Abstract 12333: Therapeutic Window of Low-Dose Prasugrel for Platelet Reactivity in the Chronic Phase of Post-Percutaneous Coronary Intervention: The Chaperon Study

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Introduction: There are many reports on the effects of on-treatment platelet reactivity using P2Y 12 reaction units (PRU) on the ischemic or bleeding risk in patients who underwent percutaneous coronary intervention (PCI). However, there was little report including low-dose prasugrel (2.5mg). Hypothesis: We assumed that low-dose prasugrel use may contribute to the effectiveness and safety in the chronic phase of PCI in Japanese patients. Methods: This prospective observational study included 398 patients who underwent PCI between 2017 and 2018 (mean age: 68±11 years, male: 83%). Serial PRU measurements were performed; the baseline was at 6 to 12 months after PCI, and the follow-up was after 6 months later. The PRU was measured by the VerifyNow® P2Y 12 assay, and we assessed the distribution of PRU in each P2Y 12 inhibitor, after defined PRU 86 to 238 as therapeutic window. Results: Among 398 patients, the follow-up PRU was obtained in 360 patients (90%), and 80 patients (22%) were taking prasugrel 2.5mg. The baseline PRUs of clopidogrel 75mg, prasugrel 3.75mg, and prasugrel 2.5mg were 175±64, 147±55, and 154±66, respectively ( p <0.001), and the portions of PRU ≤239 (ischemic risk) were 14.6%, 4.4%, and 9.5%, respectively ( p =0.007). At the time of follow-up, a statistically significant trend of PRU was revealed in 24 patients changed clopidogrel 75mg to prasugrel 2.5mg (baseline vs. follow-up: 183±64 vs. 149±43, p =0.037). Regarding distribution of PRU, prasugrel 2.5mg was less frequent in PRU ≤85 (bleeding risk) compared to prasugrel 3.75mg (7.5% vs. 21.0%, p =0.019). In addition, a multivariable logistic regression analysis revealed that prasugrel 2.5mg use was an independent predictor of therapeutic window (odds ratio: 2.15; 95% confidence intervals: 1.01-4.59, p =0.044). Conclusions: We found prasugrel 2.5mg use after PCI significantly associated with therapeutic window. Thus, we believe low dose prasugrel use may contribute to the future risk reduction after PCI.