A common diabetes drug could help slow down the progression of Parkinson’s disease, the second most common neurodegenerative condition worldwide.
In a year-long clinical trial that followed 62 people with Parkinson’s disease, researchers observed that patients who received exenatide once weekly had better performance on the end-of-study motor tests, as compared to those who only received placebo.
“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 Tom Foltynie, a professor at the University College London, and the study’s senior author. “With existing treatments, we can relieve most of the symptoms for some years, but the disease continues to worsen.”
Parkinson’s disease is characterized by progressive neurodegeneration, causing severe impairments in movement. Most often, the disease is associated with uncontrolled tremors; however, patients can also suffer from muscle stiffness and the difficulty moving or speaking. Because the disease is progressive, symptoms worsen over time. There are no cures, but medications can improve some of the symptoms, especially if the disease is diagnosed at early stages.
"There's absolutely no doubt the most important unmet need in Parkinson's is a drug to slow down disease progression, it's unarguable," said Professor Foltynie.
People who had exenatide (in addition to their usual treatments) had showed better motor function at 48 weeks. Moreover, their improvement persisted for another 12 weeks after exenatide treatment was stopped. By contrast, those who only received placebo (in addition to their usual treatments) had declined in motor function at both the 48- and 60-week evaluations.
Importantly, the improvements observed in the motor function tests did not translate to significant improvements in daily life activities, as reported by patients in the exenatide group. This suggests there are still uncertainties about how exenatide affects the underlying disease, and whether long-term improvements can be sustained.
Nevertheless, the researchers note the findings are remarkable. "This is the first clinical trial in actual patients with Parkinson's where there has been anything like this size of effect,” said Professor Foltynie. "It gives us confidence exenatide is not just masking symptoms, it's doing something to the underlying disease. We have to be excited and encouraged, but also cautious as we need to replicate these findings."
Dr. Dilan Athauda, the study’s lead author, echoes the sentiment of cautious optimism. “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.”
Similarly, Dr. Brian Fiske, senior vice president of research programs at the Michael J Fox Foundation, which funded the study, noted the ingenuity in finding a new, unmet purpose for an old diabetes drug. “Using approved therapies for one condition to treat another, or drug repurposing, offers new avenues to speed Parkinson’s therapeutic development,” he said. “The results from the exenatide studies justify continued testing, but clinicians and patients are urged not to add exenatide to their regimens until more is known about their safety and impact on Parkinson’s.”