The imaging features and clinical associations of a novel tau PET Tracer - ¹⁸F-APN1607 in alzheimer disease

Purpose of the Report In vivo tau PET imaging could help clarify the spatial distribution of tau deposition in Alzheimer disease (AD) and aid in the differential diagnosis of tauopathies. To date, there have been no in vivo 18F-APN1607 tau PET studies in patients with AD. Methods We applied tau tracer in 12 normal controls (NCs) and 10 patients in the mild to moderate stage of probable AD. Detailed clinical information, cognitive measurements, and disease severity were documented. Regional SUV ratios (SUVRs) from 18F-AV-45 (florbetapir), 18F-APN1607 PET images, and regional gray matter (GM) atrophic ratios were calculated for further analysis. Results Quantitative analyses showed significantly elevated SUVRs in the frontal, temporal, parietal, occipital lobes, anterior and posterior cingulate gyri, precuneus, and parahippocampal region (all P's < 0.01) with medium to large effect sizes (0.44-0.75). The SUVRs from 18F-APN1607 PET imaging showed significant correlations with the Alzheimer's Disease Assessment Scale (ADAS-cog) scores (all P's < 0.01) and strong correlation coefficients (R2 ranged from 0.54 to 0.68), even adjusted for age and sex effects. Finally, the SUVRs from 18F-APN1607 PET imaging of the parahippocampal region showed rapid saturation as the ADAS-cog scores increased, and the SUVRs of the posterior cingulate gyrus and the temporal, frontal, parietal, and occipital regions slowly increased. The combined SUVRs from amyloid, tau PET, and regional GM atrophic ratio showed regional specific patterns as the ADAS-cog scores increased. Conclusions Our findings suggest that the 18F-APN1607 tau tracer correlated well with cognitive changes and demonstrated the spatial pattern of amyloid, tau deposition, and GM atrophy in the progression of AD.