In vivo neutralization of unfractionated heparin and low-molecular-weight heparin by a novel salicylamide derivative.

Unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) are widely used anticoagulants for surgical and interventional use. Currently, the anticoagulant and bleeding effects of heparin are neutralized by protamine sulfate. There are several problems associated with the use of protamine sulfate, including allergic reactions, cardiovascular effects, heparin rebound, and incomplete neutralization of LMWHs. The objective of this investigation is to characterize the effectiveness of a novel salicylamide-derived heparin antagonist, PMX 60056, in neutralizing the antithrombotic and bleeding effects of UFH and LMWHs. Animals were first anticoagulated using an intravenous injection of UFH or LMWH followed by protamine sulfate or PMX 60056. Established animal models of hemorrhage (rat-tail transection) and thrombosis (jugular vein clamping) were then performed. Blood samples were collected for ex vivo analysis using activated partial thromboplastin time (aPTT), anti-Xa, and anti-IIa assays. We demonstrate that PMX 60056 neutralized the antithrombotic, anticoagulant, and bleeding effects of heparins as effectively as protamine sulfate and may be slightly more efficacious against LMWHs. These results suggest that PMX 60056 may provide an improved approach for the neutralization of UFH and LMWHs.