Ticagrelor Does Not Inhibit Adenosine Transport at Relevant Concentrations: A Randomized Cross-Over Study in Healthy Subjects In Vivo

Ticagrelor-related dyspnea beyond adenosine: Insights into retrotrapezoid hyperactivity

Ticagrelor, a P2Y12 receptor antagonist, has been demonstrated to induce dyspnea, which is not associated with cardiac or pulmonary alterations, or metabolic disturbances. The attribution of ticagrelor-related dyspnea to excess adenosine has been widely proposed, yet is not supported by experimental data. In this paper, we put forth a novel hypothesis that the hyperactivity of the retrotrapezoid nucleus, a group of ventral medullary neurons involved in respiratory modulation, is the underlying cause of ticagrelor-related dyspnea. This hypothesis offers a theoretical resolution to the discrepancies and controversies present in previous theories.

Ticagrelor Induces Angiogenesis in Progenitor and Mature Endothelial Cells In Vitro: Investigation of the Possible Role of Adenosine

Ticagrelor, a reversible platelet P2Y12 receptor antagonist, exerts various pleiotropic actions, some of which are at least partially mediated through adenosine. We studied the ticagrelor and adenosine effect on the angiogenic properties of progenitor CD34+-derived endothelial colony-forming cells (ECFCs). Angiogenesis studies were performed in vitro using capillary-like tube formation and spheroid-based angiogenesis assays. The effects of adenosine receptor antagonists, including DPCPX (A1 antagonist), SCH58621 (A2A antagonist), MRS1706 (A2B inverse agonist and antagonist), MRS1220 (A3 antagonist) and adenosine deaminase (ADA), were also investigated. Ticagrelor, adenosine, and their combination increased capillary-like tube formation and spheroid sprout formation by ECFCs in a dose-dependent manner. This effect was significantly reduced by SCH58621, MRS1706, and their combination, as well as by ADA. By contrast, DPCPX and MRS1220 did not exhibit any inhibitory effects. Similar results were obtained when mature human umbilical vein endothelial cells (HUVECs) were studied. These results show that ticagrelor stimulates angiogenesis by progenitor and mature endothelial cells in an adenosine-dependent pathway in which the adenosine receptors A2A and A2B play major roles. The significance of these results at the clinical level in patients with atherothrombotic events and treated with ticagrelor needs to be investigated.

Ticagrelor potentiates cardioprotection by remote ischemic preconditioning: the ticagrelor in remote ischemic preconditioning (TRIP) randomized clinical trial

OBJECTIVE

Remote ischemic preconditioning (RIPC) reduces periprocedural myocardial injury (PMI) after percutaneous coronary intervention (PCI) through various pathways, including an adenosine-triggered pathway. Ticagrelor inhibits adenosine uptake, thus may potentiate the effects of RIPC. This randomized trial tested the hypothesis that ticagrelor potentiates the effect of RIPC and reduces PMI, assessed by post-procedural troponin release.

METHODS

Patients undergoing PCI for non-ST elevation acute coronary syndromes were 1:1 randomized to ticagrelor (TG-Group) or clopidogrel (CL-Group). Within each treatment, patients were 1:1 randomized to a RIPC (RIPC-Group) or a control group (CTRL-Group). The primary endpoint was the difference between post- and pre-procedural troponin at 24 h following PCI, termed deltaTnI.

RESULTS

During a 12-month period, 138 patients were included in the study (34 in the CL-CTRL group, 34 in the TG-CTRL group, 35 in the CL-RIPC group, and 35 in the TG-CTRL group). There was a significant difference in deltaTnI between the study groups [ TG-RIPC:0.04 (0-0.16), CL-CTRL:0.10 (0.03-0.43), CLRIPC:0.11 (0.03-0.89), and TG-CTRL:0.24 (0.06-0.47); p = 0.007]. Eight patients (22.9%) in the TG-RIPC group developed type 4a myocardial infarction (MI), compared to 14 (40%) in the CL-RIPC group, 13 (38.2%) in the CL-CTRL group, and 19 (55.9%) in the TG-CTRL group (p = 0.048). A significant interaction between antiplatelet group allocation and RIPC on deltaTnI was observed [F (1,134) = 7.509; p = 0.007]. In multivariate analysis, the interaction between RIPC and ticagrelor treatment was independently associated with a lower incidence of Type 4a MI.

