A drug commonly used to treat type 2 Diabetes has successfully stopped Parkinson's in its tracks, leading scientists to believe that in the future they could actually treat the disease rather than just manage the symptoms.
Currently there is no cure for the degenerative neurological disease and standard therapies just manage the side effects of tremors and body stiffness, but do not prevent brain cells from dying.
The team from University College London are "excited" by the promise of this new finding, but also urge caution before the drug is tested more extensively.
Parkinson's disease, which affects 127,000 people in the UK, causes progressive damage to the brain over time and cells that produce dopamine hormone - a chemical that helps control body movement - are lost.
The drugs administered currently, work to boost dopamine levels and replace the hormone being lost, but is powerless to stop the brain continuing to die.
Tom Foltynie of National Hospital for Neurology and Neurosurgery in London, said: "That goes a good way to improving symptom control, but it does nothing for the underlying disease pathology."
In the trial 50% of the 62 volunteers, who are all diagnosed with Parkinson's, were given the diabetes drug exenatide as well as their usual medication, and the rest were given a placebo.
Over a period of 48 weeks, the control group continued to decline (as would be expected) but those taking exenatide remained stable and showed less degeneration in brain scans.
But it is worth noting that these effects were subtle – they didn't perform better on cognitive tests, and there wasn't a visible improvement in their day-to-day symptoms.
David Dexter, from Parkinson's UK charity, said: "You can say with a reasonable level of certainty that the drug is slowing the disease down, if only by a small amount."
This study also adds weight to the theory that diabetes and Parkinson's (or Alzheimer's) work in a similar way; just as neurons can become unresponsive to insulin, cells in the pancreas do in type 2 diabetes.
This is because both affect how cells produce energy, causing them to starve and become inflamed.
Dr Peter Whitton from UCL, told Parkinson's charity: "We hope our research will help people with Parkinson's relatively soon. A small scale clinical trial of exenatide is currently taking place at the Institute of Neurology, the results of which are due later this year."