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Diabetes Drug Shows Promise for Parkinson’s Disease in Trial

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Results from a Phase 2 clinical trial suggest that lixisenatide – a drug used to treat type 2 diabetes – may also slow the progression of Parkinson’s disease symptoms.

The study is published in The New England Journal of Medicine.

Expanding indications for GLP-1R agonists

Lixisenatide belongs to a group of drugs called glucagon-like peptide 1 receptor (GLP-1R) agonists. These drugs work by mimicking insulin, the natural hormone produced by the pancreas after eating that helps the body to absorb glucose.

GLP-1R agonist drugs were initially developed to treat type 2 diabetes. However, other effects observed in clinical trials, such as weight loss, have resulted in their use being expanded to also tackle obesity. Many studies are now exploring the potential effects of these drugs on a range of other health conditions.

Research suggests people with type 2 diabetes are at an increased risk of developing Parkinson’s. A previous small clinical trial investigated the effects of another GLP-1R agonist – exenatide – on Parkinson’s disease, finding that exenatide had some positive effects on slowing the progression of motor symptoms.

“GLP-1 agonists are widely used to treat type 2 diabetes and are among the leading repurposed drugs being tested for disease-modifying effects in Parkinson’s disease,” said Michele Vendruscolo, professor of biophysics at the University of Cambridge, who was not involved in the study.

The new study, led by Professors Olivier Rascol and Wassilios Meissner, investigated whether lixisenatide could also affect Parkinson’s disease progression.

Slowing down disease progression

The researchers recruited 156 people who had recently been diagnosed with Parkinson’s into the randomized, double-blinded study. These participants were assigned to receive either lixisenatide or a placebo alongside their usual Parkinson’s medication for a total of 12 months.

There was a statistically significant difference in their disease progression – lixisenatide-treated patients experienced a slower progression of their motor symptoms, whereas those who received the placebo progressed further.

The researchers used a 132-point scale to measure motor disability known as the Movement Disorder Society-Unified Parkinson’s Disease Rating Scale, or MDS-UPDRS. The scores for those taking lixisenatide changed by -0.04 points (indicating a small improvement) whereas those in the placebo group changed by 3.04 points (indicating worsening disability).

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“This cumulative clinical data therefore strongly supports the earlier laboratory and epidemiological data, that GLP1 receptor stimulation in the brain has neuroprotective effects relevant to the neurodegenerative processes of Parkinson’s disease,” said Tom Foltynie, professor of neurology in the Department of Clinical and Movement Neurosciences at University College London, who was not involved in the study.

However, patients did experience side effects of lixisenatide treatment – nearly half experienced nausea and 13% reported vomiting.

More detailed and extensive trials required

While these results show the promise of this drug for Parkinson’s, further testing is required before it can be approved clinically for the condition.

“The results of this trial are really encouraging for people with Parkinson’s disease,” said Masud Husain, professor of neurology and cognitive neuroscience at the University of Oxford, who was not involved in the study. “After a year, patients who were on the drug were significantly better off in their movements than those who weren’t on the medication. However, the findings do not provide conclusive evidence that the drug has a protective effect on the brain to effectively slow down disease progression.”

Further testing is required to unpick the effects of these drugs, as not all of the wider class of GLP-1R agonists have been tested in Parkinson’s. Some GLP-1R agonists do not have a strong ability to cross the blood–brain barrier and therefore are less likely to exert effects on the brain. Therefore, more research is required to improve our understanding of these potentially disease-modifying treatments.

“The authors are correct that further trial replication is necessary before any shift in clinical practice should be sought,” Foltynie added.

“In addition to prompting longer and larger clinical trials, these results show that a more quantitative understanding of the mechanism of action of GLP-1 agonists may reveal one or more therapeutic targets for the development of more potent drugs to treat Parkinson’s disease,” explained Vendruscolo.

Reference: Meissner Wassilios G., Remy Philippe, Giordana Caroline, et al. Trial of lixisenatide in early Parkinson’s disease. NEJM. 2024;390(13):1176-1185. doi: 10.1056/NEJMoa2312323

This article is a rework of a press release issued by the Van Andel Institute. Material has been edited for length and content.