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Gene Therapy for Advanced Parkinsonís Shows Promise

An experimental surgical treatment for Parkinson’s disease (PD) – which involves inserting the human gene known as GAD deep into a brain structure – improved motor symptoms in people with a moderately advanced stage of Parkinson’s. The results were reported in the March 17 online issue of The Lancet Neurology. 

Gene therapy is a method which delivers a therapeutic substance, made by a gene, directly to a specific area of the body. In the new study, scientists used an inactivated virus to deliver the gene called glutamic acid decarboxylase (GAD) into brain cells. GAD makes a neurotransmitter called GABA which can suppress overactivity in the brain’s subthalamic nucleus – overactivity that contributes to the movement symptoms and complications of Parkinson’s, such as dyskinesia. An earlier study showed that the use of this virus to deliver the GAD gene into the brain was a safe approach in people with PD.

Investigators at seven US research centers led by Andrew Feigin, M.D., of the Feinstein Institute for Medical Research, North Shore University Hospital, Manhasset, New York, surgically inserted catheters into the brains of 16 study participants to carry the GAD gene to the subthalamic nucleus on both sides of the brain. An additional 21 participants underwent sham surgery, an simulated injection procedure in which which the skull is not opened and participants do not receive the GAD gene. Sham surgery is important for research design and helps to maintain “blinding” of the study, meaning neither the participants nor medical personnel knew which participants had gene therapy.


  • Six months after the surgery, motor symptoms in participants who received gene therapy improved by an average of 23 percent, as measured by a standard rating scale, the Unified Parkinson’s Disease Rating Scale (UPDRS);  symptoms in participants who had sham surgery improved by an average of 13 percent.
  • Participants experienced mild to moderate side effects, mainly headache and nausea, but no other adverse consequences.


What Does it Mean?

The idea of injecting a gene into the brain to make a protein to treat PD has long been discussed in the scientific community. This study is the first rigorously designed clinical trial to test that hypothesis, and it is the first double-blinded study to show a positive benefit. As a proof of principle, this study confirmed that gene therapy can be performed safely. In terms of its larger impact, this study serves as encouragement to researchers and people with Parkinson’s, and confirms the need for more study. It is important to note that the gene injected into the brain – GAD – resulted in benefits in movement problems in the range of the effects of deep brain stimulation. GAD is not a therapy that slows down the progression of PD, an important goal for future gene therapies.

Source Date: Mar 23 2011