CONCLUSION

Our results demonstrate an interaction between ticagrelor and RIPC, which may potentiate the cardioprotective effects of RIPC during PCI by reducing PMI.

A review of the effects of ticagrelor on adenosine concentration and its clinical significance

BACKGROUND

Ticagrelor is an oral antiplatelet drug that can reversibly bind to the platelet P2Y12 receptor. Ticagrelor is metabolized mainly by CYP3A4 and produces a rapid blood concentration-dependent platelet inhibitory effect. Unlike other P2Y12 receptor antagonists, many clinical features of ticagrelor are not related to P2Y12 receptor antagonism.

PURPOSE

This review aims to gather existing literature on the clinical effects of ticagrelor after inhibiting adenosine uptake.

METHODOLOGY

The current study reviewed literature related to the effects of ticagrelor on adenosine metabolism. The review also examined the drug's biological effects and clinical characteristics to see how it could be used in a clinical setting.

RESULTS

Many studies have shown that ticagrelor can inhibit equilibrative nucleoside transporter 1 (ENT1). This inhibition leads to intracellular adenosine uptake, increased adenosine half-life and plasma concentration levels and an enhanced adenosine-mediated biological effect.

CONCLUSIONS

Based on the studies reviewed, it was found that ticagrelor essentially inhibits adenosine absorption of adenosine into cells through ENT1, which increases the concentration in the blood and subsequently increases the protection of the heart muscle by adenosine. It also prevents platelet aggregation, and extends the biological effects of coronary arteries. Moreover, it leads to a lower mortality rate in acute coronary syndrome (ACS) patients.

Translation of experimental cardioprotective capability of P2Y12 inhibitors into clinical outcome in patients with ST-elevation myocardial infarction

We studied the translational cardioprotective potential of P2Y₁₂ inhibitors against acute myocardial ischemia/reperfusion injury (IRI) in an animal model of acute myocardial infarction and in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). P2Y₁₂ inhibitors may have pleiotropic effects to induce cardioprotection against acute myocardial IRI beyond their inhibitory effects on platelet aggregation. We compared the cardioprotective effects of clopidogrel, prasugrel, and ticagrelor on infarct size in an in vivo rat model of acute myocardial IRI, and investigated the effects of the P2Y₁₂ inhibitors on enzymatic infarct size (48-h area-under-the-curve (AUC) troponin T release) and clinical outcomes in a retrospective study of STEMI patients from the CONDI-2/ERIC-PPCI trial using propensity score analyses. Loading with ticagrelor in rats reduced infarct size after acute myocardial IRI compared to controls (37 ± 11% vs 52 ± 8%, p < 0.01), whereas clopidogrel and prasugrel did not (50 ± 11%, p > 0.99 and 49 ± 9%, p > 0.99, respectively). Correspondingly, troponin release was reduced in STEMI patients treated with ticagrelor compared to clopidogrel (adjusted 48-h AUC ratio: 0.67, 95% CI 0.47-0.94). Compared to clopidogrel, the composite endpoint of cardiac death or hospitalization for heart failure within 12 months was reduced in STEMI patients loaded with ticagrelor (HR 0.63; 95% CI 0.42-0.94) but not prasugrel (HR 0.84, 95% CI 0.43-1.63), prior to PPCI. Major adverse cardiovascular events did not differ between clopidogrel, ticagrelor, or prasugrel. The cardioprotective effects of ticagrelor in reducing infarct size may contribute to the clinical benefit observed in STEMI patients undergoing PPCI.

