Pharmacodynamic effects of cangrelor on platelet P2Y12 receptor-mediated signaling in prasugrel-treated patients.

OBJECTIVES The purpose of this study was to assess the in vitro P2Y12 receptor inhibitory effects of cangrelor on platelets from patients on maintenance prasugrel therapy treated with 2 reloading dose regimens. BACKGROUND Despite its more potent and rapid antiplatelet effects compared with clopidogrel, recent studies have shown variability in prasugrel-mediated P2Y12 receptor inhibition, particularly in high-risk settings. Cangrelor is a potent intravenous P2Y12 receptor inhibitor. METHODS A total of 60 patients with coronary artery disease on maintenance prasugrel (10 mg/day) therapy were randomized to a 30- or 60-mg reload of prasugrel. The platelet reactivity index (PRI), as assessed by whole-blood vasodilator-stimulated phosphoprotein, was measured with and without in vitro incubation of cangrelor (500 nM) at baseline, and at 1 and 4 h after reload. RESULTS In the absence of cangrelor, prasugrel reloading reduced PRI (p < 0.001 for both doses), although a 60-mg reload had greater platelet inhibition compared with a 30-mg reload at 4 h (p = 0.001). Cangrelor was associated with a reduction in PRI values during the overall study time course in patients reloaded with 30 mg (p = 0.001) and 60 mg (p < 0.001) of prasugrel. In patients reloaded with 30 mg prasugrel, cangrelor decreased PRI at each time point (baseline, p < 0.001; 1 h, p = 0.013; 4 h, p = 0.001). In patients reloaded with 60 mg prasugrel, cangrelor decreased PRI at baseline (p < 0.001) and 1 h (p = 0.002); levels of platelet reactivity comparable to those achieved with cangrelor were observed only at 4 h (p = 0.325). The intergroup comparisons with cangrelor were not significant at any time point. CONCLUSIONS In patients on maintenance prasugrel therapy exposed to a reloading dose (30 or 60 mg) of prasugrel, in vitro cangrelor is associated with further platelet P2Y12 receptor inhibitory effects.