Pharmacokinetics and pharmacodynamics of ticagrelor in patients with stable coronary artery disease: results from the ONSET-OFFSET and RESPOND studies

Evaluation of the effects and plasma concentration of the platelet inhibitor ticagrelor, after crushed and non-crushed intake, after cardiac arrest and after semi-urgent coronary artery bypass surgery

BACKGROUND

Ticagrelor, used in acute coronary syndrome (ACS), can be administered via nasogastric tube when oral intake is impossible. We investigated platelet inhibition and pharmacokinetics in resuscitated ACS patients and those undergoing semi-urgent coronary artery bypass graft (CABG) surgery. Our study aimed to assess platelet inhibition with use of the Platelet Function Analyser (PFA) and measured plasma concentrations of ticagrelor and its active metabolite in these ACS patients.

METHODS

We included resuscitated cardiac arrest patients (STEMI/NSTEMI) and semi-urgent CABG patients. Crushed ticagrelor tablets were administered using a nasogastric tube. PFA closure time (CT) was determined with CT longer than 113 s as reference range. Plasma concentrations of ticagrelor and its active metabolite were measured after protein precipitation, by using liquid chromatography with mass spectrometry detection.

RESULTS

In 20 resuscitated patients, 89% showed platelet inhibition at 24 h and 92% at day 4. For semi-urgent CABG patients, 85% exhibited platelet inhibition at 24 h and 84% at day 4. For ticagrelor in resuscitated patients, the median time to peak plasma concentration (Tmax) was 100 h [8; 100] for a median maximal concentration (Cmax) of 615.5 ng/mL [217.5; 1385.0]. For AR-C124910XX median Tmax was 100 h [8; 100] for a Cmax of 131.0 ng/mL [52.1; 177.7]. Among 20 patients undergoing semi-urgent CABG, Tmax for ticagrelor was 100 h [100; 100] for a median Cmax of 857.0 ng/ml [496.8; 1157.5]. For AR-C124910XX, median Tmax was 100 h [43; 100] for a Cmax of 251.0 ng/ml [173.0; 396.5].

CONCLUSION

Crushed ticagrelor via nasogastric tube achieved targeted platelet inhibition. Pharmacokinetics aligned with previous studies.EudraCT number: 2013-004191-35; Study protocol code: AGO/2013/011; EC/2014/1061; ClinicalTrial.gov identifier: NCT02341729.

Ticagrelor vs Clopidogrel in Clopidogrel-Naive Patients With Chronic Coronary Syndrome

BACKGROUND

Whether ticagrelor may reduce periprocedural myocardial necrosis after elective percutaneous coronary intervention (PCI) in patients with and without chronic clopidogrel therapy is unclear.

OBJECTIVES

This study sought to compare ticagrelor vs clopidogrel in patients with and without chronic clopidogrel therapy before undergoing elective PCI.

METHODS

In this prespecified analysis of the ALPHEUS (Assessment of Loading With the P2Y12 Inhibitor Ticagrelor or Clopidogrel to Halt Ischemic Events in Patients Undergoing Elective Coronary Stenting) trial, patients were defined as clopidogrel(+) and clopidogrel(-) according to the presence and absence of clopidogrel treatment for ≥7 days before PCI, respectively. The primary endpoint was the composite of PCI-related myocardial infarction and major injury as defined by the third and fourth universal definition 48 hours after PCI.

RESULTS

A total of 1,882 patients were included, 805 (42.7%) of whom were clopidogrel(+). These patients were older, had more comorbidities, and had more frequent features of complex PCI. The primary endpoint was less frequently present in clopidogrel(-) compared to clopidogrel(+) patients (32.8% vs 40.0%; OR: 0.73; 95% CI: 0.60-0.88), but no significant differences were reported for the risk of death, myocardial infarction, stroke, or transient ischemic attack at 48 hours or 30 days. Ticagrelor did not reduce periprocedural myocardial necrosis or the risk of adverse outcomes, and there was no significant interaction regarding the presence of chronic clopidogrel treatment.

CONCLUSIONS

Clopidogrel-naive patients presented less periprocedural complications compared to clopidogrel(+) patients, a difference related to a lower risk profile and less complex PCI. The absence of clopidogrel at baseline did not affect the absence of a difference between ticagrelor and clopidogrel in terms of PCI-related complications supporting the use of clopidogrel as the standard of care in elective PCI in patients with or without chronic clopidogrel treatment.

Ticagrelor Steady-State Trough Concentration in Chinese Patients Undergoing Percutaneous Coronary Intervention

BACKGROUND AND OBJECTIVE: Platelets play a pivotal role in thrombotic events associated with acute coronary syndrome (ACS), making oral antiplatelet therapy a cornerstone in antithrombotic strategies. The dosing regimen for the oral antiplatelet drug ticagrelor warrants evaluation to ensure its appropriateness in clinical practice. Therefore, this study aimed to investigate the real-world clinical application of ticagrelor by determining the optimal therapeutic concentration of ticagrelor in Chinese patients undergoing percutaneous coronary intervention (PCI).

METHODS

We enrolled a cohort of 912 patients who underwent PCI with drug-eluting stent implantation for the treatment of ACS. We measured steady-state plasma drug concentrations using high-performance liquid chromatography-tandem mass spectrometry. The therapeutic drug concentration range at steady state was established on the basis of clinical pharmacodynamic indices, with verification of reliability through concentration-effect analysis and receiver operating characteristic curve assessment.

RESULTS

Analysis of plasma samples from the 912 patients revealed significant variations in the steady-state trough concentration of ticagrelor associated with factors such as gender, age, hypertension, and hyperlipidemia. On the basis of this analysis, the optimal therapeutic range for steady-state trough concentration was determined to be 240.65-335.83 ng/mL. Furthermore, the upper limit values for steady-state concentration were established at 439.97 ng/mL for male patients and 347.06 ng/mL for female patients.

CONCLUSIONS

This study provides robust and reliable insights into the optimal therapeutic steady-state trough concentrations of ticagrelor in Chinese patients with post-percutaneous coronary intervention. These findings have significant implications for guiding the rational use of antiplatelet drugs and facilitating precise drug administration in Chinese patients undergoing percutaneous coronary intervention.

Intraoperative ticagrelor removal via hemoadsorption during on-pump coronary artery bypass grafting

Objectives

Patients on ticagrelor undergoing urgent cardiac surgery are at high risk for perioperative bleeding complications. We sought to determine whether intraoperative hemoadsorption could remove ticagrelor and lower circulating drug concentrations.

Methods

The hemoadsorption device was incorporated in the cardiopulmonary bypass (CPB) circuit and remained active for the duration of the pump run. Blood samples were collected before and after CPB. The main objective of the current analysis was to compare mean total plasma ticagrelor levels (ng/mL) at baseline with ticagrelor levels obtained at the end of CPB. Plasma ticagrelor levels were measured at a certified outside laboratory (LabConnect). Data are presented as mean ± standard deviation.

