Study Evaluating of Recombinant Human Factor IX (BeneFIX) and a New Formulation of BeneFIX (rFIX-R) in Moderate to Severe Hemophilia B

Inclusion Criteria: * Moderate to severe hemophilia B (FIX: C ≤2%) * Previously treated patients (PTPs) with ≥150 documented exposure days * Age ≥ 12 years (US sites only) Exclusion Criteria: * Detectable factor IX inhibitor defined as ≥0.6 Bethesda Units for pooled plasma reported by the local laboratory (family history of inhibitors will not exclude the patient) * Patient history of factor IX inhibitor replacement therapy * Patient unable to be off factor IX replacement therapy for at least 5 days without bleeding