Measurement of plasma phosphorylated tau 217 offers transformed paradigms for clinical trials of treatments for Alzheimer’s disease
Introduction The recent report characterising the utility of a commercially available immunoassay of phosphorylated tau 217 (p-tau217) in plasma to detect Alzheimer’s disease (AD) pathology was greeted with widespread enthusiasm (Ashton et al., 2024). The report itself, and much of the comment in response to it, focused on its potential use in clinical diagnosis: augmenting the ability to distinguish AD from other causes of dementia, to distinguish early AD from mild cognitive impairment (MCI) or to detect AD in its preclinical stages. However, the full benefit of these functions would only be realised once effective drugs to prevent AD progression became available. Here, I focus on a much more immediate application, the way that p-tau217 testing allows for the development of clinical trials which are dramatically cheaper, less demanding and shorter than those which have to date been used to assess the efficacy of proposed disease-modifying treatments for AD. Key characteristics of