Anti-platelet therapy: ADP receptor antagonists.

The P2Y(12) receptor on platelets with which ADP interacts has an important role in promoting platelet function and thereby platelet involvement in both haemostasis and thrombosis. Agents that act as antagonists at this receptor are thus likely to provide effective antithrombotic therapy, provided that there are no adverse effects on haemostasis. Here we describe the ADP receptor antagonists that are available and in development. We also consider their mode of action and ask whether there are additional mechanisms through which they exert their inhibitory effects on platelet function.

Ticagrelor: a P2Y12 antagonist for use in acute coronary syndromes.

Agents that inhibit platelet function are used routinely in the treatment and prevention of acute coronary syndromes. The main antiplatelet treatments used combine aspirin with one of the thienopyridine P2Y(12) antagonists, either clopidogrel or prasugrel. By blocking the synthesis of thromboxane A(2) in platelets and by blocking the effects of ADP, respectively, these agents reduce platelet activity, platelet aggregation and thrombus formation. Ticagrelor (marketed by AstraZeneca as Brilinta™ in the USA, and as Brilique(®) or Possia(®) in Europe) is a cyclopentyl-triazolo-pyrimidine, a new chemical class of P2Y(12) antagonist that is now approved for use in the wide spectrum of acute coronary syndromes. In this article we provide an overview of ticagrelor. We discuss the differences in mode of action compared with other P2Y(12) antagonists, examine its pharmacodynamic, pharmacokinetic and safety profile, and summarize the various clinical trials that have provided information on its efficacy in combination with aspirin. Ticagrelor appears to overcome some of the difficulties that have been encountered with other antiplatelet treatments, clopidogrel in particular.