A single dose of an experimental gene therapy boosted production of a missing blood-clotting factor in people with hemophilia, a new study shows. The therapy might give patients a long-term solution for preventing dangerous bleeding episodes. Hemophilia is a rare, inherited disorder in which blood is unable to clot normally. As a result, people with hemophilia tend to bleed more than others after injury. They may also bleed without warning inside their bodies. This bleeding can damage organs and tissues and may be life threatening.
To find an alternative clotting factors replacement therapy, researchers investigated a potential gene therapy approach, focused on hemophilia B. This uncommon form of the disease affects about 1 in 5 patients with hemophilia. Hemophilia B is caused by defects in the gene that codes for human clotting factor IX. Scientists packaged a normal factor IX gene into a modified adeno-associated virus that targets liver cells. The liver is the only site that can produce a form of factor IX needed for the clotting process. The virus—acting as a delivery vehicle, or vector—was designed to transport the normal gene into liver cells and launch production of factor IX.
After gene therapy, each patient generated factor IX at between 2% and 11% of normal levels. In the short-term follow-up period (6 to 16 months), 4 of the 6 men no longer needed factor IX infusions for routine bleeding. Results from this study represent a promising step toward making gene therapy a viable treatment option for hemophilia B.
