- Participants hospitalized with acute coronary syndrome (ACS) [unstable angina (UA), non-ST elevation myocardial infarction (NSTEMI), or ST elevation myocardial infarction (STEMI)] as determined by the investigator, and who are anticipated to undergo percutaneous coronary intervention (PCI) as a treatment for the ACS event within 24 hours of the clopidogrel/placebo loading dose