Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor, more frequently clopidogrel, represents the standard of care for the long-term secondary prevention of atherothrombotic events in patients with myocardial infarction (MI) or peripheral arterial disease (PAD). However, rates of ischemic recurrences remain high. Vorapaxar is a protease-activated receptor (PAR)-1 inhibitor, which exerts potent inhibition of thrombin-mediated platelet aggregation. Patients with diabetes mellitus (DM) are known to be at increased risk of recurrent atherothrombotic events, which translates into worse outcomes, despite the use of standard of care therapy. This is in part due to the hyperreactive platelet phenotype, which characterizes DM patients, and to inadequate response to oral antiplatelet agents, including clopidogrel. Therefore, vorapaxar is an attractive treatment option for DM patients with a prior MI. The pharmacodynamic (PD) effects of vorapaxar in DM patients and how these may differentiate from non-DM patients has not been explored. Further, the role of vorapaxar as part of a dual antithrombotic treatment regimen combined with clopidogrel (and stopping aspirin) represents another important area of clinical interest. The proposed prospective, parallel-design study conducted in patients post-MI or with PAD with and without DM will aim the assess the pharmacodynamic effects of vorapaxar in addition to standard DAPT with aspirin and clopidogrel as well as in combination with clopidogrel only following aspirin withdrawal.

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor, more frequently clopidogrel, represents the standard of care for the long-term secondary prevention of atherothrombotic events in patients with myocardial infarction (MI) or peripheral arterial disease (PAD). However, rates of ischemic recurrences remain high, in part due to the fact that other platelet signaling pathways, such as thrombin-induced platelet aggregation, continue to be activated. Vorapaxar is a novel, orally active, competitive and slowly reversible protease-activated receptor (PAR)-1 inhibitor, which exerts potent inhibition of thrombin-mediated platelet aggregation. It is approved for clinical use by the Food and Drug Administration for the reduction of thrombotic cardiovascular events in patients with a history of MI or with peripheral arterial disease. Patients with DM are known to be at increased risk of recurrent atherothrombotic events, which translates into worse outcomes, despite the use of standard of care therapy. This is in part due to the hyperreactive platelet phenotype, which characterizes DM patients, and to inadequate response to oral antiplatelet agents, including clopidogrel. Importantly, in DM patients with prior MI included in the TRA 2P trial, vorapaxar reduced the primary composite end point at 3 years by 27% and led to a greater absolute risk reduction compared with those without DM. Therefore, vorapaxar is an attractive treatment option for DM patients with a prior MI. However, to date the PD effects of vorapaxar in DM patients and how these may differentiate from non-DM patients has not been explored. Further, current trends in clinical practice are seeing many patients discontinue aspirin and maintain clopidogrel. Hence, the role of vorapaxar as part of a dual antithrombotic treatment regimen combined with clopidogrel (and stopping aspirin) represents another important area of clinical interest, in order to maximize ischemic protection while reducing the risk of bleeding. The proposed prospective, parallel-design study conducted in patients post-MI or with PAD with and without DM will aim the assess the pharmacodynamic effects of vorapaxar in addition to standard DAPT with aspirin and clopidogrel as well as in combination with clopidogrel only following aspirin withdrawal. Pharmacodynamic assessments will be performed at multiple time point, with different assays exploring multiple pathways of platelet aggregation.

Inclusion criteria:

1. Patients with a prior MI between 2 weeks and 24 months or with PAD.
2. On DAPT with low-dose aspirin (81mg od) and clopidogrel (75mg od) as per standard-of-care for at least 14 days.
3. Age ≥ 18 years old.

Exclusion criteria:

1. History of acute coronary syndrome in the previous 2 weeks.
2. History of stroke, transient ischemic attack, or intracranial hemorrhage.
3. Active pathological bleeding, history of bleeding events or increased risk of bleeding.
4. Known severe hepatic impairment.
5. Use of strong cytochrome P450 3A4 inhibitors (e.g., ketoconazole, itraconazole, posaconazole, clarithromycin, nefazodone, ritonavir, saquinavir, nelfinavir, indinavir, boceprevir, telaprevir, telithromycin and conivaptan) or inducers (e.g., rifampin, carbamazepine, St. John's Wort and phenytoin).
6. On treatment with any oral anticoagulant (vitamin K antagonists, dabigatran, rivaroxaban, apixaban, edoxaban).
7. On treatment with any antiplatelet agent other than aspirin and clopidogrel in the past 14 days.
8. Creatinine clearance <30 mL/minute.
9. Platelet count <80x106/mL
10. Hemoglobin <10g/dL
11. Hemodynamic instability
12. Pregnant females

Two patients were not compliant with medications and therefore excluded from the PD analysis. Thus, a total of 64 patients (DM, n=30; non-DM, n=34) represented the PD population of the study and were analyzed for baseline characteristics and PD data.

Study duration (60 days)