Results

A total of 11 patients undergoing urgent coronary artery bypass grafting at 3 institutions were included (mean age, 67.9 ± 9.9 years; 91% male; mean European System for Cardiac Operative Risk Evaluation II of 3.0 ± 3.3%; range, 0.7%-12.4%). Mean intraoperative hemoadsorption duration was 97.1 ± 43.4 minutes with a mean flow rate through the device of 422.9 ± 40.3 mL/min. Mean ticagrelor levels pre-CPB were 103.5 ± 63.8 ng/mL compared with mean post-CPB levels of 34.0 ± 17.5 ng/mL, representing a significant 67.1% reduction (P < .001). Intraoperative integration of the device was simple and safe without any device-related adverse events reported.

Conclusions

This is the first in vivo report demonstrating that intraoperative hemoadsorption can efficiently remove ticagrelor and significantly reduce circulating drug levels. Whether active ticagrelor removal can reduce serious perioperative bleeding in patients undergoing urgent cardiac surgery is currently being evaluated in the double-blinded, randomized Safe and Timely Antithrombotic Removal-Ticagrelor (STAR-T) trial.

The effects of P2Y12 adenosine receptors' inhibitors on central and peripheral chemoreflexes

Introduction: The most common side effect of ticagrelor is dyspnea, which leads to premature withdrawal of this life-saving medication in 6.5% of patients. Increased chemoreceptors' sensitivity was suggested as a possible pathophysiological explanation of this phenomenon; however, the link between oversensitization of peripheral and/or central chemosensory areas and ticagrelor intake has not been conclusively proved. Methods: We measured peripheral chemoreceptors' sensitivity using hypoxic ventilatory response (HVR), central chemoreceptors' sensitivity using hypercapnic hyperoxic ventilatory response (HCVR), and dyspnea severity before and 4 ± 1 weeks following ticagrelor initiation in 11 subjects with chronic coronary syndrome undergoing percutaneous coronary intervention (PCI). The same tests were performed in 11 age-, sex-, and BMI-matched patients treated with clopidogrel. The study is registered at ClinicalTrials.com at NCT05080478. Results: Ticagrelor significantly increased both HVR (0.52 ± 0.46 vs. 0.84 ± 0.69 L min-1 %-1; p < 0.01) and HCVR (1.05 ± 0.64 vs. 1.75 ± 1.04 L min-1 mmHg-1; p < 0.01). The absolute change in HVR correlated with the change in HCVR. Clopidogrel administration did not significantly influence HVR (0.63 ± 0.32 vs. 0.58 ± 0.33 L min-1%-1; p = 0.53) and HCVR (1.22 ± 0.67 vs. 1.2 ± 0.64 L min-1 mmHg-1; p = 0.79). Drug-related dyspnea was reported by three subjects in the ticagrelor group and by none in the clopidogrel group. These patients were characterized by either high baseline HVR and HCVR or excessive increase in HVR following ticagrelor initiation. Discussion: Ticagrelor, contrary to clopidogrel, sensitizes both peripheral and central facets of chemodetection. Two potential mechanisms of ticagrelor-induced dyspnea have been identified: 1) high baseline HVR and HCVR or 2) excessive increase in HVR or HVR and HCVR. Whether other patterns of changes in chemosensitivities play a role in the pathogenesis of this phenomenon needs to be further investigated.

Pharmacogenetics of P2Y12 receptor inhibitors

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

Antithrombotic drug removal from whole blood using Haemoadsorption with a porous polymer bead sorbent

AIM

To evaluate the ability of the DrugSorb™-AntiThrombotic Removal (ATR) haemoadsorption device utilizing porous polymer bead sorbent technology to remove three commonly used antithrombotic drugs from whole blood.

METHODS AND RESULTS

We evaluated the removal of apixaban, rivaroxaban, and ticagrelor by the DrugSorb-ATR haemoadsorption device in a benchtop clinical scale model using bovine whole blood. Blood spiked at clinically relevant concentrations of an antithrombotic agent was continuously circulated through a 300-mL DrugSorb-ATR haemoadsorption device at a flow rate of 300 mL/min. Drug concentration was monitored over 6 h to evaluate drug removal. Results were compared with a control circuit without the haemoadsorption device. Removal rates at 30, 60, 120, and 360 minutes were: apixaban: 81.5%, 96.3%, 99.3% >99.8%; rivaroxaban: 80.7%, 95.1%, 98.9%, >99.5%; ticagrelor: 62.5%; 75%, 86.6%, >95% (all P <0.0001 vs. control). Blood pH and haematological parameters were not significantly affected by the DrugSorb-ATR haemoadsorption device when compared with the control circuit.

CONCLUSION

DrugSorb-ATR efficiently removes apixaban, rivaroxaban, and ticagrelor in a clinical-scale benchtop recirculation circuit with the bulk of removal occurring in the first 60 minutes. The clinical implications of these findings are currently investigated in patients undergoing on-pump cardiothoracic surgery in two US pivotal trials (ClinicalTrials.gov Identifiers: NCT04976530 and NCT05093504).

Efficacy and Safety of Ticagrelor and Clopidogrel in Patients with Stable Coronary Artery Disease Undergoing Percutaneous Coronary Intervention

AIM

The efficacy and safety of ticagrelor and clopidogrel in patients with stable coronary artery disease (SCAD) undergoing percutaneous coronary intervention (PCI) remain uncertain. Thus, this study aimed to compare the efficacy and safety of ticagrelor and clopidogrel in patients with SCAD treated with PCI.

METHODS

A total of 9,379 patients with SCAD undergoing PCI who received dual antiplatelet therapy (DAPT) were consecutively enrolled in two groups, namely, ticagrelor (n=1,081) and clopidogrel (n=8,298) groups. Major adverse cardiovascular and cerebrovascular events (MACCEs) and bleeding events according to ticagrelor or clopidogrel use were compared.

RESULTS

After propensity matching (n=1,081 in each group), ticagrelor was associated with fewer MACCEs compared with clopidogrel (3.6% vs. 5.7%, hazard ratio [HR]=0.62, 95% confidence interval [CI] 0.41-0.93, p=0.019), and the difference between ticagrelor and clopidogrel for bleeding events was nonsignificant (4.0% vs. 3.2%, HR=1.24, 95% CI 0.79-1.93, p=0.356). On the other hand, the difference between ticagrelor and clopidogrel for net adverse clinical events was significant (4.1% vs. 6.0%, HR=0.67, 95% CI 0.46-0.98, p=0.039). In a multivariate analysis, the use of ticagrelor, number of stents, previous history of diabetes, previous history of smoking, and ACC/AHA type B2 or C lesions were considered independent predictors of MACCEs, while radial artery access, previous history of stroke, and weight ＜60kg were independent predictors of bleeding events. Conclusions Ticagrelor was associated with a lower incidence of MACCEs without an increased risk of bleeding events in patients with SCAD receiving PCI.

