MAPT and Alzheimer disease: MK6240 is a second-generation tau-PET tracer with several advantages over first-generation tracers, including minimal OTS in the basal ganglia and choroid plexus and a higher dynamic range, especially in individuals with AD with more advanced tau pathology (Betthauser et al., 2019; Pascoal et al., 2018; Walji et al., 2016).