Synthesis and Preliminary Evaluation of 5-[18F]fluoroleucine

Title:Synthesis and Preliminary Evaluation of 5-[18F]fluoroleucine

Volume: 10 Issue: 1

Author(s): Bennett B. Chin, Darryl McDougald, Douglas H. Weitzel, Thomas Hawk, Robert E. Reiman, Michael R. Zalutsky and Ganesan Vaidyanathan

Affiliation:

Keywords: Leucine, fluoroleucine, amino acid, tumor imaging, positron emission tomography, dosimetry.

Abstract: Background: Amino acid transporters, such as LAT1, are overexpressed in aggressive prostate and breast carcinomas, directly influencing pathways of growth and proliferation.

Objective: The purpose of this study was to synthesize and characterize a novel 18F labeled leucine analog, 5-[18F]fluoroleucine, as a potential imaging agent for aggressive tumors which may not be amenable to imaging by FDG PET.

Methods: 5-fluoroleucine was synthesized and characterized, and its 18F-labeled analog was synthesized from a mesylate precursor. First, breast cancer cell line assays were performed to evaluate uptake of 3H- or 14C-labeled L-leucine and other essential amino acids. Both L-leucine and 5- [18F]fluoroleucine were tested for uptake and accumulation over time, and for uptake via LAT1. Biodistribution studies were performed to estimate radiation dosimetry for human studies. Small animal PET / CT studies of a breast cancer were performed to evaluate in vivo 5-[18F]fluoroleucine tumor uptake.

Results: Breast cancer cell lines showed increasing high net accumulation of L-[14C]leucine. Both L-leucine and 5-[18F]fluoroleucine showed increasing uptake over time in in vitro tumor cell assays, and uptake was also shown to occur via LAT1. The biodistribution study of 5-[18F]fluoroleucine showed rapid renal excretion, no significant in vivo metabolism, and acceptable dosimetry for use in humans. In vivo small animal PET / CT imaging of a breast cancer xenograft showed uptake of 5- [18F]fluoroleucine in the tumor, which progressively increased over time.

Conclusion: 5-[18F]fluoroleucine is a leucine analog which may be useful in identifying tumors with high or upregulated expression of amino acid transporters, providing additional information that may not be provided by FDG PET.

Cite this article as:

Chin B. Bennett, McDougald Darryl, Weitzel H. Douglas, Hawk Thomas, Reiman E. Robert, Zalutsky R. Michael and Vaidyanathan Ganesan, Synthesis and Preliminary Evaluation of 5-[18F]fluoroleucine, Current Radiopharmaceuticals 2017; 10 (1) . https://dx.doi.org/10.2174/1874471009666161230114954

DOI https://dx.doi.org/10.2174/1874471009666161230114954	Print ISSN 1874-4710
Publisher Name Bentham Science Publisher	Online ISSN 1874-4729