Imaging biomarkers in tauopathies.

Abnormally aggregated tau protein is central to the pathophysiology of Alzheimer's disease, frontotemporal dementia variants, progressive supranuclear palsy, corticobasal degeneration and chronic traumatic encephalopathy. The post-mortem cortical density of hyperphosphorylated tau tangles correlates with pre-morbid cognitive dysfunction and neuron loss. Selective PET ligands including [18F]THK5117, [18F]THK5351, [18F]AV1451 (T807) and [11C]PBB3 now provide in vivo imaging information about the timing and distribution of tau in the early phases of neurodegenerative diseases. They are potential imaging biomarkers for both supporting diagnosis and tracking disease progression. Here, we discuss the challenges posed in developing selective tau ligands as biomarkers, their state of development and the new clinical information that has been revealed.