Table 2.

Comparison of current tau tracers

Tracer	Radio-tracer	Spatial distribution pattern in human	Selectivity Tau/Aβ	Affinity Tau isoforms	Critical weakness	Reference
FDDNP	18F	Temporal, parietal, posterior cingulate, and frontal regions	Nonselective	3R + 4R	Nonselective	Small et al.[107]
THK-523	18F	NA	10 folds	3R + 4R No detection of non-AD tau	Defluorination	Fodero-Tavoletti et al.[108]
THK-5105	18F	Temporal, parietal, posterior cingulate, frontal, and mesial temporal cortices	25 folds	3R + 4R	Off-target binding in brainstem, thalamus, and subcortical white matter Relatively slower kinetics	Okamura et al.[109]
THK-5117	18F	Temporal lobe, parietal cortices, orbitofrontal, posterior cingulate cortices	No Aβ binding	3R + 4R	Off-target binding in subcortical white matter, cerebellum	Harada et al.[110]
THK-5351	18F	Temporal lobe	No Aβ binding	3R + 4R	Off-target binding in basal ganglia	Harada et al.[111]
PBB3	11C	Temporal lobe	50 folds	3R + 4R, able to detect non-AD tau	Short half-life retention in dural venous sinuses	Maruyama et al.[112]
T807	18F	Inferior temporal, lateral parietal, and posterior cingulate cortices	27 folds	3R + 4R, low affinity for non-AD tau	Retention in basal ganglia, anterior midbrain, venous sinuses, and choroid plexus	Chien et al.[113]
T808	18F	Temporal lobes, frontal lobe	27 folds	3R + 4R	Defluorination	Chien et al.[114]

NA: Not applicable; AD: Alzheimer’s disease.