Prasugrel Switching Study in Patients With Acute Coronary Syndrome (ACS) Who Underwent Percutaneous Coronary Intervention (PCI)

Inclusion Criteria: * Is within the age limits and has signed informed consent * Weighs at least 50 kg * Had a previous diagnosis of ACS (UA, STEMI, or NSTEMI), underwent PCI, and received one of the following treatments: * Clopidogrel MD of 75 mg and aspirin 81-100 mg for 2-8 weeks following clopidogrel loading dose (LD) of 300 mg or 600 mg at the time of PCI * Ticagrelor MD of 90 mg twice daily (BID) and aspirin 81-100 mg for 1-4 weeks and switching to clopidogrel MD of 75 mg and aspirin 81-100 mg for 2-4 weeks following ticagrelor LD of 180 mg at the time of PCI * Clopidogrel MD 75 mg and aspirin 81-100 mg for 2-8 weeks following ticagrelor LD of 180 mg at the time of PCI * Or based on investigator's judgment with at least 2 weeks continued use of clopidogrel MD and aspirin 81-100 mg per day before switching to prasugrel and maximum 8 weeks P2Y12 inhibitors MD treatment (prasugrel is not allowed) * Is willing and able to abide by the rules of the research unit and study restrictions * If a woman of child-bearing potential, has a negative serum pregnancy test at screening * Agrees to use at least one method of contraception during the study Exclusion Criteria: * Has active bleeding, significant risk of hemorrhage, or unusual susceptibility to bleed * Had previous hemorrhagic stroke at any time, or transient ischemic attack (TIA) or ischemic stroke within 3 months before the informed consent date * Has known allergies or hypersensitivity to prasugrel, aspirin, or any of their excipients * Has significant hypertension at screening or baseline assessment * Has hemoglobin levels \<10.5 g/dL or hematocrit levels \<30% * Has severe left ventricular systolic dysfunction, ejection fraction \<30% * Is currently undergoing hemodialysis * Has evidence of severe hepatic disease or any of the following: serum alanine transaminase or aspartate transaminase ≥3 times the upper limit of normal (ULN); or bilirubin ≥2 times the ULN at screening * Has any clinical laboratory result performed at screening that is determined to be detrimental to the patient or could compromise the study as determined the Investigator * Has previously participated in this study or in another interventional trial that is not compatible with this study * Has evidence of significant active neuropsychiatric disease, alcohol abuse or drug abuse as determined by the Investigator