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Twelve patients with severe Parkinson's disease have safely completed the first attempt at gene therapy for this disease. A year after surgery, a preliminary study reports that none has had any serious treatment related side effects, and, on average, the patients' motor symptoms have improved.improved.
The gene therapy was aimed at the subthalamic nucleus, which is overactive in Parkinson's disease. Surgeons injected into the nucleus a viral vector (adeno associated virus) carrying the gene coding for glutamic acid decarboxylase (GAD). This enzyme catalyses the production of the inhibitory neurotransmitter γ-aminobutyric acid. The researchers hoped that γ-aminobutyric acid would inhibit the overactive subthalamic nucleus, restore downstream neurological circuits to normal, and help restore motor function.
The researchers and the author of a linked editorial remain cautious but optimistic. This phase I trial was not designed to find out if the treatment worked, just that it could be safe. Further trials, in larger numbers of patients with a sham surgery control group, now seem justified, they say. Meanwhile, these researchers will be watching their patients closely for immunological side effects from the virus or the gene.