Tirofiban for Patients With intraCranial Artery Stenosis and High-risk Acute Non-disabling Cerebrovascular Events(CHANCE-4）

Inclusion Criteria 1. 40 years or older than 40 years; 2. Acute cerebral ischemic event due to: * Acute non-disabling ischemic stroke (NIHSS≤5 at the time of randomization) or, * TIA with moderate-to-high risk of stroke (ABCD2 score ≥ 6 at the time of randomization); 3. Accompanied with symptomatic intracranial artery stenosis, defined as ≥ 50% stenosis of the infarcted ipsilateral intracranial artery. Intracranial arteries include intracranial segments of internal carotid arteries, intracranial segments of vertebral arteries, M1-M2 segments of middle cerebral arteries, A1-A2 segments of anterior cerebral arteries, P1-P2 segments of posterior cerebral arteries, and basilar artery. The techniques for detecting intracranial artery stenosis are limited to: MRA, CTA, or DSA. The measurement for the degree of stenosis has been established by the WASID (Warfarin-Aspirin Symptomatic Intracranial Disease) study. (AJNR Am J Neuroradiol. 2000;21:643-646.); 4. Can be treated with study drug within 24 hours of symptoms onset\*(\*Symptom onset is defined by the "last seen normal" principle); 5. Informed consent signed. Exclusion Criteria 1. Malformation, tumor, abscess or other major non-ischemic brain disease (e.g., multiple sclerosis) on baseline head CT or MRI. 2. Unable to complete the evaluation of intracranial artery stenosis before randomization. 3. 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. 4. Iatrogenic causes (angioplasty or surgery) of minor stroke or TIA. 5. A score of \> 2 on the modified Rankin scale before the symptom onset. 6. Contraindication for tirofiban: * 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) 7. Tirofiban has been used since this onset. 8. Hematocrit (HCT) \<30%. 9. Clear indication for anticoagulation (presumed cardiac source of embolus, e.g., atrial fibrillation, prosthetic cardiac valves known or suspected endocarditis). 10. History of intracranial hemorrhage or amyloid angiopathy. 11. History of aneurysm (including intracranial aneurysm and peripheral aneurysm). 12. History of asthma or COPD (chronic obstructive pulmonary disease). 13. High-risk for bradyarrhythmia (sinus node disease, first-degree or second-degree AV block, and brady-arrhythmic syncope without pacemaker). 14. Planned or likely revascularization (any angioplasty or endovascular 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. Current treatment (last dose given within 10 days before randomization) with heparin therapy or oral anti coagulation. 19. Intravenous thrombolytic therapy (such as intravenous rtPA) or mechanical thrombectomy within 24 hours prior to randomization. 20. Participants who have large areas (greater than half of middle cerebral artery territory) of obvious low density on the baseline CT scan. 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.