'This is huge,' Professor John Pasi, who led the trial at Barts and Queen Mary University of London told the BBC. He added that having 'the option to think about normalising levels' of the blood clotting protein factor VIII in patients with severe haemophilia was 'mind-blowing'.
During the trial, nine men with haemophilia A received one injection of a genetically-modified virus containing functional copies of the factor VIII gene. The virus delivers the healthy genes into the cells of the patient, allowing them to produce working protein.
Little improvement was seen in the one patient given the low dose and one patient given an intermediate dose. But six of the seven patients given the high dose produced healthy levels of factor VIII up to a year after being treated. Their ability to clot returned to normal, allowing them to completely discontinue other forms of treatment.
'I feel like a new person now,' said Jake Omer, a patient in the trial, to the BBC. 'I feel my body allows me to do more.'
Patients with haemophilia A have to inject themselves with supplementary factor VIII regularly. These injections can be inconvenient and costly, and the results can vary as the levels of factor VIII in the blood slowly drop between injections. The new gene therapy could allow patients to receive just one dose with long-lasting effects.
Haemophilia appears in two forms; A and B, with haemophilia A being the most common. This latest study follows positive results in a trial in haemophilia B patients using gene therapy (see BioNews 930).
'Gene therapy is a potentially game-changing treatment,' said Liz Carroll, the chief executive of The Haemophilia Society in London, UK. Researchers say further trials will be needed to determine whether the therapy works for a wider variety of patients.