Tau PET/CT for Early Detection of Alzheimer’s Disease Pathology

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PROJECT SUMMARY Alzheimer’s disease (AD) is a heterogeneous neurodegenerative disorder characterized by the abnormal accumulation of amyloid-β plaques and neurofibrillary tangles (NFT) composed of tau. Important preliminary data has shown that tau PET with quantitative analysis can distinguish Braak III vs IV NFT pathology. However, there is a gap in knowledge and only limited numbers of participants have been evaluated with early Braak NFT stages (I-IV). We will leverage our database of 1779 participants who have had tau PET over the past 6 years who provide a well characterized cohort for this study at substantial cost savings. Our hypotheses are that novel methods of assessing tau PET will be associated with early Braak NFT stages (I-IV) and cognitive test abnormalities. We will test our hypotheses in three aims: Aim 1: Characterize tau PET measurements that are associated with early NFT. We will use innovative tau PET analysis methods to predict early Braak NFT stage in a large sample of early Braak NFT stage participants. We will use a novel method of quantitative tau PET assessment to improve on prior methodologies and test tau PET for association with early Braak NFT stages. Aim 2: Characterize tau PET features associated with cognitive test findings. We will use tau PET to predict cognitive test findings in CU participants. Cognitive test findings correlate best with tau PET in this regard vs MRI or amyloid PET and tau PET could be an optimal therapeutic biomarker. We will use innovative tau PET imaging analysis methods to predict early cognitive test findings in a large sample of CU. Aim 3: Identify associations of different tau PET radiotracers with early neuropathologic tau hyperphosphorylation and cognitive testing. Alternative tau PET radiotracers may provide improved sensitivity for early NFT pathology and early cognitive findings in CU participants. We will test the differential ability of an alternative tau PET imaging drug to predict early Braak NFT stages and demonstrate association with cognitive tests. This work will provide a rigorous assessment of the biological meaning of tau PET signal. It will have a dramatic impact on treatment algorithms by identifying a subset with early tau deposition and therefore higher risk for developing AD dementia than those with only suspected amyloid pathology. Here we propose a multipronged approach to define tau PET imaging of early NFT and correlation with cognitive test findings in cognitively unimpaired individuals. This proposal is transformative, considering the novel concept of detecting NFT at early stages with state-of-art in vivo PET with novel methods and pathologic correlation that could provide insight for asymptomatic prevention trials.