FDA Approval of Asundexian Provides a New Approach to Secondary Stroke Prevention

For patients recovering from an ischemic stroke, preventing another event remains a central concern, even when they are receiving recommended treatment. The FDA’s November 9, 2026, approval of asundexian (Sunharbo; Bayer) gives clinicians a new option: a once-daily oral Factor XIa inhibitor added to antiplatelet therapy to reduce the risk of stroke in adults with recent noncardioembolic ischemic stroke or high-risk transient ischemic attack (TIA). The approved stroke population includes patients with a National Institutes of Health Stroke Scale (NIHSS) score of 15 or less.^1,2

The approval was based on the Phase 3 OCEANIC-STROKE study, in which asundexian reduced the risk of ischemic stroke by 26% relative to placebo, with both groups receiving antiplatelet therapy. Overall major bleeding rates were similar, although the approval materials identify bleeding findings that deserve attention when selecting and counseling patients.^2,3

For Ashkan Shoamanesh, MD, a co-principal investigator of OCEANIC-STROKE and senior scientist at the Population Health Research Institute, a joint institute of Hamilton Health Sciences and McMaster University in Ontario, Canada, the findings address a longstanding challenge: how to provide additional protection against recurrent stroke without the bleeding burden that has limited more intensive antithrombotic treatment.²

“FDA approval is a key pivotal step to getting this drug to the patients who could benefit from it,” Dr Shoamanesh said in an interview with Vascular Disease Management. “Historically, with conventional antithrombotic therapies, we were limited in escalating either the intensity or the duration for added stroke prevention because of excess bleeding,” he said.

Why factor XIa is a different target

Asundexian selectively and reversibly inhibits activated factor XI, or factor XIa, reducing amplification of thrombin generation. The rationale is that this pathway contributes to pathological thrombosis while playing a more limited role in normal hemostasis. By targeting factor XIa, investigators sought to prevent harmful clot formation while preserving more of the body’s ability to control bleeding after injury.²

That distinction helps explain the interest in this drug class, and it calls for careful language: similar overall major bleeding rates in a clinical trial do not establish that a treatment is free of bleeding risk. Asundexian is the first FDA-approved factor XIa inhibitor, and its clinical use will require attention to both the efficacy results and the safety information accompanying approval.^1,2

What OCEANIC-STROKE showed

OCEANIC-STROKE was a randomized, double-blind, placebo-controlled, event-driven trial conducted at 702 centers in 37 countries. Investigators randomized 12,327 patients within 72 hours after a noncardioembolic ischemic stroke or high-risk TIA to asundexian 50 mg once daily or placebo, in addition to planned single or dual antiplatelet therapy. Median follow-up was 567 days. Bayer funded the trial.³

“In this study, we observed that randomization to asundexian led to a robust 26% reduction in the primary efficacy endpoint,” Dr Shoamanesh said. Ischemic stroke occurred in 6.2% of patients receiving asundexian and 8.4% receiving placebo, corresponding to a cause-specific hazard ratio (HR) of 0.74 (95% CI, 0.65-0.84; P < .001).³ The observed difference was 2.2 percentage points over trial follow-up. Separately, the investigators’ presentation reported a 1-year absolute risk reduction of 1.9 percentage points and a number needed to treat of 53.⁴ These figures put the relative benefit into a timeframe clinicians can discuss with patients.

Benefits extended to several secondary outcomes. All stroke, including ischemic and hemorrhagic events, occurred in 6.6% of the asundexian group and 8.8% of the placebo group. The composite of cardiovascular death, myocardial infarction, or stroke occurred in 9.2% and 11.1%, respectively (HR, 0.83; 95% CI, 0.74-0.92). The composite benefits were driven primarily by fewer ischemic strokes.²

“This is historic in that we've been able to now prove that with factor XI inhibition we can uncouple pathologic thrombus formation from hemostasis,” Dr Shoamanesh said.

