Patient description: A 62-year-old African-American man presented with left upper and lower extremity weakness, associated with dark visual spot in right eye, right facial numbness, facial drop and slurred speech. He denied dyspnea, headache, palpitations, chest pain, fever, dizziness, bowel or urinary incontinence, loss of consciousness. His medical history was significant for hypertension, hyperlipidemia and hypothyroidism. He smokes cigarette 1 pack per day for 40 years and alcohol consumption of 5 to 6 beers per week. He is not aware about his family history. He is using Levothyroxine, Atorvastatin and HTCZ. His vital signs were stable in the primary evaluation. Left-sided facial droop, dysarthria, and left-sided hemiplegia were seen in the physical exam. His National Institutes of Health Stroke Scale (NIHSS) score was calculated as 7. Initial CT angiogram of head and neck reported no acute intracranial findings. Intravenous recombinant tissue plasminogen activator (t-PA) was administered as well as high-dose statin therapy. The patient was admitted to the intensive care unit to be monitored for 24 hours. MRI of the head revealed an acute 1.7-cm infarct of the right periventricular white matter and posterior right basal ganglia.

Clinical trial eligibility criteria: eligible ages (years): 40.0-999.0,  Stroke Transient Ischemic Attack 40 years or older than 40 years； 2. Acute cerebral ischemic event due to： Acute non-disabling ischemic stroke (NIHSS≤3 at the time of randomization)or， TIA with moderate-to-high risk of stroke (ABCD2 score ≥ 4 at the time of randomization)； 3. Can be treated with study drug within 24 hours of symptoms onset*(*Symptom onset is defined by the "last seen normal" principle)； 4. CYP2C19 loss-of-function allele carriers； 5. Informed consent signed  Malformation, tumor, abscess or other major non-ischemic brain disease (e.g., multiple sclerosis) on baseline head CT or 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. Iatrogenic causes (angioplasty or surgery) of minor stroke or TIA. 4. Preceding moderate or severe dependency (modified Rankin scale [mRS] score 3-5). 5. Contraindication to clopidogrel, ticagrelor or aspirin Known allergy Severe renal (creatinine exceeding 1.5 times of the upper limit of normal range) or hepatic (ALT or AST > twice the upper limit of normal range) insufficiency Severe cardiac failure (NYHA level: III to IV) History of hemostatic disorder or systemic bleeding History of thrombocytopenia or neutropenia History of drug-induced hematologic disorder or hepatic dysfunction Low white blood cell (<2×109/L) or platelet count (<100×109/L) 6. Hematocrit (HCT) <30% 7. Clear indication for anticoagulation (presumed cardiac source of embolus, e.g., atrial fibrillation, prosthetic cardiac valves known or suspected endocarditis) 8. History of intracranial hemorrhage or amyloid angiopathy 9. History of aneurysm (including intracranial aneurysm and peripheral aneurysm) 10. History of asthma or COPD (chronic obstructive pulmonary disease) 11. High-risk for bradyarrhythmia (first-degree or second-degree AV block caused by sinus node disease, and brady-arrhythmic syncope without pacemaker) 12. History of hyperuricemia nephropathy 13. Anticipated requirement for long-term (>7 days) non-steroidal anti-inflammatory drugs (NSAIDs) 14. Planned or likely revascularization (any angioplasty or vascular surgery) within the next 3 months 15. Scheduled for surgery or interventional treatment requiring study drug cessation 16. Severe non-cardiovascular comorbidity with life expectancy < 3 months 17. Inability to understand and/or follow research procedures due to mental, cognitive, or emotional disorders 18. Dual antiplatelet treatment (or more than two antiplatelet agents) in 72 hours before randomization 19. Current treatment (last dose given within 10 days before randomization) with heparin therapy or oral anti coagulation 20. Intravenous thrombolytic therapy (such as intravenous rtPA) or mechanical thrombectomy within 24 hours prior to randomization 21. Gastrointestinal bleed within 3 months or major surgery within 30 days 22. Diagnosis or suspicious diagnosis of acute coronary syndrome 23. Participation in another clinical study with an experimental product during the last 30 days 24. Currently receiving an experimental drug or device 25. Pregnant, currently trying to become pregnant, or of child-bearing potential and not using birth control