title: Reprogrammed streptokinases develop fibrin-targeting and dissolve blood clots with more potency than tissue plasminogen activator.
abstract: BACKGROUND
  Given the worldwide epidemic of cardiovascular diseases, a more effective means of dissolving thrombi that cause heart attacks, could markedly reduce death, disability and healthcare costs. Plasminogen activators (PAs) such as streptokinase (SK) and tissue plasminogen activator (TPA) are currently used to dissolve fibrin thrombi. SK is cheaper and more widely available, but it appears less effective because it lacks TPA's fibrin-targeted properties that focus plasminogen activation on the fibrin surface.
  
  
  OBJECTIVE
  We examined whether re-programming SK's mechanism of action would create PAs with greater fibrin-targeting and potency than TPA.
  
  
  RESULTS
  When fibrinogen consumption was measured in human plasma, reprogrammed molecules SKDelta1 and SKDelta59 were 5-fold and > 119-fold more fibrin-dependent than SK (P < 0.0001), and 2-fold and > 50-fold more fibrin-dependent than TPA (P < 0.001). The marked fibrin-targeting of SKDelta59 was due to the fact that: (i) it did not generate plasmin in plasma, (ii) it was rapidly inhibited by alpha2-antiplasmin, and (iii) it only processed fibrin-bound plasminogen. To assess the fibrin-targeting and therapeutic potential of these PAs in vivo, a novel 'humanized' fibrinolysis model was created by reconstituting plasminogen-deficient mice with human plasminogen. When compared with TPA, SKDelta1 and SKDelta59 were 4-fold (P < 0.0001) and 2-fold (P < 0.003) more potent at dissolving blood clots in vivo, respectively, on a mass-dose basis and 2-3 logs more potent than TPA (P < 0.0001) when doses were calibrated by standard activity assays.
  
  
  CONCLUSIONS
  These experiments suggest that reprogramming SK's mechanism of action markedly enhances fibrin-targeting and creates, in comparison with TPA, activators with greater fibrinolytic potency.
authors: Cardiovascular Research Medical College of Georgia, Augusta, GA, USA.
authors: I Y
authors: IY
authors: Sazonova
authors: R A
authors: RA
authors: McNamee
authors: A K
authors: AK
authors: Houng
authors: S M
authors: SM
authors: King
authors: L
authors: L
authors: Hedstrom
authors: G L
authors: GL
authors: Reed
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems / Q000379:methods; D005337:Fibrin / Q000037:antagonists & inhibitors*; D005342:Fibrinolysis / Q000187:drug effects*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D015202:Protein Engineering; D013300:Streptokinase / Q000235:genetics / Q000627:therapeutic use*; D013927:Thrombosis / Q000188:drug therapy*; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use
chemical_list: D005337:Fibrin; D013300:Streptokinase; D010959:Tissue Plasminogen Activator