Factor XI Inhibitors for AFib and Stroke Prevention: Landscape

Factor XI and factor XIa inhibitors are an experimental class of blood thinners that aim to prevent clots, including strokes caused by atrial fibrillation (AFib), with less bleeding than today’s anticoagulants. The class has produced one clear win, one early stop for inferior efficacy and one futility result. This Factor XI inhibitors landscape summary sets out the record as of November 4, 2026, which has changed considerably since 2023.

Mechanism at a glance

Factor XI sits in the blood-clotting cascade, and the drugs in this class block factor XI or its active form, factor XIa. They differ in format: asundexian and milvexian are oral drugs (asundexian 50 mg once daily in its stroke trial, milvexian 100 mg twice daily in its AFib trial), while abelacimab is an antibody given by monthly subcutaneous injection in its Phase 3 trial. The authors of a commentary on the milvexian ACS trial suggested that factor XIa inhibition may target thrombosis while largely preserving normal clotting for stopping bleeding. Whether that translates into efficacy depends on the setting.

Why it matters

Established anticoagulants such as apixaban prevent AFib-related stroke but carry bleeding risk, and the class is pitched at patients and settings where that trade-off is hardest. The first large trial results have been split. In OCEANIC-AF, Bayer stopped the asundexian-versus-apixaban study in November 2023 after an independent committee found inferior efficacy for asundexian. In OCEANIC-STROKE, however, asundexian reduced recurrent ischemic stroke after a non-cardioembolic stroke or high-risk TIA, and the FDA has accepted a filing.

Competitive pressure points

• Asundexian (Bayer): OCEANIC-STROKE enrolled 12,327 patients on asundexian 50 mg daily or placebo, on top of antiplatelet therapy. Ischemic stroke occurred in 6.2% versus 8.4% (cause-specific hazard ratio 0.74). ISTH major bleeding was 1.9% versus 1.7% (HR 1.10; 95% CI 0.85 to 1.44).
• Milvexian (Bristol Myers Squibb and Johnson & Johnson): LIBREXIA-ACS (14,194 patients) was stopped for futility, with the primary composite at 5.4% on milvexian versus 5.1% on placebo (HR 1.05). Intracranial or fatal bleeding was 0.3% in both groups. LIBREXIA-AF (milvexian 100 mg twice daily versus apixaban, 20,284 participants) and LIBREXIA-STROKE (12,523 participants) are still ongoing.
• Abelacimab (Novartis, via Anthos): LILAC-TIMI 76 is testing a monthly 150 mg injection against placebo in AFib patients considered unsuitable for oral anticoagulation. It is recruiting an estimated 2,500 patients.
• Regeneron: two Phase 3 AFib trials, ROXI-INCLINE and ROXI-EVEREST, started in 2026 for its factor XI antibodies, per the registry listings.

What to watch

• Whether the FDA, the European regulators and Japan follow China in approving asundexian for secondary stroke prevention, and on what label. Bayer has not stated an action date in the sources we reviewed.
• LIBREXIA-STROKE and LIBREXIA-AF, the next large readouts. The registry lists primary completion in late 2026, but a presenter at ESC 2026 said both would report in 2027.
• Whether any agent can match apixaban’s efficacy in AFib, the setting where asundexian failed.
• Outcomes in patients who cannot take anticoagulants, where abelacimab and Regeneron are testing against placebo.

For related context, see our guide to reading a ClinicalTrials.gov record and our Lp(a) analysis, pelacarsen and the Lp(a) landscape.

Recent developments

Updated November 4, 2026. Items are drawn from company announcements, regulators and trade press; links go to the sources.

• Oct 26, 2026: Bayer announced that China’s National Medical Products Administration approved asundexian (brand name Sunharbo, 50 mg once daily) to reduce the risk of stroke in adults after a non-cardioembolic ischemic stroke or high-risk transient ischemic attack, which Bayer describes as the first Factor XIa inhibitor approved anywhere. China’s drug review center accepted the application on April 29, 2026 and granted Priority Review in May. Bayer says applications in other regions are under review. (Bayer)
• Aug 29, 2026: LIBREXIA-ACS results were reported from ESC Congress. The independent monitoring committee stopped the trial after an interim analysis. (ConsultantLive)
• May 18, 2026: Bayer announced that the FDA accepted its asundexian application with Priority Review, and that Japan’s health ministry accepted a parallel application. Asundexian has Fast Track designation from 2023. (NeurologyLive)
• Apr 3, 2026: Regeneron’s ROXI-INCLINE trial began (estimated 2,628 patients, primary completion March 2029); ROXI-EVEREST (estimated 15,364) began August 10, 2026. (ClinicalTrials.gov)
• Feb 5, 2026: Bayer reported the OCEANIC-STROKE results, presented at the International Stroke Conference and later published in the New England Journal of Medicine. (Drug Topics)
• Feb 11, 2025: Novartis agreed to acquire Anthos Therapeutics, abelacimab’s developer, for $925 million upfront plus up to $2.15 billion in milestones. (Novartis)
• Nov 19, 2023: Bayer stopped OCEANIC-AF early because of inferior efficacy of asundexian versus apixaban. (TCTMD)

Upcoming catalysts

• Nov 7, 2026, 1:45 p.m.: AHA Scientific Sessions stroke late-breaking session includes an OCEANIC-STROKE analysis by Framingham Risk Score. (TCTMD)
• Oct 15, 2026 (estimated): registry primary completion for LIBREXIA-STROKE; Dec 8, 2026 (estimated): LIBREXIA-AF.
• Dec 2027 (estimated): LILAC-TIMI 76 primary completion.

Bottom line

The class is no longer a single bet. Asundexian has a positive stroke trial, a first approval in China (October 26, 2026) and a pending FDA review, while the same molecule lost to apixaban in AFib and milvexian found no benefit after acute coronary syndrome. Population and comparator appear to decide the outcome.

The next year will show whether the AFib and secondary-stroke trials of milvexian, abelacimab and Regeneron’s antibodies repeat the stroke result or the AFib setback.

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This article is for informational and competitive-intelligence purposes only and is not medical advice. Approvals, labels and trial results change; verify details against current prescribing information and primary sources.