Pharmacodynamic Effects of Switching From Prasugrel to Ticagrelor: Results of the Prospective, Randomized SWAP-3 Study.

OBJECTIVES This study sought to assess the pharmacodynamic (PD) effects of switching to ticagrelor patients who were treated with prasugrel after undergoing percutaneous coronary intervention in the setting of an acute coronary syndrome. BACKGROUND In clinical practice, there is a frequent need to switch between P2Y12 receptor inhibitors. However, concerns on drug interactions have emerged when switching therapies. To date, the PD effects of switching from prasugrel to ticagrelor have yet to be investigated. METHODS This was a prospective, randomized, open-label, 3-arm, parallel-design study conducted in patients (n = 82) on maintenance dual antiplatelet therapy with aspirin (81 mg QD) and prasugrel (10 mg QD). Patients were randomized to continue prasugrel 10 mg QD or switch to ticagrelor 90 mg bid, with or without a 180 mg loading dose (LD), for 1 week. PD assessments included P2Y12 reaction units (PRU) by VerifyNow, platelet reactivity index by vasodilator-stimulated phosphoprotein (VASP), and platelet aggregation by light transmittance aggregometry (LTA) at a total of 6 time points: baseline, 2 h, 4 h, 24 h, 48 h, and 1 week after randomization. RESULTS After switching to ticagrelor, PRU levels decreased as early as 2 h after drug administration. Mean PRU levels remained low during the study time course, without evidence of drug interactions. The primary endpoint of noninferiority of ticagrelor (2 arms combined) versus prasugrel measured by PRU at 1 week was met (least squares mean difference: -18; 95% confidence interval: -41 to 5). There was no increase in rates of high on-treatment platelet reactivity (PRU >208), which were overall very low throughout the study time course. Similar levels of platelet reactivity were observed irrespective of the use of a ticagrelor LD. Parallel findings were observed with VASP and LTA. CONCLUSIONS Switching from prasugrel to ticagrelor leads to transiently higher levels of platelet inhibition, irrespective of the use of a LD, without evidence of drug interactions. (Pharmacodynamic Evaluation of Switching From Prasugrel to Ticagrelor [SWAP3]; NCT02016170).