Can gene therapy cure Parkinson's?

Gene therapy has shown promising results for Parkinson's disease, reports Sanjay Tanday.

What is the story?
The first gene therapy for Parkinson's disease has been shown to produce promising results, media reports claim.

US researchers treated patients with a harmless virus genetically modified to carry a gene which dampens down the nerve cells that are over stimulated in Parkinson's sufferers.

One patient's recovery astounded doctors, after tests revealed that his movement had improved by 65 per cent.

Findings could herald a landmark in the treatment of Parkinson's, which affects 120,000 people in the UK.

Gene therapy for Parkinson's could also be a promising treatment for other neurological disorders, such as Alzheimer's disease and epilepsy.

Currently, there is no cure for Parkinson's. A number of drugs are available to treat the symptoms but many produce side-effects such as dopamine deregulation syndrome.

What is the research?
The reports are based on the findings of a study that involved 11 men and one woman, aged an average of 58.

All had severe Parkinson's that had lasted for at least five years and found that current therapies were no longer effective.

The research focuses on a gene responsible for making a chemical called gamma aminobutyric acid, which reduces the activity in a key node of the motor neuron network in Parkinson's sufferers.

The gene was inserted into a harmless virus and injected into the subthalamic nucleus region of the brain in each of the Parkinson's patients.

It was applied to only one side of the brain to allow better assessment of the treatment.

Position emission tomography (PET) scans of the brains of the patients were taken before therapy and at six and 18 months after therapy. They focused on two distinct neuron networks; one that regulates movement and another that affects the thinking process.

The scans showed that the motor networks on the untreated side of the body got worse but the treated side got better.

Signs of improvement in movement were seen in the patients one month after starting therapy, and by six months the patients had improved by an average of 30 per cent. One patient even registered an improvement in movement of 65 per cent.

A second larger trial of the therapy is expected to begin early next year and will take 18 months to complete.

What do the researchers say?
Lead researcher Dr David Eidelberg, from the Feinstein Institute for Medical Research in New York, said it was 'good news' that the results from the brain scans on the gene therapy patients showed that only the motor networks were altered by the therapy.

'You want to be sure that the treatment doesn't make things worse,' he said.

'Having the information from a PET scan allows us to know that what we are seeing is real. This study demonstrates that PET scanning can be a valuable marker in testing novel therapies for Parkinson's,' he added.

What other researchers say
Dr Kieran Breen, director of research and development for the Parkinson's Disease Society, said: 'The cause of Parkinson's is not known but it is likely to be a combination of genetic susceptibility and environmental factors.

'Because of this, there are many potential ways to treat or cure Parkinson's, and gene therapy is one potential route holding a lot of promise.'

The results of the study were encouraging in terms of safety and efficacy. There was no evidence of significant side-effects and some evidence that this type of therapy produces positive benefits, he said.

'Comparison of the brain scans of the 12 people involved in the trial before and after the surgery demonstrated that some brain circuits that control movement which act abnormally in Parkinson's disease were working healthily again after surgery.

'This is important as it suggests that it was the therapy itself, rather than a placebo effect, that was having a positive impact on patients' symptoms.'

We now look forward to seeing the results of the second larger trial which is planned, added Dr Breen.

Informing Patients
  • Trials of the first gene therapy for Parkinson's disease have been completed.
  • Patients showed a 30 per cent improvement in movement six months after therapy.
  • A second larger trial is expected to begin next year.

sanjay.tanday@haymarket.com

PNAS Online 2007

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