Gene Therapy May Hold Promise for Advanced Parkinson's Disease
Study says new dopamine-producing brain cells help control motor function
By Steven Reinberg
THURSDAY, Jan. 9, 2014 (HealthDay News) -- A new, preliminary treatment involving triple-gene therapy appears safe and effective in helping to control motor function in Parkinson's disease patients, according to new research.
The therapy, called ProSavin, works by reprogramming brain cells to produce dopamine, the chemical essential for controlling movement, the researchers said. Lack of dopamine causes the tremors, limb stiffness and loss of balance that patients with the neurodegenerative disease suffer.
"We demonstrated that we are able to safely administer genes into the brain of patients and make dopamine, the missing agent in Parkinson's patients," said researcher Kyriacos Mitrophanous, head of research at Oxford BioMedica in England, the company that developed the therapy and funded the study.
ProSavin also helps to smooth out the peaks and valleys often produced by the drug levodopa, the current standard treatment, Mitrophanous said.
The treatment uses a harmless virus to deliver three dopamine-making genes directly to the area of the brain that controls movement, he explained. These genes are able to convert non-dopamine-producing nerve cells into dopamine-producing cells.
Although the study results are promising, the researchers suggest they should be "interpreted with caution" because the perceived benefits fall into the range of "placebo effect" seen with other clinical trials.
Hoping to improve on their results, the researchers have since re-engineered the therapy. "We have a new version which makes more dopamine in patients, and this new version is undergoing safety studies before we initiate trails in patients," he said.
Experts reacted positively but cautiously to the findings, which were published online Jan. 10 in The Lancet. While the treatment seems safe, its potential as a replacement for current therapy still must be proved, they noted.
"The ProSavin study was a positive and important first step for a potential gene therapy for Parkinson's disease," said Dr. Michael Okun, national medical director at the National Parkinson Foundation. "The results of this preliminary study revealed a promising safety profile, and it will be interesting to observe longer-term benefits and how ProSavin will compare to other therapies such as deep brain stimulation."
Mitrophanous thinks this new treatment will eventually outperform deep brain stimulation or levodopa.
Over time, patients need larger doses of levodopa. Its benefit starts to wear off five to 10 years after starting the drug, he said.
Patients can then try deep brain stimulation, which involves putting wires into the brain that are attached to a battery pack, Mitrophanous said.
"With our approach, the brain cells are permanently modified to make their own dopamine, so you wouldn't have to rely on external stimulation," he said.
The researchers don't say new this therapy is a cure, because brain cells continue to die. "But the hope is that we would give patients an additional five years before the disease progresses further," Mitrophanous said.