P2Y12 Inhibition in Patients Requiring Oral Anticoagulation After Percutaneous Coronary Intervention: The SWAP-AC-2 Study.

BACKGROUND: Among patients treated with a novel oral anticoagulant (NOAC) undergoing percutaneous coronary intervention (PCI), combination therapy with clopidogrel (ie, known as dual antithrombotic therapy [DAT]) is the treatment of choice. However, there are concerns for individuals with impaired response to clopidogrel. OBJECTIVES: The authors sought to assess the pharmacodynamic (PD) effects of clopidogrel vs low-dose ticagrelor in patients with impaired clopidogrel response assessed by the ABCD-GENE score. METHODS: This was a prospective, randomized PD study of NOAC-treated patients undergoing PCI. Patients with an ABCD-GENE score ≥10 (n = 39), defined as having impaired clopidogrel response, were randomized to low-dose ticagrelor (n = 20; 60 mg twice a day) or clopidogrel (n = 19; 75 mg once a day). Patients with an ABCD-GENE score <10 (n = 42) were treated with clopidogrel (75 mg once a day; control cohort). PD assessments at baseline and 30 days post-randomization (trough and peak) were performed to assess P2Y12 signaling (VerifyNow P2Y12 reaction units [PRU], light transmittance aggregometry, and vasodilator-stimulated phosphoprotein); makers of thrombosis not specific to P2Y12 signaling were also assessed. The primary endpoint was PRU (trough levels) at 30 days. RESULTS: At 30 days, PRU levels were reduced with ticagrelor-based DAT compared with clopidogrel-based DAT at trough (23.0 [Q1-Q3: 3.0-46.0] vs 154.5 [Q1-Q3: 77.5-183.0]; P < 0.001) and peak (6.0 [Q1-Q3: 4.0-14.0] vs 129.0 [Q1-Q3: 66.0-171.0]; P < 0.001). Trough PRU levels in the control arm (104.0 [Q1-Q3: 35.0-167.0]) were higher than ticagrelor-based DAT (P = 0.005) and numerically lower than clopidogrel-based DAT (P = 0.234). Results were consistent by light transmittance aggregometry and vasodilator-stimulated phosphoprotein. Markers measuring other pathways leading to thrombus formation were largely unaffected. CONCLUSIONS: In NOAC-treated patients undergoing PCI with an ABCD-GENE score ≥10, ticagrelor-based DAT using a 60-mg, twice-a-day regimen reduced platelet P2Y12 reactivity compared with clopidogrel-based DAT. (Tailoring P2Y12 Inhibiting Therapy in Patients Requiring Oral Anticoagulation After PCI [SWAP-AC-2]; NCT04483583).

Drug-drug interactions between salvianolate injection and aspirin based on their metabolic enzymes.

BACKGROUND: It is unclear whether the combination of traditional Chinese medicine and Western medicine leads to interactions in pharmacokinetics (PKs) and pharmacodynamics (PDs). In this study, the influence of salvianolate and aspirin on metabolic enzymes, and the relationship between the blood concentration and pharmacodynamic indexes, were determined. METHOD: In this, randomized, parallel-grouped, single-center clinical trial, 18 patients with coronary heart disease were randomly allocated into three groups: aspirin (AP) group, salvianolate (SV) group, and combination (A + S) group. All treatment courses lasted for 10 days, and blood samples were acquired before and after administration at different timepoints. The expression of catechol-O-methyltransferase (COMT), CD62p, procaspase-activating compound 1 (PAC-1), P2Y12, phosphodiesterase, and mitogen-activated protein kinase 8 (MAPK8) were compared with variance analysis The blood concentrations were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry. RESULTS: Sixteen subjects completed the study. No significant difference in COMT was found among groups, although there was a decrease in the SV group. The PK results indicated that the absorption time of salicylic acid was shortened and the AUC0-∞ decreased and the elimination time of salvianolic acid B was prolonged and the AUC0-∞ decreased. The PD results declined after administration. A significant difference was found in MAPK8, CD62p, and P2Y12 expression. Compared with the SV group, a significant difference in P2Y12 in the A + S group was found. CONCLUSION: A pharmacokinetic drug-drug interaction was found in the aspirin and salvianolate combination. Pharmacodynamically, there was no difference between the A + S and AP groups. However, P2Y12 expression in the combination group was superior to that in the SV group. TRIAL REGISTRATION NUMBERS: The trial was registered on October 9, 2017, ClinicalTrials.gov, NCT03306550. https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S0007D8H&selectaction=Edit&uid=U0003QY8&ts=2&cx=oiuc9g.

