Nearly 1 in 4 people who have previously had a stroke will experience a recurrent stroke. To help reduce this risk, clinicians will typically recommend antiplatelet or anticoagulant therapy, in addition to making lifestyle changes.
Prescribing blood thinners can help to prevent future clots and reduce the risk of recurrent, often severe, strokes. They can be particularly crucial for those with atrial fibrillation, or other high risk cardioembolic causes, with research suggesting they can reduce stroke risk by 64%.
However, while these medications are generally safe and can significantly reduce the risk of recurrent strokes, they carry an increased risk of bleeding. In particular, the most dangerous complication of anticoagulant therapy can result in bleeding in or around the brain, known as a hemorrhagic stroke.
Now, a study suggests that a new investigational medication could offer protection without the heightened bleeding risk associated with current treatments.
Published in The New England Journal of Medicine, the findings indicate that asundexian reduced the risk of a second stroke by 26% in people who had recently experienced a clot-related stroke or TIA, without increasing bleeding risk.
Preventing a second stroke remains a major clinical priority. However, current strategies can create a difficult balance, by aiming to reduce clot formation without exposing individuals to dangerous bleeding complications.
Various proteins, known as clotting factors, play a role in the formation of blood clots. The process of stopping bleeding, known as hemostasis, involves multiple interlinked steps. Therefore, targeting specific proteins may offer a viable option for reducing clot formation without complications.
Asundexian is an oral anticoagulant that inhibits the activity of clotting factor XIa. This protein is mainly involved in the formation of harmful blood clots.
As factor XIa plays a limited role in normal bleeding control, blocking its action may provide a viable option to safely prevent dangerous blood clots while preserving the body’s ability to stop bleeding after injury.
“Asundexian selectively inhibits factor XIa (FXIa), targeting a component of the coagulation cascade that is increasingly recognized as more important for pathologic thrombosis than for physiologic hemostasis,” said Ashkan Shoamanesh, MD, co‑principal investigator of the study and Population Health Research Institute (PHRI) senior scientist, when speaking to Medical News Today.
“This contrasts with existing anticoagulants—such as factor Xa inhibitors—which interrupt core steps required for both thrombus formation and hemostasis,” he said.
“FXI occupies a unique position within the intrinsic pathway, functioning primarily as an amplifier of thrombin generation. In the setting of vascular injury, exposure of abundant tissue factor activates the extrinsic pathway and generates a robust thrombin burst sufficient to achieve hemostasis, with only a limited contribution from FXI,” he continued.
“In contrast, in pathologic states such as atherosclerotic plaque disruption, tissue factor exposure is more modest, and sustained thrombin generation relies more heavily on FXIa-mediated amplification. In this context, FXIa promotes clot propagation and stability, contributing to vaso-occlusive and thromboembolic events,” he further explained.
“This biological distinction allows FXIa inhibition to uncouple pathologic thrombosis from hemostasis,” he added.
The findings come from the large, international OCEANIC-STROKE Phase 3 trial, which included more than 12,300 participants across 37 countries.
The average age of those in the study was 68 years, with a quarter over 75, and 33% were female. Roughly 95% of participants had recently experienced a non-cardioembolic stroke (a stroke not caused by a heart condition), with the remaining experiencing high-risk TIA.
They were randomly assigned to receive either 50 milligrams (mg) Asundexian plus standard antiplatelet therapy, or a placebo plus standard therapy.
Over the follow-up period, the researchers observed a 26% reduction in recurrent ischemic stroke in those taking Asundexian. Additionally, fewer people experienced major cardiovascular events, disabling or fatal strokes, no increase in intracranial bleeding, or a rise in serious side effects.
“Ischemic strokes account for approximately 87% of the roughly 800,000 strokes occurring in the U.S. each year,” Mike Sharma, MD, MSc, FRCPC, co-principal investigator of the study and a senior scientist at the PHRI, told MNT.
