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Molecular Imaging and Biology
Published in: Molecular Imaging and Biology 2/2012

01-04-2012 | Research Article

Tracer Level Electrophilic Synthesis and Pharmacokinetics of the Hypoxia Tracer [18F]EF5

Authors: Olli Eskola, Tove J. Grönroos, Sarita Forsback, Johanna Tuomela, Gaber Komar, Jörgen Bergman, Pirkko Härkönen, Merja Haaparanta, Heikki Minn, Olof Solin

Published in: Molecular Imaging and Biology | Issue 2/2012

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Abstract

Purpose

2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)-acetamide labeled with [18F]-fluorine ([18F]EF5), a promising tracer for tumor hypoxia, has previously been synthesized in low yields and low specific radioactivity. In pharmacokinetic evaluations, in the presence of non-radioactive EF5, a uniform and low background uptake and high in vivo stability of [18F]EF5 have been demonstrated. Our purpose was to increase the specific radioactivity of [18F]EF5 to enable to study the pharmacokinetics at trace level.

Procedures

[18F]EF5 was synthesized using high specific radioactivity electrophilic [18F]F2 as labelling reagent. Biodistribution of [18F]EF5 was determined in a prostate tumor mouse model, and formation of radiolabelled metabolites was studied in mouse, rat and human plasma.

Results

On average, 595 ± 153 MBq of [18F]EF5 was produced. Specific radioactivity was 6.6 ± 1.9 GBq/μmol and the radiochemical purity exceeded 99.0%. [18F]EF5 was distributed uniformly in tissues, with highest uptake in liver, kidney, and intestine. Several radiolabelled metabolites were detected in mouse plasma and tissues, whereas low amounts of metabolites were detected in human and rat plasma.

Conclusions

[18F]EF5 was synthesized by electrophilic labelling with high quality and high yields. Pharmacokinetics of [18F]EF5 was determined at trace level in several species. Our results suggest that the trace-level approach does not affect the biodistribution of [18F]EF5. Extensive metabolism was seen in mouse.
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Metadata
Title
Tracer Level Electrophilic Synthesis and Pharmacokinetics of the Hypoxia Tracer [18F]EF5
Authors
Olli Eskola
Tove J. Grönroos
Sarita Forsback
Johanna Tuomela
Gaber Komar
Jörgen Bergman
Pirkko Härkönen
Merja Haaparanta
Heikki Minn
Olof Solin
Publication date
01-04-2012
Publisher
Springer-Verlag
Published in
Molecular Imaging and Biology / Issue 2/2012
Print ISSN: 1536-1632
Electronic ISSN: 1860-2002
DOI
https://doi.org/10.1007/s11307-011-0484-4

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