Repurposing a diabetes drug to crack Parkinson’s

Derived from Gila monster saliva, diabetes drug exenatide may change the course of Parkinson's disease. (National Park Service)

Parkinson’s patients treated with an approved diabetes drug, exenatide, did better on movement tests than did patients who received a placebo, University College London researchers found. If they can prove the drug changes the disease itself, it could transform the way we treat Parkinson’s.

Current treatments focus on relieving symptoms, such as tremors and slowness of movement, but do not hinder or halt the disease’s progression. The researchers followed 60 patients with Parkinson’s disease, who injected themselves once a week with either exenatide or a placebo, while still taking their existing medications for 48 weeks.

The patients were then taken off their treatment temporarily so the researchers could gauge how their disease was progressing. The exenatide group performed better on motor tests—which measured factors such as tremors, agility and speech—than did the placebo group, both at 48 weeks and at a 12-week follow-up. The findings are published in The Lancet.

"This is a very promising finding, as the drug holds potential to affect the course of the disease itself, and not merely the symptoms," said senior author Tom Foltynie, Ph.D., in a statement. "With existing treatments, we can relieve most of the symptoms for some years, but the disease continues to worsen."

However, the study did not determine conclusively whether the drug modified the disease itself. The team will try to answer that question in the next stage of research.

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Exenatide, derived from Gila monster saliva, is a glucagon-like peptide-1 (GLP-1) agonist. It treats Type 2 diabetes by mimicking the hormone GLP-1, which triggers insulin secretion.

Several research groups are collaborating to find new disease-modifying treatments for Parkinson's, including Roche and Prothenia, which are working on a drug that targets alpha-synuclein, a protein that is found in high levels in Parkinson's-linked lesions. And this year, investigators began testing Novartis' blood cancer drug nilotinib to see how it fares against Parkinson's.

The UCL team is looking to pinpoint just how exenatide works in Parkinson’s, where the loss of dopamine-producing brain cells leads to motor symptoms like impaired coordination and muscle stiffness. Previous research has shown that exenatide boosts motor function in animals and that stimulating GLP receptors in the brain can improve dopamine connections.

"While we are optimistic about the results of our trial, there is more investigation to be done, and it will be a number of years before a new treatment could be approved and ready for use. We also hope to learn why exenatide appears to work better for some patients than for others," said the study's first author, Dilan Athauda, MRCP, a clinical researcher at UCL.