Dosimetry of ⁶⁴Cu-DOTA-AE105, a PET tracer for uPAR imaging

⁶⁴Cu-DOTA-AE105 is a novel positron emission tomography (PET) tracer specific to the human urokinase-type plasminogen activator receptor (uPAR). In preparation of using this tracer in humans, as a new promising method to distinguish between indolent and aggressive cancers, we have performed PET studies in mice to evaluate the in vivo biodistribution and estimate human dosimetry of ⁶⁴Cu-DOTA-AE105. MethodsFive mice received iv tail injection of ⁶⁴Cu-DOTA-AE105 and were PET/CT scanned 1, 4.5 and 22h post injection. Volume-of-interest (VOI) were manually drawn on the following organs: heart, lung, liver, kidney, spleen, intestine, muscle, bone and bladder. The activity concentrations in the mentioned organs [%ID/g] were used for the dosimetry calculation. The %ID/g of each organ at 1, 4.5 and 22h was scaled to human value based on a difference between organ and body weights. The scaled values were then exported to OLINDA software for computation of the human absorbed doses. The residence times as well as effective dose equivalent for male and female could be obtained for each organ. To validate this approach, of human projection using mouse data, five mice received iv tail injection of another ⁶⁴Cu-DOTA peptide-based tracer, ⁶⁴Cu-DOTA-TATE, and underwent same procedure as just described. The human dosimetry estimates were then compared with observed human dosimetry estimate recently found in a first-in-man study using ⁶⁴Cu-DOTA-TATE. ResultsHuman estimates of ⁶⁴Cu-DOTA-AE105 revealed the heart wall to receive the highest dose (0.0918mSv/MBq) followed by the liver (0.0815mSv/MBq), All other organs/tissue were estimated to receive doses in the range of 0.02–0.04mSv/MBq. The mean effective whole-body dose of ⁶⁴Cu-DOTA-AE105 was estimated to be 0.0317mSv/MBq. Relatively good correlation between human predicted and observed dosimetry estimates for 64Cu-DOTA-TATE was found. Importantly, the effective whole body dose was predicted with very high precision (predicted value: 0.0252mSv/Mbq, Observed value: 0.0315mSv/MBq) thus validating our approach for human dosimetry estimation. ConclusionFavorable dosimetry estimates together with previously reported uPAR PET data fully support human testing of 64Cu-DOTA-AE105.