A US study, published in the journal The Lancet last week, reported that all twelve Parkinson's patients who took part in the world's first gene therapy trial for brain disease improved markedly without experiencing side-effects.
Under the care of Dr Michael Kaplitt and colleagues of the New York-Presbyterian Hospital/ Weill Cornell Medical Centre, each patient underwent the 48 hour gene therapy-based procedure under local anaesthetic. Within three months, all patients reported decreased symptoms. After a year, measurements indicated that patients had improved by at least 25 per cent, with five patients experiencing a substantial improvement of between 40 and 60 per cent.
In an interview with The Daily Telegraph one participant, Nathan Klein, said that before the gene therapy, he had been 'in a state that nobody could survive', professing that 'the gene therapy saved my life'.
According to statistics published by the UK Parkinson's Disease Society, 10,000 people are diagnosed with Parkinson's in the UK each year; mostly those aged over 50. Symptoms of the disease, predominantly tremors and impaired movement, result when production of the brain chemical GABA (gamma aminobutyric acid) drops, triggering a key area of the brain for the control of movement, the subthalmic nucleus (STN), to over-activate.
To counteract this, the procedure uses a disabled virus, called an adeno-associated virus, to 'infect' the cells of the STN with a corrective stretch of genetic code, which triggers production of the enzyme GAD helping to restore GABA levels.
Dr Kieran Breen, Director of Research and Development for the UK Parkinson's Disease Society, said: 'The cause of Parkinson's is not known but it is likely to be a combination of genetic susceptibility and environmental factors. Because of this, there are many potential ways to treat or cure Parkinson's, and gene therapy is one potential route holding a lot of promise'.
The success of treating Parkinson's by calming the over-active STN has been demonstrated by existing treatments. However these treatments have some disadvantages, say the researchers. For example patients eventually build tolerance to drugs and deep brain stimulation requires surgery to implant a small electrical unit and wires.
Speaking to the Washington Post, Dr Matthew During, senior author of the study and professor of medical biology, immunology and medical genetics at Ohio State University, said 'it's a bit Frankensteinian, and patients hate it', referring to deep brain stimulation. 'There's about a 30-40 per cent adverse event rate', he added.
'We anticipate beginning a larger Phase II study in Parkinson's later this year [focusing more closely on effectiveness and dosage rather than safety and tolerance]' reported John Mordock, President and Chief Executive of Neurologix, in a statement. He also suggested that epilepsy would be the next disease to be trialled with this approach.