The US Food and Drug Administration has approved a new type of blood thinner designed to stop strokes happening again, the first drug of its kind to work by blocking the clotting protein Factor XIa.
The drug, asundexian, will be sold by Bayer under the brand name Sunharbo. It is a once-daily tablet approved for adults who have had a stroke that was not caused by a clot travelling from the heart, and for patients who have had a high-risk transient ischaemic attack, often called a mini-stroke.
Approval was based on the late-stage OCEANIC-STROKE trial, which enrolled 12,327 adults and was published in the New England Journal of Medicine in April 2026. Over a median of 14.2 months of treatment, the drug cut the risk of a further ischaemic stroke by 26 per cent compared with placebo, and also reduced the severity of strokes that did occur. Stroke is a leading cause of death in the United States, and Bayer estimates that about 795,000 Americans have a stroke each year.
Existing big-selling blood thinners, including Eliquis from Pfizer and Bristol Myers Squibb and Xarelto from Johnson & Johnson and Bayer, work by blocking a different clotting protein, Factor Xa. Doctors have long hoped that targeting Factor XIa could prevent harmful clots while sparing the body’s normal clotting, though bleeding risk remains a consideration — trial reporting noted that bleeding risk rises in patients over 75.
Bayer is counting on the drug to help replace revenue from older medicines such as Xarelto, which has lost patent protection and now faces cheaper generic competition. The company has previously described asundexian as having blockbuster potential, typically meaning at least $1 billion in annual sales. “We believe that we’re bringing a practice-changing innovation to the market,” Sebastian Guth, president of Bayer’s US operations, said. “There have not been any changes in the recurrence rates of stroke over the past 20 years, so there’s a genuine and very significant excitement” for the drug.
China’s drug regulator approved Sunharbo late last month, ahead of the US decision. Rival Factor XIa drugs are still in development, including Novartis’s abelacimab and milvexian, a joint effort by Bristol Myers Squibb and Johnson & Johnson, neither of which has yet reported late-stage stroke-prevention data.
Sources: Reuters — https://www.reuters.com/legal/litigation/us-fda-approves-bayers-blood-thinner-prevent-repeat-strokes-2026-11-09/ ; OCEANIC-STROKE trial, New England Journal of Medicine, April 2026.
