Automated Synthesis of 18F-Fluoropropoxytryptophan for Amino Acid Transporter System Imaging

الملخص EN

Objective.

This study was to develop a cGMP grade of [18F]fluoropropoxytryptophan (18F-FTP) to assess tryptophan transporters using an automated synthesizer.

Methods.

Tosylpropoxytryptophan (Ts-TP) was reacted with K18F/kryptofix complex.

After column purification, solvent evaporation, and hydrolysis, the identity and purity of the product were validated by radio-TLC (1M-ammonium acetate : methanol = 4 : 1) and HPLC (C-18 column, methanol : water = 7 : 3) analyses.

In vitro cellular uptake of 18F-FTP and 18F-FDG was performed in human prostate cancer cells.

PET imaging studies were performed with 18F-FTP and 18F-FDG in prostate and small cell lung tumor-bearing mice (3.7 MBq/mouse, iv).

Results.

Radio-TLC and HPLC analyses of 18F-FTP showed that the Rf and Rt values were 0.9 and 9 min, respectively.

Radiochemical purity was >99%.

The radiochemical yield was 37.7% (EOS 90 min, decay corrected).

Cellular uptake of 18F-FTP and 18F-FDG showed enhanced uptake as a function of incubation time.

PET imaging studies showed that 18F-FTP had less tumor uptake than 18F-FDG in prostate cancer model.

However, 18F-FTP had more uptake than 18F-FDG in small cell lung cancer model.

Conclusion.

18F-FTP could be synthesized with high radiochemical yield.

Assessment of upregulated transporters activity by 18F-FTP may provide potential applications in differential diagnosis and prediction of early treatment response.