Scientists at Cardiff University have developed a potential treatment for Alzheimer's disease.
Deposits of amyloid prevent the brain from functioning properly
Researchers say they have created an antibody which could block the production of brain chemicals linked to the debilitating disease.
Dr Emma Kidd, who led the research team, said the results of the tests were "highly encouraging".
There is no known cure for Alzheimer's, which causes irreversible loss of brain function and memory.
The disease affects one in 20 people aged over 65 and a fifth of all people over 80 in the UK.
The results of the study show that it is possible to decrease production of the protein amyloid, which is believed to be the main cause of the disease.
Deposits of amyloid build up in the brain, preventing it from functioning properly.
The antibody will reduce this build-up, improving the patient's memory and quality of life, say researchers.
Dr Kidd said: "Our results are highly encouraging at this stage.
"We believe that our approach could lead in time to a new therapy for this distressing and debilitating disease as it should prevent or reduce the irreversible deterioration of a patient's memory and other brain functions.
"This would also reduce the burden on carers, usually family members, who look after patients in the earlier stages of the disease."
Dr Kidd said it was possible the antibody could be used as a preventative treatment for people with a family history of Alzheimer's.
The work was carried out at the university's Welsh School of Pharmacy and was funded by the Alzheimer's Society.
A final treatment could take several years to develop and the team are now seeking more money for the next stage of the work.
Barbara Phillips, from Penarth, whose husband has Alzheimer's, said the "terrible disease" had robbed them of the future they had planned together.
Businessman Ed Phillips, 65, first showed signs of the disease six years ago.
Mrs Phillips said: "It means to me the loss of a lovely man whom I've known since I was 16 and I'm losing him slowly, quietly and insidiously.
"It's like a bereavement, but it's a living bereavement almost," she told the BBC.
"I would give my right arm if they could find a treatment for Alzheimer's. I dream about it."
Professor Clive Ballard, of the Alzheimer's Society, said: "We hope people will understand how important it is to invest more in research into all types of dementia, so that we eventually may have a selection of new treatments to change the lives of people with dementia and their carers."
The research is published in the Journal of Alzheimer's Disease.