Tau and amyloid PET imaging with 18F‐PI‐2620 and 18F‐Florbetaben in patients with early‐onset dementia and healthy controls

Abstract

AbstractBackgroundAbnormal deposits of tau protein and beta‐amyloid are the two fundamental pathological features of Alzheimer's disease (AD). The research framework for AD diagnosis proposes categorizing subjects based on biomarker evidence of pathology using the ATN classification system (amyloid, tau, neurodegeneration). In‐vivo detection of amyloid pathology using positron emission tomography (PET) is well established and new generation tau PET tracers like 18F‐PI‐2620 have shown a high binding affinity for aggregated tau without significant off‐target binding. The purpose of this study is to describe the ability of 18F‐PI‐2620 to detect tau pathology in patients with early‐onset dementia (EOD) with proven amyloid pathology.MethodTen patients with EOD and positive 18F‐Florbetaben amyloid PET (age range 54‐64y, 8 with suspected early‐onset AD (EOAD) and 2 with logopenic variant primary progressive aphasia (lvPPA)), along with 14 healthy controls (HC) (age range 54‐76y) underwent dynamic PET scans for 75 minutes after injection of 18F‐PI‐2620 to examine the presence of tau‐pathology in cortical and deep brain regions. Specific binding ratios were derived from averaged PET images from 45‐75 min post‐injection.ResultIn 9 out of 10 EOD patients, 18F‐PI‐2620 uptake was robust and extensive predominantly in cortical regions with relative sparing of deep brain regions. In the remaining EOD case, binding was low but with the same distribution pattern described for other EOD patients. In one HC, significant, specific uptake was observed predominantly in deep brain regions. 18F‐PI‐2620 administration was safe and well‐tolerated.ConclusionOur preliminary results suggest an excellent performance of the tracer 18F‐PI‐2620 to detect tau deposits in EOAD and lvPPA. Tau PET imaging with 18F‐PI‐2620, in conjunction with 18F‐Florbetaben amyloid PET, distinctly discriminates between early‐onset dementias due to AD pathology from HC. These results also support the usefulness of 18F‐PI‐2620 for visualizing tau aggregation in EOD. Finally, 18F‐Florbetaben and 18F‐PI‐2620 appear to be reliable tools for establishing the ATN biomarker status in EOD patients. Nevertheless, further studies are needed to confirm these preliminary results.