An experimental drug has slowed the rate of decline in memory and thinking in people with early Alzheimer's disease. The cognition of Alzheimer's patients given the drug, developed by Eisai and Biogen, declined by 27% less than those on a placebo treatment after 18 months. This is a modest change in clinical outcome but it is the first time any drug has been clearly shown to alter the disease's trajectory. "This is a historic moment for dementia research, as this is the first phase 3 trial of an Alzheimer's drug in a generation to successfully slow cognitive decline," said Dr Susan Kohlhaas, the director of research at Alzheimer's Research UK. "Many people feel Alzheimer's is an inevitable part of ageing. This spells it out: if you intervene early you can make an impact on how people progress." In the study, which enrolled roughly 1,800 patients with early stage Alzheimer's, patients were given twice-weekly infusions of the drug, called lecanemab. It was also shown to reduce toxic plaques in the brain and slow patients' memory decline and ability to perform day-to-day tasks. The results offer a boost to the "amyloid hypothesis", which assumes that sticky plaques seen in the brains of dementia patients play a role in damaging brain cells and causing cognitive decline. A series of previous drug candidates had been shown to successfully reduce levels of amyloid in the brain, but without any improvement in clinical outcomes, leading some to question whether the research field had been on the wrong track.