Synthesis and Biological Evaluation of an (18)Fluorine-Labeled COX Inhibitor--[(18)F]Fluorooctyl Fenbufen Amide--For Imaging of Brain Tumors.

Molecular imaging of brain tumors remains a great challenge, despite the advances made in imaging technology. An anti-inflammatory compound may be a useful tool for this purpose because there is evidence of inflammatory processes in brain tumor micro-environments. Fluorooctylfenbufen amide (FOFA) was prepared from 8-chlorooctanol via treatment with potassium phthalimide, tosylation with Ts2O, fluorination with KF under phase transfer catalyzed conditions, deprotection using aqueous hydrazine, and coupling with fenbufen. The corresponding radiofluoro product [(18)F]FOFA, had a final radiochemical yield of 2.81 mCi and was prepared from activated [(18)F]F(-) (212 mCi) via HPLC purification and concentration. The radiochemical purity was determined to be 99%, and the specific activity was shown to exceed 22 GBq/μmol (EOS) based on decay-corrected calculations. Ex-vivo analysis of [(18)F]FOFA in plasma using HPLC showed that the agent had a half-life of 15 min. PET scanning showed significant accumulation of [(18)F]FOFA over tumor loci with reasonable contrast in C6-glioma bearing rats. These results suggest that this molecule is a promising agent for the visualization of brain tumors. Further investigations should focus on tumor micro-environments.