Comparison of platelet reactivity between prasugrel and ticagrelor in patients with acute coronary syndrome: a meta-analysis.

BACKGROUND: This meta-analysis aimed to compare the effects of prasugrel and ticagrelor on high (HTPR) and low on-treatment platelet reactivity (LTPR) in patients with acute coronary syndrome (ACS). METHODS: Eligible studies were retrieved from PubMed, Embase, and the Cochrane Library. HTPR and LTPR were evaluated on the basis of the vasodilator-stimulated phosphoprotein platelet reactivity index (VASP-PRI) and P2Y12 reaction units (PRUs). HTPR and LTPR were analyzed using risk ratios (RRs) and their 95% confidence intervals (CIs). Weighted mean difference (WMD) and 95% CI were used to calculate the pooled effect size of platelet reactivity (PR). RESULTS: Fourteen eligible studies were obtained, which included 2629 patients treated with ticagrelor (n = 1340) and prasugrel (n = 1289). The pooled results showed that the prasugrel-treated patients had higher platelet reactivity than the ticagrelor-treated patients (PRU: WMD = - 32.26; 95% CI: - 56.48 to - 8.76; P < 0.01; VASP-PRI: WMD = - 9.61; 95% CI: - 14.63 to - 4.60; P = 0.002). No significant difference in HTPR based on PRU was identified between the ticagrelor and prasugrel groups (P = 0.71), whereas a lower HTPR based on VASP-PRI was found in the ticagrelor-treated patients than in the prasugrel-treated patients (RR = 0.30; 95% CI: 0.12-0.75; P = 0.010). In addition, the results showed a lower LTPR was observed in the prasugrel group than in the ticagrelor group (RR = 1.40; 95% CI: 1.08-1.81; P = 0.01). CONCLUSIONS: Prasugrel might enable higher platelet reactivity than ticagrelor. Ticagrelor could lead to a decrease in HTPR and increase in LTPR. However, this result was only obtained in pooled observational studies. Several uncertainties such as the nondeterminancy of the effectiveness of ticagrelor estimated using VASP-PRI or the definition of HTPR (a high or modifiable risk factor) might have affected our results.

Potential and Limitations of the New P2Y12 Inhibitor, Cangrelor, in Preventing Heparin-Induced Platelet Aggregation During Cardiac Surgery: An In Vitro Study.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) can put cardiac surgery patients at a high risk of lethal complications. If anti-PF4/heparin antibodies (anti-PF4/Hep Abs) are present, 2 strategies exist to prevent intraoperative aggregation during bypass surgery: first, using an alternative anticoagulant, and second, using heparin combined with an antiaggregant. The new P2Y12 inhibitor, cangrelor, could be an attractive candidate for the latter strategy; several authors have reported its successful use. The present in vitro study evaluated cangrelor's ability to inhibit heparin-induced platelet aggregation in the presence of anti-PF4/Hep Abs. METHODS: Platelet-poor plasma (PPP) from 30 patients with functional anti-PF4/Hep Abs was mixed with platelet-rich plasma (PRP) from 5 healthy donors.Light transmission aggregometry was used to measure platelet aggregation after adding 0.5 IU·mL of heparin (HIT) to the plasma, and this was compared with samples spiked with normal saline (control) and samples spiked with cangrelor 500 ng·mL and heparin 0.5 IU·mL (treatment). Friedman test with post hoc Dunn-Bonferroni test was used for between-group comparisons. RESULTS: Heparin 0.5 IU·mL triggered aggregation in 22 of 44 PPP-PRP mixtures, with a median aggregation of 86% (interquartile range [IQR], 69-91). The median aggregation of these 22 positive samples' respective control tests was 22% (IQR, 16-30) (P < .001). Median aggregation in the cangrelor-treated samples was 29% (IQR, 19-54) and significantly lower than the HIT samples (P < .001). Cangrelor inhibited heparin-induced aggregation by a median of 91% (IQR, 52-100). Cangrelor only reduced heparin-induced aggregation by >95% in 10 of the 22 positive samples (45%). Cangrelor inhibited heparin-induced aggregation by <50% in 5 of the 22 positive samples (22%) and by <10% in 3 samples (14%). CONCLUSIONS: This in vitro study found that cangrelor was an unreliable inhibitor of heparin-induced aggregation in the presence of anti-PF4/Hep Abs. We conclude that cangrelor should not be used as a standard antiaggregant for cardiac patients affected by HIT during surgery. Unless cangrelor's efficacy in a particular patient has been confirmed in a presurgery aggregation test, other strategies should be chosen.

