This study is a prospective, multicenter, double-blind, randomized, placebo-controlled clinical trial designed to evaluate whether early administration of PCSK9 inhibitors can effectively improve functional outcomes at 90 days in patients with ischemic stroke (AIS) associated with intracranial atherosclerotic stenosis (ICAS), primarily assessed using the modified Rankin Scale at 90 days.

Acute ischemic stroke (AIS) remains one of the leading causes of death and disability worldwide. Although intravenous thrombolysis and endovascular therapies have significantly improved reperfusion success rates, three critical challenges persist in clinical practice that determine prognosis: First, only a limited proportion of patients can actually receive reperfusion therapy within the therapeutic time window; Second, even with successful reperfusion, secondary injuries such as microcirculatory perfusion failure, inflammatory cascades, and thrombus reformation may still occur. Third, acute phase fluctuations, particularly early neurological deterioration and the risk of early recurrence, remain prominent, directly limiting improvements in functional outcomes. 3 Intracranial atherosclerotic stenosis (ICAS) accounts for up to 50% of ischemic stroke etiologies in China. Its pathological chain-"plaque instability-thrombosis-microcirculatory impairment"-permeates both the acute and subacute phases, closely correlating with early recurrence and poor outcomes.Proprotein convertase subtilisin/kexin type 9 (PCSK9) classically promotes the degradation of low-density lipoprotein cholesterol (LDL-C) receptors and elevates LDL-C levels, thereby driving atherosclerosis progression. More importantly, growing basic and translational research suggests that PCSK9 may not only function as a "lipid metabolism protein" but also participate in processes such as endothelial activation, inflammatory cascades, platelet reactivity, and microcirculatory dysfunction. This positions it as a potential hub connecting the "plaque-thrombus-inflammation" axis. Consequently, PCSK9 inhibitors may offer additional neurovascular protective benefits beyond lipid-lowering effects during the acute phase of acute ischemic stroke (AIS).Existing basic and clinical evidence suggests that PCSK9 inhibitors may exert a combined intervention effect on key pathological processes driving atherosclerosis during the acute phase of AIS through a dual mechanism involving both lipid-dependent and non-lipid-dependent pathways. Mechanistic studies reveal that PCSK9 inhibition simultaneously modulates inflammatory responses, endothelial activation, dysfunction, and thrombogenic tendencies. In ischemia-reperfusion models, it demonstrates neuroprotective signaling by mitigating brain injury and improving neurological function. Clinically, large randomized trials confirm its ability to rapidly enhance lipid-lowering effects beyond statins and reduce ischemic stroke risk. Further translational evidence in cerebrovascular disease indicates that in symptomatic ICAS populations, PCSK9 inhibitor plus statin-enhanced lipid-lowering therapy reduces plaque burden, alleviates stenosis, and increases plaque stability. In the acute phase of AIS, early addition of PCSK9 inhibitors correlates with reduced neurological deterioration within 7 days, decreased recurrence risk within 30 days, and improved functional outcomes at 90 days. Collectively, this evidence chain spanning mechanisms to clinical practice provides clear scientific rationale and clinical necessity for adding PCSK9 inhibitors to the treatment of ICAS-associated AIS.This study is a nationwide, prospective, multicenter, double-blind, randomized, placebo-controlled clinical trial. It will enroll 1,212 patients meeting inclusion and exclusion criteria. Patients will be randomly assigned to two groups using a randomized allocation method: (1) Experimental group: 450 mg of Recaticimab for Injection (3 vials) administered as a single subcutaneous injection. (2) Control group: Placebo of Recaticimab for Injection 450 mg (3 vials) administered as a single subcutaneous injection. Each group will include 606 patients. Both groups will receive standard guideline-recommended treatment in addition to the study drug. Long-term efficacy was assessed through patient visits and evaluations at 0 hours, 24 hours (±2 or ±12 hours), 7 days (±2 days) or at discharge, 90 days (±7 days), and 1 year.Primary outcome measures included: Analysis based on the intention-to-treat principle using an ANCOVA model for all randomized patients with baseline HRMRI and a modified Rankin Scale (mRS) score of 0-2 at 90 days. Secondary outcome measures included: (1) mRS score of 0-1 at 90 days (indicating good patient function); (2) Distribution of 90-day mRS scores; (3) Any stroke (including ischemic and hemorrhagic) within 90 days; (4) Ischemic stroke within 90 days; (5) Composite vascular events (including stroke, myocardial infarction, and vascular death) within 90 days; (6) 90-day European Quality of Life 5-Dimension 5-Level Scale (EQ-5D-5L) score; (7) 90-day Barthel Index (BI) score.Details are provided in the "Outcome Measures" section.The sample size is calculated based on the primary outcome and a total of 1212 participants are anticipated. An independent Data Safety Monitoring Board will oversee the overall conduct of the trial.

Inclusion Criteria:

• Age >=30 and <=80;2.Acute ischemic stroke within 72 hours of onset (as determined by CT/MRI in conjunction with neurological deficit symptoms)
• Acute ischemic stroke within 72 hours of onset (diagnosed by CT/MRI in conjunction with neurological deficit symptoms)
• NIHSS score of 4-25 at admission
• Imaging studies (CTA/DSA/MRA) support intracranial atherosclerosis as the cause of stroke, meeting one of the following criteria: i. The culprit vessel exhibits intracranial atherosclerotic stenosis (ICAS) with a narrowing degree of 50-99%; ii. The culprit vessel exhibits intracranial atherosclerotic occlusion (ICAS-LVO), with successful recanalization achieved via mechanical thrombectomy (immediate expanded thrombolysis in cerebral infarction [eTICI] grade 2b50-3)
• Informed consent signed

Exclusion Criteria:

• Non-atherosclerotic intracranial arterial stenosis (such as arterial dissection, Moyamoya disease, systemic vasculitis, etc.)
• Any identifiable source of cardiogenic embolism (such as atrial fibrillation, mechanical valves, left ventricular thrombus, patent foramen ovale, etc.)
• Imaging findings and clinical presentation suggest that the primary pathophysiology of this event is more consistent with cerebral small vessel disease (e.g., perforator artery occlusion/lacunar infarction)
• Pre-existing disability prior to this ischemic event (modified Rankin Scale ≥ 2 points)
• CT or MRI findings suggest extensive cerebral infarction (e.g., ASPECTS score < 6 or infarct volume ≥ 70 ml)
• Has undergone or is scheduled to undergo a vascular stent implantation procedure within the next three months
• Any intracranial hemorrhage occurring within 3 months prior to enrollment;
• Intracranial tumors, cerebral aneurysms, or arteriovenous malformations that are assessed as having indications for interventional treatment
• Severe active bleeding tendency or coagulation disorder
• Severe dysfunction of vital organs such as the heart, liver, and kidneys
• Received PCSK9 monoclonal antibody inhibitor therapy within 1 month prior to enrollment or PCSK9 siRNA inhibitor therapy within 6 months prior to enrollment
• A clear contraindication to statins or a history of intolerance to them
• Pregnancy, breastfeeding, or planning pregnancy;14.Currently participating in another study

Subjects, clinical investigators, outcome assessors, imaging evaluators, laboratory technicians, data management personnel, and statistical analysts remained blinded to treatment allocation throughout the entire study.