Jean Henrottin1, Christian Lemaire2, Dominique Egrise3, Astrid Zervosen2, Benoit Van den Eynde4, Alain Plenevaux2, Xavier Franci5, Serge Goldman3, André Luxen2. 1. Cyclotron Research Center, B30, Université de Liège, Sart-Tilman, B-4000, Liège, Belgium; Department of Chemistry, B6, Université de Liège, Sart-Tilman, B-4000, Liège, Belgium. Electronic address: Jean.Henrottin@ulg.ac.be. 2. Cyclotron Research Center, B30, Université de Liège, Sart-Tilman, B-4000, Liège, Belgium. 3. PET/Biomedical Cyclotron Unit and Department of Nuclear Medicine, Erasme Hospital, Université Libre de Bruxelles, B-1070, Brussels, Belgium; Center for Microscopy and Molecular Imaging, Rue Adrienne Bolland 8, B-6041, Gosselies, Belgium. 4. Ludwig Institute for Cancer Research, Brussels Branch and de Duve Institute, Université catholique de Louvain, B-1200, Brussels, Belgium. 5. GE Healthcare, MDx PET Chemistry System, Rue Marie Curie 10/2, B-4431, Loncin (Liège), Belgium.
Abstract
INTRODUCTION: Indoleamine 2,3-dioxygenase (IDO) catalyzes the initial step in the catabolism of l-tryptophan along the kynurenine pathway and exerts immunosuppressive properties in inflammatory and tumor tissues by blocking locally T-lymphocyte proliferation. Recently, 1-(2-[(19)F]fluoroethyl)-dl-tryptophan (1-[(19)F]FE-dl-Trp) was reported as a good and specific substrate of this enzyme. Herein, the radiosynthesis of its radioactive isotopomer (1-[(18)F]FE-dl-Trp, dl-[(18)F]5) is presented along with in vitro enzymatic and cellular uptake studies. METHODS: The one-pot n.c.a. radiosynthesis of this novel potential PET imaging tracer, including HPLC purification and formulation, has been fully automated on a FASTlab™ synthesizer. Chiral separation of both isomers and their formulation were implemented on a second cassette. In vitro enzymatic and cellular uptake studies were then conducted with the d-, l- and dl-radiotracers. RESULTS: The radiolabeling of the tosylate precursor was performed in DMF (in 5min; RCY: 57% (d.c.), n=3). After hydrolysis, HPLC purification and formulation, dl-[(18)F]5 was obtained with a global radiochemical yield of 18±3% (not decay corrected, n=7, in 80min) and a specific activity of 600±180GBq/μmol (n=5). The subsequent separation of l- and d-enantiomers was performed by chiral HPLC and both were obtained after formulation with an RCY (d.c.) of 6.1% and 5.8%, respectively. In vitro enzymatic assays reveal that l-[(18)F]5 is a better substrate than d-[(18)F]5 for human IDO. In vitro cellular assays show an IDO-specific uptake of the racemate varying from 30% to 50% of that of l-[(18)F]5, and a negligible uptake of d-[(18)F]5. CONCLUSION: In vitro studies show that l-[(18)F]5 is a good and specific substrate of hIDO, while presenting a very low efflux. These results confirm that l-[(18)F]5 could be a very useful PET radiotracer for IDO expressing cells in cancer imaging.
INTRODUCTION:Indoleamine 2,3-dioxygenase (IDO) catalyzes the initial step in the catabolism of l-tryptophan along the kynurenine pathway and exerts immunosuppressive properties in inflammatory and tumor tissues by blocking locally T-lymphocyte proliferation. Recently, 1-(2-[(19)F]fluoroethyl)-dl-tryptophan (1-[(19)F]FE-dl-Trp) was reported as a good and specific substrate of this enzyme. Herein, the radiosynthesis of its radioactive isotopomer (1-[(18)F]FE-dl-Trp, dl-[(18)F]5) is presented along with in vitro enzymatic and cellular uptake studies. METHODS: The one-pot n.c.a. radiosynthesis of this novel potential PET imaging tracer, including HPLC purification and formulation, has been fully automated on a FASTlab™ synthesizer. Chiral separation of both isomers and their formulation were implemented on a second cassette. In vitro enzymatic and cellular uptake studies were then conducted with the d-, l- and dl-radiotracers. RESULTS: The radiolabeling of the tosylate precursor was performed in DMF (in 5min; RCY: 57% (d.c.), n=3). After hydrolysis, HPLC purification and formulation, dl-[(18)F]5 was obtained with a global radiochemical yield of 18±3% (not decay corrected, n=7, in 80min) and a specific activity of 600±180GBq/μmol (n=5). The subsequent separation of l- and d-enantiomers was performed by chiral HPLC and both were obtained after formulation with an RCY (d.c.) of 6.1% and 5.8%, respectively. In vitro enzymatic assays reveal that l-[(18)F]5 is a better substrate than d-[(18)F]5 for humanIDO. In vitro cellular assays show an IDO-specific uptake of the racemate varying from 30% to 50% of that of l-[(18)F]5, and a negligible uptake of d-[(18)F]5. CONCLUSION: In vitro studies show that l-[(18)F]5 is a good and specific substrate of hIDO, while presenting a very low efflux. These results confirm that l-[(18)F]5 could be a very useful PET radiotracer for IDO expressing cells in cancer imaging.
Authors: Edit Bosnyák; Sharon K Michelhaugh; Neil V Klinger; David O Kamson; Geoffrey R Barger; Sandeep Mittal; Csaba Juhász Journal: Clin Nucl Med Date: 2017-05 Impact factor: 7.794
Authors: Sharon K Michelhaugh; Otto Muzik; Anthony R Guastella; Neil V Klinger; Lisa A Polin; Hancheng Cai; Yangchun Xin; Thomas J Mangner; Shaohui Zhang; Csaba Juhász; Sandeep Mittal Journal: J Nucl Med Date: 2016-10-20 Impact factor: 10.057
Authors: Peter Wierstra; Gerwin Sandker; Erik Aarntzen; Martin Gotthardt; Gosse Adema; Johan Bussink; René Raavé; Sandra Heskamp Journal: EJNMMI Radiopharm Chem Date: 2019-11-06