title: Safety evaluation of a recombinant plasmin derivative lacking kringles 2-5 and rt-PA in a rat model of transient ischemic stroke.
abstract: BACKGROUND
  Tissue type plasminogen activator is the only approved thrombolytic agent for the treatment of ischemic stroke. However, it carries the disadvantage of a 10-fold increase in symptomatic and asymptomatic intracranial hemorrhage. A safer thrombolytic agent may improve patient prognosis and increase patient participation in thrombolytic treatment. A novel direct-acting thrombolytic agent, Δ(K2-K5) plasmin, promising an improved safety profile was examined for safety in the snare ligature model of stroke in the rat.
  
  
  METHODS
  Male spontaneously hypertensive rats were subjected to 6 hours middle cerebral artery occlusion followed by 18 hours reflow. Beginning 1 minute before reflow, they were dosed with saline, vehicle, Δ(K2-K5) plasmin (0.15, 0.5, 1.5, and 5 mg/kg) or recombinant tissue-type plasminogen activator (10 and 30 mg/kg) by local intra-arterial infusion lasting 10 to 60 minutes. The rats were assessed for bleeding score, infarct volume, modified Bederson score and general behavioral score. In a parallel study, temporal progression of infarct volume was determined. In an in vitro study, whole blood clots from humans, canines and rats were exposed to Δ(K2-K5). Clot lysis was monitored by absorbance at 280 nm.
  
  
  RESULTS
  The main focus of this study was intracranial hemorrhage safety. Δ(K2-K5) plasmin treatment at the highest dose caused no more intracranial hemorrhage than the lowest dose of recombinant tissue type plasminogen activator, but showed at least a 5-fold superior safety margin. Secondary results include: temporal infarct volume progression shows that the greatest expansion of infarct volume occurs within 2-3 hours of middle cerebral artery occlusion in the spontaneously hypertensive rat. A spike in infarct volume was observed at 6 hours ischemia with reflow. Δ(K2-K5) plasmin tended to reduce infarct volume and improve behavior compared to controls. In vitro data suggests that Δ(K2-K5) plasmin is equally effective at lysing clots from humans, canines and rats.
  
  
  CONCLUSIONS
  The superior intracranial hemorrhage safety profile of the direct-acting thrombolytic Δ(K2-K5) plasmin compared with recombinant tissue type plasminogen activator makes this agent a good candidate for clinical evaluation in the treatment of acute ischemic stroke.
authors.affiliation: Research and Pre-clinical Development, Grifols Therapeutics, Inc., Research Triangle Park, North Carolina, USA.
authors.forename: R Christian
authors.initials: RC
authors.lastname: Crumrine
authors.affiliation: Division of Hematology/Medical Oncology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Marder
authors.affiliation: Research and Pre-clinical Development, Grifols Therapeutics, Inc., Research Triangle Park, North Carolina, USA.
authors.forename: G McLeod
authors.initials: GM
authors.lastname: Taylor
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: LaManna
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Constantinos P
authors.initials: CP
authors.lastname: Tsipis
authors.affiliation: Research and Pre-clinical Development, Grifols Therapeutics, Inc., Research Triangle Park, North Carolina, USA.
authors.forename: Valery
authors.initials: V
authors.lastname: Novokhatny
authors.affiliation: Research and Pre-clinical Development, Grifols Therapeutics, Inc., Research Triangle Park, North Carolina, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Scuderi
authors.affiliation: Research and Pre-clinical Development, Grifols Therapeutics, Inc., Research Triangle Park, North Carolina, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Petteway
authors.affiliation: Research and Pre-clinical Development, Grifols Therapeutics, Inc., Research Triangle Park, North Carolina, USA.
authors.forename: Vikram
authors.initials: V
authors.lastname: Arora