Bayer's Sunharbo, a first-in-class XIa blocker, wins FDA approval after stroke

The FDA cleared Sunharbo on Nov. 9, 2026. In a Phase 3 trial it cut second strokes from 8.4% to 6.2%.

On Monday, Nov. 9, 2026, the FDA approved Bayer's Sunharbo to lower the risk of another stroke. It is the first approved medicine in a new class of clot-prevention drugs, and it works by inhibiting a protein called XIa. In a Phase 3 trial of people who had already had a stroke and were on standard treatments, 8.4% of placebo patients had a second stroke, against 6.2% on Sunharbo. That is a 26% relative reduction, and about 53 patients would need treatment for a year to prevent one recurrent stroke.

Many existing blood thinners are not used after stroke because of bleeding risk. The XIa mechanism is thought to prevent harmful clots without raising that risk, so more stroke survivors might be able to receive preventive treatment. That bleeding benefit is described as what the mechanism is expected to do. We have no trial size or bleeding outcomes to confirm it.

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Source: STAT