Synthesis and preliminary biological evaluation of O-2((2-[(18)F]fluoroethyl)methylamino)ethyltyrosine ([(18)F]FEMAET) as a potential cationic amino acid PET tracer for tumor imaging.

Amino acid transport is an attractive target for oncologic imaging. Despite a high demand of cancer cells for cationic amino acids, their potential as PET probes remains unexplored. Arginine, in particular, is involved in a number of biosynthetic pathways that significantly influence carcinogenesis and tumor biology.

Synthesis, radiolabelling and in vitro and in vivo evaluation of a novel fluorinated ABP688 derivative for the PET imaging of metabotropic glutamate receptor subtype 5.

(E)-3-(Pyridin-2-ylethynyl)cyclohex-2-enone O-(2-(3-(18)F-fluoropropoxy)ethyl) oxime ([(18)F]-PSS223) was evaluated in vitro and in vivo to establish its potential as a PET tracer for imaging metabotropic glutamate receptor subtype 5 (mGluR5). [(18)F]-PSS223 was obtained in 20% decay corrected radiochemical yield whereas the non-radioactive PSS223 was accomplished in 70% chemical yield in a S(N)2 reaction of common intermediate mesylate 8 with potassium fluoride. The in vitro binding affinity of [(18)F]-PSS223 was measured directly in a Scatchard assay to give K(d) = 3.

Development of [(18)F]-PSS223 as a PET tracer for imaging of metabotropic glutamate receptor subtype 5 (mGluR5).

Involvement of metabotropic glutamate receptor subtype 5 (mGluR5) in physiological and pathophysiological processes in the brain has been demonstrated, and hence mGluR5 has emerged as an important drug target. [(11)C]-ABP688 is clinically the most successful mGluR5 positron emission tomography (PET) tracer to date and it allows visualization and quantification of mGluR5. Due to the short half-life of carbon-11, clinical use of [(11)C]-ABP688 is limited to facilities with an on-site cyclotron and a fluorine-18 (half-life 110 min) analogue would be more practical.