Inclusion Criteria:
* 1\. Subjects aged 18-85 years (inclusive), regardless of gender;
* 2\. Diagnosed with acute ischemic stroke according to the Chinese Guidelines for the Diagnosis and Treatment of Acute Ischemic Stroke (2023);
* 3\. Time from stroke onset ≤ 24 hours (Onset time is calculated from the time stroke symptoms appear. If the stroke occurred during sleep or if the time of symptom onset cannot be accurately determined due to aphasia, impaired consciousness, or other reasons, the time the subject was last known to be normal should be used as the onset time);
* 4\. Pre-stroke modified Rankin Scale (mRS) score ≤ 1;
* 5\. After this event and prior to thrombolysis, NIHSS score is between 6 and 20 (inclusive), and the sum of scores on NIHSS Item 5 (motor arm) and Item 6 (motor leg) is ≥ 2;
* 6\. Planned for or have already undergone thrombolytic therapy;
* 7\. Female subjects of childbearing potential must have a negative serum pregnancy test and report no sexual activity within 14 days prior to screening. Subjects of childbearing potential (female or male) must agree to have no plans for pregnancy or sperm donation throughout the study period and are willing to use at least one effective method of contraception;
* 8\. The subject or their legal guardian voluntarily signs the informed consent form (ICF).
Exclusion Criteria:
* 1\. Allergy to any component of QD202 or the placebo.
* 2\. Intracranial hemorrhage detected on cranial computed tomography (CT), including hemorrhagic stroke (e.g., epidural hematoma, intracranial hematoma, intraventricular hemorrhage, subarachnoid hemorrhage) or hemorrhagic transformation of the current cerebral infarction. Subjects with mere microbleeds may be considered for inclusion at the investigator's discretion. Hemorrhage occurring after thrombolytic therapy, as a complication of the treatment and not classified as hemorrhagic stroke, may also be considered for inclusion at the investigator's discretion.
* 3\. Transient ischemic attack (TIA).
* 4\. Poorly controlled blood pressure despite active treatment (hypertension: systolic blood pressure ≥220 mmHg and/or diastolic blood pressure ≥120 mmHg; hypotension: systolic blood pressure ≤90 mmHg and/or diastolic blood pressure ≤40 mmHg).
* 5\. Severe hyperglycemia/hypoglycemia: blood glucose ≥400 mg/dL (22.2 mmol/L) or ≤50 mg/dL (2.8 mmol/L).
* 6\. Heart rate \<50 beats per minute and/or \>120 beats per minute; second- or third-degree atrioventricular block, sinoatrial block, or sinus arrest; history within 6 months prior to screening of heart failure (NYHA Class III or IV), unstable angina, acute myocardial infarction, or severe arrhythmia (including but not limited to rapid atrial fibrillation, atrial flutter, frequent premature beats, supraventricular or ventricular tachycardia).
* 7\. Severe impairment of consciousness after the current event and prior to thrombolysis: NIHSS level of consciousness (item 1a) score ≥2.
* 8\. History of severe psychiatric disorder or severe dementia.
* 9\. History of depression or anxiety, if the investigator deems participation in this clinical trial inappropriate.
* 10\. Subjects unsuitable for thrombolytic therapy, or those who have undergone or are planned to undergo endovascular interventional therapy.
* 11\. Use of therapeutic neuroprotective agents after stroke onset, including commercially available edaravone, edaravone dexborneol injection concentrate and sublingual tablets, ginkgolides, ginkgo diterpene lactone meglumine, nimodipine, gangliosides, citicoline, piracetam, oxiracetam, butylphthalide, cinepazide maleate injection, mouse nerve growth factor, potential neuroprotective Cerebrolysin (cerebroprotein hydrolysate), deproteinized calf blood extractives injection, ulinastatin, etc. (except mannitol used to reduce intracranial pressure).
* 12\. Concurrent malignancy diagnosed previously and currently undergoing anti-tumor therapy.
* 13\. History of severe systemic disease with an estimated life expectancy of \<90 days.
* 14\. Diagnosed with severe active liver disease (e.g., acute hepatitis, chronic active hepatitis, cirrhosis) or alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \>2.0 times the upper limit of normal (ULN).
* 15\. Diagnosed with severe active kidney disease, renal insufficiency, or estimated glomerular filtration rate (eGFR) \<60 mL/min/1.73 m².
* 16\. Bleeding tendency, including platelet count (PLT) \<75.0×10⁹/L, or history of major bleeding within 3 months prior to the current event.
* 17\. Major surgery within 4 weeks prior to screening, if the investigator assesses it may affect neurological function scores or 90-day survival.
* 18\. Alcohol dependence, drug abuse, substance addiction, or propensity for addiction.
* 19\. Participation in another clinical trial involving investigational drugs, vaccines, or medical devices within 3 months prior to screening.
* 20\. Any contraindication (e.g., cardiac pacemaker or other metal implants, claustrophobia) preventing or hindering CT or MRI examinations.
* 21\. Allergy to contrast agents.
* 22\. Chronic moderate to severe respiratory disease.
* 23\. Pregnant or breastfeeding women.
* 24\. Any other condition deemed by the investigator to make the subject unsuitable for participation in this clinical trial.
