FDA approves Bayer's Sunharbo, first XIa inhibitor, to reduce recurrence of stroke

The US Food and Drug Administration on Monday, Nov. 9, 2026, approved Bayer's drug to reduce recurrence of stroke, according to statnews.com. The drug will be sold under the brand name Sunharbo. It is the first approved medicine in a new class of drugs intended to prevent blood clots more safely statnews.comstatnews.comstatnews.comOpen source ↗.

Mechanism: XIa inhibition

Sunharbo inhibits a protein called XIa. This mechanism is thought to stop the formation of harmful clots without increasing the risk of bleeding. The distinction matters in this setting, because many blood thinners are not used after a stroke due to the increased risk of bleeding.

The approval makes available the first drug of this class. Other medicines acting on the same protein are not described in the report.

Phase 3 trial results

The Phase 3 trial enrolled people who had already had a stroke and were taking common stroke treatments statnews.comstatnews.comstatnews.comOpen source ↗. It compared Sunharbo with placebo in this group of patients.

A secondary stroke occurred in 8.4% of participants who took placebo and in 6.2% of those who took Sunharbo. This corresponds to a 26% reduction in risk.

The same data can be expressed differently: over one year, 53 patients need to be treated to prevent one recurrent stroke. The 26% figure describes the proportional difference between the two groups, while the number needed to treat describes how many patients receive the drug for each prevented event.

The report does not give bleeding rates from the trial. The statement that the mechanism does not raise bleeding risk is presented as a working understanding of how XIa inhibition acts, not as a trial result statnews.comstatnews.comstatnews.comOpen source ↗.