Gene therapy trial for Parkinson's disease shows promise

Results from the first human clinical trial of gene-based therapy for Parkinson's Disease (PD) show the treatment substantially alleviates the symptoms of the condition. The trial was carried out by the US based biotech company Neurologix Inc.

People with PD are affected by tremors, stiff muscles and slow movements, caused by a gradual loss of dopamine (a neurotransmitter chemical) producing cells in an area of the brain controlling movement. It is not known what triggers this loss, but PD is not normally inherited. However, the illness does occasionally run in families, where the symptoms often appear at a younger age than in non-inherited cases. One in five hundred people suffer from the disease in the UK and there is currently no cure. Existing treatments for PD include directly replacing lost dopamine, or permanently inserting electrodes into the brain to try to stimulate the cells to produce their own.

The small-scale Phase I trial involved using a harmless virus to switch on a gene controlling the production of dopamine in the brain of twelve patients. The patients enlisted for the trial had advanced PD and were not responding to any other current treatments. After one year all of the participants demonstrated a clinical improvement of at least 25 per cent, with five patients showing substantial recovery of between 40 and 65 per cent. No negative side effects were observed.

Matthew During of the Cornell Weill Medical College in New York who recruited the twelve patients said 'This gene therapy trial is particularly unique and the clinical data unusually promising because the treatment was confined to just one side of the brain'. In its next trial the company plans to treat both sides of the brain which they hope may lead to greater improvements. Parkinson's expert Thomas Freeman warned that there was need for long-term monitoring of the trial patients to ensure no immune system or other side effects occur.