Synthesis of 2'-deoxy-2'-[18F]fluoro-5-bromo-1-β-D-arabinofuranosyluracil ([18F]-FBAU) and 2'-deoxy-2'-[18F]fluoro-5-chloro-1-β-D-arabinofuranosyl-uracil ([18F]-FCAU), and their biological evaluation as markers for gene expression

[18F]-FBAU and [18F]-FCAU have been synthesized and evaluated in vivo as markers for HSV1-tk gene expression. At 2 hours, uptake of [18F]-FBAU and [18F]-FCAU in HSV1-tk-positive tumors was 7.9-fold and 6.0-fold higher than the control tumors, respectively. Micro-PET images also showed very high uptake in HSV-tk tumors. Compared to [14C]-FMAU, total uptake of [18F]-FBAU and [18F]-FCAU was similar in tk-positive cells, but the uptake ratio (tk+/wild) was higher. [18F]-FBAU and [18F]-FCAU appear to be potential PET imaging agents for gene expression