Results from the phase 3 trial of exenatide published

Results from the phase 3 exenatide trial have been previously shared with participants back in October 2024. The full results have now been published. Read the full scientific paper on the Lancet website.

What did the trial set out to do? 

The phase 3 Exenatide-PD3 study was a UK-wide clinical trial that evaluated whether a treatment called exenatide could slow the progression of Parkinson’s.

Funded by the National Institute for Health and Care Research (NIHR), 194 individuals with Parkinson’s took part in the 96-week trial. Exenatide or an inactive placebo was delivered by an injection pen once per week.

The main way the study set out to measure whether exenatide could slow the progression of Parkinson's was by looking at a participant's movement symptoms at the start, during and after completion of the trial. The researchers compared those receiving exenatide and those receiving the placebo.  

What are the results? 

• Unfortunately, the results show that exenatide did not stop the participants' movement symptoms getting worse over the trial period. 
• There were also no other benefits to taking exenatide seen in other measurements, for instance in how the participants' felt their symptoms were changing and looking at non-motor symptoms of the condition. 
• Brain imaging, DaT-SPECT imaging to give an idea of the activity of the brain chemical dopamine, also showed no changes compared to the placebo group.

Does this mean diabetes drugs don’t work for Parkinson’s? 

These results are part of years of investigation of a group of drugs called GLP-1 receptor agonists, currently used in the treatment of some people with diabetes. Results from previous lab based research and clinical trials have shown the potential of these drugs to slow or stop the progression of Parkinson's. However, these disappointing phase 3 results are from the largest and longest trial of this type of drug for Parkinson's and leaves an uncertain future for this area of research.

Although there's still evidence to be gathered, as there are still ongoing clinical trials of 2 other GLP-1 receptor agonists called semaglutide and liraglutide. And further analysis of the phase 3 exenatide trial results is underway to get a better understanding of how exenatide might be working in the body, as well as looking at data from technology that was used to help measure movement symptoms in some participants. This information could help researchers learn more about why exenatide didn’t have the protective effect that was expected.

Read more about the research on diabetes drugs and Parkinson’s.

Dr Katherine Fletcher, Research Communications Lead at Parkinson’s UK, comments:

“This is really disappointing news and we know this will be a setback for the Parkinson’s community. We encourage people to get in touch with us if they want any information or support.

“Whilst not the result we all hoped for, every result helps to provide answers and evidence to strengthen future research. And there’s lots of exciting research happening in Parkinson’s and many other interesting and hopeful new treatment approaches being developed and tested.”