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J Pharmacol Exp Ther. 2010 Mar;332(3):1022-31. doi: 10.1124/jpet.109.159194. Epub 2009 Dec 1.

Targeting of a mutant plasminogen activator to circulating red blood cells for prophylactic fibrinolysis.

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IFEM, University of Pennsylvania School of Medicine, One John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA 19104-6068, USA.

Erratum in

  • J Pharmacol Exp Ther. 2010 Jun;333(3):976. Zaitzev, Sergei [corrected to Zaitsev, Sergei].


Chemical coupling to carrier red blood cells (RBCs) converts tissue type plasminogen activator (tPA) from a problematic therapeutic into a safe agent for thromboprophylaxis. The goal of this study was to develop a more clinically relevant recombinant biotherapeutic by fusing a mutant tPA with a single-chain antibody fragment (scFv) with specificity for glycophorin A (GPA) on mouse RBCs. The fusion construct (anti-GPA scFv/PA) bound specifically to mouse but not human RBCs and activated plasminogen; this led to rapid and stable attachment of up to 30,000 copies of anti-GPA scFv/PA per mouse RBC that were thereby endowed with high fibrinolytic activity. Binding of anti-GPA scFv/PA neither caused RBC aggregation, hemolysis, uptake in capillary-rich lungs or in the reticuloendothelial system nor otherwise altered the circulation of RBCs. Over 40% of labeled anti-GPA scFv/PA injected in mice bound to RBC, which markedly prolonged its intravascular circulation and fibrinolytic activity compared with its nontargeted PA counterpart, anti-GPA scFv/PA, but not its nontargeted PA analog, prevented thrombotic occlusion in FeCl(3) models of vascular injury. These results provide proof-of-principle for the development of a recombinant PA variant that binds to circulating RBC and provides thromboprophylaxis by use of a clinically relevant approach.

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