Hemophilia B
ICD-10 D67ICD-11 3B11.0

Treatment of Severe or Moderately Severe Hemophilia B with Factor IX Activity <2 IU/dL and No Inhibitors

This protocol addresses the management of hemophilia B in patients whose factor IX activity level is below 2 IU/dL — the threshold defining severe and moderately severe disease — and who have not developed factor IX inhibitors.

Clinical scenario

Severe or moderately severe hemophilia B with confirmed factor IX (FIX) activity level <2 IU/dL, in the absence of factor IX inhibitors. This population carries a high risk of spontaneous and provoked bleeding and requires a structured, preventive treatment strategy.

Treatment approach

Current evidence-based guidance from the ISTH Hemophilia Guideline Panel strongly favours a prophylactic strategy using factor IX concentrates over episodic (on-demand) treatment of bleeding events. Options include purified plasma-derived FIX as well as standard and extended half-life recombinant FIX formulations.

The full structured regimen — including product selection criteria, dosing schedules, and interval adjustments — is available in the complete protocol.

Instant Access to Structured Evidence-Based Regimens

References

DOI: 10.1016/j.jtha.2024.05.026
  1. In individuals with severe and moderately severe hemophilia B without inhibitors, the ISTH Hemophilia Guideline Panel recommends prophylaxis over episodic treatment of bleeding events (strong recommendation, based on moderate-certainty evidence ⨁⨁⨁◯).
  2. Therefore, we defined hemophilia as severe and moderately severe when individuals enrolled in the study population had FVIII or FIX activity levels <2 IU/dL.
  3. In individuals with severe and moderately severe hemophilia B without inhibitors, the ISTH Hemophilia Guideline Panel suggests prophylaxis with purified plasma-derived FIX or standard or extended half-life recombinant FIX concentrates (conditional recommendation, based on very low–certainty evidence ⨁◯◯◯).
  4. In this guideline, standard prophylaxis refers to dose and dose intervals of 20 to 60 IU/kg of FIX twice per week for hemophilia B as defined by Srivastava et al.
  5. The prophylactic doses, brand, and frequency of FIX infusion varied between the trials: nonacog beta pegol 10 to 40 IU/kg once weekly, albutrepenonacog alfa 35 to 50 IU/kg once weekly or 75 IU/kg every 10 or 14 days, and eftrenonacog alfa 50 IU/kg once weekly or 100 IU/kg every 10 days.
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