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Open AccessFeature PaperCommunication

Revisiting the Radiosynthesis of [18F]FPEB and Preliminary PET Imaging in a Mouse Model of Alzheimer’s Disease

Azrieli Centre for Neuro-Radiochemistry, Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
Institute of Medical Science, University of Toronto, Toronto, ON M5S1A8, Canada
Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA 02114, USA
Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland
Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N OX2, Canada
Department of Psychiatry, University of Toronto, Toronto, ON M5T-1R8, Canada
Department of Chemistry, The University of West Indies at Mona, Kingston 7, Jamaica
Authors to whom correspondence should be addressed.
Academic Editor: Svend Borup Jensen
Molecules 2020, 25(4), 982;
Received: 30 January 2020 / Revised: 19 February 2020 / Accepted: 20 February 2020 / Published: 22 February 2020
(This article belongs to the Special Issue Past, Present, and Future of Radiochemical Synthesis)
[18F]FPEB is a positron emission tomography (PET) radiopharmaceutical used for imaging the abundance and distribution of mGluR5 in the central nervous system (CNS). Efficient radiolabeling of the aromatic ring of [18F]FPEB has been an ongoing challenge. Herein, five metal-free precursors for the radiofluorination of [18F]FPEB were compared, namely, a chloro-, nitro-, sulfonium salt, and two spirocyclic iodonium ylide (SCIDY) precursors bearing a cyclopentyl (SPI5) and a new adamantyl (SPIAd) auxiliary. The chloro- and nitro-precursors resulted in a low radiochemical yield (<10% RCY), whereas both SCIDY precursors and the sulfonium salt precursor produced [18F]FPEB in the highest RCYs of 25% and 36%, respectively. Preliminary PET/CT imaging studies with [18F]FPEB were conducted in a transgenic model of Alzheimer’s Disease (AD) using B6C3-Tg(APPswe,PSEN1dE9)85Dbo/J (APP/PS1) mice, and data were compared with age-matched wild-type (WT) B6C3F1/J control mice. In APP/PS1 mice, whole brain distribution at 5 min post-injection showed a slightly higher uptake (SUV = 4.8 ± 0.4) than in age-matched controls (SUV = 4.0 ± 0.2). Further studies to explore mGluR5 as an early biomarker for AD are underway. View Full-Text
Keywords: [18F]FPEB; mGluR5; positron emission tomography (PET); iodonium-ylide; Alzheimer’s Disease (AD) [18F]FPEB; mGluR5; positron emission tomography (PET); iodonium-ylide; Alzheimer’s Disease (AD)
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Varlow, C.; Murrell, E.; Holland, J.P.; Kassenbrock, A.; Shannon, W.; Liang, S.H.; Vasdev, N.; Stephenson, N.A. Revisiting the Radiosynthesis of [18F]FPEB and Preliminary PET Imaging in a Mouse Model of Alzheimer’s Disease. Molecules 2020, 25, 982.

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