Parkinson's disease gene therapy shows promise

The first patient to receive experimental gene therapy treatment for Parkinson's disease is healthy, and has seen an improvement in his symptoms. Fifty-five year-old Nathan Klein, one of 12 people enrolled on a trial taking place at New-York Presbyterian Hospital, received the treatment a year ago. Doctors injected a virus carrying a therapeutic gene into Klein's brain in a effort to halt the progression of the disease. A further six patients have since undergone the treatment, and the gene therapy does not appear to have triggered side effects in any of them.

Klein claims to have experienced an improvement of 40-60 per cent in overall symptoms when taking low doses of medication, and a 10-20 per cent when he is not. To carry out the treatment, the scientists cut through Klein's skull to gain access to the region of the brain that controls movement. The symptoms of Parkinson's disease - uncontrollable shaking, rigidity of the limbs, slowness of movement and impaired balance and co-ordination - are caused by a gradual loss of dopamine-producing brain cells in this area of the brain.

Existing treatments for Parkinson's disease involve replacing the dopamine, a chemical that controls brain activity. But in the new trial, the doctors did not want to target dopamine production directly, as they thought many patients might already be resistant to its effects. Instead, the team injected a gene called GAD (glutamic acid decarboxylase) into Klein's brain, in order to trigger production of a protein called GABA (gamma-aminobutyric acid). It was hoped that this brain chemical would then 'quiet' the over-activity of the brain that causes the unwanted body movements. The results of phase I of the trial suggest the treatment is safe and effective, say the team, who published their findings in the journal Chemistry and Industry.

UK Parkinson's disease expert Roger Barker, who was not involved in the study, said that the lack of adverse effects is good news, but since Klein is still on low doses of medication, it is not yet possible to say whether the gene therapy was better than existing treatments for the condition. Phase II of the trial is set to begin at the start of 2005.