Targeting von Willebrand factor selectively under inflammatory conditions

It is challenging to develop anti-thrombotic therapeutics to treat or prevent pathological thrombus formation without increasing the risk of bleeding. Currently available anti-coagulant drugs render blood thinner irrespective of whether an inflammatory pro-thrombotic condition exists or whether clotting needs to occur because of traumatic vessel rupture. It is desirable to develop a drug that is active only under the oxidizing conditions present during inflammation. The blood protein von Willebrand factor (VWF) plays a key role in initiating blood clotting and it has been the target of anti-thrombotic therapies. It has been shown that oxidizing agents released during inflammation activate VWF by converting methionine residues within its domains to methionine sulfoxide. A previous study by us developed a method to computationally screen for drugs that inhibit VWF more strongly in the presence of oxidizing conditions. The computations suggested in particular a drug, lumacaftor, that could inhibit VWF function selectively in the presence of oxidized methionine residues. Here, we developed an enzyme-linked immunosorbent assay to test the effect of drugs on the ability of VWF to bind to the platelet surface receptor glycoprotein Ib comparing oxidizing and non-oxidizing conditions. The results indicate that lumacaftor may indeed have the desired properties of inhibiting VWF selectively when oxidized. Because of its simplicity, the assay provides a high-throughput method to efficiently screen multiple drugs against VWF in both its oxidized and unoxidized state.