Dose and time optimization

Four groups of five mice received an intravenous injection of 1 MBq ¹¹¹In-PSMA-N064 diluted in PBS/0.5% BSA. The effect of the ¹¹¹In-PSMA-N064 dose on the biodistribution of ¹¹¹In-PSMA-N064 was studied by administering various peptide doses: 0.1, 0.3, 1 or 3 nmol/mouse. Two hours post injection, mice were euthanized using CO₂/O₂-asphyxiation and the biodistribution of ¹¹¹In-PSMA-N064 was determined by counting relevant tissues after dissection. Five additional mice were co-injected intravenously with a 100-fold molar excess of unlabeled PSMA-617 (10 nmol/mouse) to determine the non-specific uptake of ¹¹¹In-PSMA-N064.To find the optimal imaging timepoint for ¹¹¹In-PSMA-N064, four groups of five mice received an intravenous injection of 10 MBq ¹¹¹In-PSMA-N064 (molar activity 33.3 MBq/nmol) in PBS/0.5% BSA. At 1, 2, 4, and 24 h post injection, mice underwent µSPECT/CT and NIRF imaging followed by dissection. Tumors, blood, and relevant organs and tissues were dissected, weighed, and radioactivity in each sample was quantified using a well-type gamma-counter. The results were expressed as percentage of injected dose per gram of tissue (%ID/g).