Pharmacokinetic Modeling of Morphine's Effect on Plasma Concentrations of Ticagrelor and Its Metabolite in Healthy Volunteers

This study aimed to build a mathematical model describing the pharmacokinetics of ticagrelor and its active metabolite (AR-C124910XX) in a stable setting with concomitant administration of morphine. The model consists of a set of four differential equations prepared upon the available knowledge regarding the biological processes in the pharmacokinetics of ticagrelor. The set of equations was solved numerically using the Runge–Kutta method. The data were obtained in a double-blind, randomized, placebo-controlled, crossover trial. Twenty-four healthy volunteers received a 180-mg ticagrelor loading dose together with either 5-mg morphine or placebo. Blood samples were analyzed with liquid chromatography–tandem mass spectrometry to assess plasma concentrations of ticagrelor and AR-C124910XX before ticagrelor loading dose and after that 1, 2, 3, 4, and 6 h. The model allowed us to reproduce the experimental results accurately and led us to conclusions consistent with clinical observations that morphine delays the time of maximum drug concentration and that the morphine effect occurs due to decreased gastrointestinal motility. Based on the model, we were able to predict the effect of drug dose on receptor blocking efficacy.

Tackling the gap in platelet inhibition with oral antiplatelet agents in high-risk patients undergoing percutaneous coronary intervention

Introduction: Oral P2Y₁₂ inhibitors represent the mainstay therapy for the prevention of thrombotic complications in patients presenting with an acute coronary syndrome and/or undergoing percutaneous coronary intervention (PCI). However, the onset of antiplatelet action of the oral P2Y₁₂ inhibitors is affected by their need to be absorbed in the gastrointestinal (GI) tract before becoming systemically available.Areas covered: Following oral intake of P2Y₁₂ inhibitors, the timeframe required for GI absorption leads to a window of inadequate antiplatelet protection during which patients are at increased thrombotic risk. The onset of action of the oral P2Y₁₂ inhibitors is even further delayed in high-risk patients, underscoring the need to define strategies to bridge the gap in platelet inhibitory effects following their intake.Expert opinion: Multiple mechanisms may impair GI absorption leading to a delay in the onset of action of oral P2Y₁₂ inhibitors. Several strategies have been tested to overcome the gap in platelet inhibition in high-risk patients undergoing PCI. These include administration of crushed or chewed tablets to improve the dissolution rate and use of opioid receptor antagonists or metoclopramide to counteract impairment of gastric motility induced by opioids. However, intravenous antiplatelet therapies represent the most effective strategy to bridge such gap in platelet inhibition.

TicagRelor Or Clopidogrel in severe or terminal chronic kidney patients Undergoing PERcutaneous coronary intervention for acute coronary syndrome: The TROUPER trial

Chronic kidney disease (CKD) is associated with an increased risk of acute coronary syndrome (ACS) and cardiovascular death. CKD patients suffering from ACS are exposed to an increased risk of thrombotic recurrences and a higher bleeding rate than patients with normal renal function. However, CKD patients are excluded or underrepresented in clinical trials. Therefore, determining the optimal antiplatelet strategy in this population is of utmost importance. We designed the TicagRelor Or Clopidogrel in severe or terminal chronic kidney patients Undergoing PERcutaneous coronary intervention for acute coronary syndrome (TROUPER) trial: a prospective, controlled, multicenter, randomized trial to investigate the optimal P2Y12 antagonist in CKD patients with ACS. Patients with stage ≥3b CKD are eligible if the diagnosis of ACS is made and invasive strategy scheduled. Patients are randomized 1:1 between a control group with a 600-mg loading dose of clopidogrel followed by a 75-mg/d maintenance dose for 1 year and an experimental group with a 180-mg loading dose of ticagrelor followed by a 90-mg twice daily maintenance dose for the same duration. The primary end point is defined by the rate of major adverse cardiovascular events, including death, myocardial infarction, urgent revascularization, and stroke at 1 year. Safety will be evaluated by the bleeding rate (Bleeding Academic Research Consortium). To demonstrate the superiority of ticagrelor on major adverse cardiovascular events, we calculated that 508 patients are required. The aim of the TROUPER trial is to compare the efficacy of ticagrelor and clopidogrel in stage >3b CKD patients presenting with ACS and scheduled for an invasive strategy. RCT# NCT03357874.

Carotid Stent Restenosis and Thrombosis in Rabbits: The Effect of Antiplatelet Agents

BACKGROUND

The purpose of the study was the comparative assessment of ticagrelor and clopidogrel effects on carotid post-balloon injury (PBI) and on post carotid artery stenting (CAS) rate of in-stent restenosis (ISR) and in-stent thrombosis in atherosclerotic rabbits.

METHODS

Forty-eight New Zealand white rabbits on high-fat diet were randomized into 4 groups: A1: PBI and clopidogrel (30 mg/kg/d), A2: PBI and ticagrelor (21 mg/kg twice daily), B1: PBI, CAS, and clopidogrel (30 mg/kg/d), B2: PBI, CAS, and ticagrelor (21 mg/kg twice daily). All rabbits received orally aspirin (10 mg/kg/d) and interventions were performed in their right carotid arteries (RCAs). Optical coherence tomography (OCT) and carotid angiography were performed at end point, while platelet aggregation and lipid profile were measured. After euthanasia both carotids were obtained for histological examination.

RESULTS

In B1 group, 3 rabbits presented thrombotic total occlusion of the stents, while none such episode was observed in B2 group. The neointimal areas in RCAs, calculated by OCT, did not differ between A1 and A2 groups, and between B1 and B2 groups (P > .05). From the histological findings, the intima/(media + intima) percentage (%) in RCAs of balloon-injured rabbits did not present any difference between groups (P = .812). Similarly, the immunohistochemically determined accumulation of endothelial cells and macrophages on vascular walls was equivalent between groups (P > .05).

CONCLUSION

Following carotid balloon injury and stenting, clopidogrel and ticagrelor did not show any differential effects on the extent of neointimal formation and ISR in atherosclerotic rabbits receiving aspirin. Three thrombotic stent occlusions were noted in the clopidogrel treatment group, but this finding was not statistically significant.

P2Y12 Inhibition beyond Thrombosis: Effects on Inflammation

The P2Y₁₂ receptor is a key player in platelet activation and a major target for antithrombotic drugs. The beneficial effects of P2Y₁₂ receptor antagonists might, however, not be restricted to the primary and secondary prevention of arterial thrombosis. Indeed, it has been established that platelet activation also has an essential role in inflammation. Additionally, nonplatelet P2Y₁₂ receptors present in immune cells and vascular smooth muscle cells might be effective players in the inflammatory response. This review will investigate the biological and clinical impact of P2Y₁₂ receptor inhibition beyond its platelet-driven antithrombotic effects, focusing on its anti-inflammatory role. We will discuss the potential molecular and cellular mechanisms of P2Y₁₂-mediated inflammation, including cytokine release, platelet–leukocyte interactions and neutrophil extracellular trap formation. Then we will summarize the current evidence on the beneficial effects of P2Y₁₂ antagonists during various clinical inflammatory diseases, especially during sepsis, acute lung injury, asthma, atherosclerosis, and cancer.