A Pharmacodynamic Study of CN-218, a Novel Antiplatelet and Antithrombotic Agent Primarily Targeting the P2Y12 Receptor.

PURPOSE: Drugs inhibiting the platelet P2Y12 receptor, such as clopidogrel and prasugrel, are potent antithrombotic agents and are widely used in cardiovascular disease. However, the adverse effects of these drugs have limited their clinical use. For example, clopidogrel resistance occurs in approximately one third of patients, while prasugrel increases the risk of major bleeding. Therefore, new generations of such drugs are of clinical interest. METHODS: In this study, the pharmacodynamics of a new P2Y12 antagonist, CN-218, was compared with that of clopidogrel and prasugrel in rats and mice. The differences between CN-218 and clopidogrel include deuteration of the 7-position methyl carboxylate and the introduction of cinnamate in the 2-position of thiophene. RESULTS: CN-218 had an antiaggregatory efficacy that was at least five times more potent than that of clopidogrel but not as potent as that of prasugrel. It had a significant impact on activated partial thromboplastin time (APTT), whereby the APTT of CN-218-treated rats was approximately 9 s longer than that of the vehicle- or clopidogrel-treated group, while it had no impact on prothrombin time (PT) in rats. CN-218 had a similar potent antithrombotic effect to that of prasugrel and clopidogrel and also reduced the risk of bleeding compared to prasugrel. CONCLUSION: CN-218 may be a promising antithrombotic agent, with potent antiplatelet and significant anticoagulant activity, as well as a lower risk of bleeding compared to clopidogrel and prasugrel.

Impact of Continuous P2Y12 Inhibition Tailoring in Acute Coronary Syndrome and Genetically Impaired Clopidogrel Absorption.

Clopidogrel is still widely used in acute coronary syndrome despite the development of more potent P2Y12 inhibitors. Previously, we conducted a trial that evaluated serial clopidogrel dose adjustment based on platelet function testing in acute coronary syndrome patients with initial high on-treatment platelet reactivity (HTPR). In this substudy, we performed post hoc analysis of the effect of ABCB1 genetic variants C3435T and G2677T/A on platelet inhibition and outcomes. There were no differences in the proportion of HTPR patients among C3435T carriers and noncarriers in both interventional and control group. G2677T carriers expressed significantly higher proportion of HTPR pattern throughout 12-month follow-up in the control group with no difference in the interventional group. There was no difference in ischemic outcomes between C3435T and G2677T carriers and noncarriers in both groups of patients. The results indicate that ABCB1 genotyping is not useful to guide clopidogrel therapy tailoring to improve high-risk patient management.

The efficacy and safety of P2Y12 inhibitor monotherapy in patients after percutaneous coronary intervention.

The optimal antiplatelet therapy after percutaneous coronary intervention (PCI) remains to be elucidated. Monotherapy with a P2Y12 inhibitor may be inferior to dual antiplatelet therapy in patients after PCI. PubMed, EMBASE (by Ovidsp), Web of Science, and The Cochrane Library were searched from database inception to 2 October 2019. The composite of cardiovascular outcomes, all-cause mortality, myocardial infarction (MI), stroke, stent thrombosis, and major bleeding were evaluated. Pooled outcomes were presented as relative risk (RR) and 95% confidence intervals (CIs). A total of four trials randomizing 29 089 participants were included. Compared with the dual antiplatelet therapy group (n = 14 559), the P2Y12 inhibitor monotherapy group (n = 14 530) significantly decreased the incidence of bleeding events (2.0% vs 3.1%; RR: 0.60; 95% CI: 0.43-0.84; P = .005). There were no significant differences in all-cause mortality (1.3% vs 1.5%; RR: 0.87; 95% CI, 0.71-1.06; P = .16), myocardial infarction (2.1% vs 1.9%; RR, 1.06; 95% CI, 0.90-1.25; P = .46), stroke (0.6% vs 0.5%; RR, 1.18; 95% CI, 0.67-2.07; P = .57), or stent thrombosis (0.5% vs 0.4%; RR, 1.14; 95% CI, 0.81-1.61; P = .44) between the two groups. P2Y12 inhibitor monotherapy did not show any significant difference in the adverse cardiac and cerebrovascular events, but markedly decreased the risk of bleeding among patients after PCI vs dual antiplatelet therapy. However, it still needs to be further confirmed due to limited data.

What Are Optimal P2Y12 Inhibitor and Schedule of Administration in Patients With Acute Coronary Syndrome?

