The study investigated whether early discontinuation of aspirin and switching to monotherapy with a potent P2Y12 inhibitor (ticagrelor or prasugrel) is safe and effective in patients with acute coronary syndromes after successful percutaneous coronary intervention (PCI). Patients were randomly divided 1:1 within 4 days of hospitalization into two groups: P2Y12 monotherapy or dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) for 12 months. The main primary outcomes were the composite endpoint of death from any cause, myocardial infarction, stroke, or urgent target vessel revascularization (tested for non-inferiority at a margin of 2.5 percentage points) and major or clinically relevant non-major bleeding (tested for superiority). P2Y12 monotherapy was non-inferior to dual therapy regarding the composite ischemic endpoint. Bleeding occurred in 33 patients (Kaplan-Meier estimate 2.0%) in the monotherapy group versus 82 patients (4.9%) in the dual group (absolute risk difference -2.97 percentage points; 95% CI -4.20 to -1.73). Stent thrombosis occurred in 12 patients in the monotherapy group and in 4 in the dual group.