An investigational anti-clotting medication called asundexian demonstrated significant potential for preventing recurrent strokes without increasing bleeding risks, according to preliminary findings presented at the American Stroke Association's International Stroke Conference 2026. The medication, when added to standard blood-thinning therapy, reduced the occurrence of ischemic stroke by 26% compared to placebo in a Phase III international trial involving over 12,300 stroke survivors.
This development addresses a critical limitation in current stroke prevention approaches. According to the American Stroke Association, nearly one in four stroke survivors will experience another stroke. While antithrombotic therapy is recommended for nearly all stroke survivors to prevent recurrence, existing treatments have significant limitations. "Antiplatelet therapy has limited effectiveness in preventing recurrent stroke because of bleeding risks," said Dr. Mike Sharma, principal investigator of the OCEANIC-STROKE study and professor at McMaster University.
Asundexian represents a novel approach to stroke prevention 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 that inhibit Factor Xa and increase bleeding risk, asundexian appears to reduce clot formation without compromising safety. This mechanism is supported by observations that people born with genetic Factor XI deficiencies have lower stroke risk but rarely experience spontaneous bleeding.
The OCEANIC-STROKE trial included participants who had recently experienced mild to moderate ischemic strokes not caused by heart conditions, or transient ischemic attacks (TIAs) identified as high-risk for progression to stroke. Participants received either standard antiplatelet therapy plus daily asundexian or standard therapy plus placebo, with neither patients nor researchers aware of treatment assignments during the trial.
Beyond the 26% reduction in ischemic stroke occurrence, the study found consistent benefits across all participant subgroups regardless of age, sex, stroke cause, or initial stroke severity. The medication also reduced disabling strokes and lowered cardiovascular death, stroke of any type, heart attack, and major bleeding collectively. Importantly, asundexian did not increase bleeding within the brain or major bleeding events, nor did it increase serious adverse effects.
"Asundexian holds the potential to reduce the risk of a recurrent stroke over the long term without an increased safety risk," said Sharma. "This is a major advance in our ability to prevent strokes in people at risk of stroke recurrence." If approved by regulatory agencies like the U.S. Food and Drug Administration, which has granted the medication fast-track designation, asundexian could become widely used for patients who have had non-cardioembolic strokes or high-risk TIAs.
The study's importance extends beyond clinical implications to public health impact. Stroke remains a leading cause of death and disability worldwide, with the American Heart Association's 2026 Heart Disease and Stroke Statistics identifying it as the fourth leading cause of death in the United States. Current guidelines, including the 2021 guideline from the American Stroke Association, recommend dual antiplatelet therapy only for specific patient groups and not for long-term use due to bleeding concerns.
While these findings are promising, researchers note limitations including relatively few participants with severe strokes despite broad inclusion criteria. The study findings are considered preliminary until published in a peer-reviewed journal, as abstracts presented at scientific meetings are not peer-reviewed. A substudy analyzing brain imaging data from participants may provide additional insights into asundexian's effects on both clotting and bleeding when completed.
The trial was conducted at 702 sites across 37 countries between January 2023 and February 2025, with participants followed for 3 to 31 months. Bayer, which manufactures asundexian, funded the study and provided the medication and placebo used in the trial.
