The Bristol GDNF results


Today – 27th February, 2019 – the long-awaited results of the Phase II GDNF clinical trial were published.

GDNF (or glial cell line-derived neurotrophic factor) is a protein that our bodies naturally produce to nurture and support cells. Extensive preclinical research suggested that this protein was particularly supportive of dopamine neurons – a group of cells in the brain that are affected by Parkinson’s.

The results of the Phase II clinical trial suggest that the treatment was having an effect in the brain (based on imaging data), but the clinic-based methods of assessment indicated no significant effect between the treatment and placebo groups.

In today’s post we will look at what GDNF is, review the previous research on the protein, discuss the results of the latest study, and look at what happens next.

And be warned this is going to be a long post!


Boulder, Colorado. Source: Rps

It all began way back in 1991.

George H. W. Bush was half way into his presidency, a rock band called Nirvana released their second album (‘Nevermind’), Michael Jordan and the Chicago Bulls rolled over the LA Lakers to win the NBA championship, and Arnold Schwarzenegger’s ‘Terminator 2’ was the top grossing movie of the year.

Source: Stmed

But in the city of Boulder (Colorado), a discovery was being made that would change Parkinson’s research forever.

In 1991, Dr Leu-Fen Lin and Dr Frank Collins – both research scientists at a small biotech company called Synergen, isolated a protein that they called glial cell-derived neurotrophic factor, or GDNF.

And in 1993, they shared their discovery with the world in this publication:

Title: GDNF: a glial cell line-derived neurotrophic factor for midbrain dopaminergic neurons.
Authors: Lin LF, Doherty DH, Lile JD, Bektesh S, Collins F.
Journal: Science, 1993 May 21;260(5111):1130-2.
PMID: 8493557

For the uninitiated among you, when future historians write the full history of Parkinson’s, there will be no greater saga than GDNF.

In fact, in the full history of medicine, there are few experimental treatments that people get more excited, divided, impassioned and evangelical than GDNF.

This ‘wonder drug’ has been on a rollercoaster ride of a journey.

What exactly is GDNF?

Continue reading “The Bristol GDNF results”

The road ahead: Parkinson’s research in 2018

The great ice hockey player Wayne Gretzky once said “A good hockey player plays where the puck is. A great hockey player plays where the puck is going to be” (the original quote actually came from his father, Walter). 

At the start of each year, it is a useful practise to layout what is planned for the next 12 months. This can help us better anticipate where ‘the puck’ will be, and allow us to prepare for things further ahead.

2017 was an incredible year for Parkinson’s research, and there is a lot already in place to suggest that 2018 is going to be just as good (if not better).

In this post, we will lay out what we can expect over the next 12 months with regards to the Parkinson’s-related clinical trials research of new therapies.

Charlie Munger (left) and Warren Buffett. Source: Youtube

Many readers will be familiar with the name Warren Buffett.

The charming, folksy “Oracle of Omaha” is one of the wealthiest men in the world. And he is well known for his witticisms about investing, business and life in general.

Warren Buffett. Source: Quickmeme

He regularly provides great one liners like:

“We look for three things [in good business leaders]: intelligence, energy, and integrity. If they don’t have the latter, then you should hope they don’t have the first two either. If someone doesn’t have integrity, then you want them to be dumb and lazy”

“Work for an organisation of people you admire, because it will turn you on. I always worry about people who say, ‘I’m going to do this for ten years; and if I really don’t like it very much, then I’ll do something else….’ That’s a little like saving up sex for your old age. Not a very good idea”

“Choosing your heroes is very important. Associate well, marry up and hope you find someone who doesn’t mind marrying down. It was a huge help to me”

Mr Buffett is wise and a very likeable chap.

Few people, however, are familiar with his business partner, Charlie Munger. And Charlie is my favourite of the pair.

Continue reading “The road ahead: Parkinson’s research in 2018”

Exenatide: One step closer to joblessness!


The title of today’s post is written in jest – my job as a researcher scientist is to find a cure for Parkinson’s disease…which will ultimately make my job redundant! But all joking aside, today was a REALLY good day for the Parkinson’s community.

Last night (3rd August) at 23:30, a research report outlining the results of the Exenatide Phase II clinical trial for Parkinson’s disease was published on the Lancet website.

And the results of the study are good:while the motor symptoms of Parkinson’s disease subject taking the placebo drug proceeded to get worse over the study, the Exenatide treated individuals did not.

The study represents an important step forward for Parkinson’s disease research. In today’s post we will discuss what Exenatide is, what the results of the trial actually say, and where things go from here.


Last night, the results of the Phase II clinical trial of Exenatide in Parkinson’s disease were published on the Lancet website. In the study, 62 people with Parkinson’s disease (average time since diagnosis was approximately 6 years) were randomly assigned to one of two groups, Exenatide or placebo (32 and 30 people, respectively). The participants were given their treatment once per week for 48 weeks (in addition to their usual medication) and then followed for another 12-weeks without Exenatide (or placebo) in what is called a ‘washout period’. Neither the participants nor the researchers knew who was receiving which treatment.

