This study aims to evaluate the efficacy and safety of tenecteplase (TNK) intravenous thrombolysis within the extended time window (4.5 to 24 hours) in patients with acute posterior circulation ischemic stroke.

This multicenter, prospective, randomized, controlled trial assesses the efficacy and safety of intravenous tenecteplase for acute posterior-circulation ischemic stroke treated 4.5-24 hours after onset. Participants with imaging-confirmed stroke will be randomly assigned 1:1 to receive either tenecteplase or standard medical therapy. Eligible patients must present within 4.5-24 hours from symptom onset, defined as the midpoint between last known normal and first observed neurological deficit. All participants will undergo telephone follow-up at 3 months and 1 year, with the modified Rankin Scale as the primary outcome measure.

Inclusion Criteria:

1. Age ≥18 years.
2. Meeting at least one of the following criteria: acute posterior circulation ischemic stroke confirmed by MRI; symptomatic stenosis or occlusion of a posterior circulation large vessel on vascular imaging (CTA/MRA/DSA); perfusion imaging demonstrating clinically relevant hypoperfusion in the posterior circulation territory.
3. Onset time between 4.5-24 hours (for wake-up stroke or unwitnessed stroke, onset time is defined as the midpoint between last known well and symptom detection).
4. NIHSS score>3.
5. PC-ASPECTS ≥7 (if discrepancy exists between DWI and CT findings, CT assessment takes precedence).
6. Pre-stroke mRS ≤1.
7. Signed informed consent by the patient or legally authorized representative.

Exclusion Criteria:

1. Contraindication to tenecteplase or its components.
2. Planing to receive endovascular therapy with thrombectomy, angioplasty or stenting whin 3 months.
3. Acute anterior circulation infarction confirmed by MRI, anterior circulation large vessel occlusion on vascular imaging (CTA/MRA/DSA), or anterior circulation hypoperfusion on perfusion imaging.
4. History of intracranial hemorrhage.
5. Stroke, myocardial infarction, severe traumatic brain injury, or intracranial/spinal surgery within the preceding 3 months.
6. Intracranial tumor, arteriovenous malformation (AVM), or giant aneurysm.
7. Active internal bleeding, major surgery, trauma, gastrointestinal/urinary tract bleeding within 3 weeks.
8. Non-compressible arterial puncture within 1 week.
9. Suspected aortic dissection.
10. Clinically significant bleeding or coagulopathy, including: Warfarin use with INR >1.7 or PT >15 s; Low-molecular-weight heparin within 24 hours; Direct oral anticoagulants within 48 hours; Laboratory abnormalities (e.g., APTT >40 s).
11. Platelet dysfunction or platelet count <100×10⁹/L.
12. Uncontrolled hypertension (systolic BP >180 mmHg or diastolic BP >110 mmHg unresponsive to antihypertensive therapy).
13. Uncontrolled hypoglycemia/hyperglycemia (<50 mg/dL [2.8 mmol/L] or >400 mg/dL [22.2 mmol/L]).
14. Pregnancy or lactation.
15. A life expectancy of less than three months.
16. Participation in other clinical trials within 3 months or ongoing trial enrollment.
17. Inability to follow up (e.g., no fixed residence, overseas patients).
18. Patient deemed unsuitable for the trial by site investigator.