Synthesis and preliminary evaluation of N 1 ‐methyl‐9‐[(1‐hydroxy‐3‐[ 18 F]fluoro‐2‐propoxy)methyl]guanine [ 18 F]MFHPG, a new substrate of HSV‐1‐thymidine kinase

The labelling procedure for N 1 ‐methyl‐9‐[(1‐hydroxy‐3‐[ 18 F]fluoro‐2‐propoxy)methyl]guanine ([ 18 F]MFHPG), a novel substrate of HSV1‐TK that possess potent properties to image the gene expression, and its preliminary biodistribution in rats are reported. The biodistribution studies of [ 18 F]MFHPG in male Wistar rats show a fast blood clearance. The erythrocyte binding of the tracer was negligible and no metabolites were found. In vitro studies in HSV‐TK expressing cells reveal a lower uptake of [ 18 F]MFHPG than [ 18 F]FHPG which also correlates with the decreased octanol/water ratio.