Parkinson's disease is a degenerative disorder of the brain and central nervous system which affects movement and speech causing muscle rigidity and tremor. At present no cure exists, but symptoms can be managed with a combination of drugs, surgery, physiotherapy and dietary measures. A number of exciting avenues of research are also being pursued in the field of gene therapy, and human trials have generated some promising data, according to Parkinson's UK.
Brain Degeneration
Degradation of neurons in particular regions of the brain known as the basal ganglia, substantia niagra and subthalamic nucleous is characteristic of Parkinson's disease. Affected brain cells transmit signals to one another via secretion of the neurotransmitters dopamine and GABA, and a number of research areas are targeted towards correcting chemical imbalances caused by the death of these brain cells, according to the British National Health Service.
Gene Therapy
Modification of simple viruses allows scientists to insert genes into the affected brain regions of Parkinson's patients in order to change the physiology of brain cells. Gene therapy is a young and rapidly developing science and several approaches have been developed, each showing varying degrees of success in clinical trials, according to Parkinson's UK.
ProSavin
Scientists have generated a virus that delivers a gene which stimulates dopamine production in brain cells. The virus is injected into affected brain regions, and patients continually monitored in phase two clinical trials of this drug, known as ProSavin. An average 34 percent improvement of symptoms was observed relative to pre-treatment assessment scores of these patients. Movement and posture were improved significantly after two weeks, reaching 77 and 85 percent of normal levels respectively. A sustained improvement of motor function and behavior was observed over the 12 month study, which was maintained throughout the 44 months these patients were observed, as indicated by an article published in "The Investigational drugs Journal" in February 2010.
NLX-P101
Researchers have genetically engineered a virus, NLX-P101 to stimulate production of the neurotransmitter GABA in brain cells. Administration of NLX-P101 to the subthalamic nucleous of 12 people with advanced Parkinson's disease showed promising results in a phase one clinical trial. A 27 percent decrease in symptoms was observed in these patients in comparison with control subjects, which continued for at least one year after administration of the treatment, as stated in research published in "Lancet" in June 2007. Patients showed no adverse effects to the gene therapy whatsoever. Preliminary results from phase two clinical trials with NLX-P101 indicate a positive outcome is highly likely, according to an article published in "Medical News" in June 2010.
Preventing Nerve Cell Death
A different approach is to prevent or delay the death of dopamine producing nerve cells in the brain by targeting growth factors into affected brain cells using gene therapy. A phase one clinical trial has been completed in which 12 people with advanced Parkinson's disease where treated with a virus that inserts a gene coding for the growth factor nuerturin into affected brain cells. Although patients in this initial trial showed a high degree of relief from Parkinson's symptoms with no noticeable side effects, the wider implications of such a small study are difficult to assess. A second, larger trial is underway involving 60 people, according to Issue 7 of "Progress Magazine," published by Parkinson's UK in June 2010.
References
- PubMed; "Lancet"; Safety and Tolerability of Gene Therapy with an adeno-associated virus (AAV) Borne GAD Gene for Parkinson's Disease: An Open Label, Phase I Trial; M. Kaplitt et al; June 2007
- The Medical News: Neurologix Announces Positive Results from Phase 2 Trial of NLX-P101 for Advanced PD
- PubMed; "The Investigational drugs Journal"; Parkinson's Disease and Related Disorders--XVIII WFN World Congress"; D. Grosset; February 2010
- Parkinson's UK; Progress, The Research Magazine of Parkinson's UK
- National Health Service: Parkinson's Disease
