title: Biochemical and functional characterization of a recombinant monomeric factor VIII-Fc fusion protein.
abstract: BACKGROUND
  Hemophilia A results from a deficiency in factor VIII activity. Current treatment regimens require frequent dosing, owing to the short half-life of FVIII. A recombinant FVIII-Fc fusion protein (rFVIIIFc) was molecularly engineered to increase the half-life of FVIII, by 1.5-2-fold, in several preclinical animal models and humans.
  
  
  OBJECTIVE
  To perform a biochemical and functional in vitro characterization of rFVIIIFc, with existing FVIII products as comparators.
  
  
  METHODS
  rFVIIIFc was examined by utilizing a series of structural and analytic assays, including mass spectrometry following lysyl endopeptidase or thrombin digestion. rFVIIIFc activity was determined in both one-stage clotting (activated partial thromboplastin time) and chromogenic activity assays, in the context of the FXase complex with purified components, and in both in vitro and ex vivo rotational thromboelastometry (ROTEM) assays performed in whole blood.
  
  
  RESULTS
  rFVIIIFc contained the predicted primary structure and post-translational modifications, with an FVIII moiety that was similar to other recombinant FVIII products. The von Willebrand factor-binding and specific activity of rFVIIIFc were also found to be similar to those of other recombinant FVIII molecules. Both chromogenic and one-stage assays of rFVIIIFc gave similar results. Ex vivo ROTEM studies demonstrated that circulating rFVIIIFc activity was prolonged in mice with hemophilia A in comparison with B-domain-deleted or full-length FVIII. Clot parameters at early time points were similar to those for FVIII, whereas rFVIIIFc showed prolonged improvement of clot formation.
  
  
  CONCLUSIONS
  rFVIIIFc maintains normal FVIII interactions with other proteins necessary for its activity, with prolonged in vivo activity, owing to fusion with the Fc region of IgG(1) .
authors.affiliation: Biogen Idec Hemophilia, Waltham, MA 02451, USA. robert.peters@biogenidec.com
authors.forename: R T
authors.initials: RT
authors.lastname: Peters
authors.forename: G
authors.initials: G
authors.lastname: Toby
authors.forename: Q
authors.initials: Q
authors.lastname: Lu
authors.forename: T
authors.initials: T
authors.lastname: Liu
authors.forename: J D
authors.initials: JD
authors.lastname: Kulman
authors.forename: S C
authors.initials: SC
authors.lastname: Low
authors.forename: A J
authors.initials: AJ
authors.lastname: Bitonti
authors.forename: G F
authors.initials: GF
authors.lastname: Pierce
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001777:Blood Coagulation / Q000187:drug effects*; D003001:Cloning, Molecular; D003029:Coagulants / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004195:Disease Models, Animal; D005169:Factor VIII / Q000737:chemistry / Q000235:genetics / Q000493:pharmacokinetics / Q000494:pharmacology*; D006207:Half-Life; D006467:Hemophilia A / Q000097:blood / Q000188:drug therapy*; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism; D010314:Partial Thromboplastin Time; D010449:Peptide Mapping / Q000379:methods; D011486:Protein C / Q000378:metabolism; D011487:Protein Conformation; D015202:Protein Engineering; D055550:Protein Stability; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013916:Thrombelastography; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D003029:Coagulants; D007141:Immunoglobulin Fc Fragments; D009363:Neoplasm Proteins; D011486:Protein C; D011993:Recombinant Fusion Proteins; D014841:von Willebrand Factor; C078147:F8 protein, human; D005169:Factor VIII; D003546:Cysteine Endopeptidases; C030910:cancer procoagulant