Novel approaches to antiplatelet therapy.

Platelets are the main effectors of the thrombotic events occurring at a ruptured atherosclerotic plaque and therefore antiplatelet agents are the mainstay of antithrombotic treatment for the prevention of myocardial infarction, atherotrombotic ischemic stroke and critical limb ischemia due to the thrombotic occlusion of the peripheral arteries. Despite great progress in antiplatelet agents over the last two decades, a number of important unmet medical needs still remain, like insufficient efficacy and a high incidence of hemorrhagic complications. Advances in the knowledge of the molecular mechanisms regulating platelet participation in hemostasis and in thrombosis and progress in pharmaceutical design have allowed to identify new drugs for established antiplatelet targets and novel targets for the development of new agents. Among the latter, several innovative approaches have already proceeded to clinical testing, like GPVI antagonism, PAR4 antagonism, PI3K inhibition, and some preliminary results seem promising. Here we review the pharmacologic approaches to platelet inhibition currently available and in development for their effects on platelet activation in vitro and on thrombosis in animal models and in humans. An ideal antithrombotic agent should selectively target events crucial for pathological thrombus formation without affecting hemostasis, an objective so far not achieved: if one or more of the novel agents in development will reach this goal this will represent a great step forward in the prevention of ischemic cardiovascular events.