5. Severe (factor IX activity ≤2 U/dL) hemophilia B patients with a minimum of 3 bleeding episodes over the preceding 6 months or 6 bleeding episodes over the preceding 12 months or in the event the subject is on prophylaxis, a minimum of 3 bleeding episodes over the preceding 6 months or 6 bleeding episodes over the preceding 12 months prior to being placed on prophylaxis