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May 24, 2013
ScienCentral

Parkinson’s Gene Therapy: Update


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What is Gene Therapy? from the Human Genome Project



   06.22.07
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In 2003, ScienCentral interviewed researcher Michael Kaplitt, assistant professor of neurological surgery at New York-Presbyterian/Weill Cornell Medical Center, and co-founder of Neurologix, Inc. Kaplitt and his team had gotten approval for a Phase 1 study to determine the safety of gene therapy in patients with Parkinson's disease and had performed the world's first gene therapy surgery on a patient with the disease. The findings of the completed study are published in the June 23 issue of the British medical journal The Lancet. The video to the right includes excerpts from our 2003 interview with Kaplitt. For more information on the newly published study, read on.

A Big First Step

The study reported positive results from the first ever gene therapy trial for Parkinson's disease. The clinical trial studied 12 patients, 11 men and one woman, ranging in age from 50 to 67, who had advanced Parkinson's disease. It was a "Phase 1" study, meaning it was designed primarily to test and prove that the therapy is safe. Kaplitt and his team used a harmless virus called an adeno-associated virus (AAV) as a sort of cargo ship for the corrective gene they wanted to deliver to the patient's brains. The virus carrying the gene called "GAD" (glutamic acid decarboxylase) was injected into a part of the brain called the subthalamic nucleus (STN), which usually has abnormally high activity in Parkinson's patients. This heightened activity leads to the loss of muscle control that is a hallmark of Parkinson's.

Increase in STN activity is largely due to a deficit of GABA, a major inhibitory neurotransmitter in the brain. The idea is that the GAD gene makes GABA and increasing GAD causes more GABA to be synthesized, thus helping to calm the STN over-activity typical of Parkinson's patients, and subsequently helping them regain control over their muscles.





None of the 12 patients showed adverse effects from the gene therapy. And although this study was designed primarily to test safety, the researchers also reported clear signs of improvement of symptoms over the course of a year.

Because of safety concerns, the researchers performed the procedure only on one side of the brain. However, all patients had symptoms on both sides of the brain, allowing researchers to compare the difference in abnormal brain metabolism between the two hemispheres as well as the difference in motor function of the two sides of the body. The researchers found that abnormal brain metabolism (measured by positron emission tomography or PET scanning) was less pronounced on the treated side of the brain. They also found that motor function improved on the side of the body controlled by the treated side of the brain.




Because of safety concerns, the researchers performed the procedure only on one side of the brain. However, all patients had symptoms on both sides of the brain, allowing researchers to compare the difference in abnormal brain metabolism between the two hemispheres as well as the difference in motor function of the two sides of the body. The researchers found that abnormal brain metabolism (measured by positron emission tomography or PET scanning) was less pronounced on the treated side of the brain. They also found that motor function improved on the side of the body controlled by the treated side of the brain.

Kaplitt's study was funded by Neurologix, Inc. He is a founder of and consultant to the company. A Phase 2 trial is planned for later this year, as well as a Phase 1 trial for epilepsy using the same approach.


 
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