Diabetes drugs and Parkinson’s

There is strong evidence that diabetes and Parkinson’s may be connected. 

Research has shown that:

• People with type 2 diabetes have an increased risk of developing Parkinson's. And the risk is even higher for those who’ve had type 2 for 10 years or more.
• People with Parkinson's who also have diabetes may experience more severe motor and non-motor symptoms. 
• People with Parkinson's who don't have diabetes may not respond to insulin as well as they should.

What’s behind the connection? 

In diabetes the body doesn't produce enough or any of the hormone insulin or the body doesn’t respond to it normally. This means that glucose in the blood cannot be used by cells and doesn’t get stored away.

Brain cells need lots of glucose. It’s the fuel they use to generate the energy they need to function.

Dopamine-producing brain cells (those that stop working properly and are lost in Parkinson’s) have a particularly heavy workload. So, people with diabetes may be at greater risk of getting Parkinson’s, because dopamine-producing brain cells are particularly vulnerable if they can’t produce enough energy.

Could diabetes drugs work for Parkinson’s? 

This connection between diabetes and Parkinson’s has led to important research to investigate whether drugs used by people with type 2 diabetes could help to protect the brain cells affected in Parkinson’s and thereby slow or stop the progression of the condition.

A particular type of diabetes drugs have been the focus of this research. These drugs help in diabetes by targeting the glucagon-like peptide-1 (GLP-1) receptor in the pancreas which stimulates the release of insulin and therefore helps cells absorb more glucose from the blood.

Importantly for Parkinson’s, the same GLP-1 receptors that are found in the pancreas are also found in the brain. 

Experiments carried out in the lab have shown that these drugs have powerful beneficial effects on dopamine-producing brain cells. These promising results have led to trials of GLP-1 receptor targeting drugs to see if they can slow or stop the progression of Parkinson’s in people.

Results from clinical trials to date

Four different GLP-1 drugs are either being tested or have been tested in people with Parkinson’s so far. Let’s review the topline information and results.

Lixisenatide (2024)

What? 

A phase 2 trial in France in 156 people with Parkinson’s who were less than 3 years into their diagnosis. Participants received daily injections of lixisenatide or placebo over 12 months.

Positives? 

Movement symptoms in people with Parkinson’s receiving lixisenatide treatment did not deteriorate over a 12 month period, compared to those receiving a placebo where there was a slight worsening.

Question marks? 

The study didn’t show any benefit to quality of life or non-motor symptoms in those receiving lixisenatide compared to placebo.

Read more about the 2024 lixisenatide results in our research news story.

Liraglutide (2022)

What? 

A phase 2 trial in the USA of 63 participants where people were given either once-daily injections of liraglutide or placebo injections for 52 weeks.

Positives? 

Improvements were seen in non-motor symptoms and quality of life in those who received liraglutide compared to placebo.

Question marks? 

However, there was no clear improvement in movement symptoms between those on liraglutide and those on the placebo. There is still results to come from this trial. 

Exenatide Phase 2 (2017)

What? 

A phase 2 trial in the UK in 60 people with Parkinson’s. Half injected themselves with exenatide once a week for 48 weeks. The other half (the placebo group) injected a dummy version of the drug.

Positives? 

Those who received exenatide had a slight improvement when their movement was assessed while off their regular Parkinson’s medication and this difference between the two groups was still there 12 weeks after treatment had been stopped.

Question marks? 

There was no effect on quality of life or non-motor symptoms.

Exenatide Phase 3 (2024) 

What?

194 individuals with Parkinson’s took part in the 96-week trial. Around half received exenatide and the other half a placebo. 

Results? 

Unfortunately, the results show that exenatide did not stop the participants' movement or non-motor symptoms getting worse over the trial period. And 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.

Question marks? 

It is unclear why exenatide didn’t have the protective effect that was expected. Further analysis of the phase 3 data 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 a sub group of participants. 

Professor Foltynie, lead researcher on the exenatide phase 3 trial, said: 

“It is not yet clear whether there may be a subgroup of people with Parkinson’s who may get benefit from the use of exenatide. We will continue to scrutinise the data to see whether abnormal blood test results such as having ‘pre-diabetes’ might predict a better response to exenatide, and whether there were more of these people in the earlier, smaller trials in which we found positive overall effects.”

Read more about the exenatide-PD3 results in our research news story. 

Semaglutide Phase 2 (ongoing)

What?

An ongoing phase 2 clinical trial at Oslo University Hospital. Estimated to be investigating semaglutide (taken via a tablet) or placebo in 120 people with Parkinson's over 2 years. 

What’s next for diabetes drugs and Parkinson’s?

It’s too soon to say what the latest phase 3 exenatide results mean for wider research into the potential of diabetes drugs for Parkinson’s but the future of this line of research feels uncertain. 

Although, 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.

Note: It is essential that drugs are properly tested to ensure that they are safe and beneficial for people with Parkinson’s and do not interact with any other medication that they are on. We would not recommend people to go out and take these drugs, unless they have been recommended by a medical professional for other reasons.