At the trial was completed (60 weeks post baseline), the off-medication motor scores (as measured by MDS-UPDRS) had improved by 1·0 points in the Exenatide group and worsened by 2·1 points in the placebo group, providing a statistically significant result (p=0·0318). As you can see in the graph below, placebo group increased their UPDRS motor score over time (indicating a worsening of motor symptoms), while Exenatide group (the blue bar) demonstrated improvements (or a lowering of motor score).


Reduction in motor scores in Exenatide group. Source: Lancet

This is a tremendous result for Prof Thomas Foltynie and his team at University College London Institute of Neurology, and for the Michael J Fox Foundation for Parkinson’s Research who funded the trial. Not only do the results lay down the foundations for a novel range of future treatments for Parkinson’s disease, but they also validate the repurposing of clinically available drug for this condition.

In this post we will review what we know thus far. And to do that, let’s start at the very beginning with the obvious question:

So what is Exenatide?

Continue reading “Exenatide: One step closer to joblessness!”

The GDNF trial (Bristol) initial results


We learned today that the phase 2 GDNF clinical trial in Bristol (UK) has not met the primary end point of efficacy (demonstrating a positive effect compared to a placebo treatment). That is to say, the initial results suggest that the drug has not worked. In this post we will review what we know and discuss what will happen next.


GDNF was pumped into the striatum (green area). Source: Bankiewicz lab

We have previously discussed GDNF and Parkinson’s disease (Click here to read that post). This drug was considered the great hope for Parkinson’s disease and a lot was riding on the results. Today’s announcement is extremely unwelcomed news, but it is not necessarily the end of the road for GDNF.

What is GDNF?

Glial cell-derived neurotrophic factor (or GDNF) is a neurotrophic factor (neurotrophic = Greek: neuron – nerve; trophikós – pertaining to food/to feed). It is a chemical produced in the brain. GDNF has previously been found to have miraculous effects on some of the neurons in the brain that are most affected by Parkinson’s disease (particularly the dopamine neurons).

Given the amazing results in laboratories around the world, clinical trials were set up for people with Parkinson’s disease. The first study had astounding results, but a larger follow up study did not replicate those results and so a third GDNF clinical trial was initiated: the Bristol GDNF study

What is the Bristol GDNF study?

The Bristol GDNF study run by the the North Bristol NHS Trust, was funded by Parkinson’s UK, with support from The Cure Parkinson’s Trust. The company MedGenesis Therapeutix supplied the GDNF and additional project resources/funding. MedGenesis Therapeutix itself has funding support from the Michael J. Fox Foundation for Parkinson’s Research.

The study involved participants having GDNF (or a placebo drug) pumped directly into their brains, into an area called the putamen. The putamen is where the greatest loss of dopamine occurs in people with Parkinson’s disease.

All together there were 41 people with Parkinson’s disease enrolled in the clinical trial. The trial was divided into two phases and the first of those is now complete. During the first phase 35 participants received either GDNF or a placebo drug over 9-months in a double blind fashion

What does double blind mean?

It means that neither the researchers nor the participants know which drug they are receiving. Everyone is ‘blind’ to the treatment. Single blind studies involve the researchers being aware of the treatment allocation, but the participants are blind. Single blind studies can be affected by what is called ‘investigator bias’ – where the investigators start to think that they see an effect when there may not be an effect. Double blind is considered the gold standard, but there are problems with this type of study as well.

If phase one has finished what is phase two of the trial?

The second phase of the study will involve all participants receiving GDNF. This part is already underway.

What was the “primary efficacy end point”?

The press release from the company behind the study, MedGenesis, suggested that:

‘The primary endpoint of the study is the percentage change from baseline in the practically defined OFF-state Unified Parkinson’s Disease Rating Scale (UPDRS) motor score (part III) after nine months of double-blind treatment’

With the limited information we currently have, we are assuming that the researchers were looking for a significant improvement in the motor symptoms rating scale (‘UPDRS’) of the subjects when compared to how they were at the start of the trial (‘baseline’). The subject’s motor features were assessed during periods when they were not taking their medication (‘OFF-state’), and the initial indications are that the researchers have not seen any improvement in the GDNF treated group compared to the placebo control treated group.

Is this negative result the end of the world?

NO. Most definitely not.

There are many reasons why the trial may have not achieved its primary end point, and the researchers have emphasized that they need time to analyse all of the results. It will be interesting to see the final analysis (and we will summarise it here when it is available – end of 2016 apparently).

It will also be important to follow up the participants to determine if there are any delayed positive outcomes. It may take longer than 9 months to see improvements (fetal transplant studies, for example, usually require 2-3 years before improvements are observed).


Maybe GDNF just needs a bit more time. We will keep you updated as more information comes to hand.

For more on the study, please see Parkinson’s UK and MedGenesis.