Inclusion Criteria1. Provision of informed consent.
2. Female or male aged≥ 40 years and ＜80 years.
3. Acute non-disabling ischemic stroke (NIHSS≤ 3 at the time of randomization) that can be treated with study drug within 24 hours of symptoms onset defined by the"last see normal"principle.
4. TIA (Neurological deficit attributed to focal brain ischemia, with resolution of the deficit within 24 hours of symptom onset), that can be treated with study drug within 24 hours of symptoms onset and with moderate-to-high risk of stroke recurrence (ABCD2 score ≥ 4 at the time of randomization or the stenosis of offending vessel ≥ 50%).
Exclusion Criteria1. Diagnosis of hemorrhage or other pathology, such as vascular malformation, tumor, abscess or other major non-ischemic brain disease (e.g., multiple sclerosis) on baseline head Computed Tomography (CT) or magnetic resonance imaging (MRI).
2. Isolated or pure sensory symptoms (e.g., numbness), isolated visual changes, or isolated dizziness/vertigo without evidence of acute infarction on baseline head CT or MRI.
3. Modified Rankin Scale Score > 2 at randomization (pre-morbid historical assessment)。
4. Contraindication to ticagrelor, clopidogrel or acetylsalicylic acid :
- Known hypersensitivity
- Severe renal or hepatic insufficiency
- Severe cardiac failure, asthma
- Hemostatic disorder or systemic bleeding
- History of hemostatic disorder or systemic bleeding
- History of drug-induced hematologic or hepatic abnormalities
- Low white blood cell (<2 x10^9/L) or platelet count (<100 x10^9/L)
5. Clear indication for anticoagulation (presumed cardiac source of embolus, e.g., atrial fibrillation, ventricular aneurysm, prosthetic cardiac valves known, suspected endocarditis or other suspicion of cardioembolic pathology for TIA/stroke).
6. Continuous use of ticagrelor or clopidogrel over 5 days before randomization
7. Current treatment (last dose given within 10 days before randomization) with heparin therapy or anti coagulation therapy (e.g., warfarin; thrombin inhibitors such as dabigatran , argatroban, bivalirudin, ximelagatran; factor Xa inhibitors such as rivaroxaban, edoxaban, apixaban, betrixaban, tanexaban ; hirudin; unfractionated and low molecular weight heparins ).
8. Receipt of intravenous/ intra-arterial thrombolysis or mechanical thrombectomy within 24 hours prior to randomization.
9. History of intracranial hemorrhage or cerebral artery amyloidosis.
10. History of aneurysm (including intracranial aneurysm or peripheral aneurysms)
11. Diagnosis or of acute coronary syndrome.
12. History of asthma or COPD (chronic obstructive pulmonary disease).
13. High risk of bradyarrhythmia, such as sick sinus syndrome second-degree or third-degree atrioventricular block, bradycardia-related syncope without installed pacemaker.
14. History of uric acid nephropathy.
15. Anticipated requirement for long-term (>7 days) non-study anti-platelet drugs, or NSAIDs (nonsteroidal antiinflammatory drugs) affecting platelet function.
16. History of previous symptomatic non-traumatic intracerebral bleed at any time (asymptomatic microbleeds do not qualify), gastrointestinal (GI) bleed within the past 3 months, or major surgery within 30 days.
17. Qualifying TIA or minor stroke induced by angiography or surgery.
18. Planned or likely revascularization within the next 3 months.
19. Scheduled for surgery or interventional treatment requiring study drug cessation.
20. Severe non-cardiovascular comorbidity with life expectancy < 3 months.
21. Pregnancy or lactation, and women of childbearing age not practicing reliable contraception who do not have a documented negative pregnancy test.
22. Currently receiving an investigational drug or device.
23. Participation in another clinical study with an investigational product during the last 30 days.
24. Inability of the patient to understand and/or comply with study procedures and/or follow-up, in the opinion of the Investigator.
25. Hematocrit (Hct) < 30%