IAT-MeVO is an international, multicenter, prospective, randomised, open-label, blinded end-point assessed (PROBE) trial, to evaluate the efficacy and safety of endovascular therapy (EVT) [intra-arterial thrombolysis (IAT)-based] versus best medical management (BMT) in patients with acute ischemic stroke (AIS) due to medium vessel occlusion (MeVO) who are ineligible for intravenous thrombolysis (IV) within 24 h of onset.

Inclusion Criteria:

1. Age ≥ 18 y;
2. Diagnosed as acute ischemic stroke;
3. Isolated medium distal vessel occlusion (i.e. an occlusion of the M2, the M3/M4 segment of the MCA, the A1/ A2/A3 segment of the ACA or the P1/P2/P3 segment of the PCA) confirmed by CT or MR Angiography;
4. Time from onset (or last-seen-well) to randomization < 24h;
5. Has not received intravenous thrombolysis and is considered unsuitable for it based on the treating clinician's assessment.
6. NIHSS ≥ 5, or NIHSS ≤ 4 with disabling deficit (e.g. severe aphasia, hemianopia, hemiplegia/loss of function in one side) or fluctuating symptoms at the time of randomization;
7. For patients within 6 h of onset: No visually apparent hypodensity is observed on non-contrast CT compared with the contralateral white matter, or no hyperintensity is seen on fluid-attenuated inversion recovery (FLAIR) imaging; For patients presenting 6-24 h after onset: A perfusion imaging-based ischemic core mismatch ratio >1.2 and an infarct core volume <50 mL are required;
8. Pre-stroke mRS ≤ 1；
9. Patient/Legally Authorized Representative has signed the Informed Consent form.

Exclusion Criteria:

1. Any evidence of intracranial hemorrhage on qualifying imaging;
2. Concurrent multiple (≥2) intracranial arterial occlusions;
3. Suspected cerebral vasculitis, septic embolism, or infective endocarditis as the cause of vessel occlusion;
4. Suspected arterial dissection;
5. Clinical assessment of conditions unsuitable for interventional therapy (e.g., severe contrast agent allergy or absolute contraindications to iodine contrast agent; severe renal insufficiency, glomerular filtration rate < 30ml/min or serum creatinine > 220μmol/L (2.5 mg/dl));
6. Unsuitable for arterial thrombolytic therapy (e.g., known history of hereditary or acquired hemorrhagic disease and/or platelet count <50×109/L; abnormal coagulation function (INR>1.7); oral anticoagulants were taken within 24 - 48 hours before onset within APTT > 3 times normal; recent medical history or clinical manifestations of brain tumors other than meningiomas);
7. Any terminal disease with life expectancy <1 year;
8. Pregnancy or lactation;
9. Concurrent participation in another investigational drug or device study that could interfere with the present trial;
10. Other circumstances that participation is not deemed appropriate.

This study will include individual information from multicenter and multination. To protect the participants' privacy and follow the guidelines of other center or nations' ethical committee, we don't provide or share IPD with other reasearchers.

Open-label trial; only the outcome assessors and partial data analysts will be masked to treatment allocation