Guidelines recommend treatment with a P2Y12 platelet adenosine diphosphate receptor inhibitor in patients undergoing elective or urgent percutaneous coronary intervention (PCI), but the optimal agent or timing of administration is still not clearly specified. The P2Y12 inhibitor was initially used for its platelet anti-aggregatory action to block thrombosis of the recanalized coronary artery or deployed stent. It is now recognized that these agents also offer potent cardioprotection against a reperfusion injury that occurs in the first minutes of reperfusion if platelet aggregation is blocked at the time of reperfusion. But this is difficult to achieve with oral agents which are slowly absorbed and often require time-consuming metabolic activation. Patients with ST-segment elevation myocardial infarction who usually have a large mass of myocardium at risk of infarction seldom have sufficient time for upstream-administered oral agents to achieve a therapeutic P2Y12 level of inhibition by the time of balloon inflation. However, optimal treatment could be assured by initiating an IV cangrelor infusion shortly prior to stenting followed by subsequent post-PCI transition to an oral agent, that is, ticagrelor, once success of the recanalization and absence of need for surgical intervention are confirmed. Not only should this sequence provide optimal protection against infarction, it should also negate bleeding if coronary artery bypass grafting should be required since stopping the cangrelor infusion at any time will quickly restore platelet reactivity. It is anticipated that cangrelor-induced myocardial salvage will help preserve myocardial function and significantly diminish postinfarction heart failure.

Impact of Smoking on Platelet Reactivity and Clinical Outcomes After Percutaneous Coronary Intervention: Findings From the ADAPT-DES Study.

BACKGROUND: Smoking is a potent risk factor for coronary artery disease; however, prior studies describe increased platelet inhibition with clopidogrel among smokers, and some studies report improved outcomes among smokers, a finding described as the smoker's paradox. This study assessed the relationship between platelet reactivity and clinical outcomes after percutaneous coronary interventions among current smokers and nonsmokers. METHODS: ADAPT-DES (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents) was a prospective, multicenter registry of patients treated with coronary drug-eluting stents. Platelet reactivity was assessed by the VerifyNow point-of-care assay; high on-treatment platelet reactivity (HPR) was defined as P2Y12 reaction units >208. A propensity-adjusted multivariable analysis was performed to determine the relationship between current smoking, platelet reactivity, and subsequent adverse events. RESULTS: Among 8582 patients, 22.6% were active smokers at the time of their percutaneous coronary intervention procedure. Current smokers were younger and had fewer comorbidities compared with nonsmokers. Current smokers had lower mean P2Y12 reaction units and lower rates of HPR compared with nonsmokers. Current smokers had similar rates of adverse events compared with nonsmokers. HPR was associated with higher rates of adverse events for both smokers and nonsmokers; however, there was evidence of interaction between smoking status and the effect of HPR. Smokers with HPR had significantly higher rates of stent thrombosis. Adverse event rates were highest among current smokers with HPR. CONCLUSIONS: Current smoking was associated with lower P2Y12 reaction units and lower rates of HPR on average; however, the combination of current smoking and HPR was associated with high rates of stent thrombosis. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT00638794.

Incremental role of glycaemic variability over HbA1c in identifying type 2 diabetic patients with high platelet reactivity undergoing percutaneous coronary intervention.

BACKGROUND: Diabetic patients with on-treatment high platelet reactivity (HPR) show an increased risk of thrombotic events. Whether measuring glycated haemoglobin (HbA1c) levels and/or glycaemic variability (GV) may help identifying diabetic patients at higher risk deserving tailored antiplatelet and/or glucose lowering strategies is unknown. We aimed to investigate the relationship between GV, HbA1c levels and platelet reactivity in patients with type 2 diabetes mellitus (DM) undergoing percutaneous coronary intervention (PCI). METHODS: Platelet reactivity was measured in type 2 DM patients using VerifyNow P2Y12 assay. HPR was defined as P2Y12 Reaction Unit (PRU) > 240. GV was expressed through mean amplitude of glycaemic excursions (MAGE) and coefficient of variance (CV) by using the iPro™ continuous glucose recorder. RESULTS: Thirty-five patients (age 70 ± 9 years, 86% male, mean HbA1c 7.2 ± 1.0%) on clopidogrel therapy were enrolled. HbA1c was independently associated with HPR (OR 7.25, 95% CI 1.55-33.86, p = 0.012). Furthermore, when factored into the model, GV indexes provided independent (OR 1.094, 95% CI 1.007-1.188, p < 0.034) and additional (p < 0.001) diagnostic significance in identifying diabetic patients with HPR. CONCLUSIONS: Glyco-metabolic state significantly correlates with HPR in well-controlled type 2 DM patients on clopidogrel therapy. HbA1c identifies patients at higher thrombotic risk but the highest diagnostic accuracy is achieved by combining GV and HbA1c. Whether individualized antithrombotic and glucose-lowering therapies based on the assessment of these parameters may reduce the incidence of thrombotic events in patients undergoing PCI should be further investigated.

