title: Towards effective and safe thrombolysis and thromboprophylaxis: preclinical testing of a novel antibody-targeted recombinant plasminogen activator directed against activated platelets.
abstract: BACKGROUND
  Fibrinolysis is a valuable alternative for the treatment of myocardial infarction when percutaneous coronary intervention is not available in a timely fashion. For acute ischemic stroke, fibrinolysis is the only treatment option with a very narrow therapeutic window. Clinically approved thrombolytics have significant drawbacks, including bleeding complications. Thus their use is highly restricted, leaving many patients untreated.
  
  
  OBJECTIVE
  We developed a novel targeted fibrinolytic drug that is directed against activated platelets.
  
  
  RESULTS
  We fused single-chain urokinase plasminogen activator (scuPA) to a small recombinant antibody (scFvSCE5), which targets the activated form of the platelet-integrin glycoprotein IIb/IIIa. Antibody binding and scuPA activity of this recombinant fusion protein were on par with the parent molecules. Prophylactic in vivo administration of scFvSCE5-scuPA (75 U/g body weight) prevented carotid artery occlusion after ferric chloride injury in a plasminogen-dependent process compared with saline (P<0.001), and blood flow recovery was similar to high-dose nontargeted urokinase (500 U/g body weight). Tail bleeding time was significantly prolonged with this high dose of nontargeted urokinase, but not with equally effective targeted scFvSCE5-scuPA at 75 U/g body weight. Real-time in vivo molecular ultrasound imaging demonstrates significant therapeutic reduction of thrombus size after administration of 75 U/g body weight scFvSCE5-scuPA as compared with the same dose of a mutated, nontargeting scFv-scuPA or vehicle. The ability of scFvSCE5-scuPA to lyse thrombi was lost in plasminogen-deficient mice, but could be restored by intravenous injection of plasminogen.
  
  
  CONCLUSIONS
  Targeting of scuPA to activated glycoprotein IIb/IIIa allows effective thrombolysis and the potential novel use as a fibrinolytic agent for thromboprophylaxis without bleeding complications.
authors: From Atherothrombosis and Vascular Biology Laboratory (X.W., J.P., Y.G., J.D.H., E.W., K.A., D.H., F.J., I.A., K.P.), and Vascular Biotechnology Laboratory (R.K., K.A., C.E.H.), Baker IDI, Melbourne, Australia; Department of Cardiology and Angiology, University Hospital Freiburg, Germany (I.A.); Fibrinolysis and Gene Regulation Laboratory, Australian Centre for Blood Diseases, Melbourne, Australia (R.L.M.); and Central Clinical School, Monash University, Melbourne, Australia (R.L.M., K.P., C.E.H.).
authors: Xiaowei
authors: X
authors: Wang
authors: Jathushan
authors: J
authors: Palasubramaniam
authors: Yannik
authors: Y
authors: Gkanatsas
authors: Jan David
authors: JD
authors: Hohmann
authors: Erik
authors: E
authors: Westein
authors: Ruchi
authors: R
authors: Kanojia
authors: Karen
authors: K
authors: Alt
authors: Dexing
authors: D
authors: Huang
authors: Fu
authors: F
authors: Jia
authors: Ingo
authors: I
authors: Ahrens
authors: Robert L
authors: RL
authors: Medcalf
authors: Karlheinz
authors: K
authors: Peter
authors: Christoph E
authors: CE
authors: Hagemeyer
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects* / Q000276:immunology; D016466:CHO Cells; D002339:Carotid Arteries / Q000000981:diagnostic imaging*; D006224:Cricetinae; D003412:Cricetulus; D004353:Drug Evaluation, Preclinical; D005343:Fibrinolytic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D039421:Integrin alpha2 / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D010958:Plasminogen / Q000378:metabolism; D015539:Platelet Activation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000627:therapeutic use; D057127:Single-Chain Antibodies / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use*; D013923:Thromboembolism / Q000188:drug therapy* / Q000517:prevention & control; D015912:Thrombolytic Therapy; D014463:Ultrasonography; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000627:therapeutic use*
chemical_list: D005343:Fibrinolytic Agents; C056564:ITGA2B protein, human; D039421:Integrin alpha2; D011993:Recombinant Fusion Proteins; D057127:Single-Chain Antibodies; D010958:Plasminogen; D014568:Urokinase-Type Plasminogen Activator
keywords: blood platelets; thrombolytic therapy; thrombosis; urokinase-type plasminogen activator