1
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Rahimi MN, Corlett A, Van Zuylekom J, Sani MA, Blyth B, Thompson P, Roselt PD, Haskali MB. Precision peptide theranostics: developing N- to C-terminus optimized theranostics targeting cholecystokinin-2 receptor. Theranostics 2024; 14:1815-1828. [PMID: 38505611 PMCID: PMC10945332 DOI: 10.7150/thno.89701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 01/10/2024] [Indexed: 03/21/2024] Open
Abstract
Peptides are ideal for theranostic development as they afford rapid target accumulation, fast clearance from background tissue, and exhibit good tissue penetration. Previously, we developed a novel series of peptides that presented discreet folding propensity leading to an optimal candidate [68Ga]Ga-DOTA-GA1 ([D-Glu]6-Ala-Tyr-NMeGly-Trp-NMeNle-Asp-Nal-NH2) with 50 pM binding affinity against cholecystokinin-2 receptors (CCK2R). However, we were confronted with challenges of unfavorably high renal uptake. Methods: A structure activity relationship study was undertaken of the lead theranostic candidate. Prudent structural modifications were made to the peptide scaffold to evaluate the contributions of specific N-terminal residues to the overall biological activity. Optimal candidates were then evaluated in nude mice bearing transfected A431-CCK2 tumors, and their biodistribution was quantitated ex vivo. Results: We identified and confirmed that D-Glu3 to D-Ala3 substitution produced 2 optimal candidates, [68Ga]Ga-DOTA-GA12 and [68Ga]Ga-DOTA-GA13. These radiopeptides presented with high target/background ratios, enhanced tumor retention, excellent metabolic stability in plasma and mice organ homogenates, and a 4-fold reduction in renal uptake, significantly outperforming their non-alanine counterparts. Conclusions: Our study identified novel radiopharmaceutical candidates that target the CCK2R. Their high tumor uptake and reduced renal accumulation warrant clinical translation.
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Affiliation(s)
- Marwa N. Rahimi
- Department of Radiopharmaceutical Sciences, Cancer Imaging, The Peter MacCallum Cancer Centre, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria 3010, Australia
| | - Alicia Corlett
- Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
| | - Jessica Van Zuylekom
- Models of Cancer Translational Research Centre, The Peter MacCallum Cancer Centre, Victoria 3000, Australia
| | - Marc Antoine Sani
- The Bio21 Institute, School of Chemistry, The University of Melbourne, Melbourne, Victoria, 3010 Australia
| | - Benjamin Blyth
- