DNA therapy could be safe cure for haemophilia, say American doctors

Scientists have used genetic engineering to create a safe new treatment for haemophilia, the inherited blood disease that can prove fatal if left untreated.

Scientists have used genetic engineering to create a safe new treatment for haemophilia, the inherited blood disease that can prove fatal if left untreated.

The technique, which involves implanting patients with "missing" DNA to stimulate the production of an essential blood clotting factor, has been developed by doctors in the United States.

Haemophilia affects 10,000 people in Britain and, in the most severe cases, can cause internal bleeding in joints, vital organs and soft tissue. Many victims lose so much blood they need regular injections of the blood clotting agent factor VIII.

The new technique, developed by doctors in Boston, uses genetic engineering to replace missing sequences of DNA that control the manufacture of factor VIII. It is much safer than existing treatments because there is no risk of contamination from blood products.

In the 1980s, thousands of haemophiliacs in Britain became infected by HIV and hepatitis C after being treated with contaminated blood products. More than 900 have died of Aids because of the contamination.

The new technique works by doctors extracting skin cells from patients unable to produce their own clotting agent and then welding them with snippets of synthetic DNA before they are cultivated in a test tube and implanted into tissue near the patient's stomach.

Tests on six sufferers showed success in four cases in which the patients became markedly better after the therapy. But the improvement only lasted up to 10 months.

Although so few patients have received the treatment, doctors believe it could become a safe and effective alternative to existing therapies, which can cost up to £100,000 a year for each patient.

Dr David Roth, director of haemophilia research at Beth Israel Deaconess Medical Centre in Boston, who led the research, said: "This is not a cure, but it has opened the door. It is completely safe because it uses patients' own cells, not other products. The patients felt great and were much less ill."

Haemophilia, which is transmitted through the female genes but affects mainly men, is extremely disabling in severe cases. There is no cure, but the disease is usually controlled by regular injections of plasma.