Synthesis and Biological Evaluation of O-[3-18F-fluoropropyl]-α-methyl Tyrosine in Mesothelioma-Bearing Rodents

Abstract

Radiolabeled tyrosine analogs enter cancer cells via upregulated amino acid transporter system and have been shown to be superior to18F-fluoro-2-deoxy-D-glucose (18F-FDG) in differential diagnosis in cancers. In this study, we synthesized O-[3-19F-fluoropropyl]-α-methyl tyrosine (19F-FPAMT) and used manual and automated methods to synthesize O-[3-18F-fluoropropyl]-α-methyl tyrosine (18F-FPAMT) in three steps: nucleophilic substitution, deprotection of butoxycarbonyl, and deesterification. Manual and automated synthesis methods produced18F-FPAMT with a radiochemical purity >96%. The decay-corrected yield of18F-FPAMT by manual synthesis was 34% at end-of-synthesis (88 min). The decay-corrected yield of18F-FPAMT by automated synthesis was 15% at end-of-synthesis (110 min).18F-FDG and18F-FPAMT were used forin vitroandin vivostudies to evaluate the feasibility of18F-FPAMT for imaging rat mesothelioma (IL-45).In vitrostudies comparing18F-FPAMT with18F-FDG revealed that18F-FDG had higher uptake than that of18F-FPAMT, and the uptake ratio of18F-FPAMT reached the plateau after being incubated for 60 min. Biodistribution studies revealed that the accumulation of18F-FPAMT in the heart, lungs, thyroid, spleen, and brain was significantly lower than that of18F-FDG. There was poor bone uptake in18F-FPAMT for up to 3 hrs suggesting itsin vivostability. The imaging studies showed good visualization of tumors with18F-FPAMT. Together, these results suggest that18F-FPAMT can be successfully synthesized and has great potential in mesothelioma imaging.