Effects of Methylnaltrexone on Ticagrelor-Induced Antiplatelet Effects in Coronary Artery Disease Patients Treated With Morphine

OBJECTIVES

The aim of this study was to assess if intravenous methylnaltrexone can counteract the effects of morphine on the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of ticagrelor.

BACKGROUND

Morphine delays the onset of action of oral P2Y₁₂ receptor inhibitors, including ticagrelor, by inhibiting gastric emptying and leading to delayed drug absorption. Methylnaltrexone is a peripheral opioid receptor antagonist that has the potential to prevent opioid-induced peripherally mediated side effects (e.g., gastric emptying inhibition) without affecting analgesia.

METHODS

In this prospective, randomized, double-blind, placebo-controlled, crossover study, aspirin-treated patients with stable coronary artery disease (n = 30) were randomized to receive methylnaltrexone (0.3 mg/kg intravenous) or matching placebo. After methylnaltrexone or placebo administration, all patients received morphine (5 mg intravenous). This was followed 15 min later by a 180-mg loading dose of ticagrelor. Patients crossed over to the alternative study treatment after 7 ± 2 days of washout. PK and PD assessments were performed at 12 time points (6 pre- and 6 post-crossover). PK analysis included measurement of plasma levels of ticagrelor and its major active metabolite (AR-C124910XX). PD assessments included VerifyNow P2Y₁₂, light transmittance aggregometry, and vasodilator-stimulated phosphoprotein.

RESULTS

Only marginal changes in plasma levels of ticagrelor (and its major active metabolite) were observed with ticagrelor: maximum plasma concentration and area under the plasma concentration versus time curve from time 0 to the last measurable concentration were 38% and 30% higher, respectively, in patients receiving methylnaltrexone compared with those receiving placebo, but no differences in time to maximum plasma concentration were observed. There were no differences in P2Y₁₂ reaction units by VerifyNow P2Y₁₂ between groups at each time point, including 2 h (the primary endpoint; p = 0.261). Similarly, there were no differences in PD markers assessed by light transmittance aggregometry and vasodilator-stimulated phosphoprotein.

CONCLUSIONS

In patients with coronary artery disease receiving morphine, intravenous administration of the peripheral opioid receptor antagonist methylnaltrexone leads to only marginal changes in plasma levels of ticagrelor and its major metabolite, without affecting levels of platelet reactivity. (Effect of Methylnaltrexone on the PK/PD Profiles of Ticagrelor in Patients Treated With Morphine; NCT02403830).

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 E_max 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.

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 E_max 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.

Late stent thrombosis in a patient with CYP2C19*3/*17 genotype and clopidogrel high on-treatment platelet reactivity

AIM

Recurrent thrombotic events still occur despite dual antiplatelet therapy in patient's post percutaneous coronary intervention (PCI) could be attributed to high on-treatment platelet reactivity.

METHODS

A 44-year-old male, who had staged PCI to left anterior descending (LAD) 2 weeks after an anterior MI, with a drug-coated stent was readmitted with new anterior STEMI 35 days later. Coronary angiogram revealed mid-stent thrombus in situ. He had further uncomplicated PCI. Platelet function testing and genotyping showed clopidogrel high on-treatment platelet reactivity and CYP2C19*3/*17 genotype. Ticagrelor was commenced.

RESULTS & CONCLUSION

This case study is the first reported in Malaysia to document a patient with a CYP2C19*3/*17 genotype presenting with a stent thrombosis after an uncomplicated index PCI procedure.

Metabolism of ticagrelor in patients with acute coronary syndromes

Ticagrelor is a state-of-the-art antiplatelet agent used for the treatment of patients with acute coronary syndromes (ACS). Unlike remaining oral P2Y12 receptor inhibitors ticagrelor does not require metabolic activation to exert its antiplatelet action. Still, ticagrelor is extensively metabolized by hepatic CYP3A enzymes, and AR-C124910XX is its only active metabolite. A post hoc analysis of patient-level (n = 117) pharmacokinetic data pooled from two prospective studies was performed to identify clinical characteristics affecting the degree of AR-C124910XX formation during the first six hours after 180 mg ticagrelor loading dose in the setting of ACS. Both linear and multiple regression analyses indicated that ACS patients presenting with ST-elevation myocardial infarction or suffering from diabetes mellitus are more likely to have decreased rate of ticagrelor metabolism during the acute phase of ACS. Administration of morphine during ACS was found to negatively influence transformation of ticagrelor into AR-C124910XX when assessed with linear regression analysis, but not with multiple regression analysis. On the other hand, smoking appears to increase the degree of ticagrelor transformation in ACS patients. Mechanisms underlying our findings and their clinical significance warrant further research.

Why does ticagrelor induce dyspnea?

In studies that compared the reversible P2Y12 inhibitor ticagrelor with the irreversible inhibitor clopidogrel, dyspnea was observed more frequently among ticagrelor-treated patients than among clopidogreltreated patients. Because dyspnea was not associated with acidosis, pulmonary or cardiac dysfunction, alterations in the mechanisms and pathways of the sensation of dyspnea may be involved in its pathogenesis. It has been hypothesised that the sensation of dyspnea in ticagrelor-treated patients is triggered by adenosine, because ticagrelor inhibits its clearance, thereby increasing its concentration in the circulation. However, dipyridamole, a much stronger inhibitor of adenosine clearance than ticagrelor, usually does not cause dyspnea. We hypothesise that inhibition of P2Y12 on sensory neurons increases the sensation of dyspnea, particularly when reversible inhibitors are used. We base our hypothesis on the following considerations: 1) cangrelor and elinogrel, which, like ticagrelor, are reversible P2Y12 inhibitors, also increase the incidence of dyspnea;2) it is biologically plausible that inhibition of P2Y12 on sensory neurons increases the sensation of dyspnea;3) inhibition of P2Y12 on platelets (which do not have a nucleus) by clopidogrel is permanent, despite the once daily administration and the short plasma half-life of the inhibitor;4) in contrast, inhibition of P2Y12 on neurons by clopidogrel may be temporary and transient, because neurons have a nucleus and can therefore rapidly replace the inhibited receptors with newly synthetised ones;5) inhibition of P2Y12 on neurons by reversible inhibitors is permanent, because the plasma drug concentration is maintained high by repeated dosing, in order to ensure permanent inhibition of platelet P2Y12.

