NEW YORK, Jun 09 (Reuters Health) -- An experimental gene therapy can boost blood levels of clotting protein in mice that have a disease similar to human hemophiliacs, researchers reported this week at the American Society of Gene Therapy annual meeting held in Washington, DC.
The finding raises hope that similar gene therapy may one day effectively treat humans with hemophilia.
Hemophilia is a group of inherited disorders that result in a slower clotting time and an increased risk of bleeding. The most common form of the disease, hemophilia A, is caused by a defect in the gene for the blood clotting protein, factor VIII.
While gene therapy has been attempted for hemophilia in the past, attaining a sustained increase in the factor VIII protein has been a problem.
In the new study, the gene for human factor VIII was attached to a virus known as AAV. The virus was originally believed to be too small to serve as a viable carrier, but trimming the human gene down allowed the researchers to successfully insert it into the virus, which was then successfully delivered to the liver -- the site of factor VIII production.
Following a single inoculation of the gene-carrying virus into mice, the researchers found that there was a gradual and sustained increase in factor VIII blood levels. The levels have now remained stable for 11 months following the initial injection, the investigators report.
This raises the possibility that patients with hemophilia may also be able to undergo a "one-shot" procedure to restore their own missing factor VIII and reduce serious bleeding complications, according to Dr. Christopher E. Walsh of the University of North Carolina at Chapel Hill and colleagues.
"Importantly, the levels of human factor VIII produced in these small animals would be therapeutic if produced at an equivalent scale in larger animals, including humans," Walsh said in an interview with Reuters Health.
The successful transfer of the same factor VIII gene into patients with hemophilia would not cure the disorder. Nevertheless, Walsh seemed confident that the procedure would lead to permanent production of enough factor VIII to reduce or abolish the bleeding complications associated with loss of factor VIII production.
However, much more study is needed to determine if such a genetically engineered virus would be safe and effective in humans.
