Preclinical Evaluation of Radiolabeled Peptides for PET Imaging of Glioblastoma Multiforme

In this study, we have compared four (68)Ga-labeled peptides (three Arg-Gly-Asp (RGD) peptides and substance-P) with two (18)F-tracers clinically approved for tumor imaging. We have studied in vitro and in vivo characteristics of selected radiolabeled tracers in a glioblastoma multiforme tumor model. The in vitro part of the study was mainly focused on the evaluation of radiotracers stability under various conditions. We have also determined in vivo stability of studied (68)Ga-radiotracers by analysis of murine urine collected at various time points after injection. The in vivo behavior of tested (68)Ga-peptides was evaluated through ex vivo biodistribution studies and PET/CT imaging. The obtained data were compared with clinically used (18)F-tracers. (68)Ga-RGD peptides showed better imaging properties compared to (18)F-tracers, i.e., higher tumor/background ratios and no accumulation in non-target organs except for excretory organs.