Efficient commercial scale 18F-FES production on AllinOne (Trasis)

Objectives: 16a-[18F]fluoro-17β-estradiol, [18F]FES, is a promising PET radiotracer to investigate tumor estrogen receptor activity [1-2]. Its enantioselective production has been developed by various synthetic routes differing notably by the choice of the precursor or by the hydrolysis and/or the purification methods. An optimized synthetic route has been implemented by Trasis on the AllinOne synthesizer. Methods: [18F]FES is prepared from 3-methoxymethyl-16β,17β-epiestriol-O-cyclic sulfone in two main chemical steps. After drying of the [18F]fluoride ion under mild nitrogen flow, the labelling of the precursor occurs at 105°C for 5.5 minutes. The 18F-tagged derivative is then hydrolyzed by means of sulfuric acid 1 M (Figure 1). The crude mixture is then purified by HPLC (eluents: water/ethanol mixture) to isolate the [18F]FES, which is subsequently formulated for injection. Results: The synthesis of [18F]FES is achieved with an average yield up to 50% at starting activities up to 100 GBq. The radiochemical purity is > 98 %. The final product meets the specifications of the EP/USP. Conclusion: The automated and optimized method to produce [18F]FES on an AllinOne synthesizer is appropriate for routine commercial scale purposes.