An update on GDNF trials for Parkinson’s

What is GDNF and why does it hold hope for Parkinson’s?

GDNF stands for glial cell-line derived neurotrophic factor. It’s a naturally occurring protein that is produced inside the brain. 

Experiments in the lab show that GDNF can help to protect the dopamine-producing brain cells that are damaged and lost in Parkinson’s, and may even help them to recover and regrow.

The challenge is getting GDNF to the cells affected in Parkinson’s, which are located deep inside the brain. 

Device-delivered GDNF has led the way

We were the major funder of a trial that used a custom-built device to deliver GDNF deep into the brains of people with Parkinson’s. 

41 participants underwent brain surgery to have the device implanted and then had infusions of GDNF, or placebo, every 4 weeks during the 9-month trial.

The results were inconclusive, but brain scans revealed signs that the treatment may have started to regenerate dopamine-producing brain cells and many participants reported sustained benefits.

Since 2021, we’ve been working hard with experts and people with Parkinson’s to try and make a new trial of device-delivered GDNF happen. 

While we’ve made progress in many areas, we have not been able to find a partner to help us take this complex therapy forward. 

Without the appropriate support, we’ve decided to stop our active pursuit of a new trial and focus on our other research projects. 

Moving forward with gene therapy

While this project on device-delivered GDNF may have reached the end of the road, there are now new approaches to delivering GDNF coming through led by companies who can take this research forward.

The most advanced of these, in terms of timescale, uses a modified inactive virus which carries the genetic instructions for making GDNF. 
This virus is injected into the part of the brain affected in Parkinson’s in a one-off surgical procedure. It enters the brain cells and allows them to start making their own GDNF.

Small early trials have suggested that this approach may be safe and that it can stimulate GDNF production within the brain in people with Parkinson's. 

Preparations are now underway for a major international trial to test this approach in people with Parkinson’s to explore its safety and effectiveness. We will share further information about this upcoming trial as soon as we can.

Looking to the future

Arthur Roach, Director of the Parkinson’s Virtual Biotech at Parkinson’s UK, comments:

"Over the past 3 years we’ve worked with a wide group of people sharing their experience and expertise, including people living with Parkinson’s, who have shaped and supported this latest exploration. We’re so grateful for their time and insights. 

"We’re disappointed not to be able to bring a new trial to fruition for the Parkinson’s community. However, there are still possibilities in the future for GDNF with new approaches to delivery such as gene therapy. We’ll continue to do everything we can to bring forward life-changing treatments for everyone living with the condition."

In partnership with patients

The GDNF participants group have been committed champions for the need for further investigation of the potential of this treatment. Their tireless efforts led to the formation of an Involvement Advisory Board made up of volunteers living with Parkinson’s to bring their experiences to the project.

Lesley Gosden, a participant in the previous trial and member of the Involvement Advisory Board, said:

"The group includes volunteers with Parkinson’s who are passionate about involving people with lived experience in research alongside several of us who were part of the recent Bristol trial. Together we’ve brought our collective insights to the table to shape the logistics of running a new device-delivered trial. 

"Having experienced the potential benefits first hand, the GDNF participants were determined to work with Parkinson's UK to make a new trial a reality. We are disappointed with the end result, but we fully understand and support the decision.

"However, our goal has always been to investigate GDNF fully and find the best way to deliver it, whichever that may be. 

"This is not the end of GDNF, but the beginning of a new journey. We are excited at the potential of GDNF to change and enrich lives and hope this can finally be scientifically proven through the upcoming gene therapy trials."