What is GDNF?

GDNF (Glial cell-derived neurotrophic factor) is one of many neurotrophic factors produced in the brain. GDNF has previously been found to have positive effects on some of the neurons in the brain that are most affected by Parkinson’s, particularly the dopamine neurons.

Given the remarkable laboratory results in laboratories around the world, clinical trials were set up for people with Parkinson’s. The first study had astonishing results, but a larger follow up study failed to replicate those findings and so a third GDNF clinical trial was initiated: the recent Bristol GDNF study led by Dr Alan Whone and Professor Steven Gill.

What is the Bristol GDNF study?

The Cure Parkinson’s Trust has been supporting the GDNF programme of research, including the development of the new delivery mechanism since 2007, and the North Bristol NHS Trust GDNF trial since 2011. The recent studies were funded by Parkinson’s UK, with support from The Cure Parkinson's Trust and in association with the North Bristol NHS Trust. MedGenesis Therapeutix provided the drug and additional project resources/funding and MedGenesis itself has funding support from the Michael J. Fox Foundation for Parkinson’s Research.

This was a complex trial of 41 people living with Parkinson’s which tested a pioneering Convection Enhanced Delivery system to deliver the drug with pin-point precision into the brain, but also tested whether GDNF showed any potential benefit as a disease modifying treatment for Parkinson’s.

The trial was lengthy and involved three stages:
1) a placebo controlled pilot study involving six participants, divided into two groups with only half of the group receiving active treatment via monthly infusion in Bristol
2) a nine-month placebo controlled clinical trial involving 36 participants plus the six pilot participants and
3) a nine-month open label extension to the trial, where all participants received GDNF.

Note: By the end of all parts of the study, the placebo group had received GDNF for only nine months, whereas those on GDNF for the first nine months received GDNF for a total of 18 months. Those on the pilot study received GDNF beyond 18 months.

What will happen next?

We now need to fully consider the results of the trial before we determine our next steps. If results indicate that GDNF delivered via Convection Enhanced Delivery demonstrates target engagement in the brain, is safe and viable as a treatment approach and shows benefit for people with Parkinson's then further larger studies will be necessary before it is supported as a treatment for Parkinson's. 

Note: Funding will be needed before any new studies can get underway.

** The BBC documentary 'The Parkinson’s Drug Trial: A Miracle Cure?' follows the journeys of nine participants who took part in the GDNF trial, one of whom was the late Tom Isaacs, our President and Co-founder. The first programme will air on: BBC Two, Thursday 28th February at 9pm.  

References:

https://www.ncbi.nlm.nih.gov/pubmed/8493557

https://www.ncbi.nlm.nih.gov/pubmed/12669033