Hemophilia B is an X-linked recessive inherited bleeding disorder resulting from a deficiency of coagulation factor IX (FIX).1Patients with hemophilia B are treated with FIX replacement therapies to raise FIX levels and to prevent bleeds in order to improve quality of life and allow patients to take part in their usual activities.1The current standard of care is regular prophylactic treatment with FIX replacement products.1 This evidence concerns the gene F9 and hemophilia B.