Copper-64 Labeled Macrobicyclic Sarcophagine Coupled to a GRP Receptor Antagonist Shows Great Promise for PET Imaging of Prostate Cancer

Gourni, Eleni; Del Pozzo, Luigi; Kheirallah, Emilie; Smerling, Christiane; Waser, Beatrice; Reubi, Jean-Claude; Paterson, Brett M; Donnelly, Paul S; Meyer, Philipp T; Maecke, Helmut R (2015). Copper-64 Labeled Macrobicyclic Sarcophagine Coupled to a GRP Receptor Antagonist Shows Great Promise for PET Imaging of Prostate Cancer. Molecular Pharmaceutics, 12(8), pp. 2781-2790. American Chemical Society 10.1021/mp500671j

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The gastrin-releasing peptide receptor (GRPr) is an important molecular target for the visualization and therapy of tumors and can be targeted with radiolabeled bombesin derivatives. The present study aims to develop statine-based bombesin receptor antagonists suitable for labeling with 64Cu for imaging by positron emission tomography (PET). The potent GRPr antagonist D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 was conjugated to the sarcophagine (3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane=Sar) derivative 5-(8-methyl-3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid (MeCOSar) via PEG4 (LE1) and PEG2 (LE2) spacers and radiolabeled with 64Cu2+ with >95% yield and specific activities of about 100 MBq/nmol. Both Cu(II) conjugates have high affinity for GRPr (IC50: natCu-LE1, 1.4±0.1 nM; natCu-LE2, 3.8±0.6 nM). The antagonistic properties of both conjugates were confirmed by Ca2+-flux measurements. Biodistribution studies of Cu-64-LE1 exhibited specific targeting of the tumor (19.6±4.7% IA/g at 1 h p.i.) and GRPr-positive organs. Biodistribution and PET images at 4 and 24 h postinjection showed increasing tumor-to-background ratios with time. This was illustrated by the acquisition of PET images showing high tumor-to-normal tissue contrast. This study demonstrates the high affinity of the MeCOSar-PEGx-bombesin conjugates to GRPr. The stability of 64Cu complexes of MeCOSar, the long half-life of 64Cu, and the suitable biodistribution profile of the 64Cu-labeled peptides lead to PET images of high contrast suitable for potential translation into the clinic.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Service Sector > Institute of Pathology

UniBE Contributor:

Waser, Beatrice and Reubi-Kattenbusch, Jean-Claude

Subjects:

500 Science > 570 Life sciences; biology
600 Technology > 610 Medicine & health

ISSN:

1543-8392

Publisher:

American Chemical Society

Language:

English

Submitter:

Doris Haefelin

Date Deposited:

04 Feb 2016 10:19

Last Modified:

10 Oct 2019 13:20

Publisher DOI:

10.1021/mp500671j

PubMed ID:

26132879

Uncontrolled Keywords:

64Cu; PET-imaging; gastrin-releasing peptide receptor antagonists; sarcophagine MeCOSar chelator

BORIS DOI:

10.7892/boris.74902

URI:

https://boris.unibe.ch/id/eprint/74902

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