The discovery of the first chemical to prevent the death of brain tissue in a neurodegenerative disease has been hailed as an exciting and historic moment in medical research.
More work is needed to develop a drug that could be taken by patients.
But scientists say a resulting medicine could treat Alzheimer's, Parkinson's, Huntington's and other diseases.
The University of Leicester discovery showed all brain cell death from prion disease in mice could be prevented.
End Quote Prof Giovanna Mallucci Lead researcher
What's really exciting is a compound has completely prevented neurodegeneration and that's a first"
The research team at the university's Medical Research Council Toxicology Unit focused on the natural defence mechanisms built into brain cells.
When a virus hijacks a brain cell it leads to a build-up of viral proteins. Cells respond by shutting down nearly all protein production in order to halt the virus's spread.
However, many neurodegenerative diseases involve the production of faulty or "misfolded" proteins. These activate the same defences, but with more severe consequences.
The misfolded proteins linger and the brain cells shut down protein production for so long that they eventually starve themselves to death.
It is rare to get cautious scientists keen to describe a study in mice as a turning point in treating Alzheimer's.
It is early science, a lot can go wrong between a drug for mice and a drug for humans and the only published data is for prion disease, not even Alzheimer's.
So why the excitement?
It is the first time that any form of neurodegeneration has been completely halted, so it is a significant landmark. It shows that the process being targeted has serious potential.
If this can be successfully developed, which is not guaranteed, the prize would be huge.
In Parkinson's the alpha-synuclein protein goes wrong, in Alzheimer's it's amyloid and tau, in Huntingdon's it's the Huntingtin protein.
But the errant protein is irrelevant here as the researchers are targeting the way a cell deals with any misfolded protein.
It means one drug could cure many diseases and that really would be something to get excited about.
This process, repeated in neurons throughout the brain, can destroy movement or memory or even kill, depending on the disease.'Extraordinary'
This process is thought to take place in many forms of neurodegeneration, so safely disrupting it could treat a wide range of diseases.
The researchers used a compound which prevented those defence mechanisms kicking in and in turn halted neurodegeneration.
The study, published in Science Translational Medicine, showed mice with prion disease developed severe memory and movement problems. They died within 12 weeks.
However, those given the compound showed no sign of brain tissue wasting away.
Lead researcher Prof Giovanna Mallucci told the BBC news website: "They were absolutely fine, it was extraordinary.
"What's really exciting is a compound has completely prevented neurodegeneration and that's a first.
"This isn't the compound you would use in people, but it means we can do it and it's a start."
Her lab is also testing the compound on other forms of neurodegeneration in mice but the results have not yet been published.
End Quote Prof Roger Morris King's College London
This finding, I suspect, will be judged by history as a turning point in the search for medicines to control and prevent Alzheimer's disease."
Side effects are an issue. The compound also acted on the pancreas, meaning the mice developed a mild form of diabetes and lost weight.
Any human drug would need to act only on the brain. However, this gives scientists and drug companies a starting point.A 'landmark' study
Commenting on the research Prof Roger Morris, from King's College London, said: "This finding, I suspect, will be judged by history as a turning point in the search for medicines to control and prevent Alzheimer's Disease."
He told the BBC a cure for Alzheimer's was not imminent but: "I'm very excited, it's the first proof in any living animal that you can delay neurodegeneration.
"The world won't change tomorrow, but this is a landmark study."
David Allsop, professor of neuroscience at Lancaster University described the results as "very dramatic and highly encouraging" but cautioned that more research was needed to see how the findings would apply to diseases such as Alzheimer's and Parkinson's.
Dr Eric Karran, the director of research at the charity Alzheimer's Research UK, said: "Targeting a mechanism relevant to a number of neurodegenerative diseases could yield a single drug with wide-reaching benefits, but this compound is still at an early stage.
"It will be important for these findings to be repeated and tested in models of other neurodegenerative diseases, including Alzheimer's disease."