thk-5117

THK-5117 is a small molecule diagnostic radiopharmaceutical developed as a positron-emission tomography (PET) tracer for imaging tau pathology, particularly in neurodegenerative disorders such as Alzheimer's disease[7]. It selectively binds to aggregated forms of the tau protein—notably the hyperphosphorylated tau found in neurofibrillary tangles—with higher affinity for tau over amyloid-beta (Aβ) and binding patterns consistent with tau deposits in Alzheimer’s brain tissue[1][3]. THK-5117 is a racemic mixture, with the S-enantiomer (THK-5317) showing higher affinity for human Alzheimer’s tau and more favorable in vivo pharmacokinetics[3]. The tracer has been shown to differentiate between Alzheimer’s patients and healthy controls in PET imaging, with increased uptake correlating with disease progression[2]. However, THK-5117 exhibits notable nonspecific white matter binding, which can complicate image interpretation and quantification[3][4]. The compound was originally developed by researchers at Tohoku University in Japan[7][8].