UK continues gene therapy trial despite fears over boy's leukaemia

Britain defied international opinion last night by going ahead with a gene therapy treatment for seriously ill children that has been suspended by America and France over safety fears.

Government scientists said they faced an "ethical dilemma" after a French boy given the therapy in 2000 developed "leukaemia-like" symptoms.

France and the United States said yesterday they were halting trials of the treatment, which has so far been used successfully worldwide on almost 20 people with a rare inherited immune deficiency, sometimes called "bubble-boy disease". It affects babies, who usually fail to survive beyond 12 months without the therapy.

But Professor Norman Nevin, who chairs the Gene Therapy Advisory Committee, said after an all-day meeting that it had been decided that stopping the trials would cause more fatalities than carrying on, even though the exact cause of the French child's illness is not known. The child is receiving chemotherapy and is expected to recover.

"An investigation will take 12 to 18 months to find out what happened, and during that time one could be faced with ... children who will die," Professor Nevin said. "Provided the parents are cognisant of the risks, I think that to deny [patients] gene therapy would be unethical."

There are two such trials underway at Great Ormond Street Hospital, which celebrated success in April with Rhys Evans, then 18 months old. The disease, formally known as X-SCID – for X-linked severe combined immunodeficiency – is the only one where gene therapy has consistently worked.

The usual treatment is a bone marrow transplant from a sibling, or even a non-family donor. An extract of the patient's bone marrow is treated with a virus carrying the genes needed to revive the immune system. The genes are incorporated into the DNA of the patient's bone marrow, which is reinserted.

Doctors suspect that in the French case the virus interfered with a gene needed for blood production, causing symptoms similar to leukaemia. Dr Bobby Gaspar, consultant immunologist at Great Ormond Street, said the chance of that was less than one in 10 million.

"Five years ago there were no successful gene therapies," Dr Gaspar said. "Now we have cures. This is the first step to gene therapy for a wide range of diseases."