The FDA approved a new kind of blood thinner that cut repeat ischemic stroke risk 26%

The U.S. Food and Drug Administration on Nov. 9 approved Sunharbo, Bayer’s 50 mg asundexian tablet, as the first factor XIa inhibitor cleared in the United States. In the pivotal OCEANIC-STROKE trial the pill lowered the risk of ischemic stroke by 26% compared with placebo when both groups also took antiplatelet therapy. The approval covers adults after a recent mild-to-moderate stroke or a high-risk transient ischemic attack, and the label carries bleeding cautions for patients over 75.

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Sunharbo is a once-daily pill. It is not cleared for the atrial fibrillation population that older anticoagulants serve.

OCEANIC-STROKE: 12,327 adults randomized within 72 hours

In its approval announcement, the FDA described OCEANIC-STROKE as a multicenter, randomized, double-blind, placebo-controlled phase 3 study of 12,327 adults. Eligible patients had a recent non-cardioembolic ischemic stroke with a National Institutes of Health Stroke Scale score of 15 or lower, or a high-risk transient ischemic attack, and were randomized within 72 hours of symptom onset. Both arms received antiplatelet therapy. Over a median treatment duration of 14.2 months, Sunharbo reduced ischemic stroke risk by 26% versus placebo, the figure the agency leads with.

The Population Health Research Institute in Hamilton, Ontario, ran the study across 37 countries for sponsor Bayer, with Mike Sharma as principal investigator and Ashkan Shoamanesh as co-principal investigator. Full results appeared in the New England Journal of Medicine. According to TCTMD’s coverage of the publication, ischemic stroke at two years occurred in 6.2% of patients on asundexian and 8.4% on placebo, a cause-specific hazard ratio of 0.74, with a one-year absolute reduction of 1.9% and a number needed to treat of 53. Sharma said the curves diverged early and stayed apart for the whole treatment period.

TCTMD’s tally of secondary results points the same direction. All strokes occurred in 6.6% of the asundexian group and 8.8% of the placebo group, disabling or fatal stroke in 2.1% against 3.0% (hazard ratio 0.69), and the composite of cardiovascular death, heart attack or stroke in 9.2% against 11.1% (hazard ratio 0.83). Richa Sharma of Yale, who was not involved in the trial, called the findings very groundbreaking for clinicians who care for stroke patients.

Patients in the trial were followed at one and three months and then every three months, and all of them also took standard antiplatelet therapy such as aspirin. That background matters for reading the 26%: it is the benefit of adding Sunharbo to antiplatelet treatment, not the benefit of the pill alone.

Bleeding: where major events matched placebo and where they did not

The safety picture is mixed, and the FDA spelled it out. Overall major bleeding rates were similar to placebo. Major bleeding rose with Sunharbo in patients older than 75 and during the first 90 days of treatment, and gastrointestinal bleeding was more common than with placebo. Diarrhea was the most frequently reported adverse reaction, affecting 3% or more of patients. In the published trial, ISTH major bleeding, the primary safety outcome, occurred in 1.9% of the asundexian group and 1.7% of the placebo group, a difference that was not statistically significant.

The published safety analysis found no significant differences in symptomatic intracranial hemorrhage, hemorrhagic stroke or fatal bleeding, according to TCTMD. The two windows the FDA flagged, the first 90 days and age above 75, are where the agency’s warning concentrates.

Hylton Joffe, director of the Office of Cardiology, Hematology, Endocrinology, and Nephrology in the FDA’s Center for Drug Evaluation and Research, called the approval a meaningful advance for patients.

The indication is narrower than the size of the trial might suggest. Sunharbo is to be used together with antiplatelet therapy after a recent mild-to-moderate non-cardioembolic ischemic stroke or a high-risk transient ischemic attack. Non-cardioembolic means the stroke was not traced to a clot from the heart, which is why patients with atrial fibrillation, who usually need anticoagulation for a cardiac source, sit outside the approval. The product comes from Bayer HealthCare Pharmaceuticals of Whippany, New Jersey, and the FDA granted it both Fast Track and Priority Review designations.

Label limits on interactions, liver disease and surgery timing

The label is specific about who should not take the drug or should pause it. Sunharbo is not recommended alongside strong CYP3A4 inducers that also inhibit P-gp, with carbamazepine named as an example, because they may reduce its effectiveness. It is not recommended in patients with moderate or severe hepatic impairment. Doctors are told to withhold it for at least 24 hours before elective surgery or invasive procedures, and for at least 24 hours after thrombolysis for acute ischemic stroke. The agency states plainly that the drug is not approved for stroke prevention in atrial fibrillation.

The path to approval was quick by drug-review standards. Bayer announced on May 18 that the FDA had accepted its application with Priority Review, and the drug had held Fast Track designation for this use since 2023. Yesmean Wahdan, Bayer’s senior vice president for U.S. medical affairs, said at the time that secondary stroke remains a serious and persistent challenge. What remains unsettled is how prescribers will weigh the extra bleeding seen in patients over 75 against a 26% reduction in ischemic stroke.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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