The Switching Antiplatelet-9 (SWAP-9) Study

The purpose of this study is to compare the pharmacodynamic effects of ABCD-GENE guided vs. unguided de-escalation strategies among patients on dual antiplatelet therapy (DAPT) following percutaneous coronary intervention (PCI).

Inclusion Criteria: 1. Patients who have undergone PCI and are on maintenance treatment with DAPT, composed of low-dose aspirin (81mg qd) with either prasugrel (10 mg qd) or ticagrelor (90 mg bid). In particular, patients who underwent PCI in the setting of an acute coronary syndrome will be eligible for randomization after ≥90 days post-PCI, while patients who underwent PCI in the setting of a chronic coronary syndrome ≥30 days post-PCI. 2. Age ≥18 years 3. Provide written informed consent. Exclusion Criteria: 1. Prior history of stent thrombosis 2. PCI within 30 days 3. On treatment with any oral anticoagulant (vitamin K antagonists, dabigatran, rivaroxaban, apixaban, edoxaban) or chronic low-molecular-weight heparin (at venous thrombosis treatment, not for prophylaxis) 4. Hemodynamic instability 5. Hypersensitivity to clopidogrel 6. Known platelet count less than 80x10\^6/mL 7. Known hemoglobin less than 9 g/dL 8. Pregnant and breastfeeding women \[women of childbearing age must use reliable birth control (i.e., oral contraceptives) while participating in the study\].