Chewing versus Swallowing Ticagrelor to Accelerate Platelet Inhibition in Acute Coronary Syndrome - the CHEERS study

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.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Comparison of Ticagrelor Pharmacokinetics and Pharmacodynamics in STEMI and NSTEMI Patients (PINPOINT): protocol for a prospective, observational, single-centre study

INTRODUCTION

The most common classification of acute myocardial infarction (AMI) is based on electrocardiographic findings and distinguishes ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI). Both types of AMI differ concerning their epidemiology, clinical approach and early outcomes. Ticagrelor is a P2Y12 receptor inhibitor, constituting the first-line treatment for STEMI and NSTEMI. According to available data, STEMI may be associated with lower plasma concentration of ticagrelor in the first hours of AMI, but currently there are no studies directly comparing ticagrelor pharmacokinetics or antiplatelet effect in patients with STEMI versus NSTEMI.

METHODS AND ANALYSIS

The PINPOINT study is a phase IV, single-centre, investigator-initiated, prospective, observational study designed to compare the pharmacokinetics and pharmacodynamics of ticagrelor in patients with STEMI and NSTEMI assigned to the invasive strategy of treatment. Based on an internal pilot study, the trial is expected to include at least 23 patients with each AMI type. All subjects will receive a 180 mg loading dose of ticagrelor. The primary end point of the study is the area under the plasma concentration-time curve (AUC_(0-6)) for ticagrelor during the first 6 hours after the loading dose. Secondary end points include various pharmacokinetic features of ticagrelor and its active metabolite (AR-C124910XX), and evaluation of platelet reactivity by the vasodilator-stimulated phosphoprotein assay and multiple electrode aggregometry. Blood samples for the pharmacokinetic and pharmacodynamic assessment will be obtained at pretreatment, 30 min, 1, 2, 3, 4, 6 and 12 hours post-ticagrelor loading dose.

ETHICS AND DISSEMINATION

The study received approval from the Local Ethics Committee (Komisja Bioetyczna Uniwersytetu Mikołaja Kopernika w Toruniu przy Collegium Medicum im. Ludwika Rydygiera w Bydgoszczy; approval reference number KB 617/2015). The study results will be disseminated through conference presentations and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02602444; Pre-results.

Crushed Versus Integral Tablets of Ticagrelor in ST-Segment Elevation Myocardial Infarction Patients: A Randomized Pharmacokinetic/Pharmacodynamic Study

OBJECTIVE

The objective of this study was to assess the pharmacokinetic and pharmacodynamic behavior of ticagrelor administered either as crushed (in the semi-upright sitting position) or as integral (in the supine position) tablets in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI).

METHODS

We randomized 20 patients to ticagrelor 180 mg either as 2 integral tablets administered in the supine position (standard administration) or as 2 tablets crushed and dispersed, administered in the semi-upright sitting position. Blood samples were drawn for pharmacokinetic and pharmacodynamic assessment at randomization (0 h) and at 0.5, 1, 2, and 4 h.

RESULTS

At 1 h, ticagrelor plasma exposure and area under the plasma concentration-time curve from time zero to 1 h (AUC1) (co-primary endpoints) were higher in the crushed versus integral tablets group (median 586 vs. 70.1 ng/mL and 234 vs. 24.4 ng·h/mL, respectively), with a ratio of adjusted geometric means (95% confidence interval [CI]) of 12.67 (2.34-68.51) [p = 0.005] and 19.28 (3.51-106.06) [p = 0.002], respectively. Time to maximum plasma concentration was shorter in the crushed versus integral tablets group (median 2 vs. 4 h), with a ratio of adjusted geometric means (95% CI) of 0.69 (0.49-0.97) [p = 0.035]. Parallel findings were observed with AR-C124910XX (active metabolite). Platelet reactivity (VerifyNow(®)) at 1 h was lower with crushed versus standard administration with least squares estimates mean difference (95% CI) of 92 (-158.4 to 26.6) P2Y12 reaction units (p = 0.009).

CONCLUSIONS

In patients with STEMI undergoing primary PCI, ticagrelor crushed tablets administered in the semi-upright sitting position seems to lead to a faster-compared with standard administration-absorption, with stronger antiplatelet activity within the first hour.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02046486.

Impact of Escalating Loading Dose Regimens of Ticagrelor in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention: Results of a Prospective Randomized Pharmacokinetic and Pharmacodynamic Investigation

OBJECTIVES

The goal of this study was to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of escalating ticagrelor loading dose (LD) regimens in primary percutaneous coronary intervention (PPCI).

BACKGROUND

Patients with ST-segment elevation myocardial infarction undergoing PPCI frequently have suboptimal platelet inhibition in the early hours after ticagrelor LD. The use of high ticagrelor LD regimens has been hypothesized to optimize platelet inhibition in PPCI.

METHODS

This was a prospective, randomized study of escalating ticagrelor LD regimens (180 mg, 270 mg, or 360 mg) in PPCI (N = 52). PK/PD analyses were performed before and 30 min, 1, 2, 4, 8, and 24 h post-LD. PK assessments included exposure to ticagrelor and its metabolite (AR-C124910XX). PD assessments included P2Y12 reaction units (PRU) measured by VerifyNow P2Y12 and platelet reactivity index (PRI) measured by vasodilator-stimulated phosphoprotein (VASP).

RESULTS

Platelet reactivity was elevated during the first 2 h post-LD. There were no differences in PRU between groups during the study time course (p = 0.179). There were no significant differences in PRU levels across groups at all time points, except at 1 h (p = 0.017) where platelet reactivity was lowest with a 270-mg LD. No differences were found between the 180-mg and 360-mg groups (primary endpoint; p > 0.999). High on-treatment platelet reactivity rates were not different across groups, except at 1 hour (p = 0.038). Parallel PD findings were observed with VASP-PRI. PK analysis showed a delay in ticagrelor absorption and generation of AR-C124910XX, irrespective of dose. Although morphine was associated with a delay in ticagrelor PK/PD, it was not an independent predictor of high on-treatment platelet reactivity.

CONCLUSIONS

ST-segment elevation myocardial infarction patients undergoing PPCI frequently exhibit impaired response to ticagrelor in the early hours after drug administration, which cannot be overcome by increasing LD regimens. These PD findings are largely attributed to an impaired PK profile, indicating a delay in drug absorption compared with that reported in stable clinical settings. (High Ticagrelor Loading Dose in STEMI; NCT01898442).

