The first trial of gene therapy to treat Parkinson’s disease has produced encouraging results, giving patients better control of their movements for at least a year.

Doctors in the US injected into the brains of a dozen Parkinson’s sufferers a gene designed to calm the brain cells that lead to uncontrolled movements. Although the trial was designed only to assess the safety of the procedure and not its efficacy, the patients did show marked improvements, beginning some weeks or months after the treatment.

“These exciting results need to be validated in a larger trial, but we believe this is a milestone, not only for the treatment of Parkinson’s disease but also the use of gene-based therapies against neurological conditions generally,” said Dr Michael Kaplitt of Weill Cornell Medical College.

The injections were made on only one side of the brain, although the patients had symptoms on both sides of the body. The results show that the benefits were felt primarily on the treated side of the body and persisted until the study concluded a year after the treatments had been given.

The gene used was the one responsible for making glutamic acid decarboxylase (GAD). It was linked to a common but unactivated virus to carry it into brain cells, and the compiund was then injected directly inot the brain. “GAD makes a chemical called GABA that helps quiet excessive neuronal firing,” said Dr Matthew During, a co-author of the study, published in The Lancet.

“In Parkinson’s disease, patients develop substantial reductions in the activity and amount of GABA (gamma-ami-nobutyric acid) in their brains. This causes a dysfunction in brain circuitry responsible for coordinating movement.”

By inserting the gene, the hope was that GABA production could be boosted and the brain circuits normalised. “Because this was the first study of its kind, we targeted just safety,” Dr During said. “However, since the patients were symptomatic on both sides of the brain, this also provided the untreated side for comparison.” The improvements in movement were seen both when patients were taking drugs and when they were not – the “on” and “off” states.

The improvements represented about a 25 to 30 per cent change in the standard scale used to measure the severity of Parkinson’s symptoms. Some patients showed improvements as great as 65 per cent.

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