Sunday, June 24, 2007

Gene Therapy for Parkinson's Disease (Update #2)

Some of my previous posts, like this one here and here, have mentioned Parkinson's Disease and gene therapy. Gene therapy for Parkinson's Disease looks promising as the latest report in The Lancet has an article on a Phase 1 trial for the safety and tolerability of gene therapy for Parkinson's. Here is an excerpt:

The brain is an attractive organ for gene therapy, because production of biologically active molecules within the brain might circumvent poor penetration of compounds that are delivered systemically due to a tight vascular blood–brain barrier. Local gene expression might also focus therapy in specific brain regions, thereby avoiding exposure of other areas to agents that might cause undesirable effects. Several attempts have been made to use gene therapy for malignant tumours, including those in the brain, but the main aim of these studies was to destroy target cancer cells.3 A trial aimed at correcting the genetic defect in the rare and lethal paediatric neurogenetic Canavan disease was also undertaken.4 Furthermore, a phase I study of intracerebral transplantation of genetically-modified cells in patients with Alzheimer's disease (“ex-vivo” gene therapy) was reported.5 However, the use of modified viruses (vectors) to introduce genetic material into endogenous neurons directly (so-called “in-vivo” gene therapy) has not been previously attempted for any adult neurodegenerative disorder.

....Our results show that AAV-mediated gene transfer can be done safely in the human brain, with no evidence of substantial toxic effects or adverse events in the perioperative period and for at least 1 year after treatment. Most patients have been followed up for more than 2 years after surgery, with some for more than 3 years. No deaths and no evidence of substantial adverse events were reported.

The promise of gene therapy has yet to be fulfilled; however, the ability to alter cellular function genetically remains a powerful potential opportunity for treatment of various devastating diseases. Safety and efficacy issues continue to raise concerns, especially when gene therapy is applied to diseases such as neurological disorders, in which there is limited prior experience. Indeed, our original protocol was modified by federal reviewers to restrict treatment to only one hemisphere of the brain because of the concern that unexpected toxic effects might produce a more devastating outcome if they happened bilaterally.

There is also an MP3 audio clip on this topic on this page.