Effects of P2Y12 receptor antagonists beyond platelet inhibition--comparison of ticagrelor with thienopyridines

The effect and clinical benefit of P2Y12 receptor antagonists may not be limited to platelet inhibition and the prevention of arterial thrombus formation. Potential additional effects include reduction of the pro-inflammatory role of activated platelets and effects related to P2Y12 receptor inhibition on other cells apart from platelets. P2Y12 receptor antagonists, thienopyridines and ticagrelor, differ in their mode of action being prodrugs instead of direct acting and irreversibly instead of reversibly binding to P2Y12 . These key differences may provide different potential when it comes to additional effects. In addition to P2Y12 receptor blockade, ticagrelor is unique in having the only well-documented additional target of inhibition, the equilibrative nucleoside transporter 1. The current review will address the effects of P2Y12 receptor antagonists beyond platelets and the protection against arterial thrombosis. The discussion will include the potential for thienopyridines and ticagrelor to mediate anti-inflammatory effects, to conserve vascular function, to affect atherosclerosis, to provide cardioprotection and to induce dyspnea.

Comparison of Ticagrelor Versus Thienopyridine Loading Effect on Fractional Flow Reserve in Patients With Coronary Artery Disease

Ticagrelor loading dose (LD) increases adenosine plasma levels, which might interfere with fractional flow reserve (FFR) assessment because the latter is based on adenosine-induced hyperemia. In a prospective study, consecutive patients who underwent coronary angiography with at least 1 de novo stenosis >50% and <90% in severity amenable to intervention underwent FFR assessment using intravenous adenosine 140 μg/kg/min for 3 minutes. Patients were subsequently randomized to either ticagrelor 180 mg (n = 38) or control thienopyridine (n = 38) (prasugrel 60 mg [n = 28] or clopidogrel 600 mg [n = 10]), followed by a second FFR assessment of the target lesion 2 hours after drug. Pre-drug, steady hyperemia FFR (sFFR, median, first to third quartiles) was 0.82 (0.75 to 0.88) and 0.81 (0.75 to 0.88), p = 0.9, whereas post-drug, 0.82 (0.72 to 0.87) and 0.79 (0.73 to 0.86), p = 0.5, in thienopyridine and ticagrelor-treated patients, respectively. The primary end point of percent relative change in sFFR between pre- and post-drug periods was greater in ticagrelor- than thienopyridine-treated patients, -1.24 (-5.54 to 0.0) versus -0.51 (-3.68 to 3.21), p = 0.03, respectively. Absolute change in sFFR between pre- and post-drug periods was marginally higher in ticagrelor- than thienopyridine-treated patients -0.01 (-0.04 to 0.0) versus -0.005 (-0.03 to 0.02), p = 0.048, respectively. Reclassification of treatment decision at the sFFR ≤ 0.80 cutoff post-drug occurred in 6 (15.8%) versus 5 (13.2%) of ticagrelor- and thienopyridine-treated patients, respectively. In conclusion, after ticagrelor LD, an absolute and relative reduction in sFFR compared with thienopyridine LD is observed. Administration of ticagrelor should be considered as a potential source, albeit minor, of FFR variability.

Ticagrelor: Pharmacokinetic, Pharmacodynamic and Pharmacogenetic Profile: An Update

Despite advancements in treatments for acute coronary syndromes over the last 10 years, they continue to be life-threatening disorders. Currently, the standard of treatment includes dual antiplatelet therapy consisting of aspirin plus a P2Y12 receptor antagonist. The thienopyridine class of P2Y12 receptor antagonists, clopidogrel and prasugrel, have demonstrated efficacy. However, their use is associated with several limitations, including the need for metabolic activation and irreversible P2Y12 receptor binding causing prolonged recovery of platelet function. In addition, response to clopidogrel is variable and efficacy is reduced in patients with certain genotypes. Although prasugrel is a more consistent inhibitor of platelet aggregation than clopidogrel, it is associated with an increased risk of life-threatening and fatal bleeding. Ticagrelor is an oral antiplatelet agent of the cyclopentyltriazolopyrimidine class and also acts through the P2Y12 receptor. In contrast to clopidogrel and prasugrel, ticagrelor does not require metabolic activation and binds rapidly and reversibly to the P2Y12 receptor. In light of new data, this review provides an update on the pharmacokinetic, pharmacodynamic and pharmacogenetic profiles of ticagrelor in different study populations. Recent studies report that no dose adjustment for ticagrelor is required on the basis of age, gender, ethnicity, severe renal impairment or mild hepatic impairment. The non-P2Y12 actions of ticagrelor are reviewed, showing indirect positive effects on cellular adenosine concentration and biological activity, by inhibition of equilibrative nucleoside transporter-1 independently of the P2Y12 receptor. CYP2C19 and ABCB1 genotypes do not appear to influence ticagrelor pharmacodynamics. A summary of drug interactions is also presented.

Ticagrelor Versus Clopidogrel in Black Patients With Stable Coronary Artery Disease

Background—

The burden of coronary artery disease (CAD) is high in blacks, highlighting the need for clinical research of antiplatelet agents in this population. We sought to evaluate platelet reactivity during loading and maintenance dosing of ticagrelor versus clopidogrel, and the pharmacokinetic profile of ticagrelor and its metabolite AR-C124910XX, in black patients with stable CAD taking low-dose aspirin (acetylsalicylic acid).

Methods and Results—

In a multicenter, randomized, open-label, crossover study, 34 blacks with stable CAD receiving acetylsalicylic acid 75 to 100 mg/d were randomized to clopidogrel (600 mg, then 75 mg QD for 7–9 days) or ticagrelor (180 mg, then 90 mg BID for 7–9 days). After washout 10 to 14 days, patients switched regimens. The primary end point was platelet reactivity 2 hours post loading dose (P2Y 12 reactivity units [PRU] measured by the VerifyNow assay). Least-squares mean PRU at 2 hours post loading dose was lower with ticagrelor (27.6) versus clopidogrel (211.2); least-squares mean difference was –183.6 (95% confidence interval, –213.9 to –153.3; P <0.001). At all time points, the least-squares mean PRU was significantly lower, and the percent reduction in PRU from baseline was statistically greater, with ticagrelor versus clopidogrel. At 2 hours post dose, the prevalence of high on-treatment platelet reactivity (≥208 PRU) was lower with ticagrelor (0%) than with clopidogrel (57.1%). Pharmacokinetic profiles of ticagrelor and AR-C124910XX were consistent with previous reports in stable CAD populations.

Conclusions—

In black patients with stable CAD receiving low-dose acetylsalicylic acid, ticagrelor provided a faster onset and greater degree of platelet inhibition than clopidogrel.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01523392.

Structural and functional characterization of a specific antidote for ticagrelor

Ticagrelor is a direct-acting reversibly binding P2Y12 antagonist and is widely used as an antiplatelet therapy for the prevention of cardiovascular events in acute coronary syndrome patients. However, antiplatelet therapy can be associated with an increased risk of bleeding. Here, we present data on the identification and the in vitro and in vivo pharmacology of an antigen-binding fragment (Fab) antidote for ticagrelor. The Fab has a 20 pM affinity for ticagrelor, which is 100 times stronger than ticagrelor's affinity for its target, P2Y12. Despite ticagrelor's structural similarities to adenosine, the Fab is highly specific and does not bind to adenosine, adenosine triphosphate, adenosine 5'-diphosphate, or structurally related drugs. The antidote concentration-dependently neutralized the free fraction of ticagrelor and reversed its antiplatelet activity both in vitro in human platelet-rich plasma and in vivo in mice. Lastly, the antidote proved effective in normalizing ticagrelor-dependent bleeding in a mouse model of acute surgery. This specific antidote for ticagrelor may prove valuable as an agent for patients who require emergency procedures.