Toward a Molecular Basis of Cellular Nucleoside Transport in Humans

Nucleosides play central roles in all facets of life, from metabolism to cellular signaling. Because of their physiochemical properties, nucleosides are lipid bilayer impermeable and thus rely on dedicated transport systems to cross biological membranes. In humans, two unrelated protein families mediate nucleoside membrane transport: the concentrative and equilibrative nucleoside transporter families. The objective of this review is to provide a broad outlook on the current status of nucleoside transport research. We will discuss the role played by nucleoside transporters in human health and disease, with emphasis placed on recent structural advancements that have revealed detailed molecular principles of these important cellular transport systems and exploitable pharmacological features.

The pleiotropic effects of antithrombotic drugs in the metabolic-cardiovascular-neurodegenerative disease continuum: impact beyond reduced clotting

Antithrombotic drugs are widely used for primary and secondary prevention, as well as treatment of many cardiovascular disorders. Over the past few decades, major advances in the pharmacology of these agents have been made with the introduction of new drug classes as novel therapeutic options. Accumulating evidence indicates that the beneficial outcomes of some of these antithrombotic agents are not solely related to their ability to reduce thrombosis. Here, we review the evidence supporting established and potential pleiotropic effects of four novel classes of antithrombotic drugs, adenosine diphosphate (ADP) P2Y12-receptor antagonists, Glycoprotein IIb/IIIa receptor Inhibitors, and Direct Oral Anticoagulants (DOACs), which include Direct Factor Xa (FXa) and Direct Thrombin Inhibitors. Specifically, we discuss the molecular evidence supporting such pleiotropic effects in the context of cardiovascular disease (CVD) including endothelial dysfunction (ED), atherosclerosis, cardiac injury, stroke, and arrhythmia. Importantly, we highlight the role of DOACs in mitigating metabolic dysfunction-associated cardiovascular derangements. We also postulate that DOACs modulate perivascular adipose tissue inflammation and thus, may reverse cardiovascular dysfunction early in the course of the metabolic syndrome. In this regard, we argue that some antithrombotic agents can reverse the neurovascular damage in Alzheimer's and Parkinson's brain and following traumatic brain injury (TBI). Overall, we attempt to provide an up-to-date comprehensive review of the less-recognized, beneficial molecular aspects of antithrombotic therapy beyond reduced thrombus formation. We also make a solid argument for the need of further mechanistic analysis of the pleiotropic effects of antithrombotic drugs in the future.

Ticagrelor: a cardiometabolic drug targeting erythrocyte-mediated purinergic signaling?

Cardiometabolic diseases lead to vascular complications, which cause increasing morbidity and mortality worldwide. The underlying mechanisms are multifactorial and complex but may involve altered purinergic signaling that significantly contributes to cardiovascular dysfunction. Ticagrelor is a successful purinergic drug directly targeting ADP-mediated P2Y₁₂R signaling for platelet aggregation and is widely used in patients with acute coronary syndrome. In addition, ticagrelor can target red blood cells (RBCs) to release ATP and inhibit adenosine uptake by RBCs, which subsequently activate purinergic signaling. This involvement in purinergic signaling may allow ticagrelor to mediate pleiotropic effects and contribute to the beneficial cardiovascular outcomes observed in clinical studies. Recent studies have established a novel function of RBCs, which is that RBCs act as disease mediators for the development of cardiovascular complications in type 2 diabetes (T2D). RBC-released ATP is defective in T2D, which has implications for the induction of vascular dysfunction by dysregulating purinergic signaling. Ticagrelor might target RBCs and restore the bioavailability of ATP and adenosine, thereby attenuating cardiovascular complications. The present perspective discusses the pleiotropic effect of ticagrelor, with a focus on the possibility of ticagrelor for the treatment of cardiometabolic complications by targeting RBCs and initiating purinergic activation. A better understanding of the proposed cardiometabolic effects could support novel clinical indications for ticagrelor application.

Caffeinated Beverage Intake, Dyspnea With Ticagrelor, and Cardiovascular Outcomes: Insights From the PEGASUS-TIMI 54 Trial

Background

A proposed cause of dyspnea induced by ticagrelor is an increase in adenosine blood levels. Because caffeine is an adenosine antagonist, it can potentially improve drug tolerability with regard to dyspnea. Furthermore, association between caffeine and cardiovascular events is of clinical interest.

