FDA Approves Sunharbo, First Factor XIa Drug to Cut Stroke Risk by 26%
The FDA approved Bayer's Sunharbo, the first Factor XIa inhibitor, cutting repeat stroke risk by 26% in adults after a recent stroke or high-risk mini-stroke.
Image: Wikimedia Commons / Westmead Hospital, CSIRO
WASHINGTON, Nov. 10 — The U.S. Food and Drug Administration on Monday approved Bayer's Sunharbo, a once-daily 50 mg tablet, to reduce the risk of another stroke in adults who recently had a mild-to-moderate non-cardioembolic ischemic stroke or a high-risk transient ischemic attack. It is the first U.S.-approved drug to target the clotting protein Factor XIa.
Approval rests on the Phase 3 OCEANIC-STROKE trial, which enrolled 12,327 adults at 702 centres in 37 countries within 72 hours of the event. The full results were published in the New England Journal of Medicine. About 795,000 Americans have a stroke each year, the Centers for Disease Control and Prevention says, and about 185,000 are repeat strokes.
Key Takeaways
- The FDA approved Sunharbo (asundexian) 50 mg once daily on Nov. 9, the first Factor XIa inhibitor cleared in the U.S.
- Repeat ischemic stroke hit 6.2% on Sunharbo versus 8.4% on placebo — 26% lower relative risk over a median 14.2 months.
- Major bleeding hit 1.9% on Sunharbo versus 1.7% on placebo — not statistically significant.
- Sunharbo is not approved for stroke prevention in atrial fibrillation; Bayer expects shipments in mid-to-late November.
Who Qualifies for Sunharbo After a Stroke or Mini-Stroke?
Sunharbo is approved for adults whose recent ischemic stroke was mild to moderate, with a National Institutes of Health Stroke Scale score of 15 or less, or who had a high-risk transient ischemic attack, often called a mini-stroke. The stroke must be non-cardioembolic — not caused by a clot from the heart. It is taken alongside antiplatelet therapy, not instead of it.
The approval does not extend to stroke prevention in atrial fibrillation. Bayer stopped its OCEANIC-AF trial there in 2024 after asundexian proved less effective than apixaban. Sunharbo is also not recommended with moderate or severe liver impairment, and its label warns of bleeding risk, including a higher risk in patients older than 75 and during the first 90 days.
How Sunharbo Compares With Standard Antiplatelet Therapy
Sunharbo blocks Factor XIa, a protein that amplifies thrombin generation and helps clots grow. The aim is to interrupt clot formation while leaving enough of the clotting system intact to limit bleeding, a trade-off that has limited older blood thinners. Patients received asundexian or placebo on top of antiplatelet therapy.
| OCEANIC-STROKE result | Sunharbo + antiplatelet | Placebo + antiplatelet |
|---|---|---|
| Patients enrolled | 6,162 | 6,165 |
| Repeat ischemic stroke | 6.2% | 8.4% |
| Relative risk reduction | 26% (hazard ratio 0.74) | — |
| Major bleeding (ISTH definition) | 1.9% | 1.7% |
| Median follow-up | 14.2 months | 14.2 months |
The result was not clean on every measure. A secondary outcome at 90 days missed statistical significance, with a hazard ratio of 0.84 and a confidence interval of 0.69 to 1.02, meaning the early benefit could not be separated from chance. The main result held over the full follow-up, and the bleeding figures gave the FDA the margin it needed. The agency also ordered vision-loss warnings on GLP-1 drugs this week.
When Will Sunharbo Be Available and What Will It Cost?
Bayer expects Sunharbo to begin shipping in mid-to-late November, with hospitals and pharmacies able to order it across the United States shortly thereafter. The company has not announced a U.S. price. Patient costs will depend on insurance coverage, at a time when health insurance premiums are rising sharply for 2027.
China approved asundexian on Oct. 26, and applications remain under review in Europe and Japan.
Frequently Asked Questions
Is Sunharbo approved for stroke prevention in atrial fibrillation?
No. Sunharbo is approved only to reduce the risk of another stroke after a recent non-cardioembolic ischemic stroke or high-risk transient ischemic attack. Bayer stopped its atrial fibrillation trial in 2024 because asundexian proved less effective than apixaban there.
How much does Sunharbo reduce the risk of another stroke?
Repeat ischemic stroke hit 6.2% on Sunharbo with antiplatelet therapy, against 8.4% on placebo — a 26% lower relative risk over a median of 14.2 months.
Does Sunharbo increase the risk of major bleeding?
Major bleeding occurred in 1.9% of patients on Sunharbo and 1.7% on placebo, not a statistically significant difference. The label still warns about bleeding, including a higher risk in patients older than 75 and during the first 90 days.
When will Sunharbo be available in US pharmacies?
Bayer expects shipments to begin in mid-to-late November, with hospitals and pharmacies able to order it across the United States shortly thereafter. No U.S. price has been announced.
Bayer expects Sunharbo to begin shipping in mid-to-late November.
