A Synthetic Macromolecule to Reverse Heparin Anticoagulation and Profibrinolytic Activity without Altering Clot Morphology

Heparin anticoagulants are mainstay in the treatment of thrombosis. However, anticoagulation associated haemorrhage is a major concern; an antidote is required to restore hemostasis. Protamine sulphate (PS), a cationic... [ view full abstract ]

Heparin anticoagulants are mainstay in the treatment of thrombosis. However, anticoagulation associated haemorrhage is a major concern; an antidote is required to restore hemostasis. Protamine sulphate (PS), a cationic polypeptide is the only clinically approved antidote for unfractionated heparin, but have significant limitations. PS is unable to completely reverse activity of low molecular weight heparins and fondaparinux due to its low binding affinity. In addition, PS exhibits non-specific toxicity including fibrinogen aggregation, altered clot structure and morphology, complement and platelet activation which leads to hematological complications. To address these challenges, we developed a synthetic, universal heparin reversal agent (UHRA) with high binding affinity to all clinically used heparins. Clotting assay (aPTT) show that, UHRA completely neutralize heparins and does not possess intrinsic anticoagulation effect compared to PS. Plasma clot lysis studies in the presence of exogenous t-PA demonstrate that UHRA, normalize the profibrinolytic activity of heparins. Electron microscopic evaluations of clots composed of heparins and UHRA possess comparable clot morphology and fibrin fiber size to the buffer control. However, the size of fibrin fibers formed following neutralization of heparin by PS is significantly greater than buffer control. Unlike PS, UHRA has negligible impact on fibrinogen, fibrin polymerization, clot structure, clot lysis, coagulation system and shows no binding to clot structures, revealing their excellent hemocompatibility. Our results show that UHRA could be an ideal antidote to restore hemostasis following invasive surgical procedures and to address bleeding complications by heparin based anticoagulants.