Bayer announced positive results from the Phase III OCEANIC-STROKE trial evaluating asundexian, an investigational oral Factor XIa (FXIa) inhibitor, in patients following a non-cardioembolic ischemic stroke or high-risk transient ischemic attack (TIA). The study met its primary efficacy endpoint, demonstrating that asundexian, when added to standard-of-care antiplatelet therapy, significantly reduced the risk of the composite of ischemic stroke and cardiovascular death compared to placebo plus standard-of-care. This represents a potential shift in secondary stroke prevention by targeting the contact activation pathway of coagulation without a corresponding increase in major bleeding risk.
Trial specifics
The OCEANIC-STROKE study was a large-scale, randomized, double-blind, placebo-controlled Phase III trial that enrolled 18,332 patients aged 18 and older across more than 40 countries. Participants were randomized within 72 hours of an acute non-cardioembolic ischemic stroke or within 24 hours of a high-risk TIA. The dosing regimen involved 50 mg of asundexian administered orally once daily as an add-on to standard antiplatelet therapy, which typically consisted of aspirin, clopidogrel, or a combination of both. The primary efficacy endpoint was the time to first occurrence of the composite of ischemic stroke or cardiovascular death.
Results showed that asundexian produced a 26% relative risk reduction in the primary composite endpoint compared to the placebo arm. Crucially, the trial met its primary safety endpoint, showing no significant increase in International Society on Thrombosis and Haemostasis (ISTH) major bleeding versus placebo. This safety profile is significant given that existing anticoagulants, such as Factor Xa inhibitors, are generally avoided in the acute post-stroke setting due to high intracranial hemorrhage risks. Bayer stated that these findings support the potential for “uncoupling” thrombosis prevention from bleeding risk. The company plans to present the full data at an upcoming medical meeting and intends to engage with the US FDA and other global regulatory authorities regarding potential filing timelines.
Research context
Asundexian acts as a selective inhibitor of Factor XIa, a protein in the coagulation cascade that contributes to the growth of pathological thrombi but plays a minimal role in physiological hemostasis (the body’s ability to stop bleeding from an injury). By blocking FXIa, the drug seeks to prevent the formation of clots that cause strokes while preserving the patient’s natural ability to clot elsewhere. Asundexian is currently an unapproved investigational agent globally. The current standard of care for non-cardioembolic stroke is restricted to antiplatelet therapy, as oral anticoagulants have historically been associated with prohibitive bleeding risks in this population.
The landscape for FXIa inhibitors is highly competitive, with several major pharmaceutical firms developing similar small molecules and antibodies. Key competitors include:
- Bristol Myers Squibb and Janssen’s milvexian, an oral FXIa inhibitor currently being evaluated in the comprehensive Phase III Librexia program, which includes a specific trial (Librexia-Stroke) in the same post-stroke population.
- The Swiss-based Anthos Therapeutics’ abelacimab, a dual-acting monoclonal antibody targeting both Factor XI and its activated form (XIa). It is currently in Phase III development for the prevention of venous thromboembolism and stroke prevention in atrial fibrillation.
- Ion Pharmaceuticals’ fesomersen, an antisense medicine designed to reduce the production of Factor XI in the liver, which is being explored in Phase II studies for patients with end-stage renal disease.