| Autor: |
Begum NJ; Medical Radiation Physics, Department of Nuclear Medicine, Ulm University, Ulm, Germany. nusrat.begum@uni-ulm.de., Glatting G; Medical Radiation Physics, Department of Nuclear Medicine, Ulm University, Ulm, Germany.; Department of Nuclear Medicine, Ulm University, Ulm, Germany., Wester HJ; Technical University of Munich, Pharmaceutical Radiochemistry, Munich, Germany., Eiber M; Technical University of Munich, School of Medicine, Klinikum rechts der Isar, Department of Nuclear Medicine, Munich, Germany., Beer AJ; Department of Nuclear Medicine, Ulm University, Ulm, Germany., Kletting P; Medical Radiation Physics, Department of Nuclear Medicine, Ulm University, Ulm, Germany.; Department of Nuclear Medicine, Ulm University, Ulm, Germany. |
| Abstrakt: |
The aim of this work was to investigate the effect of ligand amount, affinity and internalization of prostate-specific membrane antigen (PSMA)-specific ligands on the activity concentrations for PET/CT imaging and on the absorbed doses for therapy. A physiologically-based pharmacokinetic (PBPK) model for PSMA-specific ligands was implemented. Thirteen virtual patients with metastatic castration-resistant prostate cancer were analysed. Simulations were performed for different combinations of association rates k on (0.1-0.01 L/nmol/min), dissociation rates k off (0.1-0.0001 min -1 ), internalization rates λ int (0.01-0.0001 min -1 ) and ligand amounts (1-1000 nmol). For imaging the activity was normalized to volume and injected activity ( 68 Ga-PSMA at 1 h). For therapy the absorbed dose was calculated for 7.3 ± 0.3 GBq 177 Lu-PSMA. The effect of the investigated parameters on therapy were larger compared to imaging. For imaging, the combination of properties leading to the highest tumour uptake was k on = 0.1 L/nmol/min, k off = 0.01 min -1 for typical ligand amounts (1-10 nmol). For therapy, the higher the internalization rate, the larger was the required ligand amount for optimal tumour-to-kidney ratios. The higher the affinity, the more important was the choice of the optimal ligand amount. PBPK modelling provides insight into the pharmacokinetics of PSMA-specific ligands. Further in silico and in vivo studies are required to verify the influence of the analysed parameters. |
