A trial launching in Britain will give a drug currently used to treat Alzheimer's to healthy middle-aged and older people, testing whether it can prevent the disease before symptoms ever emerge. Screening for the first European participants begins on Monday, with more than 15 UK centres expected to take part in the global study, which researchers describe as a fundamental shift from treating dementia after diagnosis to trying to stop it developing in the first place. Should it succeed, the approach could eventually see high-risk individuals prescribed preventive treatment in mid-life, a strategy some have likened to "statins for the brain".

Around 1,600 healthy adults aged 55 to 80 will be recruited worldwide for the PrevenTron trial, which will run for four to six years and is led in the UK by Surrey and Borders Partnership NHS Foundation Trust. Participants will undergo memory tests and a blood test for the protein p-tau217, an early biological marker of Alzheimer's, before being randomly assigned the drug, trontinemab, or a placebo. Developed by Roche, trontinemab is designed to clear amyloid plaques from the brain faster than existing treatments lecanemab and donanemab, both of which are licensed in Britain but not funded on the NHS on cost-effectiveness grounds.