Personalized antiplatelet and anticoagulation therapy: applications and significance of pharmacogenomics

In recent years, substantial effort has been made to better understand the influence of genetic factors on the efficacy and safety of numerous medications. These investigations suggest that the use of pharmacogenetic data to inform physician decision-making has great potential to enhance patient care by reducing on-treatment clinical events, adverse drug reactions, and health care-related costs. In fact, integration of such information into the clinical setting may be particularly applicable for antiplatelet and anticoagulation therapeutics, given the increasing body of evidence implicating genetic variation in variable drug response. In this review, we summarize currently available pharmacogenetic information for the most commonly used antiplatelet (ie, clopidogrel and aspirin) and anticoagulation (ie, warfarin) medications. Furthermore, we highlight the currently known role of genetic variability in response to next-generation antiplatelet (prasugrel and ticagrelor) and anticoagulant (dabigatran) agents. While compelling evidence suggests that genetic variants are important determinants of antiplatelet and anticoagulation therapy response, significant barriers to clinical implementation of pharmacogenetic testing exist and are described herein. In addition, we briefly discuss development of new diagnostic targets and therapeutic strategies as well as implications for enhanced patient care. In conclusion, pharmacogenetic testing can provide important information to assist clinicians with prescribing the most personalized and effective antiplatelet and anticoagulation therapy. However, several factors may limit its usefulness and should be considered.

Projected inhibition of platelet aggregation with ticagrelor twice daily vs. clopidogrel once daily based on patient adherence data (the TWICE project)

AIM

Twice daily dosing is often perceived as inferior to once daily dosing due to a higher likelihood of missing a dose. However, more important is the extent to which drug action is maintained when doses are delayed or missed. We compared the estimated inhibition of platelet aggregation (eIPA) for ticagrelor twice daily and clopidogrel once daily, based on their pharmacokinetic/ pharmacodynamic relationships and patient dosing history data.

METHODS

Drug dosing histories of 5014 patients prescribed cardiovascular medications (primarily antihypertensive medicines) were extracted from an electronically compiled dosing history database. eIPA levels were simulated for 677 twice daily and 677 once daily dosing histories over a 30 day period, based on published onset/offset models for ticagrelor and clopidogrel IPA characteristics.

RESULTS

While many patients treated twice daily missed at least one dose in 30 days, only 25.7% missed two consecutive doses. By comparison, 46.8% of patients treated once daily missed at least one dose. Simulations based on patient adherence over time showed that the average mean eIPA for ticagrelor twice daily remained significantly higher than for clopidogrel once daily (81.1% vs. 55.0%, P < 0.001). Ticagrelor twice daily patients had an eIPA below 10% for 0.20% of the 30 day period compared with 2.05% for clopidogrel once daily (P = 0.0001).

CONCLUSIONS

The projected level of platelet inhibition remained higher for ticagrelor twice daily than clopidogrel once daily, mainly due to the higher eIPA level achieved with ticagrelor and the relatively low likelihood of missing two consecutive twice daily doses. This modelling and simulation study suggests a therapeutic benefit of ticagrelor over clopidogrel when taking into account the most common dosing omissions.

Ticagrelor for the treatment of peripheral arterial disease

INTRODUCTION

Peripheral arterial disease (PAD) is a manifestation, and marker of severity, of a generalized atherosclerotic process. Antiplatelet therapy is recommended to prevent cardiovascular events but much of the evidence to support this is drawn from studies on older drugs.

AREAS COVERED

In this review, the authors discuss the available evidence for the basis of current recommendations and review the data from Phase I to III trials on ticagrelor as a potential future treatment. This paper also reviews the properties of ticagrelor, its adverse effects, and how it differs from current recommended antiplatelet agents. As it is also more potent, a personalized approach to antiplatelet therapy may prove useful. It further highlights the additional effects of ticagrelor mediated by adenosine and their potential benefits, which may provide an explanation to its superior outcomes in trials comparing it with clopidogrel.

EXPERT OPINION

Although there is a current lack of evidence to support the use of ticagrelor in patients with PAD, its unique pleomorphic properties make it attractive for future investigations and development of similar drugs.

[Antiplatelet therapy in acute coronary syndrome. Prehospital phase: nothing, aspirin or what?]

In most cases of ST segment elevation myocardial infarction (STEMI) a major coronary vessel is occluded by a thrombus. This is why early and effective antiplatelet therapy plays a key role. The current guidelines recommend the administration of dual antiplatelet therapy as early as possible. Despite the lack of convincing clinical evidence, prehospital administration appears reasonable, primarily because of pharmacokinetic considerations. Ticagrelor should be preferentially administered because the largest amount of evidence is available and it appears to be safe. In high-risk patients undergoing transfer to a catheterization laboratory, upstream use of a glycoprotein (GP) IIb/IIIa receptor antagonist (tirofiban) may be considered. Acute coronary syndrome without ST segment elevation (NSTE-ACS) represents a clinically heterogeneous group. Current guidelines recommend that antiplatelet therapy should be initiated as early as possible when the diagnosis of NSTE-ACS is made. If there is high clinical suspicion of NSTE-ACS acetylsalicylic acid (ASA) should be given before hospital admission. In high-risk patients prehospital administration of ticagrelor may be considered.

A comparison of the pharmacological profiles of prasugrel and ticagrelor assessed by platelet aggregation, thrombus formation and haemostasis in rats

BACKGROUND AND PURPOSE

Prasugrel is a third-generation thienopyridine prodrug and ticagrelor is a non-competitive P2Y12 receptor antagonist. In their phase 3 studies, both agents reduced rates of ischemic events relative to treatment with clopidogrel.

EXPERIMENTAL APPROACH

The pharmacodynamic profile of anti-platelet effects of prasugrel was compared with that of ticagrelor in rats.

KEY RESULTS

The active metabolite of prasugrel was less potent than ticagrelor and its active metabolite on platelet aggregation in vitro. In contrast, prasugrel was a more potent antiplatelet agent than ticagrelor on ex vivo platelet aggregation: their ED50 values at peak for ADP 20 μmol·L(-1) were 1.9 and 8.0 mg·kg(-1) , respectively. Prasugrel's inhibition of platelet aggregation was maintained for up to 24 h after administration, but ticagrelor's duration of action was substantially shorter. Prasugrel and ticagrelor significantly inhibited thrombus formation with ED50 values of 1.8 and 7.7 mg·kg(-1) , respectively. Both agents also prolonged bleeding times (ED200 values of 3.0 and 13 mg·kg(-1) respectively) suggesting that at equivalent levels of inhibition of platelet aggregation, the agents would show comparable antithrombotic activity with similar bleeding risk. Platelet transfusion significantly increased blood platelet numbers similarly in prasugrel- and ticagrelor-treated rats. In the prasugrel-treated group, platelet transfusion caused significant shortening of bleeding time, while in the ticagrelor-treated group, platelet transfusion showed no influence on bleeding time under the experimental conditions employed.

