Pharmacodynamic Comparison of Prasugrel Versus Ticagrelor in Patients With CYP2C19 Loss-of-function Genotype: a Validation Study in Patients With Stable Coronary Artery Disease

Therapeutic inhibition of platelet activation is essential for the management of ischemic cardiovascular disease. The use of platelet adenosine diphosphate (ADP) P2Y12 receptor antagonists (clopidogrel, prasugrel, and ticagrelor) in addition to aspirin are associated with a decrease in cardiovascular events in high-risk coronary artery disease (CAD) patients. Clopidogrel is the most broadly utilized P2Y12 receptor antagonist. However, among clopidogrel treated patients, there is broad variability in antiplatelet drug response which is known carry prognostic implications. Polymorphisms of the cytochrome P450 (CYP) 2C19 enzyme has been consistently shown to modulate clopidogrel response. Accordingly, the Food and Drug Administration (FDA) has issued a warning on the potential for reduced efficacy of clopidogrel among carriers of loss-of-function alleles (LOF) for CYP2C19 and suggest considering alternative antiplatelet therapies for these individuals.

The pharmacodynamic (PD) effects of prasugrel and ticagrelor are not affected by CYP2C19 genetic polymorphisms. However, to date there are no head-to-head PD comparisons between these agents among patients with different CYP2C19 genetic polymorphisms which is currently under investigation in CAD patients undergoing PCI at UF Health-Jacksonville (UFJ 2014-12, NCT 02065479). In order to rule out play of chance findings, pharmacogenetic investigations require external validation cohorts to support the study findings. Therefore, the present randomized study is designed to serve as an external validation cohort conducted in patients with established CAD not undergoing PCI testing the non-inferiority in platelet reactivity of prasugrel versus ticagrelor among CYP2C19 LOF allele carriers.