Annette von Drygalski, MD, PharmD, Associate Clinical Professor of Medicine in the Division of Hematology/Oncology, and Director of the Hemophilia and Thrombosis Treatment Center, Department of Medicine, at the University of California, San Diego, discusses the mechanism of action of of efanesoctocog alfa, which is currently being investigated in the XTEND-1 study in previously treated adults and adolescents ≥12 years with severe hemophilia A.

Hemophilia A is a rare bleeding disorder in which the ability of a person’s blood to clot is impaired due to a lack of factor VIII. Hemophilia A occurs mostly in males. People with hemophilia can experience bleeding episodes that can cause pain, irreversible joint damage and life-threatening hemorrhages. Factor replacement therapy remains a cornerstone of care and can be used across multiple treatment scenarios.

As Dr. von Drygalski explains, efanesoctocog alfa is a novel and investigational recombinant factor VIII therapy that is designed to extend protection from bleeds with once-weekly prophylactic dosing for people with hemophilia A. It builds on the innovative Fc fusion technology by adding a region of von Willebrand factor and XTEN® polypeptides to extend its time in circulation. It is the first investigational factor VIII therapy that has been shown to break through the von Willebrand factor ceiling, which imposes a half-life limitation on current factor VIII therapies, meaning patients require multiple infusions a week

To learn more about hemophilia A and other rare hematological disorders, visit