Research Highlights:
- When added to standard blood-thinning medications such as aspirin, the new anti-clotting medication asundexian reduced the risk of a second stroke by reducing the formation of blood clots without increasing the risk of bleeding.
- This is the first completed trial of a Factor XI inhibitor investigating whether the medication asundexian is better than standard therapy at safely preventing recurrent strokes.
- Note: The study featured in this news release is a research abstract. Abstracts presented at the American Heart Association's scientific meetings are not peer-reviewed, and the findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.
NEW ORLEANS, Feb. 5, 2026 — An investigational anti-clotting medication, asundexian, demonstrated a reduction in the risk of a second ischemic (clot-caused) stroke without raising bleeding concerns, according to a preliminary late-breaking science presentation at the American Stroke Association's International Stroke Conference 2026. The meeting, Feb. 4 - 6, 2026, in New Orleans, is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health.
"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 Mike Sharma, M.D., M.Sc., principal investigator of the study, the Michael G. Degroote Chair in Stroke Prevention, professor of medicine at McMaster University and senior scientist at the Population Health Research Institute, a joint institute of McMaster University and Hamilton Health Sciences, in Hamilton, Ontario, Canada.
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.
The 2021 guideline from the American Stroke Association states that antithrombotic therapy, including antiplatelet or anticoagulant agents, is recommended for nearly all stroke survivors to prevent a second stroke. Dual antiplatelet therapy (treatment with two anti-clotting or blood-thinning medications) is recommended only in very specific patients, including those with early-arriving minor stroke and high-risk transient ischemic attack or severe symptomatic intracranial stenosis. Antiplatelets, most commonly aspirin, prevent platelets in the blood from sticking together and forming clots that lead to stroke. Dual antiplatelet therapy, which includes a second medication (such as clopidogrel or dipyridamole), is given in addition to aspirin, however, it is not recommended for long-term use.
"Antiplatelet therapy has limited effectiveness in preventing recurrent stroke because of bleeding risks," said Sharma, who is also director of the Brain Health and Stroke program of the Population Health Research Institute. "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 is a novel investigational medication that inhibits a clotting protein called Factor XI (FXIa), which is involved in producing large blood clots that can block blood vessels. Other anticoagulants, such as rivaroxaban and apixaban, inhibit a different clotting protein (Factor Xa) to reduce the risk of stroke. However, unlike these medications, asundexian does not increase the risk of bleeding. People born with a genetic deficiency of Factor XI are known to have a lower risk of ischemic stroke and rarely have spontaneous bleeding.
This research, the OCEANIC-STROKE (Oral faCtor Eleven A iNhibitor asundexian as novel antithrombotiC) study, is a Phase III international trial that included more than 12,300 stroke survivors. It is investigating whether adding daily asundexian to antiplatelet therapy could reduce the risk of a new stroke caused by a blood clot without increasing the risk of bleeding or other adverse events.
Participants recently had a mild to moderate ischemic stroke that was not caused by a heart condition such as an irregular heart rhythm. This type of stroke is called a non-cardioembolic ischemic stroke. Some participants had experienced a transient ischemic attack (TIA), which involves symptoms that go away within minutes to hours and do not cause lasting damage to the brain. The TIA patients included in the trial were 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. Neither patients nor researchers were aware of which treatment they received during the trial.
Participants were followed for 3 to 31 months, and researchers found that compared to a placebo, adding asundexian to antiplatelet medication:
- Reduced the occurrence of ischemic stroke by 26%, and this reduction was consistent for all participants regardless of several key factors: age or sex, the cause of stroke or the severity of the first stroke;
- Reduced the occurrence of a disabling stroke;
- Did not increase bleeding within the brain or major bleeding;
- Did not increase the occurrence of any serious adverse effects; and
- Lowered cardiovascular death, stroke of any type, heart attack and major bleeding, indicating an overall benefit to patients.
"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. If approved by the FDA, asundexian could be widely used for patients who have had a non-cardioembolic stroke or a TIA," he said.
The study is limited by having relatively few participants with severe strokes, despite broad inclusion criteria that could have included them.
In a substudy of OCEANIC-STROKE, brain imaging and standardized MRI images were collected for participants. Analysis of that data is not yet complete; however, the results should provide further information on the impact of asundexian on both clotting and bleeding.
Asundexian is an investigational medication that has not been approved in any country. 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.
Study details, background and design:
- The study was conducted at 702 sites in 37 countries, with participants enrolled between January 2023 and February 2025.
- The participants (12,327 adults; average age of 68; 67% male) were enrolled within 72 hours of a mild-to-moderate ischemic stroke (up to 15 on the NIH Stroke Scale) or a transient ischemic attack deemed to represent a high risk of a more severe stroke (scoring 6-7 on the 7-point ABCD2 scale that is based on the patient's age, blood pressure, diabetes status, and the type and duration of TIA symptoms).
- 43% of the participants had a stroke assumed to be caused by plaque buildup in the large arteries leading to the brain; 30% had a stroke of undetermined cause; and 22% had a stroke thought to be due to blockages in small arteries feeding deep brain tissues.
- None of the participants had atrial fibrillation, an artificial heart valve or other conditions that can lead to a blood clot that travels from the heart to the brain to cause a stroke. None had other conditions known to increase the risk of stroke or bleeding.
- Participants were randomly chosen to receive either 50 mg/day of asundexian or a placebo in addition to standard antiplatelet therapy (aspirin only or dual antiplatelet therapy).
- Participants were monitored for a minimum of 3 months and up to 31 months for the occurrence of ischemic stroke or major bleeding as defined by the International Society on Thrombosis and Hemostasis (resulting in death or significant blood loss or occurring in a critical site in the body, such as the brain, spinal cord or around the heart).
- In addition, participants were monitored for significant cardiovascular events, including any type of stroke, cardiovascular death, heart attack, stroke, death from any cause, heart attack, stroke or disabling stroke.
The co-principal investigator of OCEANIC-STROKE is Ashkan Shoamanesh, M.D., associate professor of medicine at McMaster University and senior scientist at the Population Health Research Institute of Hamilton Health Sciences. Other study co-authors and their disclosures are listed in the abstract.
Bayer, who manufactures asundexian, funded the study and provided the medication and placebo used in the trial.
Statements and conclusions of studies that are presented at the American Heart Association/American Stroke Association's scientific meetings are solely those of the study authors and do not necessarily reflect the Association's policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. Abstracts presented at the Association's scientific meetings are not peer-reviewed, rather, they are curated by independent review panels and are considered based on the potential to add to the diversity of scientific issues and views discussed at the meeting. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.
