This study is testing a new drug called **DM199** to treat people who've had a type of stroke called an **Acute Ischemic Stroke (AIS)**. A stroke happens when blood flow to the brain is blocked, and this study focuses on strokes caused by small and medium blocked blood vessels. Participants can't join if they've had a mechanical thrombectomy (MT), which is a procedure to remove the blockage, or if they've recently been treated with clot-busting drugs called fibrinolytics unless they still have moderate symptoms after 6 hours. The study is **double-blinded**, meaning neither the participants nor the doctors know who gets DM199 or a placebo (a fake treatment). - The study lasts about 90 days, and participants will have to visit the study site multiple times for treatments and check-ups. - DM199 is given through an IV (intravenous) first, then under the skin (subcutaneous) twice a week for up to 21 days. - Safety checks will be done after 200 people finish to decide if the study continues or stops early. This trial happens at about 100 locations, and the goal is to see if DM199 is safe and effective. Participants must be between 18 and 90 years old and meet specific health criteria.