The novel P2Y12 antagonist AZD6140 rapidly and reversibly reduces platelet activation in diabetic rats

In-vivo platelet activation and aggregation during and after acute atherothrombotic myocardial infarction in patients with and without Type-2 diabetes mellitus treated with ticagrelor

INTRODUCTION

Patients with type-2 diabetes are twice as likely to suffer from acute myocardial infarction (AMI) and have a higher incidence of recurrent events than their non-diabetic counterparts. Ticagrelor is a platelet inhibitor known to reduce major adverse cardiovascular events (MACE) in AMI patients. This study measures the level and change in platelet activation and aggregation at the time of and following an AMI in patients with and without diabetes treated with ticagrelor.

MATERIALS/METHODS

P₂Y₁₂ receptor inhibitor naïve patients presenting with AMI were prospectively enrolled. Blood collection occurred before coronary angiography (baseline: T₀), 2, 4, 24, 48 h after baseline, and at a three-month follow-up. Ticagrelor was administered within five minutes of T₀. We assessed platelet activation via measurements of surface P-selectin and platelet activated glycoprotein IIb/IIIa-1 (PAC-1) and assessed platelet aggregation via monocyte, lymphocyte, and granulocyte aggregates. We hypothesize that platelet activation and aggregation will be proportionally impacted to the same degree by ticagrelor, regardless of diabetes status.

RESULTS

Ninety-seven patients were prospectively enrolled (diabetes, N = 33; no diabetes, N = 64). No difference was observed in the expression of P-selectin and PAC-1 at any given point between diabetes and non-diabetes groups (p > 0.05). No difference was observed in the percentage of platelet bound to leukocytes at any measured timepoint between patients with and without diabetes (p > 0.05). Platelet leukocyte aggregation was suppressed during the acute phase compared to quiescence equally among both groups.

DISCUSSION

Ticagrelor demonstrated similar in-vivo effects on platelet activation and aggregation regardless of diabetes status in patients presenting with AMI.

Effects of Dual Purinoceptor-dependent Approach on Release of Vascular Endothelial Growth Factor From Human Microvascular Endothelial Cell (HMEC-1) and Endothelial Cell Condition

In the recent years, the awareness of the role purinergic signaling plays as a therapeutic target has increased considerably. The purinoceptor allows the action of extracellular nucleotides (P2 receptors) and intermediary products of their metabolism, such as adenosine (P1 receptors), regulating pivotal processes occurring in the cardiovascular system. This study focuses on a dual purinoreceptor-dependent approach, based on the activation of adenosine P1 receptors with the simultaneous inhibition of P2Y12 receptors that can be used as novel platelet inhibitors in antithrombotic therapy. Endothelial cells are directly exposed to the drugs circulating in the bloodstream. That is why effects of our concept on human microvascular endothelial cells (HMEC-1) were examined in in vitro studies, such as enzyme-linked immunosorbent assay and scratch assays. In response to adenosine receptor agonists, levels of secreted vascular endothelial growth factor varied. Two of them, 5'-N-ethylcarboxamidoadenosine and MRE0094 remarkably increased vascular endothelial growth factor release. The elevated levels were reduced when used together with the P2Y12 receptor antagonist. Also, rates of wound closure in a scratch assay were significantly reduced in these cases. The results suggest that the proposed treatment does not impair endothelial cell condition. In addition, it is suggested as a collateral benefit, namely solving the problem of excessive activation of endothelial cells during antiplatelet therapy.

Effects of Ticagrelor on Ionic Currents and Contractility in Rat Ventricular Myocytes

PURPOSE

Antiplatelet therapy has been widely used for management of patients with ischaemic heart diseases or thrombotic events. Experimental studies have shown that ticlopidine and clopidogrel decreased L-type Ca(2+) currents (ICaL), altered action potential (AP) duration and thence exerted negative inotropic effects. In this study we tested if ticagrelor, a non-thienopyridine agent, has any influence on contractile and electrical properties of isolated ventricular myocytes.

METHODS

Cardiomyocytes were isolated from male rat hearts with an enzymatic dissociation procedure and left ventricular myocytes were used for experiments. The effects of ticagrelor (1 μM) on sarcomere shortening, ionic currents and action potentials were measured at 36 ± 1 °C.

RESULTS

Ticagrelor significantly reduced ICaL density (~18%, p < 0.01) of ventricular myocytes and this effect was reversible. In consistence, it also decreased sarcomere shortening of electrically stimulated cardiomyocytes (13%, p < 0.05), while it did not change relaxation rates. Repolarizing K(+) currents and AP duration were unaffected by 1 μM ticagrelor application.

