updated 3/16/2011 7:52:50 PM ET 2011-03-16T23:52:50

An experimental treatment improved symptoms of Parkinson's disease in a mid-stage test, echoing results of an earlier pilot study.

The new research is the first to show positive results in a test of gene therapy against a sham operation in about three dozen U.S. Parkinson's patients.

After six months, those who got the gene therapy scored 23 percent better on a standard test to measure motor skills while those who got the sham operation did about 13 percent better.

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"Gene therapy is no longer just a theory," said Michael Kaplitt, a neurosurgeon at New York-Presbyterian Hospital and Weill Cornell Medical Center, and one of the study authors. "We are getting much closer to a reality where this treatment can be offered to patients." Kaplitt said the results might spur similar treatments for other brain disorders like Alzheimer's, epilepsy and depression.

Kaplitt and colleagues tested the gene therapy on 16 people while 21 others received a sham surgery. The patients were aged 30 to 75 and all were taking Parkinson's medication.

In patients with Parkinson's disease, their brains get overactive after losing the normal supply of a chemical called GABA. The new treatment, gene therapy, works by inserting billions of copies of a gene into patients' brains that helps them produce more GABA.

For patients who got the gene therapy, doctors drilled a hole into their brains while they were still awake. Doctors then slipped in a virus engineered to bring in billions of copies of a gene to help the brain pump out more GABA. Patients who didn't get the gene therapy had holes drilled halfway into their skull — enough to trick them they were getting the therapy but apparently not enough to do any harm.

The study was published online Thursday in the journal, Lancet Neurology. It was paid for by Neurologix Inc., the biotechnology company that devised the therapy. Kaplitt is a company cofounder and holds stock options and many of the other authors reported ties to Neurologix and other pharmaceuticals.

Parkinson's disease is a degenerative brain illness that causes problems including tremors, rigidity and slow movements. It affects about one in every 500 people. There is no cure, but some drugs help control symptoms.

"This is promising research but we need to know how long these benefits of gene therapy might last," said Michelle Gardner, research development manager at Parkinson's U.K. She was not linked to the study. "We don't know if there could be long-term consequences of introducing viruses into the brain."

In an accompanying commentary in the Lancet, Michael Hutchinson of New York University School of Medicine questioned whether gene therapy offers any advantages over deep brain stimulation, which has been used to treat Parkinson's disease for about a decade.

Walter Liskiewicz, a former oral surgeon in Michigan with the disease, could barely move before receiving the gene therapy in 2009 as part of the experiment.

Now, he plays jazz music and recently returned from a holiday in Brazil. "Everything was taken away from me and to just have them handed back is pretty special," he said. "It's like a miracle."

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


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