Radiosynthesis and preliminary evaluation of 4-[18F]fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide as a new positron emission tomography ligand for metabotropic glutamate receptor subtype 1

Abstract

The purpose of this study was to develop 4-[(18)F]fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide ([(18)F]FITM, [(18)F]4) as a new PET ligand for imaging metabotropic glutamate receptor subtype 1 (mGluR1). [(18)F]4 was synthesized by [(18)F]fluorination of a novel nitro precursor 3 with [(18)F]KF in the presence of Kryptofix 222. At the end of synthesis, 429-936 MBq (n=8) of [(18)F]4 was obtained with >99% radiochemical purity and 204-559GBq/μmol specific activity starting from 6.7 to 13.0 GBq of [(18)F]F(-). The brain distribution of [(18)F]4 was determined by the in vitro and ex vivo autoradiography using rat brain sections. The in vitro and in vivo specific binding of [(18)F]4 to mGluR1 was detected in the cerebellum, thalamus, hippocampus, and striatum. These results suggest that [(18)F]4 is a promising PET ligand for the in vivo evaluation of mGluR1.