Reasons for the Failure of Platelet Function Testing to Adjust Antiplatelet Therapy: Pharmacodynamic Insights From the ARCTIC Study.

BACKGROUND: In the ARCTIC trial (Assessment by a Double Randomization of a Conventional Antiplatelet Strategy Versus a Monitoring-Guided Strategy for Drug-Eluting Stent Implantation and of Treatment Interruption Versus Continuation One Year After Stenting), treatment adjustment following platelet function testing failed to improve clinical outcomes. However, high-on-treatment platelet reactivity (HPR) is considered as a predictor of poor ischemic outcome. This prespecified substudy evaluated clinical outcomes according to the residual platelet reactivity status after antiplatelet therapy adjustment. METHODS: We analyzed the 1213 patients assigned to the monitoring arm of the ARCTIC trial in whom platelet reactivity was evaluated by the VerifyNow P2Y12 test before percutaneous coronary intervention and during the maintenance phase (at 14 days). HPR was defined as platelet reaction unit≥235U. The primary ischemic end point, a composite of death, myocardial infarction, stent thrombosis, stroke, or urgent revascularization and the safety end point of major bleeding were assessed according to the platelet reactivity status. RESULTS: Before percutaneous coronary intervention, 35.7% of patients displayed HPR (n=419). During the acute phase, between percutaneous coronary intervention and the 14-day platelet function testing, ischemic (adjusted hazard ratio, 0.94 [95% CI, 0.74-1.18]; P=0.58) and safety outcomes (hazard ratio, 1.28 [95% CI, 0.22-7.59]; P=0.78) were similar in HPR and non-HPR patients. During the maintenance phase, the proportion of HPR patients (n=186, 17.4%) decreased by 56%. At 1-year, there was no difference for the ischemic end point (5.9% versus 6.0%; adjusted hazard ratio, 0.79 [95% CI, 0.40-1.58]; P=0.51) and a nonsignificant higher rate of major bleedings (2.7% versus 1.0%, hazard ratio, 2.83 [95% CI, 0.96-8.41]; P=0.06) in HPR versus non-HPR patients. CONCLUSIONS: The proportion of HPR was halved after platelet function testing and treatment adjustment but without significant ischemic benefit at 1 year. HPR seems more as a modifiable risk marker than a risk factor of ischemic outcome. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT00827411.

Ticagrelor Does Not Improve Endothelial Dysfunction in Stable Survivors of Acute Coronary Syndrome.

BACKGROUND: Ticagrelor is an intriguing antiplatelet agent with a potentially beneficial impact on endothelial dysfunction and confers a mortality benefit beyond 1 month after acute coronary syndrome (ACS). However, little data exist on whether ticagrelor improves endothelial dysfunction in stable patients who survive the acute period and receive guideline-directed medical therapy. METHODS AND RESULTS: This study is a prospective, randomized, parallel, open-labeled study that enrolled 30-day survivors of non-ST-segment elevation ACS (NSTE-ACS). Forty patients with NSTE-ACS were randomly assigned to ticagrelor or clopidogrel groups. The primary end point was the change in the percentage brachial artery flow-mediated dilation (baFMD) from baseline. Baseline characteristics were not different between the 2 groups. The median time from the stent implantation to screening was 269 days. After 30 days of study medication administration, the change in the percentage baFMD value was similar between the ticagrelor and clopidogrel groups (-0.08 [1.42] vs 0.30 [1.69], P = .66). There was no difference in the change in high-sensitive C-reactive protein (-0.61 [1.48] vs -0.01 [0.57], P = .28); however, the change in platelet inhibition significantly differed (P2Y12 reaction units, -140.5 [49.5] vs -3.9 [51.4], P < .001). CONCLUSIONS: This dual time point baFMD study demonstrated that treatment with ticagrelor was not superior to clopidogrel for improving endothelial dysfunction in stabilized patients with NSTE-ACS.

Preprocedural P2Y12 inhibition and decrease in platelet count following transcatheter aortic valve replacement.

