title: Correction of human hemophilia A whole blood abnormalities with a novel bypass agent: zymogen-like FXa(I16L).
abstract: BACKGROUND
  Approximately 30% of hemophilia A (HA) and 5% of hemophilia B patients develop inhibitors to protein replacement therapy, and this is the major cause of disease-related morbidity in the developed world. We previously developed zymogen-like factor Xa (FXa) molecules with impaired active site maturation, enabling a greater half-life than wild-type FXa while maintaining full procoagulant function in the prothrombinase complex. Here we evaluated the ability of zymogen-like FXa(I16L) to correct whole blood thromboelastometry abnormalities of severe HA subjects with and without inhibitors.
  
  
  METHODS
  Fourteen severe HA subjects without and five with inhibitors were enrolled at baseline (
  C < 1%) > 5 half-lives from factor or bypass therapy. The subjects' whole blood was evaluated by thromboelastography (ROTEM(®) ) using INTEM analysis with two concentrations of FXa(I16L) or recombinant factor VIIa (rFVIIa).
  
  
  RESULTS
  With 0.1 nm FXa(I16L) , clot time (CT, in minutes [min]) among HA subjects without and with inhibitors (mean = 2.87 min, 95% CI = 2.58-3.15 min, and mean = 2.9 min, 95% CI = 2.07-3.73 min, respectively) did not significantly differ from control CT (mean = 2.73 min, 95% CI = 2.62-2.85 min). Addition of 20 nm rFVIIa, simulating a 90-μg/kg dose, resulted in significantly prolonged CTs for HA subjects without and with inhibitors (mean = 5.43 min, 95% CI = 4.53-6.35 min, and mean = 4.25 min, 95% CI = 3.32-5.17 min, respectively) relative to controls.
  
  
  CONCLUSIONS
  FXa(I16L) restored thromboelastometry CT to control values in severe HA subjects with and without inhibitors. The findings corroborate previous animal data and demonstrate the first evidence of zymogen-like FXa(I16L) correcting human HA subjects' whole-blood abnormalities and support the use of FXa(I16L) as a novel hemostatic agent.
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.|Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: George
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.|Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.|Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: N K
authors.initials: NK
authors.lastname: Thalji
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.|Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Raffini
authors.affiliation: Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Gimotty
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.|Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.|Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Camire
mesh_terms: D001777:Blood Coagulation / Q000187:drug effects; D001780:Blood Coagulation Tests; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005169:Factor VIII / Q000276:immunology; D015942:Factor VIIa / Q000494:pharmacology; D015951:Factor Xa / Q000494:pharmacology*; D006467:Hemophilia A / Q000097:blood / Q000188:drug therapy* / Q000276:immunology; D006490:Hemostatics / Q000494:pharmacology*; D006801:Humans; D007518:Isoantibodies / Q000276:immunology; D008297:Male; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000494:pharmacology; D013916:Thrombelastography; D013997:Time Factors
chemical_list: D006490:Hemostatics; D007518:Isoantibodies; D011994:Recombinant Proteins; D005169:Factor VIII; C103587:recombinant FVIIa; D015942:Factor VIIa; D015951:Factor Xa
keywords: coagulation time, whole blood; deficiency, factor VIII; factor X, activated; hemophilia A, congenital; hemophilia B; inhibitor, blood coagulation factor