Prasugrel (CS-747; LY-640315) is a novel, third-generation oral thienopyridine that is a specific, irreversible antagonist of the platelet adenosine 5'-diphosphate P2Y(12) receptor. Laboratory results with prasugrel support more potent antiplatelet effects, a lower incidence of interpatient variability in antiplatelet response, and a reduced time to onset of antiplatelet activity compared with clopidogrel. Phase II results indicate that prasugrel produces a greater antiplatelet effect than clopidogrel administered even at doses higher than the currently approved 300-mg loading dose and 75-mg/d maintenance dose. Recent phase III data show that prasugrel is superior to clopidogrel in preventing ischemic events in patients with acute coronary syndrome undergoing percutaneous coronary intervention, although this was associated with a greater risk of bleeding.