Methods and Results

This prespecified analysis used data from the PEGASUS TIMI 54 (Prevention of Cardiovascular Events in Patients With Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin–Thrombolysis in Myocardial Infarction 54) trial, which randomized 21 162 patients with prior myocardial infarction to ticagrelor 60 mg or 90 mg or matching placebo (twice daily). Baseline caffeine intake in cups per week was prospectively collected for 9694 patients. Outcomes of interest included dyspnea, major adverse cardiovascular events (ie, the composite of cardiovascular death, myocardial infarction, or stroke), and arrhythmias. Dyspnea analyses considered the pooled ticagrelor group, whereas cardiovascular outcome analyses included patients from the 3 randomized arms. After adjustment, caffeine intake, compared with no intake, was not associated with lower rates of dyspnea in patients taking ticagrelor (adjusted hazard ratio (HR), 0.91; 95% CI, 0.76–1.10; P=0.34). There was no excess risk with caffeine for major adverse cardiovascular events (adjusted HR, 0.78; 95% CI, 0.63–0.98; P=0.031), sudden cardiac death (adjusted HR, 0.98; 95% CI, 0.57–1.70; P=0.95), or atrial fibrillation (adjusted odds ratio, 1.07; 95% CI, 0.56–2.04; P=0.84).

Conclusions

In patients taking ticagrelor for secondary prevention after myocardial infarction, caffeine intake at baseline was not associated with lower rates of dyspnea compared with no intake. Otherwise, caffeine appeared to be safe in this population, with no apparent increase in atherothrombotic events or clinically significant arrhythmias.

Registration

URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT01225562.

Infarct size following loading with Ticagrelor/Prasugrel versus Clopidogrel in ST-segment elevation myocardial infarction

BACKGROUND

Treatment with newer direct-acting anti-platelet drugs (Ticagrelor and Prasugrel) prior to primary percutaneous coronary intervention (PCI) is associated with improved outcome in patients with ST-segment elevation myocardial infarction (STEMI) when compared with Clopidogrel. We compared infarct size following treatment with Ticagrelor/Prasugrel versus Clopidogrel in the DANish trial in Acute Myocardial Infarction (DANAMI-3) population of STEMI patients treated with primary PCI.

METHODS AND RESULTS

Patients were loaded with Clopidogrel, Ticagrelor or Prasugrel in the ambulance before primary PCI. Infarct size and myocardial salvage index were calculated using cardiac magnetic resonance (CMR) during index admission and at three-month follow-up. Six-hundred-and-ninety-three patients were included in this analysis. Clopidogrel was given to 351 patients and Ticagrelor/Prasugrel to 342 patients. The groups were generally comparable in terms of baseline and procedural characteristics. Median infarct size at three-month follow-up was 12.9% vs 10.0%, in patients treated with Clopidogrel and Ticagrelor/ Prasugrel respectively (p < 0.001), and myocardial salvage index was 66% vs 71% (p < 0.001). Results remained significant in a multiple regression model (p < 0.001).

CONCLUSIONS

Pre-hospital loading with Ticagrelor or Prasugrel compared to Clopidogrel, was associated with smaller infarct size and larger myocardial salvage index at three-month follow-up in patients with STEMI treated with primary PCI.

Ticagrelor Increases SIRT1 and HES1 mRNA Levels in Peripheral Blood Cells from Patients with Stable Coronary Artery Disease and Chronic Obstructive Pulmonary Disease

