Aspirin 50mg vs 100mg Combined With P2Y12 Inhibitor After PCI

Background Dual antiplatelet therapy (DAPT) - aspirin combined with a P2Y12 inhibitor - is the standard of care to prevent stent thrombosis and ischemic events after PCI. However, the optimal aspirin dose in combination with modern P2Y12 inhibitors remains undefined, especially in Chinese populations. Current practice widely uses 100 mg daily aspirin, but pharmacological and clinical evidence suggests that lower doses may achieve comparable antiplatelet effect with a lower bleeding risk.

Study Design This is a multicenter, randomized, open-label, active parallel-controlled non-inferiority trial. Enrollment will include 2640 adults with acute or chronic coronary syndrome who have undergone successful PCI and are scheduled for at least 12 months of DAPT. Randomization will be stratified by study center with a 1:1 allocation ratio.

Treatment Regimens

* Experimental group: enteric-coated aspirin 50 mg once daily + a P2Y12 inhibitor
* Control group: enteric-coated aspirin 100 mg once daily + a P2Y12 inhibitor The choice of P2Y12 inhibitor (ticagrelor or clopidogrel) is at the treating physician's discretion based on patient characteristics and clinical guidelines. DAPT will be maintained for a minimum of 12 months.

Outcome Assessment All suspected endpoint events will be independently adjudicated by a blinded Clinical Endpoint Committee according to standardized international definitions. A Data Monitoring Committee will periodically review safety data and study conduct.

Follow-up visits are scheduled at 1 month, 6 months, and 12 months after randomization, including clinical assessment, medication adherence evaluation, and event verification.

• Aspirin (Drug), also known as Acetylsalicylic Acid: Enteric-coated aspirin for oral administration, once daily. Two dose levels are studied: 50 mg in the experimental arm and 100 mg in the active comparator arm.
• P2Y12 inhibitor (Drug), also known as Ticagrelor, Clopidogrel: Background antiplatelet therapy used in both study arms. Either ticagrelor 90 mg orally twice daily or clopidogrel 75 mg orally once daily, prescribed at the treating physician's discretion according to clinical guidelines.

Primary outcomes

• Incidence of Major Adverse Cardiac and Cerebrovascular Events (MACCE) [12 months after randomization]: Composite endpoint including cardiovascular death, non-fatal myocardial infarction, definite or probable stent thrombosis, and ischemic stroke, independently adjudicated by a blinded clinical endpoint committee.

Secondary outcomes

• Incidence of Clinically Relevant Bleeding Events [12 months after randomization]: Bleeding events classified by the Bleeding Academic Research Consortium (BARC) criteria, including BARC grade 2, 3 and 5.
• Net Adverse Clinical Events (NACE) [12 months after randomization]: Composite of all-cause death, myocardial infarction, ischemic stroke and major bleeding.

Sex: All, ages: 18 Years to 85 Years

Inclusion Criteria:

* Aged 18 to 85 years at the time of screening
* Diagnosed with acute coronary syndrome (ACS) or chronic coronary syndrome (CCS)
* Has undergone successful percutaneous coronary intervention (PCI) with stent implantation
* Planned to receive at least 12 months of dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor after PCI
* Able to provide written informed consent and comply with study follow-up requirements

Exclusion Criteria:

* Known hypersensitivity or contraindication to aspirin, P2Y12 inhibitors, or related excipients
* High bleeding risk: history of intracranial hemorrhage, gastrointestinal bleeding within 6 months, active bleeding diathesis, or coagulopathy
* Severe hepatic dysfunction (Child-Pugh class C) or severe renal impairment (eGFR < 30 mL/min/1.73 m²)
* Ischemic or hemorrhagic stroke within 3 months before enrollment
* Pregnant or lactating women; women of childbearing potential unwilling to use effective contraception
* Life expectancy < 12 months due to other severe comorbidities such as advanced malignancy
* Participation in another interventional clinical trial within 30 days before screening
* Any other condition judged by the investigator to make the patient unsuitable for the study

• Patrono C, Ciabattoni G, Patrignani P, Pugliese F, Filabozzi P, Catella F, Davi G, Forni L. Clinical pharmacology of platelet cyclooxygenase inhibition. Circulation. 1985 Dec;72(6):1177-84. doi: 10.1161/01.cir.72.6.1177. PMID 3933848
• Patrono C, Garcia Rodriguez LA, Landolfi R, Baigent C. Low-dose aspirin for the prevention of atherothrombosis. N Engl J Med. 2005 Dec 1;353(22):2373-83. doi: 10.1056/NEJMra052717. No abstract available. PMID 16319386
• Davi G, Patrono C. Platelet activation and atherothrombosis. N Engl J Med. 2007 Dec 13;357(24):2482-94. doi: 10.1056/NEJMra071014. No abstract available. PMID 18077812