Investigational Treatments Parkinson’s Disease
A number of therapeutic strategies are being investigated as possible treatments for Parkinson’s, including new drugs and novel therapies such as cell transplantation, stem cells and growth factors:* The search for a true neuroprotective drug – one that prevents dopamine neurons from dying – is being aggressively pursued through government-funded clinical trials as well as basic research, but results are still several years away.
* Transplantation, which entails grafting neurons from other sources into a person with advanced Parkinson’s, has proven to be a feasible strategy. However, in the largest clinical trial to date of this therapy, a small number of treated patients developed severe side effects, and scientists have taken a step back to understand why the problems developed and to better refine this approach.
* Various groups of scientists have shown that it is possible to induce embryonic stem cells to develop into dopamine-producing neurons in laboratory settings. Many experts believe Parkinson’s may be the brain disease that is most amenable to treatment with stem cells, but it may be years before the science has developed enough to use stem cells clinically.
* Growth factors are naturally occurring chemicals that support the development and survival of neurons. One growth factor, called GDNF (glial cell line-derived neurotrophic factor), has been recently shown to significantly improve symptoms of advanced Parkinson’s in a small, uncontrolled clinical trial. Experts are cautiously optimistic about this therapeutic strategy; more and better-controlled studies are needed to demonstrate its benefit.
* Elucidated numerous signaling pathways inside neurons by which dopamine produces its effects on target neurons.
* Discovered the “master molecule” DARPP-32, a critical regulatory protein whose actions change the function of a large number of signalling proteins inside neurons.
* Characterized several signaling pathways that interact with dopamine signaling in positive or negative ways.
* Identified naturally occurring biochemicals that amplify the effects of dopamine, fueling hope for developing a drug that could allow even small amounts of dopamine remaining in the brains of people with Parkinson’s to be used to maximum advantage.
* Analyzed the interactions of dopamine signaling pathways with the antidepressant drug Prozac and other compounds that affect brain levels of the neurotransmitter serotonin. This has led to a possible biochemical explanation for the high incidence of co-occurring depression in people with Parkinson’s.
* Traced the molecular pathways through which the neurotransmitters glutamate and acetylcholine interact with the dopamine pathway to counteract or enhance dopamine’s effects.