Background: Direct oral factor Xa inhibitors are widely used as alternatives to conventional vitamin K antagonists in managing venous thromboembolism and nonvalvular atrial fibrillation. Unfortunately, bleeding-related adverse events remain a major concern in clinical practice. In case of bleeding or emergency surgery, rapid-onset reversal agents may be required to counteract the anticoagulant activity.
Objectives: The ability of factor Xa variants to bypass the direct oral factor Xa inhibitors was assessed.
Methods: Human factor Xa variants were generated through substitution of phenylalanine 174 (F174) for either alanine, isoleucine, or serine. Factor Xa variants were stably expressed in HEK293 cells and purified to homogeneity using ion-exchange chromatography.
Results: F174-substituted human factor X variants demonstrated efficacy in restoring thrombin generation in plasma containing direct factor Xa inhibitors (apixaban, rivaroxaban, edoxaban). Their ability to bypass the anticoagulant effects stems from a significant reduced sensitivity for the direct factor Xa inhibitors, due to a decrease in binding affinity determined using molecular dynamics simulations and free energy computation. Furthermore, F174 modification resulted in a partial loss of inhibition by tissue factor pathway inhibitor, enhancing the procoagulant effect of F174-substituted factor X. Consequently, the F174A- and F174S-substituted factor X variants effectively counteracted the effects of two widely used anticoagulants, apixaban and rivaxoraban, in plasma of atrial fibrillation and venous thromboembolism patients.
Conclusions: These human factor X variants have the potential to serve as a rescue reversal strategy to overcome the effect of direct factor Xa inhibitors in case of life-threatening bleeding events or emergency surgical interventions.
Keywords: Anticoagulants; Antidotes; Factor Xa inhibitors; Hemorrhage; Molecular Dynamics Simulation.
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