Advances in the development of tau PET radiotracers and their clinical applications.

Alzheimer's disease and other neurodegenerative dementias belong to the family of tauopathies. These diseases are characterized by the deposition of insoluble tau aggregates possessing an enriched β-sheet structure. In vivo imaging of the tau deposits by positron emission tomography (PET) will facilitate the early and accurate diagnosis of these diseases, tracking of disease progression, assessment of disease severity, and prediction of disease prognosis. Furthermore, this technology is expected to play a vital role in the monitoring of treatment outcomes and in the selection of patients for the therapeutic trials of anti-dementia drugs. Recently, several tau PET tracers have been successfully developed and demonstrated as having high binding affinity and selectivity to tau protein deposits. Recent clinical studies using these tracers have demonstrated significant tracer retention in sites susceptible to tau deposition in Alzheimer's disease, as well as correlations with the disease severity and cognitive impairment in cases with dementia. These tracers, thus, have the potential to effectively diagnose the tauopathies. Further longitudinal assessment will clarify the effect of the tau deposition on the neurodegenerative process and cognitive decline and the interaction of tau with amyloid-β in the human brain.