e-5555 and Myocardial-Ischemia

Platelet activation is a key process in the pathogenesis of acute coronary syndromes (ACS). Of the many triggers involved in this process, three are presumed to be critical: thromboxane A(2) (TBXA(2)) via the TBXA(2) receptor, adenosine diphosphate via the P2Y(12) receptor, and thrombin via the protease-activated receptor (PAR)-1. Despite the effective inhibition of the first two pathways with aspirin and an expanding family of P2Y(12) inhibitors, the incidence of recurrent ischemic events remains high after ACS. PAR-1 inhibitors are a novel class of antiplatelet agents that inhibit thrombin-mediated platelet activation. Preclinical data and phase 2 clinical trials in patients with stable and unstable coronary disease support the potential of these compounds to improve clinical outcome. In this review we discuss the rationale for developing this novel class of agents with a focus on the two compounds in most advanced clinical development, vorapaxar (SCH 530348) and atopaxar (E5555).

Topics: Acute Coronary Syndrome; Aspirin; Female; Humans; Imines; Lactones; Male; Myocardial Ischemia; Platelet Activation; Platelet Aggregation Inhibitors; Pyridines; Randomized Controlled Trials as Topic; Receptor, PAR-1; Recurrence; Treatment Outcome

The unifying basis of acute coronary syndrome (ACS) is the complication of a vulnerable coronary plaque, an event primarily mediated by platelet activation. Three major pathways are predominantly involved in this process: thromboxane A(2) via the thromboxane A(2) receptor, adenosine diphosphate via the P2Y(12) receptor, and thrombin via the protease-activated receptor (PAR)-1, with the latter being the most potent platelet activator. Despite the effective inhibition of the first two pathways with aspirin and an expanding family of P2Y(12) inhibitors, respectively, the recurrence of ischemic events in patients with ACS remains high. There is also a growing concern regarding the safety profile in terms of bleeding with more powerful antiplatelet agents, which has tempered expectations of newly developed compounds. PAR-1 inhibitors are a novel class of antiplatelet agents that inhibit thrombin-mediated platelet activation. Preliminary data indicate that these compounds have the potential to improve ischemic prognosis without increasing the bleeding risk. In this chapter we will discuss the rationale for developing this novel class of antiplatelet agents and specifically, the two compounds in most advanced clinical development, vorapaxar and atopaxar.

Topics: Acute Coronary Syndrome; Animals; Humans; Imines; Lactones; Myocardial Ischemia; Platelet Aggregation; Pyridines; Receptor, PAR-1; Receptors, Thrombin