Hemophilia B is an inherited (genetic) disease in which a protein (factor IX) that promotes blood clotting is missing or does not work properly. Hemophilia B is caused by a defect in the gene that produces the factor IX protein. Factor IX protein is important in blood clotting. Patients with severe hemophilia B have very low levels of the normal factor IX protein. Such low levels can result in spontaneous bleeding events that cause destruction of bone and tissue. 

Bleeding events can include hemorrhage in the brain and can cause severe symptoms (like stroke) and death. Bleeding events can be effectively controlled and prevented with infusion by vein of plasma-derived factor IX protein concentrate (made from the plasma of blood donors) or recombinant factor IX protein product (made in the laboratory in cultured cells). The cost of these factor IX protein products and the difficulty associated with frequent intravenous (IV) infusions often make it not feasible to prevent bleeding events. The gene transfer you were given in the C0371005 formerly SPK-9001-101 study may offer a way for levels of factor IX protein in the blood to be raised and kept raised to stop or reduce spontaneous bleeding episodes. 

You are being asked to take part in this research study because you previously received an intravenous (IV) infusion of the investigational gene therapy product, SPK-9001 (fidanacogene elaparvovec/ PF-06838435), during a gene transfer study (Sponsor Protocol Number: C0371005) for hemophilia B. The gene transfer you were given in the C0371005 study may offer a way for levels of factor IX protein in the blood to be raised and kept raised to stop or reduce spontaneous bleeding episodes. The purpose of this research study (C0371003) is to find out the long term effects to your health after having participated in the gene transfer study (C0371005) where you received a single administration of SPK-9001 (fidanacogene elaparvovec/ PF-06838435).