Gene therapy offers hope to sufferers of Parkinson's disease

The first gene-therapy trial for treating Parkinson's disease has resulted in a significant improvement in all the patients who took part, with none suffering any side-effects, it was announced yesterday.

Doctors believe the trial marks a milestone in the treatment of one of the most common neurodegenerative disorders of elderly people for which there is no effective cure.

The phase 1 clinical trial, the first in a three-stage process, was designed to test the safety of the technique but the apparent benefits of the treatment to the 12 patients who took part was clear up to a year after they were treated.

Not only did the patients improve in terms of being able to control the movements of their muscles, brain scans also showed that there were real improvements to the nerve activity within the central nervous system.

Parkinson's disease affects about one in every 500 people, and there are about 120,000 patients in Britain, with 10,000 people newly diagnosed with the condition each year. Although drugs can alleviate symptoms, there is no treatment that can stop the progression of the disease.

The latest findings, published in The Lancet, are the first to suggest that injecting genes into regions of the brain that are affected by Parkinson's may arrest at least some of the severely debilitating symptoms.

"These exciting results need to be validated in a larger trial," said Michael Kaplitt, a neurosurgeon at the Weill Cornell Medical Centre in New York and a member of the team that conducted the research. "We believe this is a milestone, not only for the treatment of Parkinson's, but for the use of gene-based therapies against neurological conditions generally."

Parkinson's results in loss of nerve cells in a region of the brain called the substantia nigra. These cells are responsible for producing dopamine, a vital chemical messenger in the brain that helps to control muscle movements.

However, another problem with Parkinsonism is the underproduction of a second chemical messenger called Gaba which inhibits nerve transmission and "calms" excessive nerve activity. Dr Kaplitt and his colleagues targeted this problem by injecting a gene called glutamic acid decarboxylase into the subthalamic region of the brain.

"Our hope was that with a single operation to this single site, we could boost Gaba production and thereby normalise the function of the entire circuit," Dr Kaplitt said.

The scientists genetically modified a virus that had been rendered harmless to carry the human gene into the brain cells. They injected only one side of the brain andused this to compare the effects of the therapy with the untreated hemisphere.

Standard methods of monitoring Parkinson's patients showed they fared better as a result of the treatment, with a 25-30 per cent improvement when they were not talking their usual medication, and a 40-65 per cent improvement when they were talking their drugs.