The purpose of this study is to evaluate that milvexian is superior to placebo, in addition to standard-of-care, in reducing the risk of major adverse cardiovascular event (MACE) (the composite of cardiovascular [CV] death, myocardial infarction [MI], and ischemic stroke).

Inclusion Criteria:

• Participants must have an index event that meets all 3 of the following criteria within 7 days prior to randomization: a) clinical syndrome consistent with spontaneous cardiac ischemia, b) diagnosis of acute coronary syndrome (ACS) (that is, ST-elevation myocardial infarction [STEMI], non-STEMI, or unstable angina [UA]), c) cardiac biomarker elevation (example, troponin I, troponin T, creatine kinase-MB [CK-MB]) above the upper limit of normal as determined by the local laboratory
• Participants must have at least 2 of the following risk factors:a) age 65 or older, b) diabetes mellitus, c) history of a prior myocardial infarction (MI) (other than index ACS event), d) multivessel coronary artery disease (CAD), e) history of coronary artery bypass graft (CABG) surgery prior to index ACS event, f) history of peripheral artery disease (PAD) or cerebrovascular disease (example, carotid atherosclerosis, intracranial artery stenosis, g) conservative management (that is, no percutaneous intervention [PCI] or CABG after index ACS event), h) Any one or more of the following high-risk angiographic features i) total stent length of greater than (>) 30 millimeters (mm), ii) thrombotic target lesion, iii) bifurcation lesion treated with more than one stent, iv) calcified target lesion treated with atherectomy, v) treatment of obstructive left main or proximal left anterior descending artery for index ACS (or clinical diagnosis of an anterior STEMI)
• All female participants of childbearing potential must have a negative highly sensitive serum beta-human chorionic gonadotropin (hCG) or urine test at screening
• A female participant must not be pregnant, breastfeeding, or planning to become pregnant until 4 days (5 half-lives) after the last dose of study intervention

Exclusion Criteria:

• MI secondary to ischemia due to either increased oxygen demand or decreased supply (Type 2 MI) or periprocedural MI as the index ACS event
• Planned CABG or staged PCI after randomization
• Any condition that requires chronic anticoagulation at the discretion of the investigator and/or local guidelines
• Conditions with a significant increased risk of bleeding (example, clinically significant bleeding within previous 3 months, known bleeding diathesis, et cetera)

The data sharing policy of the Janssen Pharmaceutical Companies of Johnson & Johnson is available at www.janssen.com/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at yoda.yale.edu