Last updated July 15, 2022, by Teresa Carvalho, MS
✅ Fact-checked by Joana Carvalho, PhD
What is Obizur for Hemophilia?
The therapy was originally developed by Baxalta, now part of Takeda.
How does Obizur work?
Patients with acquired hemophilia have blood clotting problems due to the presence of antibodies that target proteins required for blood clotting, most often one called factor VIII (FVIII).
Obizur is a recombinant, or man-made, version of FVIII produced by a gene that carries instructions to make the protein in pigs. It mimics how human FVIII works, but is slightly different structurally. Therefore, it can replace the human FVIII and help restore blood clotting without being recognized and deactivated by antibodies circulating in a person’s bloodstream.
Who can take Obizur?
The U.S. Food and Drug Administration (FDA) approved Obizur in 2014 for treating bleeding episodes in adults with acquired hemophilia A. In 2015, the European Commission authorized its use in the EU for the same indication. The therapy was approved in Canada that year also.
Who should not take Obizur?
Obizur should not be used by patients with a history of life-threatening allergic reactions to the treatment or any of its components, such as hamster and pig proteins. It’s also not recommended for patients with congenital hemophilia A or von Willebrand disease.
How is Obizur administered?
Obizur is given as a shot directly into a vein. The recommended starting dose is 200 units/kg. Following doses should be taken every four to 12 hours and the frequency may be adjusted based on the clinical response and FVIII levels, as follows:
- for minor and moderate bleeds, 50 to 100 units per deciliter (U/dL) of FVIII levels are required
- for major bleeds, 100 to 200 U/dL of FVIII levels are required to treat an acute bleed, followed by 50 to 100 U/dL once the acute bleed is controlled, if necessary.
For an appropriate confirmation of dosing effectiveness, FVIII levels should be assessed as soon as 30 minutes and three hours after the first dose, then 30 minutes after following doses.
The therapy is available as a white lyophilized powder supplied in single-dose bottles with 500 units of its active ingredient per bottle. Before injection, Obizur has to be reconstituted with sterile water. It should be injected at a rate of 1 to 2 mL per minute.
Following reconstitution, the solution should be colorless and should not be given if solid and liquid particles are present or discoloration is observed. Injection under the supervision of an experienced healthcare provider is recommended.
Obizur in clinical trials
The approval of Obizur to treat acquired hemophilia was based on data from a multicenter Phase 2/3 trial (NCT01178294). This international study assessed Obizur’s safety and effectiveness in 29 patients with acquired hemophilia. Participants were initially treated with 200 units/kg of Obizur, followed by additional doses, depending on their response and FVIII activity levels. Patients also received immunosuppressive treatment during the study.
Within 24 hours, Obizur either stopped or reduced bleeding in all the patients, meeting the primary endpoint, or goal, of a positive clinical response. This positive response was seen in all 18 patients evaluated at 16 hours, and in all but one assessed after eight hours.
Common side effects of Obizur
Development of antibodies
Neutralizing antibodies directed against porcine FVIII is the most common side effect associated with Obizur. The therapy’s label recommends assessing the presence of those antibodies before starting treatment.
If expected plasma factor VIII levels are not reached, or bleeding is not controlled after an adequate dose, the presence of inhibitors should be reassessed. If antibodies are detected, it’s recommended that alternative therapeutic options be considered in consultation with the patient’s care team.
Allergic reactions to Obizur may also occur, particularly in patients with allergies to pig or hamster proteins. Symptoms of allergic reactions may include burning at the injection site, swelling under the skin — also known as angioedema — hives, low blood pressure, chest tightness, and shortness of breath. In these cases, treatment should be stopped.
Use in pregnancy and breastfeeding
It’s unknown if Obizur can affect the developing fetus or pass to breast milk. Patients who plan to become pregnant or to breastfeed should talk with their healthcare professionals and only continue treatment during these periods if the benefit justifies the potential risks to the fetus or child.
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