A Phase II/III Clinical Study of SIM0811 in the Treatment of Acute Ischemic Stroke

The study will evaluate the efficacy and safety of SIM0811 in participants with acute ischemic stroke who are present within 4.5 to 24 hours since last known well. The main questions it aims to answer are: 1. Does SIM0811 improve overall functional outcome, measured by the ability to perform daily activities independently without help 90 days after treatment? 2. What medical problems do participants have when taking SIM0811? Researchers will compare different doses of SIM0811 to a placebo (a look-alike substance that contains no drug) to see if SIM0811 works to treat acute ischemic stroke. Participants will: 1. Receive SIM0811 or a placebo . 2. Receive standard medical care for stroke. On the first day, all participants will also take an aspirin pill or an aspirin placebo to keep the treatment assignment a secret. 3. Stay in the hospital for a few days to undergo medical tests, including CT or MRI scans and blood draws. 4. Return to the clinic for follow-up visits for up to 90 days to check their recovery and overall health.