Ticagrelor is a powerful P2Y₁₂ inhibitor with pleiotropic effects in the cardiovascular system. Consistently, we have reported that in patients with stable coronary artery disease (CAD) and concomitant chronic obstructive pulmonary disease (COPD) who underwent percutaneous coronary intervention (PCI), 1-month treatment with ticagrelor was superior in improving biological markers of endothelial function, compared with clopidogrel. The objective of this study was to investigate the mechanisms underlying these beneficial effects of ticagrelor by conducting molecular analyses of RNA isolated from peripheral blood cells of these patients. We determined mRNAs levels of markers of inflammation and oxidative stress, such as RORγt (T helper 17 cells marker), FoxP3 (regulatory T cells marker), NLRP3, ICAM1, SIRT1, Notch ligands JAG1 and DLL4, and HES1, a Notch target gene. We found that 1-month treatment with ticagrelor, but not clopidogrel, led to increased levels of SIRT1 and HES1 mRNAs. In patients treated with ticagrelor or clopidogrel, we observed a negative correlation among changes in both SIRT1 and HES1 mRNA and serum levels of Epidermal Growth Factor (EGF), a marker of endothelial dysfunction found to be reduced by ticagrelor treatment in our previous study. In conclusion, we report that in stable CAD/COPD patients ticagrelor positively regulates HES1 and SIRT1, two genes playing a protective role in the context of inflammation and oxidative stress. Our observations confirm and expand previous studies showing that the beneficial effects of ticagrelor in stable CAD/COPD patients may be, at least in part, mediated by its capacity to reduce systemic inflammation and oxidative stress.

Ticagrelor Enhances Release of Anti-Hypoxic Cardiac Progenitor Cell-Derived Exosomes Through Increasing Cell Proliferation In Vitro

Despite the widespread clinical use of cardioprotection by long-term direct antagonism of P2Y12 receptor, underlying mechanisms are unclear. Here, we identify how release of pro-survival exosomes from human cardiac-derived mesenchymal progenitor cells (hCPCs) is regulated by clinically relevant dose of ticagrelor (1 μM), an oral selective and reversible non-thienopyridine P2Y₁₂ inhibitor. Ticagrelor-induced enhancement of exosome levels is related to increased mitotic activity of hCPCs. We show a drug-response threshold above which the effects on hCPCs are lost due to higher dose of ticagrelor and larger adenosine levels. While it is known that pan-Aurora kinase inhibitor halts cell proliferation through dephosphorylation of histone H3 residue Ser10, we demonstrate that it also prevents ticagrelor-induced effects on release of cardiac progenitor cell-derived exosomes delivering anti-apoptotic HSP70. Indeed, sustained pre-treatment of cardiomyocytes with exosomes released from explant-derived hCPCs exposed to low-dose ticagrelor attenuated hypoxia-induced apoptosis through acute phosphorylation of ERK42/44. Our data indicate that ticagrelor can be leveraged to modulate release of anti-hypoxic exosomes from resident hCPCs.

Promiscuity of in Vitro Secondary Pharmacology Assays and Implications for Lead Optimization Strategies

We conducted an analysis on screening data generated from 1445 compounds against a panel of 130 enzymes, ion channels, and receptors to assess secondary pharmacological risks. Hit rates of these targets as well as physicochemical properties for those hits were evaluated. A majority of targets yielded hits with higher clogP, molecular weight, and more basic character than inactive compounds. Although most targets favored lipophilic hits, the average clogP of hits at a given target did not correlate with its hit rate. Furthermore, a matched pair analysis was completed to determine structural changes that impacted off-target activities. A correlation of binding assays used in this analysis illustrated that some pharmacologically related binding assays are highly correlative and may be substituted for a smaller set of surrogate assays.

Evaluation of Microvascular Injury in Revascularized Patients With ST-Segment-Elevation Myocardial Infarction Treated With Ticagrelor Versus Prasugrel

BACKGROUND

Despite successful restoration of epicardial vessel patency with primary percutaneous coronary intervention, coronary microvascular injury occurs in a large proportion of patients with ST-segment-elevation myocardial infarction, adversely affecting clinical and functional outcome. Ticagrelor has been reported to increase plasma adenosine levels, which might have a protective effect on the microcirculation. We investigated whether ticagrelor maintenance therapy after revascularized ST-segment-elevation myocardial infarction is associated with less coronary microvascular injury compared to prasugrel maintenance therapy.

METHODS

A total of 110 patients with ST-segment-elevation myocardial infarction received a loading dose of ticagrelor and were randomized to maintenance therapy of ticagrelor (n=56) or prasugrel (n=54) after primary percutaneous coronary intervention. The primary outcome was coronary microvascular injury at 1 month, as determined with the index of microcirculatory resistance in the infarct-related artery. Cardiovascular magnetic resonance imaging was performed during the acute phase and at 1 month.

