Promising Gene Therapy Results in Treating Hemophilia B

St. Jude Children’s Research Hospital announced the results of their ongoing gene therapy partnership with University College London and the Royal Free Hospital. The report indicates success in the trial, which used a modified adeno associated virus (AAV) 8 to deliver genetic material for making Factor IX in Hemophilia B patients.
In this study, 10 patients with severe hemophilia B were infused with the AAV 8 vector, and monitored for safety and longevity of the therapy over the past three years. The results of this study reports all 10 patients who received gene therapy continue to have positive results today.
In these patients:

  • Factor IX levels rose in all 10 men.
  • Episodes of spontaneous bleeding declined 90%.
  • Use of Factor IX replacement therapy dropped about 92% in the first 12 months after treatment.
  • In the 6 participants given high-dosage therapy, levels of clotting protein rose from <15 to 5% or more, transforming their condition from severe to mild. 
  • Some patients have reportedly discontinued factor injections for over four years.

Six of these 10 patients were treated with a high-dosage therapy.
In these patients:

  • Clotting protein levels rose from <1% to 5%, or more.
  • Their condition improved from severe to moderate.
  • Spontaneous bleeding and use of Factor IX replacement therapy declined more than 94% in 12 months.
  • Enabled the patients to participate in sports without the need for Factor IX replacement therapy, and without an increase in bleeding risk.
  • Four of the 6 saw an increase in liver enzymes as a result of therapy, possibly due to an immune response against the AAV8 vector, but these levels returned to normal after steroid treatment.

The report indicates that the approach used here could be used in treating hemophilia  A, though more studies will be needed. We will closely monitor this situation and continue to provide the bleeding disorders community with updates as they become available.

  • St. Jude Children’s Research Hospital’s release can be read here.
  • More information about the study can be found at the New England Journal of Medicine.
  • Reuters Health published an article about this study.

Source: St. Jude Children’s Research Hospital