Inclusion Criteria:
* Clinical diagnosis of ischemic stroke with National Institutes of Health Stroke Scale (NIHSS) score of 1-15
* Ischemic lesions on diffuse-weighted imaging located in the territory of symptomatic intracranial atherosclerosis (ICAS).
* Symptomatic ICAS (above 30%) at the M1 or M2 of the middle cerebral artery, basilar artery or at the intracranial portion of the internal carotid artery or vertebral artery.
* Serum LDL-C ≥70 mg/dL for subjects on lipid-lowering therapies (such as a statin and/or ezetimibe) or LDL-C ≥100 mg/dL for subjects without lipid-lowering therapies.
* Ability to randomize within 7 days of time last known free of new ischemic symptoms.
* Ability to receive alirocumab or statin treatment within 7 days of stroke onset.
* Head CT or MRI ruling out hemorrhage or other pathology, such as vascular malformation, tumor, or abscess, that could explain symptoms or contraindicate therapy.
* Pre-stroke modified Rankin Scale (mRS)≦2
Exclusion Criteria:
* Age \<20 years.
* Judged by clinical physician.
* After endovascular intervention or endarterectomy for the symptomatic ICAS.
* Patients with more than 50% stenosis of extra-cranial arteries the relevant arteries on magnetic resonance angiography (MRA), including extra-cranial carotid artery or vertebral arteries.
* Patients with high risk of cardioembolic source, such as atrial fibrillation, acute myocardial infarction, severe heart failure or valvular heart disease.
* Other determined stroke etiology, such as vasculitis, shock, antiphospholipid antibody syndrome, arterial dissection, CADASIL and etc.
* Qualifying ischemic event induced by angiography or surgery.
* Severe non-cardiovascular comorbidity with life expectancy \<6 months.
* Contraindication or allergy to alirocumab or Gadolinium
* Severe renal (serum creatinine \>2 mg/dL) or calculated glomerular filtration rate \<30 mL/min/ 1.73 m2 by estimated glomerular filtration rate (eGFR) using Cockcroft Gault methodology.
* Hepatic insufficiency (INR\>1.2; ALT\>40 U/L or any resultant complication, such as variceal bleeding, encephalopathy, or jaundice)
* Hemostatic disorder or systemic bleeding in the past 3 months
* Current thrombocytopenia (platelet count \<100 x109/L) or leukopenia (\<2 x109/L)
* Anemia（\<10 mg/dL）
* History of drug-induced hematologic or hepatic abnormalities
* History of malignancy that required surgery, radiation therapy or systemic therapy.
* Females who are pregnant or nursing, or who are of childbearing potential and unwilling to use effective contraception.
* Other neurological conditions that would complicate assessment of outcomes during follow-up.
