Engineering procoagulant variants of blood coagulation factor X for therapeutic purposes

In this public-private consortium, the Leiden University Medical Center and VarmX B.V. will join forces to engineer novel variants of blood coagulation factor X that are resistant to direct oral anticoagulants and have maintained normal functionality in clotting, with the overall goal of restoring blood coagulation in individuals treated with factor Xa-inhibiting anticoagulants.

Thrombosis, an ‘unwanted’ blood clot, is the leading cause of mortality and morbidity in the western world, and the direct oral anticoagulants that target blood coagulation factor Xa are among the most commonly used drugs to prevent or treat thrombosis. Efficacious reversal of the anticoagulant effect of these drugs is a prerequisite for safe drug usage, which is underscored by the fact that the risk of major bleeding inherent to anticoagulant treatment is 1-3% per year, with one-in-five cases being fatal. While a reversal agent has been approved for the current generation of factor Xa-inhibiting anticoagulant drugs, given its practical limitations and limited indication there is a continued need for the development of specific reversal agents capable of overcoming the inhibitory effect of the direct factor Xa inhibitors.

By selectively tweaking the active site of factor X through targeted amino acid replacements, the aim is to modify factor X such that synthetic small-molecule inhibitors can no longer engage the modified active site. In contrast, the natural macromolecular substrate should still be able to engage the active site for protease-mediated catalysis. As such, normal functionality of the modified factor X variant will be preserved. Knowledge acquired on the substrate selectivity and catalytic efficiency of blood coagulation factor X will have direct bearings on other chymotrypsin-like serine proteases, which are involved in many critical biological processes. Moreover, the novel factor X variants will have the potential to restore hemostasis in individuals treated with direct oral anticoagulants that suffer from an adverse bleeding event or require acute surgery.