Abstract 12498: Antiplatelet Effects of Ticagrelor versus Clopidogrel in Native American Patients With Stable Coronary Artery Disease

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Introduction: Ticagrelor is a potent, reversibly binding, P2Y12 platelet inhibitor that, compared with clopidogrel, decreased the rate of myocardial infarction and vascular mortality in acute coronary syndrome. Although Native Americans have the highest death rate attributable to premature heart disease among all races, they are generally under-represented in clinical trials. Hypothesis: Native Americans with stable CAD on low dose aspirin administered with ticagrelor, compared with clopidogrel, will exhibit a faster onset and higher platelet inhibition, and maintain this difference on day 7 of the treatment. Methods: Single center, randomized, open-label, crossover study of Native Americans with stable CAD randomly allocated to either ticagrelor (180 mg loading dose [LD] and 90 mg twice daily maintenance dose [MD] for 7-9 days) or clopidogrel (600 mg LD and 75mg once daily MD for 7- 9 days), and then received the alternative P2Y 12 inhibitor after a washout period. All patients received aspirin 81 mg daily. Platelet reactivity was measured with the VerifyNow P2Y 12 assay, which reports results in P2Y 12 reaction units (PRU). Results: A total of 28 patients were evaluated. At 30 minutes after the LD, on-treatment reactivity after ticagrelor (mean ± standard error of mean) was 205 ± 53 compared with 275 ± 71 PRU after clopidogrel ( P <0.001) (Figure 1). At 2 hours after the LD, on-treatment reactivity was 36 ± 52 and 225 ± 71 PRU for ticagrelor and clopidogrel, respectively ( P <0.001). At 8 hours after last MD, on-treatment reactivity was 40 ± 36 with ticagrelor compared with 197 ± 78 PRU with clopidogrel ( P <0.001). At 24 hours after last MD residual reactivity was 140 + 55 for ticagrelor and 192 + 58.3 PRU for clopidogrel ( P <0.001). No significant adverse events were noted with either study drug. Conclusions: In Native Americans with stable CAD on low dose ASA, ticagrelor provided a significantly faster onset, greater extent of platelet inhibition and faster offset than clopidogrel.

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