HAMILTON, ONTARIO- A large international study has found that asundexian, an investigational anti‑clotting medication, reduces the risk of a stroke in people who recently experienced a stroke or transient ischemic attack (TIA) caused by a clot forming outside of the heart (non-cardioembolic stroke), without increasing bleeding, the most serious and feared complication of existing stroke prevention treatments.
The study involved 12,327 adults from 37 countries who were enrolled within 72 hours of a non‑cardioembolic stroke or a temporary blockage of blood flow to the brain (TIA). The study evaluated the safety and effectiveness of asundexian for the prevention of another stroke in these patients. Currently, preventing another stroke in these situations relies mainly on antiplatelet medications, a type of anti-clotting medication that reduces risk only modestly and increases bleeding when combined or used for long term.
Findings from the OCEANIC‑STROKE trial were published in The New England Journal of Medicine (NEJM) on April 15, 2026.
"This is something researchers have been working toward for decades," said Mike Sharma, principal investigator of the study and a senior scientist at the Population Health Research Institute (PHRI), a joint institute of McMaster University and Hamilton Health Sciences. "Asundexian reduced the occurrence of a stroke by 26 per cent, and this benefit was consistent across patients of different ages, sexes, stroke severity, and stroke causes, without increasing major bleeding or other serious side-effects."
Participants were randomly assigned to receive either asundexian (50 mg once daily) or a placebo, in addition to standard antiplatelet therapy like aspirin. The average age of participants was 68 years; 25 per cent were over the age of 75, and 33 per cent were women. Most participants (95 per cent) had experienced a non-cardiometabolic stroke, while the remainder had a high‑risk TIA. Non-cardioembolic strokes are common and
account for the majority of ischemic strokes (clot-related strokes), and the trial enrolled a widely representative sample of these patients.
Patients were followed regularly at one month and three months and then at three-month intervals to track outcomes. Researchers found:
- 6.2 per cent of patients taking asundexian experienced another ischemic stroke, compared with 8.4 per cent of those taking placebo, leading to a 26 per cent reduction in this outcome.
- 9.2 per cent experienced a major cardiovascular event (stroke, heart attack or cardiovascular death), compared with 11.1 per cent on placebo (17 per cent reduction).
- Disabling or fatal strokes occurred in 2.1 per cent of patients taking asundexian versus three per cent in the placebo group (31 per cent reduction).
- No increase in bleeding was observed in patients receiving asundexian.
"Until now, reducing stroke risk has often been associated with higher bleeding risk. These findings give us hope for a safer way to prevent recurrent strokes," said Ashkan Shoamanesh, co‑principal investigator of the study and PHRI senior scientist. "That's something physicians, patients and families have been waiting for."
Asundexian works differently from existing anti-clotting drugs by blocking Factor XIa, a protein involved in harmful clot formation but plays only a small role in stopping bleeding. By blocking Factor XIa, asundexian aimed to prevent dangerous clots while preserving the body's natural bleeding control, a novel paradigm in anti-clotting medication that is now supported by the OCEANIC-STROKE results.
OCEANIC-STROKE is the first completed Phase 3 trial of a Factor XIa inhibitor for secondary stroke prevention. Previous studies evaluating therapy for long-term secondary stroke prevention have failed due to lack of efficacy, increased bleeding, or both.
"This trial marks a major step toward safer and more effective long‑term treatment for stroke prevention," added Sharma. "It was completed with remarkable scale and efficiency right here in Canada through our global research network."
Asundexian is still under regulatory review and is not yet approved for clinical use. The study was sponsored by Bayer AG.