CONCLUSIONS AND IMPLICATIONS

Prasugrel and ticagrelor showed several differences in their pharmacological profiles and these disparities may reflect their differing reversibility and/or pharmacokinetic profiles.

Ticagrelor: pharmacokinetics, pharmacodynamics, clinical efficacy, and safety

Dual antiplatelet therapy, composed of aspirin plus a P2Y₁₂-receptor antagonist, is the cornerstone of treatment for patients with acute coronary syndrome (ACS). A number of U.S. Food and Drug Administration–approved P2Y₁₂-receptor antagonists are available for treating patients with ACS, including the thienopyridine compounds clopidogrel and prasugrel. Ticagrelor, the first of a new class of antiplatelet agents, is a noncompetitive, direct-acting P2Y₁₂-receptor antagonist. Unlike the thienopyridine compounds, ticagrelor does not require metabolism for activity. Also, whereas clopidogrel and prasugrel are irreversible inhibitors of the P2Y₁₂ receptor, ticagrelor binds reversibly to inhibit receptor signaling and subsequent platelet activation. In pharmacodynamic studies, ticagrelor demonstrated faster onset and more potent inhibition of platelet aggregation than clopidogrel. These properties of ticagrelor may contribute to reduced rates of thrombotic outcomes compared with clopidogrel, as demonstrated in a phase III clinical trial. However, in addition to bleeding, distinctive adverse effects of this new chemical entity have not been reported with the thienopyridine P2Y₁₂-receptor inhibitors. Although ticagrelor represents an advancement in P2Y₁₂-receptor inhibition therapy, a thorough understanding of this compound as an antiplatelet therapy remains to be elucidated.

Reversal strategy in antagonizing the P2Y12 -inhibitor ticagrelor

BACKGROUND

Patients on antiplatelet therapy have a higher incidence of bleeding complications. Reversal of antiplatelet drug effects is an important issue at trauma or emergency departments. For old and conventional anticoagulants, reversal strategies are established. While the effects of ticagrelor are reversible, developing a method to restore platelet function in patients is of importance due to its longer half-life (approximately 8 h), compared with other P2Y12 -inhibitors.

MATERIALS AND METHODS

We report an ex vivo model to reverse the effects of the novel and highly effective P2Y12 -inhibitor ticagrelor in 20 healthy volunteers. To normalize platelet reactivity, we added increasing amounts of autologous platelet-rich plasma (PRP) to whole blood which was obtained 3 h after the intake of 180 mg of ticagrelor. Platelet aggregation was assessed by whole blood multiple electrode aggregometry (MEA), which is based on impedance aggregometry.

RESULTS

The basal ADP-induced platelet aggregation averaged 71 ± 16 U (Units). Ticagrelor decreased ADP-induced platelet aggregation to 16 ± 8 U. A clear dose-response was obtained after spiking whole blood with increasing amounts of PRP. It is estimated that ≥2 units of apheresis platelet concentrates will be necessary to completely restore baseline platelet aggregation in the majority of patients after ticagrelor.

CONCLUSIONS

Platelets dose dependently improve ex vivo platelet aggregation of subjects after a loading dose of 180 mg of ticagrelor, making transfusion of platelet concentrates potentially useful in bleeding patients and those who need to undergo emergency surgery.

Comparison of antiplatelet effects of prasugrel and ticagrelor in cynomolgus monkeys by an ELISA-based VASP phosphorylation assay and platelet aggregation

Prasugrel is the third generation thienopyridine prodrug, and ticagrelor is a non-competitive direct acting P2Y12 antagonist. In phase 3 studies, both agents reduced ischaemic event rates compared to clopidogrel. The present in vitro human and monkey studies showed that ticagrelor's active metabolite (AM) was more potent than ticagrelor and prasugrel's AM on inhibition of ADP-induced platelet aggregation by light transmission aggregometry and ELISA-based vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay. In contrast, on an oral dosage basis (mg/kg), prasugrel showed more potent platelet inhibition compared to ticagrelor on ex vivo aggregation and VASP phosphorylation assays in monkeys. Single oral doses of prasugrel (0.3 and 1 mg/kg) resulted in robust antiplatelet effects, which were sustained up to 24 hours after administration. Ticagrelor (3 and 10 mg/kg, p.o.) also showed significant antiplatelet effects but its effects were diminished at 24 hours after the dosing. Repeat administration of prasugrel (1.8 mg/kg loading dose [LD], 0.3 mg/kg once daily maintenance dose [MD]) showed more rapid antiplatelet effects and longer duration of action throughout the entire day. Twice a day repeat administration of ticagrelor (10 mg/kg bid MD following a single 20 mg/kg LD) also showed significant antiplatelet effects but with more intra-day variability compared to prasugrel. The in vitro and ex vivo studies showed strong correlations between platelet aggregation and VASP phosphorylation for prasugrel, ticagrelor and their AMs. These strong correlations between platelet aggregation and VASP phosphorylation in non-human primates also suggest that ELISA-based human VASP assay can be utilised for non-human primate platelet studies.

Review of ticagrelor in the management of acute coronary syndromes

INTRODUCTION

Ticagrelor, an oral P2Y(12) receptor antagonist used as part of dual antiplatelet therapy in the treatment of acute coronary syndromes (ACS), has many favorable characteristics when compared with the more frequently used P2Y(12) receptor antagonist clopidogrel. Ticagrelor binds reversibly, with a rapid onset and offset of action, and produces high levels of platelet inhibition without variation secondary to genetic polymorphism. Ticagrelor produces increased platelet inhibition and an overall reduction in adverse cardiac events compared with clopidogrel. Clinically relevant side effects include an increase in non-CABG-related bleeding events as well as off-target adverse effects including ventricular pauses and dyspnea.

AREAS COVERED

This article details ticagrelor's pharmacokinetic and pharmacodynamic characteristics, development and chemical properties. The authors review relevant clinical trials looking at the efficiency and safety of ticagrelor focusing predominantly on the management of patients with ACS. Finally, the review article concludes with discussion of ticagrelor's current role and future integration into clinical practice.

EXPERT OPINION

Ticagrelor is a promising P2Y(12) receptor antagonist with characteristics that offer advantages for patients beyond those currently demonstrated by other P2Y(12) receptor antagonists. The challenge for prescribers is to identify those most likely to benefit from ticagrelor treatment while minimizing unnecessary bleeding events for 'real-world' ACS patients.