Amyloid and tau positron emission tomography (PET) scans, as well as cerebrospinal fluid (CSF) biomarkers such as Aβ42, phosphorylated tau (p-tau) and total tau (t-tau) are used to select participants in AD trials, to evaluate target engagement, as well as to evaluate the disease-modifying effect reflected by the changes in AD pathology[5]. The gene discussed is MAPT; the disease is Alzheimer disease.