Effects of ticagrelor versus clopidogrel in troponin-negative patients with low-risk ACS undergoing ad hoc PCI

Background Many low-risk acute coronary syndrome (ACS) patients are not pre-treated with a P2Y₁₂ receptor inhibitor, and percutaneous coronary interventions (PCIs) are often performed on an ad hoc basis in this population. Pharmacodynamic (PD) studies comparing ticagrelor versus clopidogrel in patients undergoing ad hoc PCI are lacking. Objectives This study sought to assess PD effects of ticagrelor versus clopidogrel loading dose (LD) in the peri-procedural period among troponin-negative ACS patients undergoing ad hoc PCI. Methods This was a prospective, open-label, randomized, multicenter, parallel-group, phase IV PD study. One hundred P2Y₁₂ inhibitor-naïve patients presenting with biomarker-negative ACS and undergoing ad hoc PCI, on a background of aspirin therapy, were randomized to receive either ticagrelor 180 mg LD or clopidogrel 600 mg LD. Platelet reactivity (P2Y₁₂ reaction units [PRU]; VerifyNow assay) was measured at 5 time points: pre-LD, at 0.5, 2, and 8 h post-LD, and at end of PCI. The primary endpoint was PRU levels 2 h post-LD; secondary endpoints included PRU levels at all other time points and inhibition of platelet aggregation; an exploratory analysis evaluated rates of high on-treatment platelet reactivity (HPR) (PRU >208). Results At 2 h, PRU levels were significantly lower with ticagrelor versus clopidogrel (98.4 ± 95.4 vs. 257.5 ± 74.5; p < 0.001; primary endpoint). PRU levels diverged as early as 0.5 h post-LD, with significant differences observed by the end of PCI (mean 0.6 h post-LD) and maintained up to 8 h post-LD. HPR rates were also significantly reduced with ticagrelor compared with clopidogrel at the end of PCI (p = 0.030), and at 2 h (p < 0.001) and 8 h (p < 0.001) after LD. Conclusions In low-risk ACS patients undergoing ad hoc PCI, ticagrelor LD provides more prompt and potent platelet inhibition, and lower HPR rates, compared with clopidogrel LD.