Asundexian Reduces Recurrent Stroke Without Increasing Major Bleeding

The Bleeding Barrier in Secondary Stroke Prevention

Patients who survive a noncardioembolic ischemic stroke or transient ischemic attack face a persistently high risk of recurrent cerebrovascular events despite standard antiplatelet therapy [1]. Historically, attempts to intensify secondary prevention by adding systemic anticoagulation have been thwarted by unacceptable increases in major bleeding, particularly intracranial hemorrhage [2]. To bypass this limitation, researchers have turned to factor XIa inhibitors, a class of drugs designed to prevent pathological clot formation without disrupting normal bleeding control by targeting the intrinsic coagulation pathway [3, 4]. While these agents have demonstrated favorable bleeding profiles but mixed efficacy in atrial fibrillation trials [5, 6], their role in noncardioembolic stroke has remained an open question. A newly published phase 3 trial now clarifies whether adding an oral factor XIa inhibitor to standard antiplatelet regimens can safely suppress recurrent strokes without triggering dangerous bleeding.

Targeting Factor XIa in High-Risk Patients

Clinical observations have long shown that naturally low levels of factor XI are associated with a reduced risk of ischemic stroke, making the activated factor XI inhibitor asundexian a logical therapeutic candidate. To determine whether adding this agent to standard care improves secondary prevention, researchers conducted a phase 3, double-blind trial (OCEANIC-STROKE, NCT05686070). The investigators randomly assigned patients within 72 hours after the onset of a high-risk transient ischemic attack or a noncardioembolic ischemic stroke (a stroke not originating from a cardiac source like atrial fibrillation, but rather from large artery atherosclerosis or small vessel disease). To ensure the cohort represented a high-risk clinical demographic, included patients had to demonstrate at least one specific risk factor: a history of atherosclerosis, evidence of atherosclerotic plaque on cerebrovascular imaging, or a nonlacunar infarct (a larger stroke involving cortical or major subcortical regions, rather than a small deep penetrating artery). Participants received either asundexian (50 mg once daily) or a placebo, administered in addition to their planned dual or single antiplatelet therapy. The investigators established clear endpoints to balance therapeutic efficacy against potential harm, defining the primary efficacy outcome as recurrent ischemic stroke and the key secondary outcome as a composite of cardiovascular death, myocardial infarction, or stroke. To monitor the well-known risks of combining antithrombotic agents, the primary safety outcome was major bleeding.

Efficacy: Significant Reduction in Recurrent Ischemic Events

The trial randomized 12,327 patients, with 6162 assigned to the asundexian group and 6165 to the placebo group. The primary efficacy analysis demonstrated a clear benefit for the active treatment arm, showing that the incidence of ischemic stroke was 6.2% in the asundexian group compared to 8.4% in the placebo group. This absolute risk reduction translates to a highly significant relative decrease in recurrent events, yielding a cause-specific hazard ratio of 0.74 (95% confidence interval [CI], 0.65 to 0.84; P<0.001). For practicing neurologists and internists, this indicates that adding asundexian to standard antiplatelet regimens effectively prevents recurrent neurological deficits in a highly vulnerable population. Beyond the primary endpoint, the researchers evaluated broader cardiovascular outcomes to determine the overall protective effect of the drug. They found that the incidence of the composite of death from cardiovascular causes, myocardial infarction, or stroke was lower in the asundexian group than in the placebo group. Ultimately, the findings confirm that in patients with noncardioembolic ischemic stroke or high-risk transient ischemic attack treated with antiplatelet therapy, asundexian at 50 mg daily resulted in lower risks of ischemic stroke and major cardiovascular events than placebo, without a higher risk of major bleeding.

Safety Profile: No Increase in Major Bleeding

For clinicians managing secondary stroke prevention, the primary barrier to intensifying antithrombotic therapy is the risk of severe hemorrhage. In this trial, the addition of a factor XIa inhibitor did not exacerbate this risk, offering critical reassurance for prescribing physicians who must balance clot prevention against the catastrophic consequences of intracranial or gastrointestinal bleeding. The primary safety outcome analysis revealed that the incidence of major bleeding was 1.9% in the asundexian group and 1.7% in the placebo group. This slight numerical difference was not statistically significant, yielding a cause-specific hazard ratio of 1.10 (95% CI, 0.85 to 1.44). This finding suggests that clinicians can achieve the ischemic benefits of asundexian without exposing patients to the unacceptable bleeding risks historically associated with adding traditional systemic anticoagulation to antiplatelet therapy. Beyond major bleeding, the overall safety and tolerability profiles were highly comparable between the two study arms. The incidence of adverse events was 69.3% in the asundexian group and 70.1% in the placebo group. Furthermore, severe complications were balanced across the cohorts, with the incidence of serious adverse events at 19.2% in the asundexian group and 19.5% in the placebo group. These data indicate that adding 50 mg of daily asundexian to standard antiplatelet regimens does not introduce new systemic toxicities or increase the burden of severe adverse reactions for patients recovering from an ischemic stroke or transient ischemic attack.

References

1. Hirano T, Matsuo R, Okami S, et al. Abstract DP297: Characteristics and Outcomes of the Real-World Cohort of Patients with Non-Cardioembolic Ischemic Stroke or Transient Ischemic Attack Compatible With the OCEANIC-STROKE Clinical Trial Population in Japan. Stroke. 2026. doi:10.1161/str.57.suppl_1.dp297

2. Seiffge D, Cancelloni V, Räber L, et al. Secondary stroke prevention in people with atrial fibrillation: treatments and trials. The Lancet Neurology. 2024. doi:10.1016/s1474-4422(24)00037-1

3. Xue Z, Liao S, Fan H, Shen Y, Nie Z. A Systematic Review of Factor XI/XIa Inhibitors Versus Direct Oral Anticoagulants in Patients with Atrial Fibrillation. Clinical and Applied Thrombosis/Hemostasis. 2025. doi:10.1177/10760296251335967

4. Gómez‐Outes A, Suárez‐Gea ML, Pérez-Cabeza A, García‐Pinilla JM. Pharmacotherapy for stroke prevention in nonvalvular atrial fibrillation: current strategies and future directions. Expert Opinion on Pharmacotherapy. 2022. doi:10.1080/14656566.2022.2149323

5. Khater J, Frazzetto M, Mahmud S, et al. Balancing Safety and Efficacy: Factor XIa INHIBITORS vs. DOACs in Patients with Atrial Fibrillation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials †. Journal of Clinical Medicine. 2025. doi:10.3390/jcm14228234

6. Piccini JP, Patel MR, Steffel J, et al. Asundexian versus Apixaban in Patients with Atrial Fibrillation. New England Journal of Medicine. 2024. doi:10.1056/nejmoa2407105