e-5555 and Cardiovascular-Diseases

Platelets are the key in the pathogenesis of atherothrombotic disease such as acute coronary syndromes, stroke, and peripheral arterial disease. Current anti-platelet treatments are mainly based on inhibition of two important pathways of platelet activation: thromboxane A2 (TXA2) mediated (aspirin) and adenosine diphosphate (ADP)-P2Y12 receptor mediated (clopidogrel, prasugrel, and ticagrelor). Despite the dual anti-platelet therapy with aspirin and P2Y12 inhibitors have reduced ischemic events in patients with acute coronary syndromes (ACS), the rate of recurrent ischemic complication after ACS remains high. Combination of multiple anti-platelet agents is also associated with increased risk of bleeding. Thrombin is a potent platelet agonist and the increase of its activity has been reported in patients with ACS. Platelet effects of thrombin are mediated by protease-activated receptors (PAR), and PAR-1 is the most important receptor in human platelets. Two PAR-1 antagonists, vorapaxar and atopaxar, have undergone clinical investigation. In this review, we will describe the pharmacology of PAR-1 antagonists and will review and discuss results of randomized clinical trials with PAR-1 antagonists.

Topics: Animals; Blood Platelets; Cardiovascular Diseases; Drug Design; Humans; Imines; Lactones; Ligands; Platelet Activation; Platelet Aggregation Inhibitors; Pyridines; Receptor, PAR-1; Signal Transduction; Thrombin; Treatment Outcome

Despite the availability of dual antiplatelet therapy comprised of aspirin and clopidogrel, there is still significant unmet medical need for treating and preventing arterial thrombotic diseases. To achieve further reduction of cardiovascular events without exceeding bleeding tolerability and safety limits, novel antiplatelet strategies might need to trade in antiplatelet efficacy by partial inhibition of an important platelet activation pathway or by differentially targeting pathological versus physiological thrombogenesis pathways. Thrombin, the central enzyme in coagulation and the most potent platelet agonist tested in vitro, is one of the key factors driving the formation of occlusive thrombi. Platelet thrombin receptors, namely protease-activated receptor 1 (PAR-1) and protease-activated receptor 4 (PAR-4), act in concert to elicit robust platelet responses to thrombin. PAR-1 is the high affinity thrombin receptor and represents a novel antithrombotic target. PAR-4 is a low affinity thrombin receptor with less understood function. This review discusses the genetic and pharmacological evidence for PAR-1 target validation and highlights the progresses and challenges in developing oral PAR-1 antagonists, especially SCH 530348 from Merck/Schering-Plough and E-5555 from Eisai Co. Recent patents disclosing several novel chemical series of PAR-1 antagonists from Sanofi-Aventis and Pierre Fabre are also presented.

Topics: Administration, Oral; Animals; Cardiovascular Diseases; Humans; Imines; Lactones; Platelet Aggregation Inhibitors; Pyridines; Receptor, PAR-1; Receptors, Thrombin; Thrombin; Thrombosis

The role of antiplatelet therapy in the management of coronary artery disease and its sequalae is of great significance. Acetil Salycilic Acid (ASA) has continued to dominate the field as a potent antiplatelet agent, due to its ease of use and cost effectiveness. In addition to this, clopidogrel has also been widely used with better long term administration results in patients with atherosclerotic disease. However, interpatient variability and resistance to clopidogrel has opened the doors for further investigative research to find another agent which potentially meets the pharmacokinetic demands whilst having a satisfactory safety profile. Prasugrel and other novel nonthienopyridine derivatives are currently under investigation, with previous trials showing very reassuring outcomes. Patented inventions along with large trials have shown that prasugrel significantly reduces ischemic end points, ultimately resulting in a decrease in Myocardial infarctions, thromboocculusive episodes and death. Further studies are required to support these findings before we are aware of all clinical effects of Prasugrel.

Topics: Adenosine; Adenosine Monophosphate; Cardiovascular Diseases; Clinical Trials as Topic; Clopidogrel; Humans; Imines; Lactones; Patents as Topic; Piperazines; Platelet Aggregation Inhibitors; Prasugrel Hydrochloride; Purinergic P2 Receptor Antagonists; Pyridines; Receptor, PAR-1; Receptors, Purinergic P2Y12; Receptors, Thrombin; Thiophenes; Ticagrelor; Ticlopidine