A Safety and Efficacy Extension Study of a Recombinant Fusion Protein Linking Coagulation Factor IX With Albumin (rIX-FP) in Patients With Hemophilia B

Inclusion criteria: Main study inclusion criteria: For previously treated subjects, either: * Completed a CSL-sponsored rIX-FP (CSL654) study, including study CSL654\_3001 \[NCT01496274\] or study CSL654\_3002 \[NCT01662531\]. Or: * Scheduled to have a major non-emergency surgery within approximately 8 weeks from the anticipated date of receiving the first rIX-FP injection. * Not previously completed a CSL-sponsored rIX-FP lead-in study. * Male, 12 to 70 years of age. * Documented severe hemophilia B (FIX activity of ≤ 2%), or confirmed at screening by the central laboratory. * Subjects who have received FIX products (plasma-derived and / or recombinant FIX) for \> 150 exposure days (EDs), confirmed by their treating physician. * No confirmed history of FIX inhibitor formation at screening by the central laboratory For previously untreated subjects: * Male, up to 18 years of age. * Documented severe hemophilia B (FIX activity of ≤ 2%), or confirmed at screening by the central laboratory. * Never previously been treated with FIX clotting factor products (except previous exposure to blood components). * No confirmed history of FIX inhibitor formation Surgery substudy inclusion criterion: * Must require non-emergency surgery Subcutaneous substudy inclusion criteria: * Male, at least 18 years of age. * Subjects currently enrolled in Study CSL654\_3003 * Subjects who have received rIX-FP for ≥ 100 EDs (single-dose cohorts) or for ≥ 50 EDs (repeated-dose cohort) Exclusion criteria: Main study exclusion criteria: * Currently receiving a therapy not permitted during the study. * Any issue that, in the opinion of the investigator, would render the subject unsuitable for participation in the study. For subjects who have previously completed a CSL-sponsored rIX-FP study: * Unwilling to participate in the study for a total of 100 exposure days. For subjects requiring major non-emergency surgery who have not previously completed a CSL-sponsored rIX-FP lead-in study: * Known hypersensitivity (ie, allergic reaction or anaphylaxis) to any FIX product or hamster protein. * Known congenital or acquired coagulation disorder other than congenital FIX deficiency. * Currently receiving IV immunomodulating agents such as immunoglobulin or chronic systemic corticosteroid treatment. * Low platelet count, kidney or liver disease. * Human immunodeficiency virus positive with a CD4 count \< 200/mm3. For previously untreated subjects: * Known congenital or acquired coagulation disorder other than congenital FIX deficiency (except for vitamin K deficiency of the newborn). * Known kidney or liver dysfunction or any condition which, in the investigator's opinion, place the patient at unjustifiable risk. The surgical substudy does not have any additional exclusion criteria, although subject(s) in France will not be eligible for the surgery sub-study. Subcutaneous substudy exclusion criteria: * Intravenous use of rIX-FP within 14 days of subcutaneous administration of rIX-FP. * Life-threatening bleeding episode or major surgery during the 3 months prior to substudy entry