An investigational anti-clotting medication called asundexian demonstrated a reduction in the risk of a second ischemic stroke without raising bleeding concerns, according to preliminary findings presented at the American Stroke Association’s International Stroke Conference 2026. The OCEANIC-STROKE study, a Phase III international trial involving over 12,300 stroke survivors, represents the first completed trial of a Factor XI inhibitor investigating whether this new class of medication is better than standard therapy at safely preventing recurrent strokes.
When added to standard blood-thinning medications such as aspirin, asundexian reduced the occurrence of ischemic stroke by 26% compared to placebo. This reduction was consistent across all participants regardless of age, sex, cause of stroke, or severity of the first stroke. The medication also reduced the occurrence of disabling stroke and lowered cardiovascular death, stroke of any type, heart attack, and major bleeding, indicating an overall benefit to patients. Crucially, the treatment did not increase bleeding within the brain or major bleeding, nor did it increase the occurrence of any serious adverse effects.
According to the American Stroke Association, a division of the American Heart Association, nearly 1 in 4 stroke survivors will have another stroke, called a secondary stroke. Current guidelines recommend antithrombotic therapy for nearly all stroke survivors to prevent a second stroke, but existing treatments have limitations. "Antiplatelet therapy has limited effectiveness in preventing recurrent stroke because of bleeding risks," said Dr. Mike Sharma, principal investigator of the study. "Previous efforts to improve outcomes by adding other anticlotting or blood thinning medications have not succeeded due to the increased risk of bleeding, lack of benefit or both."
Asundexian works differently from existing anticoagulants by inhibiting a clotting protein called Factor XI (FXIa), which is involved in producing large blood clots that can block blood vessels. Unlike other anticoagulants such as rivaroxaban and apixaban, which inhibit Factor Xa, asundexian does not increase the risk of bleeding. This safety profile is supported by observations that people born with a genetic deficiency of Factor XI have a lower risk of ischemic stroke and rarely have spontaneous bleeding.
The study included participants who recently had a mild to moderate ischemic stroke that was not caused by a heart condition, known as non-cardioembolic ischemic stroke, or a transient ischemic attack (TIA) identified as having a high risk of progressing to a stroke within one week. Participants were randomly selected to receive either standard antiplatelet therapy plus a daily dose of asundexian or standard antiplatelet therapy plus a placebo, with neither patients nor researchers aware of which treatment they received during the trial.
"Asundexian holds the potential to reduce the risk of a recurrent stroke over the long term without an increased safety risk. This is a major advance in our ability to prevent strokes in people at risk of stroke recurrence," said Sharma. "If approved by the FDA, asundexian could be widely used for patients who have had a non-cardioembolic stroke or a TIA." The U.S. Food and Drug Administration has granted the medication fast-track designation for its potential use in stroke prevention after ischemic stroke not caused by a blood clot originating in the heart.
The study was conducted at 702 sites in 37 countries, with participants enrolled between January 2023 and February 2025. Participants were followed for 3 to 31 months and monitored for ischemic stroke or major bleeding as defined by the International Society on Thrombosis and Hemostasis. Additional information about stroke prevention and guidelines is available through the American Stroke Association at https://www.stroke.org.
It is important to note that the study findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal. The study was funded by Bayer, who manufactures asundexian and provided the medication and placebo used in the trial. The American Heart Association maintains strict policies to prevent any donations from influencing its science content and policy positions, with overall financial information available https://www.heart.org.