RESULTS

The primary outcome of index of microcirculatory resistance was not superior in ticagrelor- or prasugrel-treated patients (ticagrelor, 21 [interquartile range, 15-39] U; prasugrel, 18 [interquartile range, 11-29] U; P=0.08). Recovery of microcirculatory resistance over time was not better in patients with ticagrelor versus prasugrel (ticagrelor, -13.9 U; prasugrel, -13.5 U; P=0.96). Intramyocardial hemorrhage was observed less frequently in patients receiving ticagrelor (23% versus 43%; P=0.04). At 1 month, no difference in infarct size was observed (ticagrelor, 7.6 [interquartile range, 3.7-14.4] g, prasugrel 9.9 [interquartile range, 5.7-16.6] g; P=0.17). The occurrence of microvascular obstruction was not different in patients on ticagrelor (28%) or prasugrel (41%; P=0.35). Plasma adenosine concentrations were not different during the index procedure and during maintenance therapy with ticagrelor or prasugrel.

CONCLUSIONS

In patients with ST-segment-elevation myocardial infarction, ticagrelor maintenance therapy was not superior to prasugrel in preventing coronary microvascular injury in the infarct-related territory as assessed by the index of microcirculatory resistance, and this resulted in a comparable infarct size at 1 month.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02422888.

Adenosine and the Cardiovascular System

Adenosine is an endogenous nucleoside with a short half-life that regulates many physiological functions involving the heart and cardiovascular system. Among the cardioprotective properties of adenosine are its ability to improve cholesterol homeostasis, impact platelet aggregation and inhibit the inflammatory response. Through modulation of forward and reverse cholesterol transport pathways, adenosine can improve cholesterol balance and thereby protect macrophages from lipid overload and foam cell transformation. The function of adenosine is controlled through four G-protein coupled receptors: A₁, A_2A, A_2B and A₃. Of these four, it is the A_2A receptor that is in a large part responsible for the anti-inflammatory effects of adenosine as well as defense against excess cholesterol accumulation. A_2A receptor agonists are the focus of efforts by the pharmaceutical industry to develop new cardiovascular therapies, and pharmacological actions of the atheroprotective and anti-inflammatory drug methotrexate are mediated via release of adenosine and activation of the A_2A receptor. Also relevant are anti-platelet agents that decrease platelet activation and adhesion and reduce thrombotic occlusion of atherosclerotic arteries by antagonizing adenosine diphosphate-mediated effects on the P2Y12 receptor. The purpose of this review is to discuss the effects of adenosine on cell types found in the arterial wall that are involved in atherosclerosis, to describe use of adenosine and its receptor ligands to limit excess cholesterol accumulation and to explore clinically applied anti-platelet effects. Its impact on electrophysiology and use as a clinical treatment for myocardial preservation during infarct will also be covered. Results of cell culture studies, animal experiments and human clinical trials are presented. Finally, we highlight future directions of research in the application of adenosine as an approach to improving outcomes in persons with cardiovascular disease.

Does Ticagrelor Improve Endothelial Function?

Ticagrelor is a P2Y12 receptor antagonist with proven clinical benefit in patients with acute coronary syndrome. Apart from its principal antiplatelet action, pleiotropic effects have been implicated in the clinical profile of ticagrelor, including a potentially beneficial impact on endothelial function. In light of the common presence and prognostic value of endothelial dysfunction in patients with coronary artery disease, several clinical studies have investigated the postulated effect of ticagrelor on endothelial function, yielding conflicting results. Limitations of the relevant studies as well as substantial differences in patient population, study design, and methods may account for these controversial findings. Most of these studies, however, support a beneficial impact of ticagrelor on endothelial function, which seems to be significant in the higher risk patients. In order to elucidate this effect, further research efforts should aim to clarify how quickly does endothelial function respond to ticagrelor, how sustained this response is during the dosing intervals and in the long term, which mechanisms are implicated, and whether this pleiotropic action is clinically significant. Future studies should include larger and diverse populations of patients, assess endothelial function at several time points after treatment initiation, and use multiple methods of endothelial function measurement, while implementing strict methodology. Nevertheless, the extent of the clinical benefit of ticagrelor attributable to actions beyond its potent and consistent antiplatelet effect remains uncertain.