Reading the safety findings 

Major bleeding, defined by International Society on Thrombosis and Haemostasis criteria, was the primary safety endpoint. The approval announcement reports rates of 1.6 vs 1.5 events per 100 patient-years with asundexian and placebo, respectively.²

However, gastrointestinal bleeding occurred more often with asundexian: 2.7 vs 2.1 events per 100 patient-years. Higher major bleeding rates were reported with asundexian during the first 90 days and among patients older than 75 years, patients planned to receive dual antiplatelet therapy, and the high-risk TIA subgroup. These findings qualify any broad statement that treatment carries no additional bleeding risk.²

Where the treatment may fit

Dr Shoamanesh views the findings as relevant across the eligible population. Discussing the trial’s subgroup analyses, he said, “We found consistency of the overall benefit irrespective of the subgroups examined. I don't see any reason to limit this treatment to any particular high-risk subgroups.” That view supports considering treatment across the approved population, while individual decisions still require assessment of bleeding risk, comorbidities, concomitant medications, and the prescribing information. Consistency across subgroups does not establish that every individual patient will benefit.

The distinction between noncardioembolic stroke and stroke associated with atrial fibrillation remains essential. Dr Shoamanesh emphasized that asundexian is not intended to replace anticoagulation in patients with conditions such as atrial fibrillation that require anticoagulant therapy. Its approved role is as an addition to antiplatelet treatment for the specified secondary stroke prevention population.²

It also remains one part of prevention. Dr Shoamanesh stressed that care should continue to address the underlying stroke mechanism, blood pressure, cholesterol, diabetes, smoking, physical activity, and diet. For vascular specialists, the approval adds an antithrombotic option to that broader effort to reduce recurrent vascular events.

Questions that continue after approval

The trial answers an important efficacy question, but Dr Shoamanesh identified practical issues that require further study. These include the safety of thrombolysis if a patient experiences an acute ischemic stroke while taking asundexian and the best management of a major bleeding event. He described preliminary observations as reassuring but emphasized that these questions remain unresolved.

“Could bleeding events be larger and require hemostatic treatments?” he asked, identifying one of the questions that further research needs to address. “We are in the process of developing a post-approval phase four registry to try to gain some additional insights on some of these remaining questions.”

Adoption will depend on more than familiarity with the mechanism. Dr Shoamanesh identified physician education, incorporation of the findings into clinical practice guidelines, and access through reimbursement pathways as important next steps. These are priorities for implementation, rather than evidence that guidelines or coverage policies have already changed. 

For Dr Shoamanesh, the value of preventing another stroke extends beyond the event itself. “This is an important advance in secondary stroke prevention,” he said, “offering us a new opportunity to prevent recurrent strokes, preserve brain health, and protect our patients from the disability and loss of independence that can follow another stroke.”

References

1. US Food and Drug Administration. FDA approves first factor XIa inhibitor to help prevent stroke in certain adults at high risk. November 9, 2026. Accessed November 10, 2026. https://www.fda.gov/news-events/press-announcements/fda-approves-first-factor-xla-inhibitor-help-prevent-stroke-certain-adults-high-risk

2. Bayer. Bayer’s SUNHARBO® (asundexian), 50 mg tablets, the First and Only Factor XIa Inhibitor, Approved by the U.S. FDA to Reduce the Risk of Stroke in Adults With Recent Non-Cardioembolic Ischemic Stroke or High-Risk Transient Ischemic Attack. Accessed November 10, 2026. https://www.businesswire.com/news/home/20261021770347/en/Bayers-SUNHARBO-asundexian-50-mg-tablets-the-First-and-Only-Factor-XIa-Inhibitor-Approved-by-the-U.S.-FDA-to-Reduce-the-Risk-of-Stroke-in-Adults-With-Recent-Non-Cardioembolic-Ischemic-Stroke-or-High-Risk-Transient-Ischemic-Attack...

3. Sharma M, Dong Q, Hirano T; OCEANIC-STROKE Investigators. Asundexian for secondary stroke prevention. N Engl J Med. 2026;394(15):1467-1479. doi:10.1056/NEJMoa2513880

4. OCEANIC-STROKE investigators. Primary results presentation. International Stroke Conference 2026. Accessed November 10, 2026. https://clinicaltrialresults.org/wp-content/uploads/2026/02/26-02-02_ISC_OCEANIC-STROKE-primary.pdf