Prolonged activity of factor IX as a monomeric Fc fusion protein

Blood. 2010 Mar 11;115(10):2057-64. doi: 10.1182/blood-2009-08-239665. Epub 2010 Jan 7.


Treatment of hemophilia B requires frequent infusions of factor IX (FIX) to prophylax against bleeding episodes. Hemophilia B management would benefit from a FIX protein with an extended half-life. A recombinant fusion protein (rFIXFc) containing a single FIX molecule attached to the Fc region of immunoglobulin G was administered intravenously and found to have an extended half-life, compared with recombinant FIX (rFIX) in normal mice, rats, monkeys, and FIX-deficient mice and dogs. Recombinant FIXFc protein concentration was determined in all species, and rFIXFc activity was measured in FIX-deficient animals. The half-life of rFIXFc was approximately 3- to 4-fold longer than that of rFIX in all species. In contrast, in mice in which the neonatal Fc receptor (FcRn) was deleted, the half-life of rFIXFc was similar to rFIX, confirming the increased circulatory time was due to protection of the rFIXFc via the Fc/FcRn interaction. Whole blood clotting time in FIX-deficient mice was corrected through 144 hours for rFIXFc, compared with 72 hours for rFIX; similar results were observed in FIX-deficient dogs. Taken together, these studies show the enhanced pharmacodynamic and pharmacokinetic properties of the rFIXFc fusion protein and provide the basis for evaluating rFIXFc in patients with hemophilia B.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bleeding Time
  • Blood Coagulation / drug effects*
  • Blood Coagulation / genetics
  • Cells, Cultured
  • Dog Diseases / blood
  • Dog Diseases / drug therapy
  • Dogs
  • Drug Evaluation, Preclinical
  • Factor IX / genetics
  • Factor IX / metabolism
  • Factor IX / pharmacokinetics*
  • Factor IX / physiology
  • Factor IX / therapeutic use
  • Female
  • Hemophilia B / blood
  • Hemophilia B / drug therapy
  • Hemophilia B / veterinary
  • Humans
  • Immunoglobulin Fc Fragments / genetics
  • Immunoglobulin Fc Fragments / metabolism
  • Immunoglobulin Fc Fragments / pharmacology*
  • Immunoglobulin Fc Fragments / therapeutic use
  • Macaca fascicularis
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Protein Multimerization
  • Rats
  • Recombinant Fusion Proteins / metabolism*
  • Recombinant Fusion Proteins / pharmacokinetics*
  • Recombinant Fusion Proteins / therapeutic use
  • Time Factors


  • Immunoglobulin Fc Fragments
  • Recombinant Fusion Proteins
  • factor IX Fc fusion protein
  • Factor IX