BACKGROUND: Thrombocytopenia after transcatheter aortic valve replacement (TAVR) is associated with adverse clinical outcomes. Whether preprocedural P2Y12 inhibition prevents postprocedural thrombocytopenia is uncertain. METHODS: This retrospective analysis identified consecutive patients (n = 266) undergoing TAVR between November 2016 and July 2017. Preprocedure clopidogrel load ≥300 mg or maintenance P2Y12 inhibitor therapy defined preprocedural P2Y12 inhibition. Patients who did not consent for the registry (n = 8), with baseline severe thrombocytopenia (<90 × 103 platelets/µL; n = 14), or without baseline platelet count (n = 4) were excluded. The primary outcome was proportion of patients who developed >20% decrease in platelet count from baseline to day 1 post-TAVR. RESULTS: Patients with (n = 134) versus without (n = 106) preprocedural P2Y12 inhibition had no differences in platelet count at baseline. Patients with preprocedural P2Y12 inhibition had a significantly lower proportion of the primary outcome (34.3% vs. 57.5%, p = .001) and a lower absolute decrease in platelet count (32.8 × 103 vs. 45.8 × 103 platelet/µL, p = .01). Of patients without baseline thrombocytopenia (n = 198), a numerically lower rate of patients with versus without preprocedural P2Y12 inhibition developed thrombocytopenia on day 1 post-TAVR (25.5% vs. 36.4%, p = .1). CONCLUSION: Patients who received preprocedural P2Y12 inhibition prior to TAVR were less likely to demonstrate a decrease in platelet count after TAVR. Prospective studies to further understand the clinical implication of these findings are warranted.

Switching between P2Y12 inhibitors: Rationale, methods, and expected consequences.

The pharmacological and clinical differences of the three recommended oral P2Y12 inhibitors (clopidogrel, prasugrel, ticagrelor) enable physicians to switch from one agent to another that it is considered more appropriate in the specific clinical setting. Moreover, the recent availability of cangrelor, the only intravenous P2Y12 inhibitor with a rapid onset and offset of its antiplatelet action, makes it necessary to switch from this agent to an oral P2Y12 inhibitor for a continued platelet inhibition after percutaneous coronary intervention. Several pharmacodynamic studies have provided information on how to change drug, in terms of timing and dosage, without running the risk of a temporary impairment of platelet inhibition. In addition, several studies have assessed the impact of the switching between P2Y12 inhibitors on clinical outcomes. Overall, these evidences have prompted the development of an extensive expert consensus document, have set the basis for recent practice guidelines recommendations, and have stimulated several systematic overviews. The present article provides a brief and schematic summary on the topic of switching between P2Y12 inhibitors, focusing on three main practical issues: why and how to switch therapies and what are the clinical consequences of such strategy.

Role of Platelet Size Revisited-Function and Protein Composition of Large and Small Platelets.

Epidemiological studies found an association between increased platelet size and the risk for thrombotic complications, but functional differences of large and small platelets remain poorly understood due to a lack of standardized protocols separating platelets with different size. We designed a protocol to separate large and small platelets from 15 mL whole blood. Separated large and small platelet fractions differed in mean platelet volume: 12.1 fl (10.3-13.8 fl) versus 7.7 fl (6.8-9.5 fl, p < 0.01), and forward scatter mean fluorescence intensity: 24.75 (19.9-30.9) versus 16.85 (11.3-20.6; p < 0.01). Similar fold differences were observed in cell diameter and plateletcrit. Large platelets express 30 to 50% more glycoprotein (GP) Ia, GPIb, GPIIIa, GPVI and P2Y12 on their membranes compared with small ones. Single large platelets covered a 50% larger area on a collagen surface. Adhesion to collagen was faster in large platelets compared with small ones indicating enhanced outside-in signal transduction in large platelets via collagen receptors. In contrast, integrin activation was more pronounced in small platelets after ADP stimulation. Proteome analysis revealed that 80 of the 894 proteins quantified differed in abundance: ADP-ribosylation factor 1/3, guanosine triphosphate-binding protein SAR1a, Voltage-dependent anion-selective channel protein 3 and guanylate cyclase soluble sub-unit α-3 were higher abundant in large, whereas immunoglobulins, haptoglobin, hemopexin, α-1-antitrypsin, serotransferrin and vitronectin were more abundant in small platelets. We conclude that some functions and the protein composition of large and small platelets differ, which cannot only be explained by the size difference. Our data suggest different functional roles of large and small platelets.

Platelet inhibition with standard vs. lower maintenance dose of ticagrelor early after myocardial infarction (ELECTRA): a randomized, open-label, active-controlled pharmacodynamic and pharmacokinetic study.

