Gene Therapy May Ease Tremors in Parkinson's Patients

Inserting a particular gene into the brains of patients with Parkinson's disease could reduce symptoms of the disease, including tremors, and also improve patients' ability to move, according to a new study.

The work is the first rigorously designed study to show that this technique, known as gene therapy, can be effective for people with Parkinson's disease, or any neurological disease for that matter. Patients who received the gene therapy showed greater benefits than those who received a placebo. Both groups of patients underwent brain surgery, but only one group received gene therapy.

The treatment is intended for a subgroup of Parkinson's patients — those who do not respond to medication very well. Of the 1 million to 1.5 million Americans with Parkinson's, about 10 to 15 percent of them, or 100,000 to 200,000 people, fit into this category, said study researcher Dr. Michael Kaplitt, vice chairman for research in the Department of Neurological Surgery at Weill Cornell Medical College in New York.

The study "brings us much closer to having a gene therapy that might be ready for general use," Kaplitt said. The work paves the way for gene therapies for other types of brain diseases, he said. "I think we are now helping to facilitate and to accelerate the development of a whole host of gene therapies … for diseases such as Alzheimer's disease, epilepsy [and] depression," he said.

Others argue that the effect, while real, is minimal.

"It's important that there was a change, but it was a very small change," said Dr. William Weiner, a professor of neurology at the University of Maryland Medical Center, who studies Parkinson's disease and was not involved in the study. The idea that inserting a single gene is the answer for neurodegenerative diseases is probably simplistic, Weiner added.  He also notes that gene therapy does not cure the disease, it only treats the symptoms.

The findings still need to be confirmed in a larger group of patients, since this study involved just 22 individuals, and it remains to be seen how long the benefits last.

Gene therapy

In those with Parkinson's disease, brain cells deteriorate in an area of the brain that controls muscle movement. Symptoms can include tremors, stiffness in the arms and legs, and trouble with coordination, according to the National Institutes of Health.

In these patients, the levels of a brain chemical called GABA are substantially reduced, Kaplitt said. This chemical is "used to quiet down neurons when they're firing excessively," Kaplitt said. Reductions in GABA cause problems in the parts of the brain responsible for coordinating movement, he said.

In the trial, 22 Parkinson's patients had a gene inserted in their brains to produce more GABA. The gene is delivered into cells with the help of a virus. Twenty-three patients received the placebo.

The researchers rated the patients' symptoms, including the severity of tremors and stiffness, and came up with a single "motor score" that represented how well they could move.

Six months after the surgery, patients given the gene therapy had a 2.1 percent improvement on their motor scores on average, while patients in the placebo group had a 12.7 percent improvement on their scores.

Treating more patients

Patients in this study also would be candidates for deep brain stimulation, another surgical treatment for Parkinson's disease. But gene therapy has several advantages over deep brain stimulation. For instance, gene therapy requires only one surgery, while deep brain stimulation requires multiple surgeries to maintain the hardware (a nerve control device) involved.

Only a small portion of those eligible for deep brain stimulation actually receive it, for various reasons, including the cost and long-term upkeep, Kaplitt said.

"We believe we may be able to expand that pool of patients that would be good candidates for surgical interventions," he said.

The study appears today (March 17) in the journal Lancet Neurology.

Pass it on: Gene therapy can improve symptoms in Parkinson's disease patients. The effects, while real, are quite small, experts say.

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