Synthesis of 2′-Deoxy-2′-[18F]Fluoro-9-β-D-Arabinofuranosylguanine: a Novel Agent for Imaging T-Cell Activation with PET
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9-(β-D-Arabinofuranosyl)guanine (AraG) is a guanosine analog that has a proven efficacy in the treatment of T-cell lymphoblastic disease. To test the possibility of using a radiofluorinated AraG as an imaging agent, we have synthesized 2′-deoxy-2′-[18F]fluoro-9-β-D-arabinofuranosylguanine ([18F]F-AraG) and investigated its uptake in T cells.
We have synthesized [18F]F-AraG via a direct fluorination of 2-N-acetyl-6-O-((4-nitrophenyl)ethyl)-9-(3′,5′-di-O-trityl-2′-O-trifyl-β-D-ribofuranosyl)guanine with [18F]KF/K.2.2.2 in DMSO at 85°C for 45 min. [18F]F-AraG uptake in both a CCRF-CEM leukemia cell line (unactivated) and activated primary thymocytes was evaluated.
We have successfully prepared [18F]F-AraG in 7–10% radiochemical yield (decay corrected) with a specific activity of 0.8–1.3 Ci/μmol. Preliminary cell uptake experiments showed that both a CCRF-CEM leukemia cell line and activated primary thymocytes take up the [18F]F-AraG.
For the first time to the best of our knowledge, [18F]F-AraG has been successfully synthesized by direct fluorination of an appropriate precursor of a guanosine nucleoside. This approach maybe also useful for the synthesis of other important positron emission tomography (PET) probes such as [18F]FEAU, [18F]FMAU, and [18F]FBAU which are currently synthesized by multiple steps and involve lengthy purification. The cell uptake studies support future studies to investigate the use of [18F]F-AraG as a PET imaging agent of T cells.
Key wordsImaging T cells 9-(β-D-Arabinofuranosyl) guanine (AraG) Positron emission tomography (PET)
This work was supported in part by NCI In Vivo Cellular Molecular Imaging Center grant P50 CA114747 (SSG). We also thank Dr. David Dick for the [18F] production, Dr. Frederick T. Chin for modification of a GE TRACERlab FX-FN synthetic module for radiosynthesis, and Dr. Jelena Levi for her review of the manuscript.
Conflict of interest disclosure
The authors declare that they have no conflict of interest.
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