A pharmacodynamic study of the optimal P2Y12 inhibitor regimen for East Asian patients with acute coronary syndrome

Background/Aims: Newer $P2Y_{12}$ inhibitors, such as prasugrel and ticagrelor, have greater antiplatelet efficacy but may increase the risk of bleeding. In this study, we compared the pharmacodynamic efficacy of prasugrel and ticagrelor in East Asian patients with acute coronary syndrome (ACS). Methods: We selected 83 ACS patients undergoing percutaneous coronary intervention who were discharged with 90 mg ticagrelor twice daily (n = 24), 10 mg prasugrel daily (n = 39) or 5 mg prasugrel daily (n = 20). After 2 to 4 weeks, on-treatment platelet reactivity (OPR) was assessed in terms of $P2Y_{12}$ reaction units (PRUs) using the VerifyNow $P2Y_{12}$ assay (Accumetrics). We compared East Asian ($85<PRU{\leq}275$) and Caucasian ($85<PRU{\leq}208$) criteria for assessing the therapeutic window of OPR. Results: OPR was lowest in the ticagrelor group, followed by the 10 mg prasugrel and 5 mg prasugrel groups ($49.1{\pm}29.9$ vs. $83.7{\pm}57.1$ vs. $168.5{\pm}60.8$, respectively; p < 0.001). The 5 mg prasugrel group had the highest proportion of patients with OPR values within the therapeutic window, followed by the 10 mg prasugrel and ticagrelor groups (90.0% vs. 46.2% vs. 12.5%, respectively; p < 0.001 for East Asian criteria; 60.0% vs. 43.6% vs. 12.5%, respectively; p < 0.001 for Caucasian criteria). Conclusions: Short-term administration of 5 mg prasugrel facilitated maintenance within the therapeutic window of OPR compared with the 10 mg prasugrel and ticagrelor groups. Thus, 5 mg prasugrel daily may be the optimal antiplatelet regimen for stabilized East Asian ACS patients.