Scope: This policy covers recombinant extended‑half‑life Factor IX products (Alprolix, Idelvion, Rebinyn), recombinant standard‑half‑life Factor IX products (BeneFIX, Ixinity, Rixubis), and plasma‑derived Factor IX products (AlphaNine SD, Profilnine) for management of patients with hemophilia B and selected other factor deficiencies where supported (see Profilnine for Factor II/X).
Incidence and clinical features: Hemophilia B is an X‑linked recessive bleeding disorder caused by factor IX gene mutations occurring in about 1 in 30,000 male births and affecting roughly ~5,000 people in the US. Severity is classified by factor IX activity level: <1% = severe, 1%–5% = moderate, and >5%–40% = mild. Severe disease is associated with spontaneous bleeding (eg, hemarthrosis, intracerebral hemorrhage) and risk of joint disease and disability.
Inhibitor risk and treatment implications: Development of inhibitors to factor concentrates is less frequent than in hemophilia A but can occur in up to ~5% of patients; higher doses and specialized management may be required if inhibitors develop.
Guideline support: The policy references contemporary guideline sources including the National Bleeding Disorders Foundation / MASAC recommendations and the International Society on Thrombosis and Haemostasis (ISTH) clinical practice guideline (both cited 2024) as supporting documents for the role and use of Factor IX products.