Synthesis of [18F] 4‐amino‐N‐(3‐chloro‐4‐fluorophenyl)‐N′‐hydroxy‐1,2,5‐oxadiazole‐3‐carboximidamide (IDO5L): a novel potential PET probe for imaging of IDO1 expression |
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| Authors: | Xuan Huang Robert J. Gillies Haibin Tian |
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| Affiliation: | Department of Cancer Imaging and Metabolism, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA |
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| Abstract: | To synthesize 18F‐labeled positron emission tomography (PET) ligands, reliable labeling techniques inserting 18F into a target molecule are necessary. The 18F‐fluorobenzene moiety has been widely utilized in the synthesis of 18F‐labeled compounds. The present study utilized [18F]‐labeled aniline as intermediate in [18F]‐radiolabeling chemistry for the facile radiosynthesis of 4‐amino‐N‐(3‐chloro‐4‐fluorophenyl)‐N′‐hydroxy‐1,2,5‐oxadiazole‐3‐carboximidamide ([18F]IDO5L) as indoleamine 2,3‐dioxygenase 1 (IDO1) targeted tracer. IDO5L is a highly potent inhibitor of IDO1 with low nanomolar IC50. [18F]IDO5L was synthesized via coupling [18F]3‐chloro‐4‐fluoroaniline with carboximidamidoyl chloride as a potential PET probe for imaging IDO1 expression. Under the optimized labeling conditions, chemically and radiochemically pure (>98%) [18F]IDO5L was obtained with specific radioactivity ranging from 11 to 15 GBq/µmol at the end of synthesis within ~90 min, and the decay‐corrected radiochemical yield was 18.2 ± 2.1% (n = 4). |
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| Keywords: | indoleamine 2 3‐dioxygenase IDO1 PET imaging fluorine‐18 radiolabeling |
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