Peter A. LeWitt, MD
In March, the journal Lancet Neurology published the positive results of a study that investigated a new form of treatment for Parkinson's disease, gene therapy. Gene therapy refers to an experimental technique for transforming brain cells to follow new genetic instructions, such as producing an enzyme. In this case, a harmless virus was used as a transfer vehicle to bring a laboratory-engineered gene selectively into a brain region called the subthalamic nucleus. This location is also the target zone of the electrode in the Parkinson's disease therapy called deep brain stimulation. The goal of the gene therapy study was to learn if various problems of advanced Parkinson's disease could be helped, much as deep brain stimulation of the subthalamic nucleus can be effective for similar problems.
The study was carried out at 7 US Parkinson's disease research centers, led by Peter Le- Witt MD at Henry Ford Hospital in West Bloomfield. The gene therapy product, termed AAV2-GAD, was developed by Neurologix, Inc and underwent careful review by the Food and Drug Administration and institutional review boards before it was offered to the study participants. The experimental treatment plan, which involved a neurosurgical procedure to implant the engineered gene, resulted in clinically-meaningful improvements at 6 months for the group of subjects receiving AAV2-GAD as compared to other study participants who underwent a "sham" (placebo) treatment. The procedure proved to be safe and is now under review for its 12-month outcomes.
A follow-up study is planned to confirm the effectiveness and safety of treatment with AAV2-GAD. Other applications of this approach with different genes are also under investigation or in planning stages. The notion of modifying brain function, as an alternative to medications, provides an exciting alternative since it may lead to more permanent benefits without limitations that drugs can sometimes impose. It is also possible that gene therapy-based treatments that offer more than symptomatic therapies might be in the spectrum of future gene therapy for Parkinson's disease therapy.