AIMS: Currently available data indicate that reduction of ticagrelor maintenance dose (MD) 1-3 years after acute myocardial infarction (AMI) not only provides sufficient platelet inhibition but also can improve ticagrelor's safety profile. The aim of this study was to compare the antiplatelet effect of reduced and standard ticagrelor MD in stable patients beginning 1 month after AMI. METHODS AND RESULTS: In a single-centre, randomized, open-label, active-controlled trial, on Day 30 following AMI, 52 patients (26 in each study arm) were assigned in a 1:1 ratio to receive either reduced (60 mg b.i.d) or standard (90 mg b.i.d) ticagrelor MD for the following 2 weeks. On Day 45 after AMI the antiplatelet effect of ticagrelor was evaluated with the VASP assay and Multiplate, and there were no significant differences in platelet inhibition between patients on reduced vs. standard MD [VASP: 10.4 (5.6-22.2) vs. 14.1 (9.4-22.1) platelet reactivity index; P = 0.30; Multiplate: 30.0 (24.0-39.0) vs. 26.5 (22.0-35.0) U; P = 0.26]. Likewise, no differences were found regarding the prevalence of on-ticagrelor high platelet reactivity between patients on ticagrelor 60 mg b.i.d vs. 90 mg b.i.d (VASP: 4% vs. 8%; P = 0.67; Multiplate: 15% vs. 8%; P = 0.54). Administration of reduced MD resulted in proportionally lower plasma concentrations of ticagrelor and its active metabolite on Day 45 after AMI. CONCLUSION: These results suggest that lowering ticagrelor MD 1 month after AMI confers an adequate antiplatelet effect that is comparable to the standard dose. The tested strategy warrants further research to assess its clinical efficacy and safety. CLINICALTRIALS.GOV IDENTIFIER: NCT03251859.

Evaluation of platelet activity by multiple electrode impedance aggregometry in acute coronary syndromes: pilot study in a Brazilian tertiary-care public hospital.

There is no definite recommendation for testing platelet aggregation (PA) in acute coronary syndromes (ACS) due to inconclusive evidence on the usefulness of platelet function tests to guide therapy and improve clinical outcomes. The evaluation of PA with multiple electrode impedance platelet aggregometry (MEA) may be useful to manage antiplatelet therapy and possibly influence patient outcome. The primary aim of this study was to measure PA with MEA in Brazilian patients with ACS and evaluate the association between PA and adverse clinical outcomes. Forty-seven consecutive patients admitted with ACS to a Brazilian tertiary-care public hospital were studied and PA was evaluated using MEA. Patients were followed for six months for the occurrence of all-cause death, acute myocardial infarction, or stroke. Suboptimal inhibition of PA was found in 7 patients (14.9%); 5 (10.6%) in response to ASA (acetylsalicylic acid), 2 (5.0%) to clopidogrel, and none to ticagrelor. Inadequate PA inhibition in response to ASA was significantly associated with the composite end point, but there was no significant association for insufficient PA inhibition in response to clopidogrel. This study suggested that the evaluation of PA in ACS using MEA may identify non-responders to ASA. Larger studies are necessary to define, in a public health scenario, the value of MEA in the management of ACS.

Platelet Inhibition With Cangrelor and Crushed Ticagrelor in Patients With ST-Segment-Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention.

BACKGROUND: The platelet inhibitory effects induced by oral P2Y12 receptor antagonists are delayed in patients with ST-segment-elevation myocardial infarction undergoing primary percutaneous coronary intervention (P-PCI). In turn, this leads to a gap in platelet inhibition, exposing patients to an increased risk of early thrombotic complications and underscoring the need to define strategies associated with more effective platelet inhibition in the peri-primary percutaneous coronary intervention period. Cangrelor is an intravenous P2Y12 inhibitor with prompt and potent antiplatelet effects. However, to date, there are limited data on the effects of cangrelor used in combination with ticagrelor in patients undergoing primary percutaneous coronary intervention. Moreover, questions have emerged on the potential for drug-drug interactions during the transition from cangrelor to oral P2Y12 inhibitors. METHODS: This was a prospective, randomized, double-blind, placebo-controlled pharmacodynamic study conducted in patients undergoing primary percutaneous coronary intervention (n=50) who were randomized to treatment with either cangrelor or matching placebo (bolus followed by 2-hour infusion). All patients received ticagrelor 180-mg loading dose administered as crushed tablets at the time of cangrelor/placebo bolus administration. Pharmacodynamic analyses were performed at 8 time points. Pharmacodynamic effects were measured as P2Y12 reaction units by VerifyNow and platelet reactivity index by vasodilator-stimulated phosphoprotein. RESULTS: Compared with placebo, cangrelor was associated with reduced P2Y12 reaction units as early as 5 minutes after bolus, which persisted during the entire duration of drug infusion, including at 30 minutes (63 [32-93] versus 214 [183-245]; mean difference, 152 [95% CI, 108-195]; P<0·001; primary end point). Parallel findings were shown with platelet reactivity index. Accordingly, high on-treatment platelet reactivity rates were reduced with cangrelor. After discontinuation of cangrelor/placebo infusion, there were no differences in levels of platelet reactivity between groups, ruling out a drug-drug interaction when cangrelor and ticagrelor are concomitantly administered. CONCLUSIONS: In patients undergoing primary percutaneous coronary intervention, cangrelor is an effective strategy to bridge the gap in platelet inhibition associated with the use of oral P2Y12 inhibition induced by ticagrelor. Ticagrelor can be administered as a crushed formulation concomitantly with cangrelor without any apparent drug-drug interaction. The clinical implications of these pharmacodynamic findings warrant investigation in an adequately powered clinical trial. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT03247738.

