Dogs with the bleeding disorder haemophilia A have been successfully treated using gene therapy, reports a paper published in Nature Communications this week. The study, in which dogs were found to be free of severe bleeding episodes for 2.5 years, is the first to demonstrate correction of haemophilia A in a large animal model using gene therapy that targets blood cells and represents a step towards the clinical translation to patients with severe haemophilia A.
Haemophilia A, a genetic bleeding disorder associated with a deficiency in the blood clotting protein Factor VIII, affects 1 in 10,000 men. David Wilcox and colleagues use a virus to introduce a functional Factor VIII gene into peripheral blood stem cells of dogs with haemophilia A. This gene therapy, variations of which the team tested on three dogs, led to the production and storage of Factor VIII in platelets – something that was not previously possible in these animals. The authors report that the two dogs that produced the highest levels of Factor VIII after gene therapy had no episodes of severe bleeding over the entire follow-up period of 2.5 years. None of the three dogs, received immunosuppressant medication for up to 90 days post gene therapy, developed antibodies against Factor VIII that could have limited the efficacy of the therapy.