CONCLUSIONS

Ticagrelor exerts a significant influence on contractile properties and membrane currents of ventricular myocytes similarly to thienopyridine agents. The impact of ticagrelor on cardiac excitation-contraction coupling elements is important, since it is widely used for the treatment of patients with heart diseases.

Ticagrelor: positive, negative and misunderstood properties as a new antiplatelet agent

Dual antiplatelet therapy is essential for the management of acute coronary syndrome. In particular, combination therapy using aspirin with a platelet ADP (i.e. P2Y12 ) receptor inhibitor, such as clopidogrel, prasugrel or, more recently, ticagrelor, has been recommended for patients with acute coronary syndrome. Pharmacological agents that reversibly inhibit platelet aggregation without metabolic activation in the liver are believed to reduce cardiovascular mortality compared with the current drug of choice for antiplatelet therapy, namely clopidogrel. These findings are based on a multicentre, double-blind, double-dummy, randomized controlled trial. Numerous factors are postulated to contribute to the improved survival of patients who take ticagrelor compared with those taking clopidogrel, including the risk of myocardial infarction, heart failure, arrhythmia and bleeding. In addition, clopidogrel may lead to a much higher incidence of infection. Although ticagrelor has recently been approved for use in the US and exhibits superiority over other antiplatelet agents, certain concerns remain regarding its use, including lung injury and dyspnoea, thus raising the issue of its true superiority over clopidogrel or prasugrel. Recent studies into ticagrelor report conflicting data, with certain aspects of its mechanisms of action still not fully understood. Ticagrelor has beneficial effects following its clinical application, such as achieving overall higher reductions in mortality compared with the use of clopidogrel and prasugrel. Harmful effects associated with the use of ticagrelor include a higher incidence of dyspnoea and major bleeding compared with clopidogrel.

Randomized assessment of ticagrelor versus prasugrel antiplatelet effects in patients with diabetes

OBJECTIVE

It has been postulated that prasugrel might be the preferred treatment option in diabetes mellitus (DM) patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI). We aimed to compare the pharmacodynamic action of ticagrelor versus prasugrel.

RESEARCH DESIGN AND METHODS

In a prospective, single-center, single-blind, crossover study, 30 consecutive ACS patients with DM who had been pretreated with clopidogrel were randomized to either 90 mg ticagrelor twice daily or 10 mg prasugrel once daily with a 15-day treatment period. Platelet reactivity (PR) was assessed with the VerifyNow P2Y12 function assay, measured in P2Y12 reaction units (PRU).

RESULTS

PR was significantly lower after ticagrelor (45.2 PRU [95% CI 27.4-63.1]) compared with prasugrel (80.8 PRU [63.0-98.7]), with a least squares mean difference of -35.6 PRU (-55.2 to -15.9, P = 0.001). High PR rate was 0% for ticagrelor and 3.3% for prasugrel (P = 1.0).

CONCLUSIONS

In DM patients with ACS who had been pretreated with clopidogrel and who undergo PCI, ticagrelor achieves a significantly higher platelet inhibition than prasugrel. Both antiplatelet agents effectively treat high PR. The relevance of these findings to the clinical efficacy and safety of ticagrelor and prasugrel in DM patients needs further elucidation.

Ticagrelor: from discovery to Phase III clinical trial

Ticagrelor (AZD6140), a cyclopentyl-triazolo-pyrimidine, is the first orally available antagonist of the ADP receptor of the P2Y12 subtype. Ticagrelor inhibits platelets in a reversible manner and does not require hepatic bioactivation. The pharmacology of ticagrelor indicates that it provides more consistent, more rapid and more potent platelet inhibition than clopidogrel. Preclinical and clinical studies with ticagrelor have demonstrated that this drug has excellent oral bioavailability. The Phase III clinical study of Platelet Inhibition and Patient Outcomes (PLATO) has shown that ticagrelor reduced ischemic events and all-cause mortality without an increase in major bleeding complications. Potential advantages of ticagrelor include more flexibility in its use if rapid onset of action is needed before percutaneous coronary interventions or when cessation is required before coronary artery bypass graft surgery. Potential disadvantages include more side effects such as dyspnea, ventricular pauses or an increase in concentrations of uric acid and creatinine. However, ticagrelor did not only reduce death due to vascular causes but also all-cause mortality. Further clinical trials in indications other than acute coronary syndrome are awaited.