Phase 3 trial of exenatide for Parkinson’s starting soon
Following encouraging signs in recent phase 2 studies, a large UK-wide trial of the diabetes drug exenatide will investigate whether this therapy can slow the course of Parkinson’s.
For the last decade researchers have been investigating whether exenatide — an injectable drug that is used to treat type 2 diabetes — could be ‘repurposed’ to treat people with Parkinson’s. This has painstaking work has led to a definitive phase 3 clinical trial that will test whether this treatment can slow the course of Parkinson’s, something no currently available drug can do.
If the results are positive it could lead to the first completely new treatment for Parkinson’s in years.
What is ‘repurposing’?
Drug repurposing means finding new uses for existing medicines.
Developing a new drug from scratch is a long, slow and expensive process. So the idea that we can use treatments that are already approved and in use for other conditions to treat Parkinson’s means cutting out a huge chunk of the work, expense and time required to develop a brand new therapy.
In short, drug repurposing has the power to get new treatments to the people who need them faster. And exenatide is one of the first of this new wave of potentially repurposable drugs to make it to large-scale phase 3 trials in Parkinson’s.
Exenatide — the journey so far
Exenatide works by targeting a receptor in the pancreas called GLP-1 which triggers insulin release. Crucially these receptors are also present inside the brain and research in the lab has suggested they play a role in a variety of processes that may be beneficial or protective for the brain cells affected in Parkinson’s.
Encouraging results from the lab quickly led to the first clinical trial in 2010 — a small 12 month study in 45 people with Parkinson’s. The results, published in 2013, showed that participants who received the drug had improved slightly over the 12 months of the study, whereas those in the control group had experienced a slight decline in their condition.
However, because people in the control group did not receive a placebo (an identical dummy version of the therapy), these promising findings could have been down to the placebo effect.
To investigate further a phase 2 double-blind, placebo-controlled study involving 60 people began in 2014. The results, published in 2017, again showed that those who received exenatide improved slightly over the course of the study, whereas those who received placebo deteriorated, when their movement symptoms were assessed while off their usual Parkinson’s medications.
However, when those who received exenatide were assessed 12 weeks after stopping exenatide, their scores had slipped back towards what they were before starting the trial. If the effects of exenatide are lost this quickly does it mean that it simply improves symptoms rather than slowing the course of Parkinson’s?
Another perplexing finding was that people who received exenatide did no better than those who received placebo on other important assessments including quality of life and non-motor symptoms such as mood, memory and thinking.
A comprehensive phase 3 study is due to start soon across the UK to attempt to provide definitive answers to these questions.
About the new trial
The upcoming study will involve 200 participants with mild to moderate Parkinson’s in London, Plymouth, Oxford, Manchester and Edinburgh.
It is a double-blind, placebo-controlled trial. This means that participants will be randomly assigned to inject either the study drug (exenatide) or an identical but inactive version (a placebo) once a week.
Neither the participants nor the study team will know who is receiving exenatide and who is receiving placebo until the study is complete. This is important for minimising the effects of expectation and bias.
Detailed assessments will be made of all participants before starting treatment and then at regular intervals throughout the 2 year study.
“We are excited to begin this important study which we hope will provide us with conclusive answers about the potential effects of exenatide for people with Parkinson’s.
“In particular, we’re keen to understand whether this treatment can meaningfully slow the progression of Parkinson’s rather than just improving movement symptoms — which would make it the first drug that can do so. We’re also going to be closely examining whether it may be helpful for the non-motor symptoms of the condition which current medications often fail to address.
“While we’re hopeful that we’ll see positive results, our job is to do the most rigorous clinical trial we can. A vital part of this is to manage expectations, of ourselves and the individuals who participate — so we do not exacerbate the placebo effect — and also of the wider Parkinson’s community.
“The reality is that so far no treatment has ever been proven to meaningfully slow the course of Parkinson’s in a phase 3 trial. We must all approach this next study with open minds, hope but no expectations.”
Interested in taking part?
This trial is not currently seeking participants but you can stay in touch with the study by keeping an eye on their web page here.
There are currently many Parkinson’s research studies underway in the UK that do need participants — including clinical trials testing potential new therapies.
Find studies to suit you using our Take Part Hub.