A pioneering treatment has been used to hold back a rare fatal brain disease in two children

A pioneering treatment combining gene and stem cell therapy has been used to hold back a rare fatal brain disease in two children.

The two-year pilot study used a harmless, disabled version of the Aids virus to ferry corrective genes into blood stem cells.

Both patients suffered from X-linked adrenoleukodystrophy (ALD), a hereditary condition that affects boys aged six to eight. Usually, death occurs before the patient reaches adolescence.

Sufferers of ALD lose the fatty myelin sheath that insulates and protects nerve fibres in the brain. As in multiple sclerosis, which has a similar effect, physical and mental disability result.

Progression of the disease can be slowed with transplants of donor bone marrow, which contain myelin-producing blood stem cells. But finding a matching donor can be a long and difficult process, and the procedure is very risky.

The new treatment relies on correcting the genetic fault in the patient's own bone marrow, making a donor unnecessary. A stripped down version of HIV was used as a "vector" to carry the corrective gene into the stem cells.

Both patients went on to show improvements similar to those seen with marrow transplants. Two years after the treatment, their condition had stabilised with no adverse side effects.

Professor Patrick Aubourg, from the University Paris-Descartes in France, a member of the team whose results are published in the journal Science, said: "This is the first time we were able to successfully use an HIV-derived lentivirus vector for gene therapy in humans, and also the first time that a very severe brain disease has been treated with efficacy by gene therapy."

Eve Lapin, a founding member of the Stop ALD Foundation who lost a son to the disease, said: "I know the urgency of boys stricken by ALD and the pain of their parents.

"These gene therapy results are exciting, but they are just the beginning. Time is of the essence in finding the safest and most effective therapies. Every day more children become afflicted with ALD, and their chances of surviving depend on the success of trials such as this."