18F-flortaucipir PET imaging: Biodistribution in the Japanese population and diagnostic accuracy by Japanese readers.

OBJECTIVE: 18F-flortaucipir (Tauvid™) is an 18F-labeled diagnostic positron emission tomography (PET) radiopharmaceutical, which was developed to detect tau pathology in the brain and to estimate the density and/or distribution of aggregated tau neurofibrillary tangles for patients being evaluated for Alzheimer's disease (AD). The objective of this article is to report findings from two studies. The primary objective of the first (dose and biodistribution) study was to investigate the consistency of 18F-flortaucipir PET biodistribution between Japanese and non-Japanese individuals. In the second (reader) study, the comparability of visual reads performed by Japanese and US expert readers who followed the same training program was evaluated.

METHODS: This article reports findings from two separate studies and datasets. In the dose and biodistribution study, whole-body distribution of 18F-flortaucipir was assessed (N = 9). Standardized uptake value ratios, normalized to the entire cerebellum, were calculated, and whole-body effective dose was calculated using a 73.7 kg bodyweight model. In the reader study (Study A27; I7E-AV-A27), five Japanese physicians visually interpreted 60 PET scans randomly selected from a previous US reader study (Study FR01; NCT03901092). Scan positivity was determined based on increased activity of 18F-flortaucipir in posterolateral temporal, occipital, or parietal/precuneus regions with or without frontal activity. Each scan was visually interpreted by all Japanese readers, who determined whether scans were consistent with an AD or non-AD pattern. Concordance between Japanese and US readers who underwent the same training on the interpretation of 18F-flortaucipir PET images was then evaluated (reader study primary endpoint).

RESULTS: The biodistribution of 18F-flortaucipir was consistent between Japanese and non-Japanese individuals. When interpreting 18F-flortaucipir PET images to distinguish between AD versus non-AD patterns, Japanese and US readers who underwent the same training showed 100% agreement on the majority reads, with a Cohen's Kappa value of 1.

CONCLUSIONS: 18F-flortaucipir whole-body biodistribution for Japanese individuals was consistent with that of non-Japanese individuals. After completing the same training, Japanese readers showed high concordance with US readers on the interpretation of 18F-flortaucipir PET images to distinguish between AD and non-AD patterns. Data and scans were from previous studies registered with ClinicalTrials.gov (registration numbers: NCT04474405; NCT03901092).