Tenecteplase for Late-Window Stroke Guided by DWI-FLAIR Mismatch

The goal of this clinical trial is to evaluate the efficacy and safety of tenecteplase administered 4.5-9 hours after stroke onset (defined as the time the patient was first found with symptoms, including wake-up stroke and unwitnessed stroke) in patients with acute ischemic stroke (AIS) guided by DWI-FLAIR mismatch on MRI. The main questions it aims to answer are: 1. Does tenecteplase improve functional outcomes at 90 days compared with standard treatments in AIS patients administered 4.5-9 hours after stroke onset guided by DWI-FLAIR mismatch? 2. The safety of tenecteplase thrombolysis for AIS patients in the 4.5-9 hours guided by DWI-FLAIR mismatch. Researchers will compare tenecteplase to placebo to see if it is effective and safe for these patients. Participants will be randomly assigned (1:1) immediately after randomization: * Tenecteplase group: received tenecteplase, intravenously as a bolus administered over a period of 5 to 10 seconds at a dose of 0.25 mg per kilogram (maximum dose, 25 mg), plus aspirin placebo (300 mg). * Control group: aspirin (300 mg) plus tenecteplase placebo. From day 2 to day 90, all patients will be conformed to the 2023 Chinese Guidelines for Diagnosis and Treatment of Acute Ischemic Stroke.