Merck announced the completion of patient enrollment for its Phase 3 Thrombin Receptor Antagonist in Secondary Prevention of Atherothrombotic Ischemic Events (TRA 2˚P-TIMI 50) trial, one of its two Phase 3 studies of SCH 530348 for the treatment of acute coronary syndrome (ACS). TRA 2˚P-TIMI 50 is a randomized, double-blind, placebo-controlled study evaluating more than 26,000 patients with prior MI or stroke, as well as patients with existing peripheral arterial disease. Patients have been randomized to either placebo plus standard medical care (including aspirin and clopidogrel) or to SCH 530348 as a 2.5mg once daily maintenance dose plus standard medical care. The primary endpoint of the trial is the composite of cardiovascular death, MI, urgent coronary revascularization or stroke. The key secondary endpoint is the composite of cardiovascular death, MI or stroke. Patients will be followed for a minimum of one year.

The second trial, Phase 3 Thrombin Receptor Antagonist Clinical Event Reduction in acute coronary syndrome (TRA-CER), is a randomized, double-blind, placebo-controlled study in patients with non-ST-segment elevation acute coronary syndrome. Patients are being randomized to either placebo plus standard medical care (including aspirin or clopidogrel) or to SCH 530348 plus standard medical care. The Phase 3 TRA-CER trial uses the oral 40 mg loading dose and the 2.5 mg maintenance dose. The primary endpoint of the Phase 3 TRA-CER trial is the composite of cardiovascular death, MI, rehospitalization for ACS, urgent coronary revascularization or stroke. The key secondary endpoint is the composite of cardiovascular death, MI or stroke.

SCH 530348 is a member of a potentially new class of drugs called PAR-1 inhibitors that bind selectively to the thrombin receptor on platelets. It is being investigated to determine whether it has the potential to provide clinical benefit through inhibition of this thrombin-mediated platelet activation without the liability of significantly increased major bleeding (when added to aspirin or aspirin plus an ADP inhibitor), a tendency associated with drugs that block thromboxane or ADP pathways. Specifically, this compound is being investigated as an oral antiplatelet agent for patients with established vascular disease, to evaluate whether it can provide incremental benefit when given with current standard antiplatelet (including aspirin and clopidogrel) and other antithrombotic therapies, without causing a significant increase in major bleeding.

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