Stroke remains a major global health burden, with acute ischemic stroke (AIS) accounting for more than 65% of all cases. Endovascular thrombectomy (EVT) has been established as the standard treatment for large vessel occlusion (LVO) stroke; however, the phenomenon of "futile recanalization" remains common, with nearly half of patients failing to achieve favorable outcomes despite successful vessel reperfusion. Increasing evidence indicates that neutrophils and neutrophil extracellular traps (NETs) play pivotal roles in post-reperfusion inflammation, thrombosis, and microcirculatory dysfunction, contributing to thrombolysis resistance and poor prognosis. Neutrophil elastase (NE), a key component of NETs, exacerbates vascular injury and thrombus formation. Sodium sivelestat, a selective NE inhibitor, has demonstrated significant anti-inflammatory and organ-protective effects in patients with acute respiratory distress syndrome and in experimental models of cerebral ischemia. It can preserve blood-brain barrier integrity, attenuate brain edema, and improve neurological outcomes. Based on these findings, we propose a prospective, single-center, single-arm exploratory clinical trial to evaluate the efficacy and safety of sodium sivelestat as an adjunct to EVT in patients with acute LVO stroke within 24 hours of onset. The results of this study are expected to provide new clinical evidence for anti-inflammatory interventions aimed at reducing futile recanalization and improving functional outcomes in AIS.

Inclusion Criteria:

1. Symptoms and signs consistent with focal ischemia in the anterior or posterior circulation;
2. Large vessel occlusion of the anterior or posterior circulation (internal carotid artery, M1/M2 segment of the middle cerebral artery, vertebral artery, or basilar artery) confirmed by CTA/MRA/DSA;
3. Undergoing mechanical thrombectomy;
4. Age ≥18 years, both male and female;
5. Pre-stroke modified Rankin Scale (mRS) score ≤1;
6. Time from symptom onset to thrombectomy ≤24 hours, including wake-up stroke or unwitnessed stroke; symptom onset is defined as the "last known well" (LKW);
7. National Institutes of Health Stroke Scale (NIHSS) score ≥6 at admission;
8. ASPECTS ≥3 for anterior circulation occlusion, or pc-ASPECTS ≥6 for posterior circulation occlusion;
9. Written informed consent provided by the patient or their legal representative.

Exclusion Criteria:

1. Simultaneous acute occlusion of both anterior and posterior circulation or bilateral hemispheric large vessel occlusions;
2. Complete clinical recovery at the end of EVT procedure;
3. Arterial dissection or intraoperative hemorrhage indicated by post-thrombectomy DSA;
4. Sedated and intubated patients without baseline NIHSS assessment;
5. Seizure at stroke onset interfering with baseline NIHSS assessment;
6. Bilateral fixed dilated pupils;
7. Severe allergy or absolute contraindication to sodium sivelestat;
8. Severe allergy or absolute contraindication to iodinated contrast agents;
9. Systolic blood pressure >185 mmHg or diastolic blood pressure >110 mmHg, uncontrolled despite antihypertensive therapy;
10. Blood glucose <50 mg/dl (2.8 mmol/L) or >400 mg/dl (22.2 mmol/L);
11. Platelet count <50×10⁹/L;
12. Congenital or acquired bleeding diathesis, coagulation factor deficiency, or current use of oral anticoagulants with INR >1.7;
13. Severe renal impairment, defined as serum creatinine >3.0 mg/dl (265.2 μmol/L), GFR <30 ml/min, or requirement for hemodialysis/peritoneal dialysis;
14. Inability to complete 90-day follow-up (e.g., no fixed residence, overseas patient);
15. Suspected vasculitis or septic embolism;
16. Suspected aortic dissection;
17. Pre-existing neurological or psychiatric disorders interfering with stroke assessment;
18. Pregnancy or lactation;
19. Confirmed rheumatic/autoimmune disease with long-term use of immunosuppressants or corticosteroids;
20. Current treatment with chemotherapy or other immunomodulatory agents (e.g., recombinant human granulocyte colony-stimulating factor, Xuebijing, ulinastatin, etc.);
21. Participation in another clinical trial that may interfere with study outcomes;
22. Any other condition that investigators deem unsuitable for participation or that may pose significant risk to the patient.