1. Radiometal-Dependent Biological Profile of the Radiolabeled Gastrin-Releasing Peptide Receptor Antagonist SB3 in Cancer Theranostics: Metabolic and Biodistribution Patterns Defined by Neprilysin.
- Author
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Lymperis E, Kaloudi A, Sallegger W, Bakker IL, Krenning EP, de Jong M, Maina T, and Nock BA
- Subjects
- Animals, Coordination Complexes chemistry, Coordination Complexes metabolism, Humans, Indium Radioisotopes chemistry, Indium Radioisotopes metabolism, Lutetium chemistry, Lutetium metabolism, Male, Mice, Neprilysin chemistry, Neprilysin metabolism, Oligopeptides chemistry, Oligopeptides metabolism, PC-3 Cells, Positron-Emission Tomography methods, Radioisotopes chemistry, Radioisotopes metabolism, Receptors, Bombesin antagonists & inhibitors, Theranostic Nanomedicine methods, Tissue Distribution, Coordination Complexes pharmacokinetics, Indium Radioisotopes pharmacokinetics, Lutetium pharmacokinetics, Neprilysin pharmacokinetics, Oligopeptides pharmacokinetics, Prostatic Neoplasms diagnostic imaging, Radioisotopes pharmacokinetics, Receptors, Bombesin analysis
- Abstract
Recent advances in oncology involve the use of diagnostic/therapeutic radionuclide-carrier pairs that target cancer cells, offering exciting opportunities for personalized patient treatment. Theranostic gastrin-releasing peptide receptor (GRPR)-directed radiopeptides have been proposed for the management of GRPR-expressing prostate and breast cancers. We have recently introduced the PET tracer
68 Ga-SB3 (SB3, DOTA- p-aminomethylaniline-diglycolic acid-DPhe-Gln-Trp-Ala-Val-Gly-His-Leu-NHEt), a receptor-radioantagonist that enables the visualization of GRPR-positive lesions in humans. Aiming to fully assess the theranostic potential of SB3, we herein report on the impact of switching68 Ga to111 In/177 Lu-label on the biological properties of resulting radiopeptides. Notably, the bioavailability of111 In/177 Lu-SB3 in mice drastically deteriorated compared with metabolically robust68 Ga-SB3, and as a result led to poorer111 In/177 Lu-SB3 uptake in GRPR-positive PC-3 xenografts. The peptide cleavage sites were identified by chromatographic comparison of blood samples from mice intravenously receiving111 In/177 Lu-SB3 with each of newly synthesized111 In/177 Lu-SB3-fragments. Coinjection of the radioconjugates with the neprilysin (NEP)-inhibitor phosphoramidon led to full stabilization of111 In/177 Lu-SB3 in peripheral mouse blood and resulted in markedly enhanced radiolabel uptake in the PC-3 tumors. In conclusion, in situ NEP-inhibition led to indistinguishable68 Ga/111 In/177 Lu-SB3 profiles in mice emphasizing the theranostic prospects of SB3 for clinical use.- Published
- 2018
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