An investigational anti-clotting medication, asundexian, demonstrated a reduction in the risk of a second ischemic stroke without raising bleeding concerns, according to a late-breaking science presentation at the American Stroke Association’s International Stroke Conference 2026. The findings, from the OCEANIC-STROKE trial, suggest a potential major advance in secondary stroke prevention.
“Asundexian holds the potential to reduce the risk of a recurrent stroke over the long term without an increased safety risk,” said Mike Sharma, M.D., M.Sc., principal investigator of the study and professor of medicine at McMaster University. Nearly 1 in 4 stroke survivors experience another stroke, and current antiplatelet therapies have limited effectiveness due to bleeding risks.
The Phase III international trial included more than 12,300 stroke survivors who had recently experienced a mild to moderate non-cardioembolic ischemic stroke or a high-risk transient ischemic attack (TIA). Participants were randomly assigned to receive either standard antiplatelet therapy plus a daily 50 mg dose of asundexian or standard antiplatelet therapy plus a placebo. Over a follow-up period of 3 to 31 months, researchers found that adding asundexian reduced the occurrence of ischemic stroke by 26% compared to placebo. This reduction was consistent across age, sex, cause of stroke, and severity of the first stroke. Importantly, asundexian did not increase intracranial bleeding or major bleeding, and it lowered the composite of cardiovascular death, any stroke, heart attack, and major bleeding.
Asundexian inhibits Factor XIa, a clotting protein involved in producing large blood clots that can block blood vessels. Unlike other anticoagulants such as rivaroxaban and apixaban, which inhibit Factor Xa and increase bleeding risk, asundexian’s mechanism appears to dissociate antithrombotic effects from bleeding risk. People with a genetic deficiency of Factor XI have a lower risk of ischemic stroke and rarely have spontaneous bleeding, supporting this approach.
The study was conducted at 702 sites in 37 countries, with participants enrolled between January 2023 and February 2025. Participants were within 72 hours of a mild-to-moderate ischemic stroke (NIH Stroke Scale up to 15) or a high-risk TIA (ABCD2 score 6-7). None had atrial fibrillation, artificial heart valves, or other conditions causing cardioembolic stroke. Standard antiplatelet therapy included aspirin alone or dual antiplatelet therapy (aspirin plus clopidogrel or dipyridamole).
“Asundexian, when combined with standard antiplatelet therapy, helped reduce the chances of having another stroke without increasing the risk of bleeding. This benefit applies to all types of strokes, not just those caused by plaque build-up in large arteries,” Sharma said. The U.S. Food and Drug Administration has granted asundexian fast-track designation for stroke prevention after non-cardioembolic ischemic stroke.
The study is limited by relatively few participants with severe strokes, despite broad inclusion criteria. A substudy analyzing brain imaging data is ongoing. Asundexian is investigational and not yet approved in any country. Bayer, who manufactures asundexian, funded the study. The findings are considered preliminary until published in a peer-reviewed journal.
For more information on stroke prevention, visit the American Stroke Association website. The full abstract is available in the ISC 2026 Online Program Planner.
