Original ArticleImpact of Continuous P2Y12 Inhibition Tailoring in Acute Coronary Syndrome and Genetically Impaired Clopidogrel AbsorptionSamardzic, Jure MD, PHD*; Bozina, Nada MD, PHD†; Skoric, Bosko MD, PHD*; Ganoci, Lana MMedBiochem†; Krpan, Miroslav MD*; Petricevic, Mate MD, PhD‡; Pasalic, Marijan MD*; Bozina, Tamara PhD§; Pavasovic, Sasa MD*; Cikes, Maja MD, PHD*; Milicic, Davor MD, PHD*Author Information *Departments of Cardiovascular Diseases; †Laboratory Diagnostics; and ‡Cardiac Surgery, School of Medicine, University Hospital Center Zagreb, University of Zagreb, Zagreb, Croatia; and §Department of Medical Chemistry, Biochemistry and Clinical Chemistry, School of Medicine, University of Zagreb, Zagreb, Croatia. Reprints: Sasa Pavasovic, MD, Department for Cardiovascular Diseases, School of Medicine, University Hospital Center Zagreb, University of Zagreb, Kispaticeva 12, 10000 Zagreb, Croatia (e-mail: email@example.com). This study was funded by Croatian Ministry of Science, Education and Sports. The authors report no conflicts of interest. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. Received June 25, 2019 Accepted September 23, 2019 Journal of Cardiovascular Pharmacology: February 2020 - Volume 75 - Issue 2 - p 174-179 doi: 10.1097/FJC.0000000000000767 Buy Metrics Abstract Clopidogrel is still widely used in acute coronary syndrome despite the development of more potent P2Y12 inhibitors. Previously, we conducted a trial that evaluated serial clopidogrel dose adjustment based on platelet function testing in acute coronary syndrome patients with initial high on-treatment platelet reactivity (HTPR). In this substudy, we performed post hoc analysis of the effect of ABCB1 genetic variants C3435T and G2677T/A on platelet inhibition and outcomes. There were no differences in the proportion of HTPR patients among C3435T carriers and noncarriers in both interventional and control group. G2677T carriers expressed significantly higher proportion of HTPR pattern throughout 12-month follow-up in the control group with no difference in the interventional group. There was no difference in ischemic outcomes between C3435T and G2677T carriers and noncarriers in both groups of patients. The results indicate that ABCB1 genotyping is not useful to guide clopidogrel therapy tailoring to improve high-risk patient management. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.