Via EurekAlert!: "A gene therapy called NLX-P101 dramatically reduces movement impairment in Parkinson's patients, according to results of a Phase 2 study ... The approach introduces a gene into the brain to normalize chemical signaling. ... The study is the first successful randomized, double-blind clinical trial of a gene therapy for Parkinson's or any neurologic disorder ... Half of patients receiving gene therapy achieved dramatic symptom improvements, compared with just 14 percent in the control group. Overall, patients receiving gene therapy had a 23.1 percent improvement in motor score, compared to a 12.7 percent improvement in the control group. ... Improved motor control was seen at one month and continued virtually unchanged throughout the six-month study period. ... Gene therapy is the use of a gene to change the function of cells or organs to improve or prevent disease. To transfer genes into cells, an inert virus is used to deliver the gene into a target cell. In this case, the glutamic acid decarboxylase (GAD) gene was used because GAD makes a chemical called GABA, a major inhibitory neurotransmitter in the brain that helps 'quiet' excessive neuronal firing related to Parkinson's disease. ... In Parkinson's disease, not only do patients lose many dopamine-producing brain cells, but they also develop substantial reductions in the activity and amount of GABA in their brains. This causes a dysfunction in brain circuitry responsible for coordinating movement."

Link: http://www.eurekalert.org/pub_releases/2011-03/nyph-gtr031411.php