Sustained Clinical Benefit of AAV Gene Therapy in Severe Hemophilia B

Strategic Insights -

Researchers have made a significant breakthrough in the treatment of severe hemophilia B, a rare bleeding disorder, using adeno-associated virus (AAV)-mediated gene therapy. The study, conducted at the Royal Free Hospital in London, involved 10 men with severe hemophilia B who received a single intravenous infusion of the scAAV2/8-LP1-hFIXco vector. The research team, led by Amit C. Nathwani, observed a sustained clinical benefit, with factor IX activity remaining stable across the dose cohorts, and a significant reduction in the annualized bleeding rate.

Key Takeaways:

  • The study found that a single administration of scAAV2/8-LP1-hFIXco gene therapy resulted in durable factor IX expression, sustained clinical benefit, and no late-onset safety concerns over a period of 13 years.
  • The median annualized bleeding rate decreased from 14.0 episodes to 1.5 episodes, representing a reduction by a factor of 9.7.
  • Use of factor IX concentrate decreased by a factor of 12.4.
  • The treatment had a significant impact on the quality of life for the patients, with reductions in hospitalizations and improved mobility.
  • The study's findings support the long-term efficacy and safety of AAV gene therapy for severe hemophilia B.
  • The research team noted that the presence of neutralizing antibodies to AAV8 could be a barrier to readministration of the vector.

Statistics:

  • 10 men with severe hemophilia B participated in the study.
  • The patients received a single intravenous infusion of the scAAV2/8-LP1-hFIXco vector in one of three dose groups.
  • The treatment resulted in a reduction in the annualized bleeding rate by a factor of 9.7.
  • The participants experienced a reduction in hospitalizations by a factor of 12.2.
  • The treatment had a significant impact on the quality of life for the patients, with 75% of participants reporting improved mobility.

Sources:

  • Sustained Clinical Benefit of Aav Gene Therapy In Severe Hemophilia B. New England Journal of Medicine, 2025;392(22):2226-2234.
  • Researchers at Royal Free Hospital Target Cancer Gene Therapy (Sustained Clinical Benefit of Aav Gene Therapy In Severe Hemophilia B). Hematology Week. July 14, 2025; p 54.
  • Medical Research Council UK (MRC).
  • Katharine Dormandy Trust.
  • National Institutes of Health Research (NIHR).
  • NHS Blood and Transplant.
  • Innovative Medicines Initiative.
  • Assisi Foundation of Memphis.
  • Hemophilia of Georgia Foundation.
  • ACEV Foundation.
  • American Lebanese Syrian Associated Charities (ALSAC).
  • NIH National Heart Lung & Blood Institute (NHLBI).