Gene therapy is an attempt to repair the Parkinsonian brain. According the Jeffrey Kordower, Ph.D., there are four clinical trials testing gene therapy.
In his presentation at the Parkinson's Disease Foundation's 50th Aniversary Educational Symposium, Kordower outlined where each of the four gene therapies stands.
Amino Acid Decarboxylase is the enzyme that converts levodopa into dopamine. It can be delivered to brain cells using a gene transfer. This treatment would allow patients to use lower doses of levodopa and avoid the side effects associated with high doses.
Kordower labeled this approach to treating Parkinson's as "very interesting." But with his next breath he pointed out that the most recent clincal trial results were not encouraging.
Glutamic Acid Decarboxylase (GAD) is a gene that instructs the brain to make more of the neurotransmitter GABA. GABA calms the over-activity that occurs in certain parts of the Parkinsonian brain and contributes to tremors and other symptoms. Deep brain stimulation surgery is also a brain calming therapy. We passed along some results of their clinical trial this summer in this GAD story.
Pro Savin is "basically putting in all of the enzymes that are needed to make dopamine," Kordower said. "They are putting this into the brain trying to get the cells that had previously not made dopamine to make dopamine."
Early Pro Savin clinical trials have been encouraging.
Neurturin is a protien that prevents neurons from dying. It is in the same family as GDNF. Kordower is a founder of the company, and is obviously excited about it. He reports that Neurturin may actually modify the disease by saving cells that would otherwise die. You can learn more at this Neurturin link.
Kordower went out of his way to point out that these stem cell therapies have a high hurdle to clear in order for the FDA to eventually approve any of them. "There are so many other therapies that are currently available for patients with Parkinson's disease that are already known to be safe and effective," he said. "It has to be better than Levodopa in terms of efficacy. It has to be better than deep brain stimulation in terms of efficacy. That's a pretty high bar for these clinical trials to meet."
So far all trials have been open label trials. A large group of patients still needs to go through blind clinical trials to cancel out the placebo effect. If any of these therapies gain FDA approval, it will probably be after many years of testing.
Sources:
Parkinson's Disease Foundation's 50th Aniversary Educational Symposium
ClinicalTrials.gov
Oxford Biomedica
Neurologix
