PCSK9 Inhibitor for Intracranial Atherosclerotic Symptomatic Stenosis

Inclusion Criteria: 1\. Aged ≥30 years and ≤80 years. Patients aged between 30 to 49 are required to meet at least one of the following criteria: 1. Insulin dependent diabetes for at least 15 years. 2. At least 2 of the following atherosclerotic risk factors: hypertension (BP \> 140/90 or on antihypertensive therapy); dyslipidemia (LDL \> 130 mg /dL or HDL \< 40 mg/dL or fasting triglycerides \> 150 mg/dL or on lipid lowering therapy); smoking; non-insulin dependent diabetes or insulin dependent diabetes of less than 15 years duration; family history of any of the following: myocardial infarction, coronary artery bypass, coronary angioplasty or stenting, stroke, carotid endarterectomy or stenting, peripheral vascular surgery in parent or sibling who was \< 55 years of age for men or \< 65 for women at the time of the event. 3. History of any of the following: myocardial infarction, coronary artery bypass, coronary angioplasty or stenting, carotid endarterectomy or stenting, or peripheral vascular surgery for atherosclerotic disease. 4. Any stenosis of an extracranial carotid or vertebral artery, another intracranial artery, subclavian artery, coronary artery, iliac or femoral artery, other lower or upper extremity artery, mesenteric artery, or renal artery that was documented by non-invasive vascular imaging or catheter angiography and is considered atherosclerotic. 5. Aortic arch atheroma documented by non-invasive vascular imaging or catheter angiography vi. any aortic aneurysm documented by non-invasive vascular imaging or catheter angiography that is considered atherosclerotic. 2\. Diagnosed with acute ischemic stroke or moderate-to-high risk transient ischemic attack (ABCD2 score ≥4). 3\. CTA or DSA confirmed intracranial atherosclerotic stenosis \>50%, which was responsible for the incident. 4\. The time from symptom onset to initiation of study treatment is within 7 days. 5\. Signed informed consent. Exclusion Criteria: 1. Baseline NIHSS ≥26. 2. Suspected cardiogenic ischemic cerebrovascular diseases (e.g., combined with atrial fibrillation, heart valve prosthesis, atrial myxoma, endocarditis, etc.). 3. Source of symptoms is possible related to ipsilateral carotid disease. 4. Other ischemic cerebrovascular diseases with specific causes (e.g., aortic dissection, vasculitis, vascular malformation, etc.). 5. Non-cerebral vascular disease (e.g., intracranial tumors, multiple sclerosis). 6. Hemorrhagic stroke or hemorrhagic transformation of cerebral infarction before randomization. 7. Pre-existing contraindications of using PCSK9 inhibitors. 8. Use of any PCSK9 inhibitors within the past 3 months. 9. Pregnant or childbearing-age women who have no effective contraceptives or positive pregnancy test records. 10. Patients who are participating in other trials. 11. Hepatic or renal dysfunction, defined as AST and/or ALT \>3ULN，eGFR\<30mL/min, or Crea \>220μmol/L (2.5mg/dL). 12. Uncontrolled hypertension defined as systolic blood pressure (BP) \>220mmHg or diastolic BP \>120mmHg. 13. Life expectancy is less than 1 year due to severe non-cardiovascular disease. 14. Angioplasty or stenting procedure is planned before randomization. 15. Unable to finish the follow-up visit due to geographical factor or other reasons (e.g., dementia, alcoholism, substance abuse, severe mental disease, etc.)