A sadly familiar disappointment in Alzheimer’s research

After years of failed attempts to treat Alzheimer’s disease by targeting a toxic brain plaque called amlyoid, a critical mass of scientists turned their attention to a seemingly more promising target: a tangled cranial protein called tau. But the failure of a closely watched tau treatment suggests history may repeat itself for neurology’s next-best idea.

Yesterday, the Swiss drug maker AC Immune said its anti-tau antibody missed its primary and secondary goals in a placebo-controlled study that enrolled more than 450 people with early-stage Alzheimer’s. The 18-month study was widely perceived as a well-designed proving ground for other tau-targeting medicines, and its failure is sure to shift the conversation.

AC Immune is yet to release detailed data from the study, which means there could be a silver lining for tau. If the company’s treatment, semorinemab, had a negligible effect on tau proteins in the brain, there’s a chance that a more potent medicine could still prove its worth. But this logic will sound familiar to anyone who followed the amyloid saga, in which every failed study has left scientific breadcrumbs for the next in a two-decade process that is yet to produce an approved drug.