Efficacy of P2Y12 Receptor Blockers After Myocardial Infarction and Genetic Variability of their Metabolic Pathways.

BACKGROUND: Various antiplatelet drugs are used following Acute Coronary Syndromes (ACS). Of them, adenosine diphosphate receptor P2Y12 inhibitors clopidogrel, prasugrel and ticagrelor are currently used for post-ACS long-term treatment. Although they act on the same receptor, they differ in pharmacodynamics and pharmacokinetics. Several enzymes and transporters involved in the metabolism of P2Y12 inhibitors show genetic variability with functional impact. This includes Pglycoprotein, carboxylesterase 1 and, most notably, CYP2C19 that is important in clopidogrel activation. Common gain-of-function or loss-of-function alleles of CYP2C19 gene are associated with lower or higher platelet reactivity that may impact clinical outcomes of clopidogrel treatment. Prasugrel is considered to be less dependent on CYP2C19 variability as it is also metabolized by other CYP450 isoforms. Some studies, however, showed the relevance of CYP2C19 variants for platelet reactivity during prasugrel treatment as well. Ticagrelor is metabolized mainly by CYP3A4, which does not show functionally relevant genetic variability. Its concentrations may be modified by the variants of Pglycoprotein gene ABCB1. While no substantial difference between the clinical efficacy of prasugrel and ticagrelor has been documented, both of them have been shown to be superior to clopidogrel in post-ACS treatment. This can be partially explained by lower variability at each step of their metabolism. It is probable that factors influencing the pharmacokinetics of both drugs, including genetic factors, may predict the clinical efficacy of antiplatelet treatment in personalized medicine. CONCLUSION: We summarize the pharmacokinetics and pharmacogenetics of P2Y12 inhibitors with respect to their clinical effects in post-myocardial infarction treatment.

P2Y12 antagonist ticagrelor inhibits the release of procoagulant extracellular vesicles from activated platelets.

BACKGROUND: Activated platelets release platelet extracellular vesicles (PEVs). Adenosine diphosphate (ADP) receptors P2Y1 and P2Y12 both play a role in platelet activation, The present hypothesis herein is that the inhibition of these receptors may affect the release of PEVs. METHODS: Platelet-rich plasma from 10 healthy subjects was incubated with saline, P2Y1 antagonist MRS2179 (100 µM), P2Y12 antagonist ticagrelor (1 µM), and a combination of both antagonists. Platelets were activated by ADP (10 µM) under stirring conditions at 37°C. Platelet reactivity was assessed by impedance aggregometry. Concentrations of PEVs- (positive for CD61 but negative for P-selectin and phosphatidylserine) and PEVs+ (positive for all) were determined by a state-of-the-art flow cytometer. Procoagulant activity of PEVs was measured by a fibrin generation test. RESULTS: ADP-induced aggregation (57 ± 13 area under curve {AUC] units) was inhibited 73% by the P2Y1 antagonist, 86% by the P2Y12 antagonist, and 95% when combined (p < 0.001 for all). The release of PEVs- (2.9 E ± 0.8 × 108/mL) was inhibited 48% in the presence of both antagonists (p = 0.015), whereas antagonists alone were ineffective. The release of PEVs+ (2.4 ± 1.6 × 107/mL) was unaffected by the P2Y1 antagonist, but was 62% inhibited by the P2Y12 antagonist (p = 0.035), and 72% by both antagonists (p = 0.022). PEVs promoted coagulation in presence of tissue factor. CONCLUSIONS: Inhibition of P2Y1 and P2Y12 receptors reduces platelet aggregation and affects the release of distinct subpopulations of PEVs. Ticagrelor decreases the release of procoagulant PEVs from activated platelets, which may contribute to the observed clinical benefits in patients treated with ticagrelor.