[18F]-3′-deoxy-3′-fluorothymidine ([18F]FLT) is an established positron emission tomograph (PET)—radiopharmaceutical to study cell-proliferation rate in tumors.
Very low practical yield, uncertain and time-consuming high performance liquid chromatography (HPLC) purification, are the
main obstacles for the routine use of [18F]FLT in clinical PET. To obviate these difficulties, we have developed a fully automated radiosynthesis procedure for [18F]FLT using 5′-O-(4,4′-dimethoxytriphenylmethyl)-2,3′-anhydro-thymidine (DMTThy) and simplified single neutral alumina column purification.
The [18F]FLT yield was 8.48 ± 0.93% (n = 5) (without radioactive decay correction) in a synthesis time of 68 ± 3 min. The radiochemical purity was greater than
95% as confirmed by analytical HPLC using reference standard FLT and also free of non-radioactive impurity. Soluble aluminum
in the final product was much below the permissible limits. Di-methyl sulfoxide (DMSO), the reaction medium, could be detected
in the final product in trace amounts, well below the permissible levels. The synthesized [18F]FLT was sterile and bacterial endotoxin free by appropriate tests. PET imaging study in normal rabbits showed distinct localization
of [18F]FLT in organs having rapid cell division rate like bone marrow, guts and snout and the excretion was through the renal route.
There were no significant uptakes in bone and brain. The former finding confirms the in vivo stability of the [18F]FLT. This simplified radiosynthesis procedure can easily be adapted in any commercial or indigenous [18F]FDG synthesis module for routine [18F]FLT synthesis without the need of additional automation for HPLC purification.