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Background/purpose: Pharmacogenetics is a potential driver of the "East Asian paradox," in which East Asian acute coronary syndrome (ACS) patients receiving dual antiplatelet therapy (DAPT) with clopidogrel following percutaneous coronary intervention (PCI) demonstrate higher levels of platelet reactivity on treatment than Western patients, yet have lower ischemic risk and higher bleeding risk at comparable doses. However, the impact of pharmacogenetics, particularly regarding CYP2C19 genotype, on the pharmacodynamics of P2Y12 inhibitors has not been extensively studied in Taiwanese ACS patients as yet., Methods: CYP2C19 genotyping and pharmacogenetic analysis was conducted on 102 subjects from the Switch Study, a multicenter, single-arm, open-label intervention study that examined the effects on platelet activity and clinical outcomes of switching from clopidogrel (75 mg daily) to low-dose prasugrel (3.75 mg daily) for maintenance DAPT after PCI in 203 Taiwanese ACS patients., Results: Genotyping results revealed that 43.1% were CYP2C19 extensive metabolizers (EM), while 56.9% were reduced metabolizers (RM). After switching to prasugrel, mean P2Y12 reaction units (PRU) values were significantly reduced in both EM and RM populations, while the proportion of high on-treatment platelet reactivity (HPR) patients significantly declined in RM patients. No increase in bleeding risk after switching was observed during follow-up. Multivariate analysis indicated that for RM patients, low estimated glomerular filtration rate (eGFR) and low hemoglobin were associated with greater HPR risk on clopidogrel, but not after switching to prasugrel., Conclusion: Switching to low-dose prasugrel from clopidogrel reduced mean PRU levels and proportion of HPR patients, with more significant reduction in RM patients., Competing Interests: Declaration of competing interest ST, WCY, and LCC are employees of Daiichi Sankyo. WLL served as chair of a meeting sponsored by Daiichi Sankyo. FYK, CHL, WRL, CHS, WLL, YCW, WSL, PHC, TML, PHL, CLH, WHY, and PYL received study funding from Daiichi Sankyo., (Copyright © 2022 Formosan Medical Association. Published by Elsevier B.V. All rights reserved.)

The recommended maintenance dose of prasugrel for East Asian populations (i.e., Japanese and Taiwanese) is 3.75 mg as part of dual antiplatelet therapy (DAPT) for the prevention of recurrent ischemia and stent thrombosis in acute coronary syndrome (ACS). This modified dosage regimen has been established in studies conducted in Japan; however, the efficacy and safety of switching from clopidogrel to prasugrel DAPT among Taiwanese patients remain to be explored. In this phase IV, multicenter, single-arm, open-label study, we evaluated the 4-week pharmacodynamic response, and the 48-week safety outcomes of prasugrel 3.75 mg after a switch from clopidogrel in Taiwanese ACS patients. A total of 203 prasugrel-naïve ACS patients (over 90% male) who had received post-PCI clopidogrel DAPT for at least 2 weeks were enrolled from ten medical centers in Taiwan and subsequently switched to prasugrel 3.75 mg DAPT. Four weeks after the switch, P2Y12 reaction unit (PRU) values were significantly decreased in the total cohort (mean - 18.2 ± 48.1; 95% confidence interval - 24.9 to - 11.5, p < 0.001), and there was an overall consistent antiplatelet response in the treated subjects. The proportion of patients with high on-treatment platelet reactivity (HPR; PRU > 208) dropped from 23.5 to 10% (p < 0.001). Female sex was associated with a greater PRU reduction with prasugrel, whereas HPR at baseline, age ≥ 65 years, and body mass index ≥ 25 best predicted HPR at Week 4. Throughout the 48-week treatment with prasugrel, the incidences of MACE (1.0%) and TIMI major bleeding (2.0%) were rather low, accompanying an acceptable safety profile of TIMI minor (6.4%) and non-major, non-minor clinically relevant bleeding (3.0%). Overall, switching to the maintenance dose of prasugrel (3.75 mg) was observed to be effective and well tolerated among post-PCI ACS patients in Taiwan. Clinical Trial Registration Number: NCT03672097., (© 2021. The Author(s).)

Background: No randomized controlled trials evaluating metformin therapy efficacy in patients with type 2 diabetes mellitus (DM) and acute coronary syndrome (ACS) have been reported. We aimed to examine the mortality benefit of metformin therapy in patients with type 2 DM and ACS, compared with non-metformin anti-diabetes agents users., Methods: Data were extracted from the prospective nationwide ACS-DM Taiwan Society of Cardiology registry. Propensity score (PS) matching on baseline characteristics and treatment measures was performed for metformin versus non-metformin users. The Cox proportional hazards model was used to compare mortality outcomes among the PS-matched cohort as the primary analysis. The Cox proportional hazards models adjusting for all pre-determined covariates and quintiles of the PS among the overall population were performed as the secondary analyses., Results: Of 1157 patients with type 2 DM and ACS receiving anti-diabetes agents, 78 patients (6.7%) died over the 2-year follow-up period. After PS matching, 318 metformin users were matched with 318 non-metformin users. Metformin users had a lower all-cause mortality rate (adjusted hazard ratio [aHR] 0.50, 95% confidence interval [CI] 0.26-0.95) in the primary analysis. The survival benefit of metformin therapy was consistent in the secondary analyses (aHR 0.30, 95% CI 0.17-0.54 while adjusting for all pre-determined covariates, and aHR 0.34, 95% CI 0.19-0.59 while adjusting for quintiles of the PS)., Conclusions: Among patients with type 2 DM and ACS, metformin was associated with lower all-cause mortality. However, a detrimental effect of any of the comparators could not be excluded., (Copyright © 2019 Elsevier B.V. All rights reserved.)