Ticagrelor Improves Endothelial Function by Decreasing Circulating Epidermal Growth Factor (EGF)

Ticagrelor is one of the most powerful P2Y₁₂ inhibitor. We have recently reported that, in patients with concomitant Stable Coronary Artery Disease (SCAD) and Chronic Obstructive Pulmonary Disease (COPD) undergoing percutaneous coronary intervention (PCI), treatment with ticagrelor, as compared to clopidogrel, is associated with an improvement of the endothelial function (Clinical Trial NCT02519608). In the present study, we showed that, in the same population, after 1 month treatment with ticagrelor, but not with clopidogrel, there is a decrease of the circulating levels of epidermal growth factor (EGF) and that these changes in circulating levels of EGF correlate with on-treatment platelet reactivity. Furthermore, in human umbilical vein endothelial cells (HUVEC) incubated with sera of the patients treated with ticagrelor, but not with clopidogrel there is an increase of p-eNOS levels. Finally, analyzing the changes in EGF and p-eNOS levels after treatment, we observed an inverse correlation between p-eNOS and EGF changes only in the ticagrelor group. Causality between EGF and eNOS activation was assessed in vitro in HUVEC where we showed that EGF decreases eNOS activity in a dose dependent manner. Taken together our data indicate that ticagrelor improves endothelial function by lowering circulating EGF that results in the activation of eNOS in the vascular endothelium.

Ticagrelor - toward more efficient platelet inhibition and beyond

Novel antiplatelet drugs, including ticagrelor, are being successively introduced into the therapy of atherothrombotic conditions due to their superiority over a standard combination of clopidogrel with acetylsalicylic acid in patients with acute coronary syndromes (ACS). A P2Y12 receptor antagonist, ticagrelor, is unique among antiplatelet drugs, because ticagrelor inhibits the platelet P2Y12 receptor in a reversible manner, and because it demonstrates a wide palette of advantageous pleiotropic effects associated with the increased concentration of adenosine. The pleiotropic effects of ticagrelor comprise cardioprotection, restoration of the myocardium after an ischemic event, promotion of the release of anticoagulative factors and, eventually, anti-inflammatory effects. Beyond the advantageous effects, the increased concentration of adenosine is responsible for some of ticagrelor's adverse effects, including dyspnea and bradycardia. Large-scale clinical trials demonstrated that both standard 12-month therapy and long-term use of ticagrelor reduce the risk of cardiovascular events in patients with ACS, but at the expense of a higher risk of major bleeding. Further trials focused on the use of ticagrelor in conditions other than ACS, including ischemic stroke, peripheral artery disease and status after coronary artery bypass grafting. The results of these trials suggest comparable efficacy and safety of ticagrelor and clopidogrel in extra-coronary indications, but firm conclusions are anticipated from currently ongoing studies. Here, we summarize current evidence on the superiority of ticagrelor over other P2Y12 antagonists in ACS, discuss the mechanism underlying the drug-drug interactions and pleiotropic effects of ticagrelor, and present future perspectives of non-coronary indications for ticagrelor.

Absence of differential effect of ticagrelor versus prasugrel maintenance dose on endothelial function in patients with stable coronary artery disease

BACKGROUND

Endothelial function may be improved by ticagrelor through adenosine-mediated mechanisms. We aimed to assess the effect of ticagrelor versus prasugrel on endothelial function in patients with stable coronary artery disease (CAD).

