After decades of disappointments, an experimental drug has been shown to slow the progress of Alzheimer’s disease for the first time. Lecanemab attacks clumps of protein called amyloid which are thought to be a central component of the most common form of dementia. Trial data published at a conference in San Francisco showed the drug slowed patients’ mental decline by around a quarter over 18 months of treatment. Despite Lacanemab only having a slight effect and only working on patients in the early stages of Alzheimer's, the results have been heralded as a major breakthrough. Professor John Hardy, a geneticist and molecular biologist who was one of the leading researchers to support research targeting amyloid 30 years ago, said the drug breakthrough was “historic,” while Alzheimer’s Research UK called the findings “momentous.”