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December 2007
News this month Parkinson’s Disease sufferers got some very encouraging news recently when study results revealed that a gene injected into the midbrains of 12 patients improved their motor coordination without causing any adverse effects. It was the first experiment in which gene therapy was used to control Parkinson’s symptoms. Although the goal of the study was only to show that the procedure was safe, follow-up testing indicated that patients experienced an improvement in motor function on the side of the body that correlated with the side of the brain treated. The study was published in The Lancet on June 22, 2007. Parkinson’s Disease is a degenerative disorder that causes tremors, stiffness, loss of balance and speech difficulties. It typically affects people 60 and older, and it afflicts an estimated 500,000 people in the United States. Among prominent sufferers are former attorney general Janet Reno and actor Michael J. Fox. Symptoms can be treated with drugs and with deep-brain stimulation, but there is no cure. Disease symptoms appear when neurons in a region of the midbrain called the subtantia nigra stop producing sufficient dopamine, a chemical that allows proper movement control. As dopamine levels decline, an adjacent area of the brain called the subthalamic nucleus goes into overdrive and produces too much glutamate, a chemical messenger that can unleash an inhibitory response. The result is the jerky, halting movement associated with Parkinson’s. In this study, which was conducted at the Feinstein Institute for Medical Research on Long Island, researchers sought to prevent the subthalamic nucleus from going into overdrive. They used a non-harmful virus to carry a gene that stimulates production of a calming chemical through an extremely thin, hollow glass wire into the subthlamic nucleus on one side of each patient’s brain. The surgery was done under a local anesthetic. Patients left the hospital within 48 hours and were monitored using brain-imaging PET scans and standard motor control tests at three-month intervals for one year. Encouraging results The patients, 11 men and one woman, showed between 25 percent and 65 percent improvement in motor control on the side of their bodies associated with the side of their brains in which the treatment took place. (Researchers were limited to testing just one side of each patient’s brain.) In addition, PET scans after one year showed a decline in abnormal brain activity on the treated side, and an increase in abnormalities on the untreated side. Three different doses were administered to different patients, but results did not indicate which was most effective. The most critical finding, according to lead study author Dr. Michael Kaplitt, a neurological surgeon and director of movement disorders at New York- Presbyterian Hospital/Weill Cornell Medical Center, is that the procedure is safe. None of the patients experienced any negative effects. Researchers plan to launch a wider trial of the effectiveness of the procedure. Kaplitt and collaborator Dr. Matthew During, a professor of molecular medicine at the University of Auckland in New Zealand, are investors and/or principals in Neurologix Inc., the company that funded the study. For a referral to a neurologist or neurosurgeon who specializes in Parkinson’s Disease treatment,
call 203.688.2000 or toll-free 888.700.6543. Yale-New Haven Hospital is home to a certified Primary Stroke Center
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 A small but promising study Although the study was very small and it was preliminary, the results are optimistic for patients with Parkinson’s Disease and other degenerative brain diseases because it showed that the method of treatment did no harm. The fact that the 12 patients showed improvement in motor coordination for as long as a year after the genes were injected into the region of their brains called the subthalamic nucleus was the icing on the cake. Study looked only at safety Better treatment methods sought 'The research benefits other
studies using the same or
similar virus vectors,
and those targeting other
areas of the brain with
other genes.'
This research is important because the available Parkinson’s treatments do not cure the disease; they only dampen the symptoms. A number of drugs lessen the tremors and rigidity, among them, L-dopa, which replaces the dopamine in cells that are still functioning normally. But drugs often lose their effectiveness over time. Increased doses of L-dopa, for example, are often associated with dyskinesias, or involuntary uncontrolled movement. In fact, patients are instructed to take “drug holidays” on a regular schedule to prolong the effectiveness of the medications. And once a critical number of the brain’s dopamine-producing cells die, the medication becomes completely ineffective. Electric pulses
That’s why gene therapy that tweaks the brain’s chemistry and regulatory behavior holds a lot of promise. A solid first step of research A randomized, controlled, doubleblinded study is the best way for researchers to determine whether they are doing something good. It may turn out that the answer to Parkinson’s is some combination of cell therapy – such as replacing the dopamine-producing cells – and gene therapy. This study is just the first step of many. But it is a encouraging and solid first step. Dr. Kenneth Vives is chief of stereotactic and functional neurosurgery in the department of neurosurgery at Yale School of Medicine.
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