Clinical Results for Milvexian
The phase 3 LIBREXIA ACS trial concluded that adding milvexian to standard antiplatelet therapy provides no clinical reduction in cardiovascular events for patients recovering from acute coronary syndrome. Researchers stopped the trial early in November 2025 due to a lack of evidence suggesting the drug would reach its primary efficacy goals. Findings presented at the European Society of Cardiology Congress 2026 show the primary composite endpoint of cardiovascular death, myocardial infarction, or ischemic stroke occurred in 5.4% of the treatment group versus 5.1% in the placebo group.
While the drug failed to demonstrate superior efficacy, it did prove biologically active. Patients receiving 25 mg of milvexian twice daily showed a 1.59-fold increase in activated partial thromboplastin time. This change confirms the drug exerted its intended effect on the coagulation pathway. Still, this pharmacodynamic success did not translate into a measurable improvement in patient outcomes after a median follow-up of 12.2 months.
Understanding the Safety Profile
A positive takeaway from the data involves safety. Investigators found no significant difference in the principal safety endpoint of intracranial, vision-threatening intraocular, or fatal bleeding between the two groups. Milvexian maintained this safety profile despite the high intensity of background therapy. Roughly 95% of participants remained on dual antiplatelet therapy throughout the study. Approximately 60% of these patients used potent P2Y12 receptor inhibitors, which typically heightens bleeding risks.
P. Gabriel Steg, the trial presenter from Hôpital Bichat, noted that the absence of increased fatal bleeding is reassuring. He pointed out that while clinically relevant non-major bleeding occurred slightly more often in the treatment group, the study suggests factor XIa inhibition may offer a safer profile than traditional anticoagulants. This balance is exactly what cardiologists hope to find when treating patients who already require potent antiplatelet regimens.
Potential Reasons for the Outcome
Experts are now evaluating why the study failed to meet its targets. Steg suggested the 25-mg dose might be insufficient for this specific population. It is also possible that the benefits of dual-pathway inhibition are limited to the immediate period following an event or that modern, potent antiplatelet combinations already address much of the thrombotic risk in revascularized patients. Because 92% of trial participants underwent percutaneous coronary intervention, the background standard of care is significantly more effective than in studies conducted decades ago.
The research included 14,194 patients across 44 countries. Because the trial was cut short, questions remain regarding whether different dosing or specific patient subgroups might still benefit from factor XIa inhibition. Marc S. Sabatine of the TIMI Study Group argued that the confidence intervals were narrow enough to suggest a major benefit was not simply missed during the analysis. He emphasized that the scientific community still needs to define the optimal level of factor XIa inhibition required for various cardiac conditions.
Looking ahead, the medical community will await data from ongoing trials. The LIBREXIA AF study, which tests a much higher dose of 100 mg twice daily, and the LIBREXIA Stroke study, which uses the 25-mg regimen, will clarify if these results are drug-specific or indicative of a broader challenge with factor XIa inhibitors. Until those results arrive, the current findings serve as a benchmark for the limitations of adding low-dose anticoagulation to modern, aggressive antiplatelet therapy.