Oral antiplatelet therapy for atherothrombotic disease: current evidence and new directions

HD White - American Heart Journal, 2011 - Elsevier
HD White
American Heart Journal, 2011Elsevier
Despite the proven efficacy of dual antiplatelet therapy with aspirin and one of the first-
generation P2Y12 antagonists (clopidogrel, prasugrel) in patients with atherothrombotic
disease, residual ischemic risk remains substantial, and bleeding rates are increased.
Incomplete protection against ischemic events can be attributed to the fact that these
therapies each target a single platelet activation pathway, allowing continued platelet
activation via other pathways, including the protease-activated receptor-1 (PAR-1) pathway …
Despite the proven efficacy of dual antiplatelet therapy with aspirin and one of the first-generation P2Y12 antagonists (clopidogrel, prasugrel) in patients with atherothrombotic disease, residual ischemic risk remains substantial, and bleeding rates are increased. Incomplete protection against ischemic events can be attributed to the fact that these therapies each target a single platelet activation pathway, allowing continued platelet activation via other pathways, including the protease-activated receptor-1 (PAR-1) pathway stimulated by thrombin. Increased bleeding with dual antiplatelet therapy can be attributed to blockade of the thromboxane A2 (by aspirin) and adenosine diphosphate (by P2Y12 antagonist) platelet activation pathways that are essential to hemostasis. The second-generation P2Y12 inhibitor ticagrelor plus aspirin demonstrated superior ischemic outcomes, including reduction in total mortality, versus clopidogrel plus aspirin, but event rates remain high, and major bleeding not related to coronary artery bypass grafting is increased. The novel P2Y12 antagonist elinogrel, available in intravenous and oral formulations, may have a more favorable benefit-to-risk profile than existing agents in this class because of reversible and competitive binding to the P2Y12 receptor. Inhibition of PAR-1 is an attractive, novel approach in antiplatelet therapy because it may provide incremental ischemic protection without increasing bleeding. The PAR-1 antagonist vorapaxar (SCH 530348) has been associated with favorable efficacy and safety in phase 2 trials. Two phase 3 trials are evaluating the efficacy and safety of vorapaxar in patients presenting with non–ST-segment elevation acute coronary syndromes and in patients with documented atherothrombotic disease.
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