N Engl J Med

ASH 2025: Gene therapy delivers sustained results for hemophilia B

December 12, 2025

The final 5-year analysis of the phase 3 HOPE-B trial (NCT03569891), presented at the annual American Society of Hematology meeting, found that a single infusion of etranacogene dezaparvovec achieved durable factor IX activity (~36 IU/dL) and reduced exogenous factor IX use by 96%, from 257,339 IU/year during lead-in to 10,924 IU/year through months 7 to 60 post-treatment. Efficacy was consistent regardless of baseline AAV5 neutralizing antibodies. Treatment-related adverse events were rare beyond month 6.

Source:

Pipe SW, et al; HOPE-B Study Group Investigators. (2025, December 7). N Engl J Med. Final Analysis of a Study of Etranacogene Dezaparvovec for Hemophilia B. https://pubmed.ncbi.nlm.nih.gov/41358585/