Clinical trial of GDNF

This pioneering trial aimed to find out whether GDNF treatment can slow, stop or reverse Parkinson's - something no current treatment can do. 

About the trial

GDNF is a special protein that is naturally produced inside the brain and supports the survival of many types of brain cells – including the cells lost in Parkinson's. 41 people with Parkinson’s underwent robot-assisted surgery to have four tubes carefully placed into their brains, which allowed GDNF to be infused directly to the affected brain areas via a port in the side of their head with pinpoint accuracy.

Results on the way

The full results are due to be published on 27 February 2019 and will help us understand whether GDNF has the potential to be a future treatment for Parkinson's.

They will be closely followed by 'The Parkinson's Drug Trial: A Miracle Cure?' - a 2 part documentary charting the experiences of 9 participants in this unique study. Episode 1 will be broadcast at 9pm on 28 February 2019 on BBC2.

Update on the GDNF trial

GDNF trial - your questions answered

What is GDNF?

GDNF (or glial cell line-derived neurotrophic factor) is a special protein that is naturally produced inside the brain and supports the survival of many types of brain cells – including the cells lost in Parkinson's.

Research studies have suggested that GDNF has the ability to encourage these cells to grow again and may be able to stop the progression of Parkinson's.

An experimental new treatment involving GDNF has been tested in a group of people with Parkinson's in a clinical trial funded by Parkinson's UK.

About the clinical trial

41 people with Parkinson's took part in the clinical trial in Bristol.

GDNF is a large protein that needs to be delivered to the brain cells affected by Parkinson's. It’s too big to cross from the blood into the brain, so it can't be given using a pill or a simple injection.

To get GDNF to the brain cells that need it, participants had 4 tubes carefully placed into their brains that were connected to a small port behind their ear. This device allowed GDNF to be passed directly through the tubes to the affected brain areas with pinpoint accuracy.

In the first phase, participants received either GDNF or a placebo (a dummy drug) for 9 months. In the second phase all participants received GDNF for a second 9 months. The treatment was delivered in Bristol once a month.

Participants also underwent brain scans and regular assessments of every aspect of their Parkinson's throughout the course of the trial.

What will happen next?

What happens next depends on the full results of the current trial.

If the results of the current trial show that GDNF is safe and beneficial for people with Parkinson's, larger trials with more participants will be needed before it can be approved as a treatment for Parkinson's.

However, if the overall results of the trial show that GDNF is not beneficial, it's highly unlikely that there will be further trials, even if some individuals have experienced benefits.

Who carried out and funded the study?

This groundbreaking trial has been made possible through a phenomenal collaborative effort, involving charities, companies, researchers and most important of all, the people with Parkinson's taking part and their families.

This £2.5million 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 active GDNF and placebo (dummy) medications were supplied by MedGenesis – the company that owns the licence for GDNF. MedGenesis have also provided additional funding, support and expertise throughout the trial.

The delivery device was manufactured by Renishaw LLC, a leading engineering company, who also provided additional technical and analytical support.

Has GDNF been tested in people with Parkinson's before?

Yes. A number of trials of GDNF were carried out in people with Parkinson's around a decade ago but gave mixed results.

While the previous trials produced inconsistent results overall, some people experienced significant improvements in their Parkinson’s symptoms – which left unanswered questions about the potential of GDNF.

Some experts believe that some of the original trials did not work because they used different techniques to deliver the GDNF to the specific part of the brain affected in Parkinson's.

In this trial we used a new and innovative delivery device to ensure the drug got to the right spot in the brain each time.

Christine Proctor - participant in the GDNF trial

"When we sat down to plan this clinical trial, I knew this study would be the most complex and challenging I had ever been involved in — but also the most exciting."

Blog: Meet the team behind the GDNF trial

GDNF-7: protecting dopamine neurons

In this video Dr Oscar Cordero-Llana from the University of Bristol explains his research, which aims to boost the effectiveness of GDNF even further using a cutting-edge new approach.

Help us find better treatments and a cure

We're working hard to support more research, like the GDNF trial, to bring forward promising new treatments, faster. But we can't do it without you.