Inhibitor Development in Patients With Hemophilia A Undergoing Surgery

Overview

Hemophilia A is a genetic deficiency of factor VIII that causes blood to clot too slowly. The disease is classified based on how much factor VIII is in the blood. People with mild or moderate hemophilia A have low, but detectable, blood levels of factor VIII and bleed with trauma or surgery. At the time of surgery, they need to receive factor VIII replacement by infusion into the vein so that blood can clot normally and abnormal bleeding can be avoided. A complication of hemophilia A is the development of an antibody that binds factor VIII and makes the factor VIII infused for treatment not work properly. This antibody is called an inhibitor. In mild and moderate hemophilia A, inhibitors are not common, but have been reported to occur after intensive factor VIII infusions, as may occur at the time of surgery. This study is designed to observe people with mild and moderate hemophilia A who are having surgery. Information on the surgery, treatments given, bleeding, and infection will be gathered. Also, blood will be drawn to determine how the immune system is reacting to the factor VIII. No specific treatments will be given as part of this study. We will use the information to determine what influences inhibitor development. A better understanding of inhibitor development will help medical providers do things to avoid inhibitor development in this population or researchers to design new treatments.

The development of neutralizing anti-factor VIII (fVIII) antibodies, fVIII inhibitor, is the most significant complication affecting patients with hemophilia A (HA). Once an inhibitor develops, treatment is less effective and costly. Although inhibitors occur most commonly in those with severe HA, 25% of new inhibitors occur in those with non-severe HA. In patients with non-severe HA, the development of a fVIII inhibitor can change the course of disease from one that is easily managed to one with the potential for spontaneous life-threatening difficult to treat bleeding. Although significant advances have been made in understanding risk factors for fVIII inhibitor development in patients with severe HA, studies that seek to understand the risk for fVIII inhibitor development in those with non-severe disease have been limited to retrospective analyses. In these retrospective analyses, intensive fVIII treatment and surgery have been identified as risk factors for fVIII inhibitor development in non-severe HA. Additionally, receiving fVIII by continuous infusion has been associated with fVIII inhibitor development in non-severe HA in some but not all studies and may be due in part to a more robust proinflammatory response during continuous infusion. Accordingly, the next logical step to evaluate the risk of inhibitor development associated with continuous fVIII infusion is a prospective observational cohort study. Additionally, knowledge of the immune response to fVIII in the surgical setting is essential for identification of patients at high risk for inhibitor development and development of strategies to prevent inhibitor development and is best evaluated in the setting of an prospective cohort study. This multicenter prospective observational cohort study will enroll a total of 140 subjects at 10 centers who have mild or moderate hemophilia a (fVIII activity 1-40%) who are scheduled to undergo surgery for which at least 5 consecutive days of fVIII replacement therapy is required. The study will gather clinical data and collect blood specimens on 4 occasions over a 3 month period. Outcomes include: inhibitor development, total fVIII usage, bleeding, and markers of T cell activation.