Inclusion Criteria:

• Any of the following presentations of acute ischemic stroke (AIS): ① Within 24 hours of time last known well and ineligible for intravenous thrombolysis (IVT) or endovascular treatment (EVT). ② More than 24 hours and less than 96 hours after time last known well but within 24 hours of ischemic stroke progression [worsening of ≥ 2 points on the NIHSS]; and ineligible for IVT or EVT without ICH confirmed by CT scan or MRI. ③ Treated with IVT followed by early neurological deterioration (worse NIHSS by ≥ 4 points) within the first 24 hours after IVT without ICH confirmed by CT scan or MRI. ④ Treated with IVT followed by no neurological improvement (Neurological improvement is defined as decrease in the NIHSS score by ≥ 2 points) from baseline within 4 to 24 hours after IVT without ICH confirmed by CT scan or MRI.
• NIHSS score ≥ 3 immediately prior to trial entry.
• Without visible large or medium intracranial vessel occlusion on CT angiography (CTA), MR angiography (MRA), or digital subtraction angiography (DSA). (Qualifying mechanisms are: 1. hypoperfusion caused by arterial stenosis; 2. the initial occluded large or medium artery spontaneously recanalized or recanalized with IVT before the vascular imaging performed; 3. multiple or single distal emboli from cardiac or other sources in arterial branches too small to visualized on CTA or MRA; 4. lacunar infarct due to small vessel occlusion).
• Written informed consent obtained from patients or their legal representatives.

Exclusion Criteria:

• CT or MR evidence of intracranial haemorrhage.
• Pre-morbid disability with a mRS score ≥ 2.
• Presence of any of the following unequivocal cardiac sources of embolism: chronic or paroxysmal atrial fibrillation, sick sinus syndrome, mitral stenosis, mechanical valve, endocarditis, intracardiac clot or vegetation, myocardial infarction within three months, dilated cardiomyopathy, left atrial spontaneous echo contrast, ejection fraction less than 30%.
• Planned treatment with dual antiplatelet therapy within 1week of the index stroke.
• Any history of a primary or other intracerebral (parenchymal) haemorrhage (intraventricular, subarachnoid, subdural, epidural).
• Any untreated or incompletely treated intracranial aneurysm, any intracranial vascular malformation or any intracranial tumour.
• Currently pregnant or lactating, and those planned to conceive.
• Subjects with positive urine HCG test results.
• Known allergy to study medication or concomitant medications.
• Gastrointestinal bleeding, urinary tract bleeding, or other major systemic haemorrhage within 30 days.
• Any major surgery within 6 weeks of the index stroke.
• History of heparin-induced thrombocytopenia.
• Expected lifespan less than 3 months.
• Pre-existing neurological or psychiatric disease that would confound the neurological functional outcome evaluations.
• Any of the following laboratory tests: INR [International Normalized Ratio]>2.0, PT>1.3 times normal value, platelet count<100 × 109/L, Hb<10g/dl.
• Systolic pressure greater than 180 mmHg or diastolic pressure greater than 110 mmHg after aggressive treatment.
• Severe renal insufficiency (glomerular filtration rate < 30 ml/min or serum creatinine > 220 μmol/L [2.5 mg/dl]).
• History of liver dysfunction (AST/ALT exceeding the upper limit of normal by more than twice) or cirrhosis.
• Arterial tortuosity and/or other arterial diseases that prevent the expected internal thrombectomy device from reaching the target vessel.
• Unlikely to be available for 90-day follow-up.
• Current participation in another treatment clinical trial.
• Other conditions that are not suitable for participation in the study.