A Newly Approved Blood Thinner Cut the Risk of a Second Stroke

CATEGORY: HEART & CIRCULATION

What would it take to prevent second strokes without the bleeding that blood thinners usually bring? That question now has a randomized answer, and as of this week, an approved drug. Among 12,327 adults who started asundexian within three days of an ischemic stroke or a high-risk transient ischemic attack (a brief, stroke-like episode that resolves on its own), 6.2% had another ischemic stroke over roughly a year and a half, versus 8.4% on placebo. That’s a 26% lower risk, with no rise in major bleeding.¹ The FDA approved the drug on November 9, 2026.

Borrowed From People Who Rarely Clot

Clotting does two jobs. It seals injured blood vessels, which you want, and it enlarges clots forming inside arteries, which you don’t. A protein called factor XI works mostly on the second job. People born with low levels of it have fewer strokes but don’t bleed much more than others. Researchers created asundexian to imitate this: a tablet taken once a day that stops the active form of the protein. Older attempts to add a conventional blood thinner on top of aspirin-type drugs after a stroke mostly foundered on bleeding. Researchers designed this drug to dodge that trap.

Seven Hundred Hospitals, One Coin Flip

The OCEANIC-STROKE trial enrolled patients at 702 hospitals in 37 countries, typically about two days after a mild-to-moderate stroke. Researchers excluded people whose strokes came from atrial fibrillation, because those clots form in the heart and need a different drug. Everyone stayed on standard antiplatelet therapy, such as aspirin or clopidogrel, and about two-thirds took two such drugs at the start. On top of that, half received asundexian 50 mg daily and half an identical placebo. Researchers randomly assigned patients to treatment groups, and neither patients, doctors, nor the committee judging each event knew who was taking what. Follow-up ran a median of 19 months. The typical participant was 68 years old; a third were women. Most strokes here were on the milder end, with a median severity score of 2 on a 42-point scale, and only about one in twenty entered after a TIA rather than a full stroke. How well the drug serves people with severe strokes is a question this trial largely leaves open.

Two Fewer Strokes per Hundred, No Extra Major Bleeds

The gap amounted to roughly two fewer strokes for every hundred people treated: 384 strokes in the asundexian group against 518 on placebo, or 4.4 versus 6.0 strokes per 100 people per year of treatment. Disabling or fatal strokes were 31% less common, 2.1% versus 3.0%. The wider composite of cardiovascular death, heart attack, or stroke fell too, 9.2% versus 11.1%. Deaths overall didn’t budge, 4.0% against 4.1%. And the safety side held: major bleeding occurred in 1.9% of asundexian takers and 1.7% on placebo, a difference small enough to be chance. Symptomatic bleeding into the brain, the complication stroke doctors fear most, was 0.7% versus 0.6%. The FDA’s label still carries cautions. Bleeding ran somewhat higher in people over 75, stomach and intestinal bleeding was more common on the drug, and diarrhea was its most frequent side effect.

A Bigger Trial Than Planned, and a Slow Start

The investigators expected a 20% risk reduction and midway through, after a blinded check of the data, enlarged the trial from about 9,300 people to over 12,300 to be sure of detecting it. The final 26% beat their assumption. The benefit took time, though. Within the first 90 days, strokes were only slightly and not significantly fewer, 3.0% versus 3.5%; the separation grew with continued treatment. The approval covers adults after a recent mild-to-moderate stroke not caused by atrial fibrillation, or a high-risk TIA, taken alongside antiplatelet therapy. It’s the first drug of its class, and Bayer, which funded the trial, will not be alone for long: competing factor XI blockers are in late-stage testing. For a condition in which the event itself announces the risk of the next one, this is the first genuinely new preventive drug in years.

Key Takeaways

• Adding daily asundexian to standard antiplatelet drugs after a stroke cut repeat ischemic strokes by 26%: 6.2% versus 8.4% over a median of 19 months, about two fewer strokes per hundred people treated.
• Major bleeding didn’t rise measurably, 1.9% versus 1.7%, though the FDA notes more bleeding in people over 75 and more gastrointestinal bleeding on the drug.
• Deaths overall were unchanged within the trial, and the benefit emerged with months of treatment rather than in the first 90 days.
• The approval is specific: strokes not caused by atrial fibrillation. Clots that form in the heart call for different drugs, and asundexian isn’t approved for them.

References

1. Sharma M, Dong Q, Hirano T, et al. Asundexian for Secondary Stroke Prevention. New England Journal of Medicine. 2026;394(15):1467–1479. link