A new drug, which could be used to treat Alzheimer's, shows 'a really clear benefit' for patients.
Immunologist Professor Luke O'Neill was speaking after two drug companies - Eisai and Biogen - said it slowed cognitive and functional decline in a large trial of patients.
The patients are in the early stages of Alzheimer's disease.
Lecanemab is designed to remove clumps of beta amyloid proteins which build up in the brain of people with the disease.
Prof O'Neill told Pat Kenny this proves the hypothesis.
"It's a 20% benefit, overall, it seems in the study - which isn't too bad.
"But it certainly seemed to slow down cognitive decline in the treated group, and that was a nice thing to see.
"What's important is it confirms a hypothesis, called the beta amyloid hypothesis: that that protein builds up in the brain, causes Alzheimer's.
"This clears that protein and seems to be beneficial to people."
He said the next steps are likely to improve its effectiveness.
"Of course what happens now - it's like fingertips on a cliff face - they've seen it statistically work in these patients, can you now improve it?
"And maybe get 30/40/50% effective? And the future trials now will test that.
"Maybe different doses, different timings - so it'll start the process.
"There's other drugs that are very similar, that showed similar effects.
"But this is one of the first trails that shows a really clear benefit", he added.