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The behavior of factor IX in the body is complex

Factors VIII and IX follow different patterns of movement in the body1-4

  • Endogenous factor IX distributes outside of the plasma and into areas such as the tissues, muscles, and joints, which is also called the extravascular space
  • Factor VIII, however, is largely limited to the plasma, also called the intravascular space
Blood vessel graphic
  • Factor IX binds to type IV collagen,
    which is located outside of the plasma5

  • Factor VIII binds to von Willebrand,
    a protein located inside the plasma2-4

Type IV collagen binding may explain the activity of factor IX in the extravascular space and play a role in coagulation, as shown in preclinical data6

  • Additional research is needed to confirm these findings

This distinct behavior means that a single PK parameter alone may not reflect all of the factor IX activity in the body7,8

Preclinical data are not correlated with outcomes. Animal studies may not apply to humans. Additional research for preclinical data and research in humans is needed to confirm these findings.


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  • ALPROLIX is contraindicated in patients who have a known history of hypersensitivity reactions, including anaphylaxis, to the product or its excipients.


  • Allergic-type hypersensitivity reactions, including anaphylaxis, are possible with factor replacement therapies, and have been reported with ALPROLIX. Discontinue use of ALPROLIX if hypersensitivity symptoms occur, and initiate appropriate treatment.
  • Formation of neutralizing antibodies (inhibitors) to Factor IX has been reported following administration of ALPROLIX. Patients using ALPROLIX should be monitored for the development of Factor IX inhibitors. Clotting assays (e.g., one-stage) may be used to confirm that adequate Factor IX levels have been achieved and maintained.
  • The use of Factor IX products has been associated with the development of thromboembolic complications.
  • Nephrotic syndrome has been reported following attempted immune tolerance induction in hemophilia B patients with Factor IX inhibitors and a history of allergic reactions to Factor IX. The safety and efficacy of using ALPROLIX for immune tolerance induction have not been established.


  • The most common adverse reactions (incidence ≥1%) in previously untreated patients were injection site erythema, hypersensitivity, and Factor IX inhibition. The most common adverse reactions (incidence ≥1%) in previously treated patients were headache, oral paresthesia, and obstructive uropathy.


ALPROLIX® is a recombinant DNA derived, coagulation Factor IX concentrate indicated in adults and children with hemophilia B for:

  • On-demand treatment and control of bleeding episodes
  • Perioperative management of bleeding
  • Routine prophylaxis to reduce the frequency of bleeding episodes

Limitation of Use
ALPROLIX is not indicated for induction of immune tolerance in patients with hemophilia B.

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References: 1. Chang P, Aronson DL, Borenstein DG, Kessler CM. Coagulant proteins and thrombin generation in synovial fluid: a model for extravascular coagulation. Am J Hematol. 1995;50:79-83 2.2. Iorio A, Fischer K, Blanchette V, Rangarajan S, Young G, Morfini M. Tailoring treatment of haemophilia B: accounting for the distribution and clearance of standard and extended half-life FIX concentrates. Thromb Haemost. 2017;117(6):1023-1030. 3. Lenting PJ, van Schooten CJM, Denis CV. Clearance mechanisms of von Willebrand factor and factor VIII. J Thromb Haemost. 2007;5(7):1353-1360. 4. Morfini M. The history of clotting factor concentrates pharmacokinetics. J Clin Med. 2017;6(3):35. 5. Iorio A, Fischer K, Blanchette V, et al. Tailoring treatment of haemophilia B: accounting for the distribution and clearance of standard and extended half-life FIX concentrates. Thromb Haemost. 2017;117(6):1023-1030. 6. Gui T, Reheman A, Ni H, et al. Abnormal haemostasis in a knock-in mouse carrying a variant of factor IX with impaired binding to collagen type IV. J Thromb Haemost. 2009;7:1843-1851. 7. Feng D, Stafford KA, Broze GJ, Stafford DW. Evidence of clinically significant extravascular stores of factor IX. Thromb Haemost. 2013;11(12):2176-2178. 8. Stafford DW. Extravascular FIX and coagulation. Thrombosis J. 2016;14(suppl 1);35.