Hemophilia: Inhibitors
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Inhibitor Treatment
Treating bleeding episodes when factor doesn’t work can be challenging. Fortunately, there are specialized products manufactured for the treatment of bleeding episodes, including factor VIIa (brand name NovoSeven®) and FEIBA VH. Both of these products bypass the point in the coagulation process where factor VIII and IX are activated. Both NovoSeven and FEIBA VH activate factor X. The coagulation process proceeds from that point, causing a clot to form and stopping the bleed. The clot is not as stable as one that would be formed if all the “ingredients” of the process were present, but it does work.
Immune Tolerance Therapy
The most commonly prescribed program designed to rid the body of a factor VIII inhibitor altogether is known as either “immune tolerance therapy” (ITT) or “immune tolerance induction” (ITI). This treatment consists of giving a large dose of factor VIII every day to overwhelm and tolerize the body’s natural immune system. In most cases, the body eventually accepts the factor and reduces the amount of antibody being produced. The downside is that an ITT program may take up to two years to be successful, and because each person with an inhibitor is different, the program doesn’t work for everybody.
Immune Tolerance Therapy with Continuous Infusion
Some physicians have used continuous factor replacement therapy, or “continuous infusion,” to induce immune tolerance. Continuous infusion can be administered at home using a small, portable infusion pump. Unlike bolus administration (with a syringe), which requires regular high-dose infusions to maintain a minimum level of clotting factor in the blood stream, continuous infusion delivers a steady, constant level of clotting factor to overwhelm the antibody. Continuous infusion requires the patient to be connected to the pump 24 hours a day, so there may be lifestyle trade-offs to consider with this mode of ITT.
Co-Protein Factor Products
One of the latest developments in ITT involves the use of factor products that also contain von Willebrand factor. Since the von Willebrand molecule attaches itself to the same space on the factor VIII molecule that some factor antibodies do, researchers believe that it may protect the factor VIII from being attacked in some patients. There are currently three therapies containing von Willebrand factor: Alphanate®, Koāte®-DVI and Humate-P®.
Prophylaxis
Another treatment being considered for inhibitors that are resistant to ITT is prophylactic (preventive) infusions of FEIBA VH. Researchers have recently found that the use of FEIBA VH on a regular basis (as decided by a physician) may help prevent bleeding episodes in some patients. It is not totally clear how it works, but rather than just stopping an active bleed, there is evidence that prophylactic infusions of FEIBA may actually decrease the number of bleeding episodes that occur.
