The US Food and Drug Administration (FDA) has approved a recombinant porcine factor VIII (FVIII) product known as Obizur to treat bleeding episodes in adults with acquired hemophilia A.
Obizur replaces the inhibited human FVIII with a recombinant porcine sequence FVIII based on the rationale that porcine FVIII is less susceptible to inactivation by circulating human FVIII antibodies.
Physicians can manage Obizur’s efficacy and safety by measuring FVIII activity levels.
The ability to measure FVIII levels gives physicians an objective marker of hemostasis that can guide dosing and prevent overdosing, said Rebecca Kruse-Jarres, MD, Director of the Hemophilia Care Program at Puget Sound Blood Center in Seattle and principal investigator of a phase 2/3 trial of Obizur.
Trial results
The FDA approved Obizur based on results of a prospective, multicenter, phase 2/3 trial in which adults with acquired hemophilia A received the product to treat serious bleeding episodes.
Twenty-nine patients were enrolled and evaluated for safety. Researchers determined that one of the patients did not actually have acquired hemophilia A, so this patient could not be evaluated for efficacy.
At 24 hours after the initial infusion, all 28 patients in the efficacy analysis had a positive response to Obizur. This meant that bleeding stopped or decreased, the patients experienced clinical stabilization or improvement, and FVIII levels were 20% or greater.
Eighty-six percent of patients (24/28) had successful treatment of their initial bleeding episode. The overall treatment success was determined by the investigator based on the ability to discontinue or reduce the dose and/or dosing frequency of Obizur.
The adverse reaction most frequently reported in the 29 patients in the safety analysis was the development of inhibitors to porcine FVIII.
Nineteen patients were negative for anti-porcine FVIII antibodies at baseline, and 5 of these patients (26%) developed anti-porcine FVIII antibodies following exposure to Obizur. Of the 10 patients with detectable anti-porcine FVIII antibodies at baseline, 2 (20%) experienced an increase in titer, and 8 (80%) decreased to a non-detectable titer.
About acquired hemophilia A and Obizur
Acquired hemophilia A is a rare but potentially life-threatening bleeding disorder caused by the development of antibodies directed against the body’s own FVIII.
Acquired hemophilia A development has been related to other medical conditions or health states, such as pregnancy, cancer, or the use of certain medications. However, in about half of acquired hemophilia A cases, no underlying cause can be found.
Diagnosis of this condition can be difficult, and the severity of bleeding can make treatment challenging.
“The approval of [Obizur] provides an important therapeutic option for use in the care of patients with this rare disease,” said Karen Midthun, MD, director of the FDA’s Center for Biologics Evaluation and Research.
The FDA previously granted Obizur orphan drug designation because it is intended for use in the treatment of a rare disease or condition. The product is manufactured by Baxter Healthcare Corporation.
Baxter said Obizur will be commercially available in the US in the coming months and is currently under regulatory review in Europe and Canada.
For more details on Obizur, see the full prescribing information.