METHODS

In a prospective, randomized, crossover study, 22 stable CAD patients under prasugrel 10 mg once daily maintenance dose (MD) for at least 3 months were randomized to either ticagrelor 90 mg twice daily or prasugrel 10 mg once daily for 15 days with a direct treatment-crossover for another 15 days. Endothelial function was assessed by peripheral arterial tonometry (EndoPAT 2000 system, Itamar Medical, Caesarea, Israel) at Day 0 (randomization), Day 15, and Day 30. Reactive Hyperemia Index (RHI) was calculated by using an automated software, and endothelial dysfunction (ED) was defined as RHI <1.67. RHI at the end of the two treatment periods did not differ between ticagrelor and prasugrel MD treatments. Least squares estimates (95% confidence interval) were 1.78 (1.58-1.99) versus 1.88 (1.67-2.08), with a fixed estimate of -0.099 (95% CI: -0.45 to 0.25) for the difference between them (p = 0.5). ED rate did not differ significantly between ticagrelor and prasugrel (45.5% vs 45.5%, p = 0.6).

CONCLUSIONS

In CAD patients, we have failed to find evidence of alteration of endothelial function following ticagrelor compared to prasugrel MD treatment, as assessed by peripheral arterial tonometry. CLINICALTRIALS.

GOV UNIQUE IDENTIFIER

NCT01957540.

A randomised trial on the effect of anti-platelet therapy on the systemic inflammatory response in human endotoxaemia

The use of acetylsalicylic acid (ASA) is associated with improved outcome in patients with sepsis, and P2Y₁₂ inhibitors have been suggested to also have immunomodulatory effects. Therefore, we evaluated the effects of clinically relevant combinations of antiplatelet therapy on the immune response in experimental endotoxaemia in humans in vivo. Forty healthy subjects were randomised to seven days of placebo, placebo with ASA, ticagrelor and ASA, or clopidogrel and ASA treatment. Systemic inflammation was elicited at day seven by intravenous administration of Escherichia coli endotoxin. ASA treatment profoundly augmented the plasma concentration of pro-inflammatory cytokines, but did not affect anti-inflammatory cytokines. Addition of either P2Y₁₂ antagonist to ASA did not affect any of the circulating cytokines, except for an attenuation of the ASA-induced increase in TNFα by ticagrelor. Systemic inflammation increased plasma adenosine, without differences between groups, and although P2Y₁₂ inhibition impaired platelet reactivity, there was no correlation with cytokine responses.

A semi-quantitative translational pharmacology analysis to understand the relationship between in vitro ENT1 inhibition and the clinical incidence of dyspnoea and bronchospasm

Adenosine contributes to the pathophysiology of respiratory disease, and adenosine challenge leads to bronchospasm and dyspnoea in patients. The equilibrative nucleoside transporter 1 (ENT1) terminates the action of adenosine by removal from the extracellular environment. Therefore, it is proposed that inhibition of ENT1 in respiratory disease patients leads to increased adenosine concentrations, triggering bronchospasm and dyspnoea. This study aims to assess the translation of in vitro ENT1 inhibition to the clinical incidence of bronchospasm and dyspnoea in respiratory disease, cardiovascular disease and healthy volunteer populations. Four marketed drugs with ENT1 activity were assessed; dipyridamole, ticagrelor, draflazine, cilostazol. For each patient population, the relationship between in vitro ENT1 [³H]-NBTI binding affinity (K_i) and [³H]-adenosine uptake (IC₅₀) to the incidence of: (1) bronchospasm/severe dyspnoea; (2) tolerated dyspnoea and; (3) no adverse effects, was evaluated. A high degree of ENT1 inhibition (≥13.3x K_i, ≥4x IC₅₀) associated with increased incidence of bronchospasm/severe dyspnoea for patients with respiratory disease only, whereas a lower degree of ENT1 inhibition (≥0.1x K_i, ≥0.05x IC₅₀) associated with a tolerable level of dyspnoea in both respiratory and cardiovascular disease patients. ENT1 inhibition had no effect in healthy volunteers. Furthermore, physicochemical properties correlative with ENT1 binding were assessed using a set of 1625 diverse molecules. Binding to ENT1 was relatively promiscuous (22% compounds K_i<1μM) especially for neutral or basic molecules, and greater incidence tracked with higher lipophilicity (clogP >5). This study rationalises inclusion of an assessment of ENT1 activity during early safety profiling for programs targeting respiratory disorders.