Clinical impact of genetically determined platelet reactivity

Dual antiplatelet therapy with aspirin and clopidogrel dramatically reduced the rate of major adverse cardiac events following percutaneous coronary intervention. Clopidogrel is a prodrug which requires a two-step hepatic biotransformation thanks to the cytochrome P450 (CYP450) enzyme system. Genetic polymorphism of CYP450 system (e.g., CYP2C19*2) responsible for altered clopidogrel metabolism is a major cause of high on-treatment platelet reactivity (HTPR), which translates into thrombotic events in stented patients. Studies demonstrated that HTPR could be overcome in poor metabolizers thanks to increased loading doses or maintenance doses of clopidogrel or with the use of more potent antiplatelet agents such as prasugrel. Other genetic polymorphisms have also been correlated with HTPR: ABCB1, ATP2B2, and TIAM2. Large-scale randomized trials with clinical endpoints remain necessary to determine the optimal antiplatelet therapy in patients carrying genetic polymorphism associated with HTPR and thrombotic events.