SISTER is a study to help improve stroke treatment. It tests a drug called TS23, which is a monoclonal antibody that can help with blood flow during an acute ischemic stroke (a stroke caused by blocked blood flow to the brain). The study aims to find a safe and effective dose of TS23. Participants must have had a stroke recently and show potential for brain recovery. This study uses a placebo (a harmless pill or treatment) to compare with TS23. The study will involve 300 people across 50 locations. Researchers will assess safety by checking for brain bleeding 30 hours after receiving the drug and will check how well it helps using a stroke rating scale. Participants will be followed for 90 days to track outcomes.

• The study lasts for 3 months with follow-up visits.
• Participants must be 18 or older and have had a recent stroke.
• Some medical history might make someone ineligible, like recent surgeries or certain medications.