Artery Disease; NCT01260584).