The five-year trial tested a treatment involving a drug, called GDNF, being administered directly into the brain of patients with Parkinson’s disease. GDNF stands for ‘glial-cell derived neurotrophic factor’. It is a natural protein, found in the brain. High doses of GDNF have been found in animal and lab studies to regenerate dying dopamine brain cells – the same brain cells that die in people with Parkinson’s disease. During the £3 million trial, which ran from 2012 to 2017, the 42 patients were split into two groups: one of which was given GDNF, while the second received a placebo.
Neither group, nor the doctors, knew which group had received GDNF or placebo.
The patients received 10 monthly infusions of the drug, or placebo, over the course of nine months, following which those receiving GDNF saw an improvement in symptoms of six per cent over the placebo group.
However, this was not “statistically significant” as results needed to be recorded at 20 per cent.
Despite this, PET scan imaging showed a 100 per cent increase in dopamine nerve endings in those on GDNF, versus no increase in those on placebo, suggesting the drug does have a biological effect.
The patients then underwent an extension phase, during which all 42 volunteers received GDNF for a further nine months.
By the end of the extension period, the participants saw a 30 per cent improvement, on average, since the start of the trial.
Some patients had stopped having tremors and could walk from one side of a room to another without help.
However, as all patients received GDNF in the second phase and there was no placebo to compare it to, scientifically the evidence was deemed inconclusive.
The reason all patients received the drug in the second phase was because “it wasn’t considered ethical to put people through brain surgery without ever giving them a chance to have the drug”, according to principal investigator Dr Alan Whone.
The trial involved brain surgery to embed a titanium port into the skull behind the ear, through which the drug could be delivered, via catheters, directly into a deep part of the brain affected by Parkinson’s.
The device was pioneered by Professor Stephen Gill, who carried out the surgery on each of the patients at Frenchay and Southmead Hospitals in Bristol.
At the end of the trial many patients reported they felt they had benefited from GDNF.
Bryn Williams, 44, from Glasgow, told journalists: “From my perspective the trial was incredible. It was hope, it was genuine hope. I believe it works as a drug.
“Fluidity of movement is the single biggest thing that I don’t have. Being able to move fluidly is what the drug gave me back and it’s such a nice feeling.”
Vicki Dillon, 47, from Tyneside, added: “It changed my life and a lot of other people’s lives for the best.
“It [GDNF] does work, there’s no doubt in my mind that this works, and to deny it to hundreds of thousands of people across the world would be just sinful. We need this back and we need it soon.”
The study was funded by Parkinson’s UK with support from The Cure Parkinson’s Trust and in association with the North Bristol NHS Trust.
The company which owns the drug, MedGenesis, is now seeking funding to further trial GDNF.
About £4 million is needed for further research, which may be used to test GDNF at higher doses over longer periods.
The results of the trial have been published in the ‘Journal of Parkinson’s Disease’, while a research paper has been released in peer-reviewed journal ‘Brain’.
A two-part documentary on the trial, ’The Parkinson’s Drug Trial: A Miracle Cure?’, will air on BBC Two. Part one will air tomorrow (February 28) and part two will air on March 7 at 9pm.