Hemophilia B, a rare genetic disorder affecting approximately 1 in 25,000 male births, is characterized by low levels of factor IX, a crucial protein for blood clotting.

A 13-year follow-up study published in The New England Journal of Medicine represents the longest reported duration for any gene therapy for hemophilia B, demonstrating long-term safety and effectiveness.

The results revealed a significant reduction in the annualized bleeding rate from 14.0 to 1.5 episodes per year, greatly enhancing the quality of life for participants.

This improvement validates the potential of gene therapy as a transformative one-time treatment option, significantly reducing the need for lifelong factor IX supplementation.

No significant side effects or toxic events were observed during the long-term follow-up, although minor liver inflammation was initially noted and resolved with steroid treatment.

The findings underscore the importance of ongoing evaluation of the long-term safety and immune response effects associated with AAV gene therapy.

The use of factor IX concentrate decreased by a factor of 12.4, significantly alleviating the disease burden for patients.

Overall, the study highlights the potential of gene therapy as a groundbreaking solution for hemophilia B, offering hope for improved patient outcomes.

Between March 2010 and November 2012, ten adults with severe hemophilia B received a one-time intravenous infusion of a gene therapy drug, with initial positive outcomes reported in 2014.

Patients maintained stable levels of factor IX throughout the study, with many experiencing significant freedom from bleeding and not requiring factor IX prophylaxis.

The gene therapy vector primarily targeted the liver, with over 90% of the administered vector reaching this organ, and only minor inflammation was effectively managed.

Throughout the study period, no late-onset safety concerns were identified, further supporting the long-term safety of the therapy.