MAPT and Mental deterioration: Although cognitive decline is typically considered as a primary outcome measure for clinical trials,51 recent work has highlighted the potential role of tau PET in clinical trials.19,29 This is further evidenced by antitau drugs entering the clinical trial pipeline.52 Although further comparative studies are required, due to large within- and between-patient variability in frequently used cognitive measures,53 tau PET may allow for AD trials of shorter duration and with fewer participants.