“Despite guideline-recommended therapy, these patients remain at substantial risk of recurrence, with approximately 1 in 10 experiencing another stroke within the first year. In this context, we observed a significant 26% relative reduction in the hazard of ischemic stroke with asundexian. This corresponded to an absolute risk reduction of 1.9% and a number needed to treat of 54 at one year,” he said.
“Notably, this represents a meaningful incremental benefit on top of contemporary secondary stroke prevention strategies. We also observed a 31% reduction in the risk of disabling or fatal strokes. Importantly, these benefits were achieved without an associated increase in bleeding risk.”
— Mike Sharma, MD, MSc, FRCPC
These benefits were consistent regardless of age, sex, stroke severity, or underlying cause.
The researchers suggest that Asundexian’s ability to reduce stroke risk without increasing bleeding risk may offer a new paradigm in stroke prevention. Commenting on the key clinical takeaways, Shoamanesh told MNT:
“For one, OCEANIC-STROKE demonstrates that meaningful breakthroughs in secondary stroke prevention—with substantial treatment effects—remain achievable on top of existing guideline-recommended therapies.”
“Second, FXIa inhibitors represent a novel class of antithrombotic agents capable of reducing stroke risk without increasing bleeding, thereby providing a substantial net clinical benefit,” he continued.
“For about 50 years the mainstay of secondary stroke prevention has been aspirin monotherapy. This represents the first significant improvement for most ischemic strokes apart from short term use of dual antiplatelet therapy.”
— Ashkan Shoamanesh, MD
Similarly, Christopher Yi, MD, board certified vascular surgeon at MemorialCare Orange Coast Medical Center in Fountain Valley, CA, who was not involved in the study, suggests it may represent a new strategy for secondary prevention after non-cardioembolic ischemic stroke or high risk TIA.
“It should not replace aggressive risk-factor control, statins, blood pressure management, smoking cessation, diabetes control, and appropriate antiplatelet therapy, but it may eventually become an additional tool for selected high-risk patients,” he said.
However, despite the promising results, the study authors caution that Asundexian remains investigational and is not yet approved for clinical use. Further evaluation, regulatory review, and real-world data will be necessary before it becomes widely available.
Additionally, although the trial was large and diverse, certain patient groups, such as those with more severe strokes, were less represented, which may limit how broadly the findings apply.
If approved, Asundexian could provide a safer long-term option for preventing recurrent strokes, particularly for those at high risk of bleeding or unable to tolerate existing therapies.
“Within the framework of trial eligibility, there was no evidence of heterogeneity in treatment effect according to pre-specified subgroups,” Sharma said to MNT.
“For instance, patients benefited similarly irrespective of age, race, sex, index event type (ischemic stroke versus TIA), history or vascular imaging evidence of atherosclerosis, acute lacunar versus non-lacunar infarction on brain imaging, or ischemic stroke subtype. We expect the results to apply to the majority of patients with non-cardioembolic ischemic stroke.”
— Mike Sharma, MD, MSc, FRCPC
“Taken together, these findings support the broad generalizability of the trial results to the majority of patients with non-cardioembolic ischemic stroke or high-risk TIA encountered in clinical practice,” Sharma said.
“This is further strengthened by the inclusion of patients with moderate-severe stroke severity up to an NIHSS of 15 and those who received acute revascularization therapies, including intravenous thrombolysis or endovascular thrombectomy,” he added.
Yi also suggests that Asundexian is likely to benefit are those with recent non-cardioembolic ischemic stroke or high risk TIA who remain at elevated risk for recurrence despite standard antiplatelet therapy.
“This may include patients with atherosclerotic disease, multiple vascular risk factors, or other markers of high recurrent stroke risk,” Yi told MNT. “It would not necessarily apply to patients with cardioembolic stroke from atrial fibrillation, where established anticoagulation strategies remain the standard of care.”
For now, the findings provide cautious optimism that effective stroke prevention without added bleeding risk may be within reach.
