The FDA has approved Bayer’s asundexian to slash the risk of stroke for certain patients, with the drug serving as the first factor XIa inhibitor to hit the market.
The oral drug, set to be sold as Sunharbo, is a next-gen blood thinner paired with anti-platelet therapy for adults after recent non-cardioembolic ischemic stroke or high-risk transient ischemic attack, also known as a “mini-stroke.” The factor XIa (FXIa) inhibitor held FDA fast track status and was granted priority review in May.
A month supply of the once-daily drug reportedly costs $748.5, or about $9,100 a year, according to a Monday night note from BMO analysts.
Sunharbo works by blocking factor XIa, a protein produced by the liver that helps blood clot. The Bayer drug is the first of its kind, with currently approved blood thinners—such as Bristol Myers Squibb and Pfizer’s Eliquis or Johnson and Johnson and Bayer’s own Xarelto—inhibitors of Factor Xa, a different blood-clotting enzyme.
The drug also recently secured approval in China and is currently under regulatory review in several other regions, according to Bayer’s Monday release.
The fresh approval is based results from the Phase 3 OCEANIC-STROKE trial, which found that 50 mg of Sunharbo taken daily reduced the risk of ischemic stroke by 26% compared to placebo over a median of 14.2 months.
While bleeding was elevated in certain scenarios, Sunharbo wasn’t tied to an increase in overall major bleeding, with the trial providing “the strongest evidence that Factor XIa inhibition can deliver clinically meaningful antithrombotic benefits with a favorable bleeding profile,” according to BMO.
Sunharbo’s approval derisks the regulatory path for other factor XIa inhibitors, namely Bristol Myers Squibb and J&J’s milvexian, BMO analysts wrote. The investigational oral Factor XIa inhibitor is one of BMS’ key pipeline assets set up as a potential revenue replacement amid looming patent cliffs.
BMO Capital Markets is more impressed by Merck’s plans to replace lost Keytruda revenue than on Bristol Myers Squibb’s efforts to fill the expected void that will come from loss of exclusivity for both Opdivo and Eliquis.
October 2, 2026
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Bayer’s OCEANIC-STROKE trial and subsequent approval provide “meaningful clinical validation of Factor XIa as a drug target” and boost analyst confidence in the mechanism for secondary stroke prevention, BMO said. Late-stage data for milvexian in the indication is set to read out sometime before the year ends.
While milvexian’s twice-daily dosing is less convenient than Sunharbo’s once-daily regimen, superior stroke reduction could support premium pricing for J&J and BMS’ drug, especially if it doesn’t carry a meaningfully higher bleeding risk, the analysts wrote.
BMO remains more cautious on milvexian’s potential in atrial fibrillation (AFib)—for which data are expected in 2027—after Sunharbo’s own failure among patients with the condition—characterized by an irregular and often very rapid heart rhythm—who were at risk for stroke. In 2023, Bayer stopped its Phase 3 OCEANIC-AF trial comparing asundexian to Eliquis in AFib early due to lack of efficacy.