Bayer Reports Asundexian Approval for Secondary Stroke Prevention
Key Takeaways
- The FDA approved asundexian (Sunharbo) 50 mg, the first factor XIa inhibitor, for use with antiplatelet therapy to reduce stroke risk in adults after a recent mild-to-moderate non-cardioembolic ischemic stroke or high-risk TIA.
- In OCEANIC-STROKE, ischemic stroke occurred in 6.2% of patients taking asundexian versus 8.4% taking placebo, both on antiplatelet therapy (cause-specific hazard ratio 0.74).
- Overall major bleeding was similar (1.9% vs 1.7%), but the FDA reported increased major bleeding in patients older than 75 and during the first 90 days of treatment, and more gastrointestinal bleeding.
- The drug isn’t approved for stroke prevention in atrial fibrillation.
OCEANIC-STROKE was an international, multicenter, randomized, double-blind, placebo-controlled, event-driven phase III trial funded by Bayer. It randomized 12,327 participants within 72 hours of a non-cardioembolic ischemic stroke or high-risk TIA to once-daily asundexian 50 mg (6,162) or placebo (6,165), each added to planned single or dual antiplatelet therapy. Time to ischemic stroke was the primary efficacy endpoint, and major bleeding defined by the International Society on Thrombosis and Haemostasis (ISTH) was the primary safety endpoint. Results were published in The New England Journal of Medicine.
On November 9, 2026, the US Food and Drug Administration (FDA) announced approval of Sunharbo (asundexian) 50 mg tablets, and Bayer announced the authorization on November 10. The FDA granted Fast Track and Priority Review designations. The approved indication is use with antiplatelet therapy to reduce the risk of stroke in adults after a recent mild-to-moderate non-cardioembolic ischemic stroke (National Institutes of Health Stroke Scale score of 15 or less) or a high-risk TIA; the severity cutoff applies to the stroke group, not the TIA group. Bayer described asundexian as the first approved factor XIa inhibitor and said it has also been approved in China and is under review in other markets.
Over a median follow-up of about 19 months, ischemic stroke occurred in 6.2% of patients taking asundexian and 8.4% taking placebo (cause-specific hazard ratio 0.74; 95% confidence interval [CI] 0.65–0.84; P<0.001), a 26% relative reduction and an absolute difference of 2.2 percentage points, which corresponds to roughly 45 patients treated to prevent one ischemic stroke (calculated from the reported incidences). The composite of death from cardiovascular causes, myocardial infarction, or stroke was 9.2% versus 11.1% (hazard ratio 0.83; 95% CI 0.74–0.92). The FDA cites a median treatment duration of 14.2 months.
ISTH major bleeding occurred in 1.9% of patients taking asundexian and 1.7% taking placebo (hazard ratio 1.10; 95% CI 0.85–1.44; P=0.46); major or clinically relevant nonmajor bleeding was 5.5% versus 5.0% (hazard ratio 1.12; 95% CI 0.96–1.30). The confidence interval for major bleeding does not exclude a clinically meaningful increase, so the similar rates do not show that the risks are equivalent. The FDA states that major bleeding was increased with asundexian in patients older than 75 years and during the first 90 days of treatment, and that gastrointestinal bleeding occurred more often than with placebo. Bayer reports that treatment effects on the primary endpoint were consistent across age, sex, index event, non-cardioembolic stroke subtype, stroke severity, and planned antiplatelet therapy.
The FDA reports diarrhea as the most frequent adverse reaction (3% or more of treated patients). Sunharbo is not recommended in patients with moderate or severe hepatic impairment; elevated liver enzymes have been seen with treatment, mostly mild according to Bayer. It should be withheld at least 24 hours before elective surgery or invasive procedures and for at least 24 hours after thrombolysis for acute ischemic stroke. The drug is not approved for stroke prevention in patients with atrial fibrillation; an earlier trial in that setting, OCEANIC-AF, was stopped early because asundexian was less effective than apixaban.
The trial compared asundexian with placebo on a background of antiplatelet therapy and was sponsored by Bayer, so it does not show how the drug performs against other secondary-prevention strategies. The company’s description of the trial and the approval comes with its own interests, and the FDA’s announcement adds safety qualifiers that Bayer’s announcement did not emphasize. For adults within the approved indication, factor XIa inhibition alongside antiplatelet therapy is an additional approach to secondary stroke prevention, with a reduction in recurrent ischemic stroke weighed against higher bleeding risk in older patients and early in treatment.
Clinician Questions
What is the absolute reduction in recurrent ischemic stroke with asundexian after non-cardioembolic stroke or high-risk TIA?
In OCEANIC-STROKE, ischemic stroke occurred in 6.2% of patients taking asundexian plus antiplatelet therapy and 8.4% of those taking placebo plus antiplatelet therapy over a median follow-up of about 19 months, an absolute difference of 2.2 percentage points (a relative reduction of 26%).
How does factor XIa inhibition by asundexian relate to clot formation and bleeding?
Factor XIa participates in coagulation and is thought to contribute to pathological thrombus growth and vessel blockage while playing a smaller role in forming a hemostatic plug at an injury site. Asundexian inhibits factor XIa. That rationale does not establish that the drug avoids bleeding: major bleeding was similar overall in the trial, but the FDA reported increased bleeding in patients older than 75 and in the first 90 days of treatment, and more gastrointestinal bleeding.
Is asundexian approved for stroke prevention in patients with atrial fibrillation?
No. The approval covers adults after a recent non-cardioembolic ischemic stroke or high-risk TIA, in combination with antiplatelet therapy. In the earlier OCEANIC-AF trial, asundexian was less effective than apixaban for preventing stroke or systemic embolism in atrial fibrillation, and that study was stopped early.
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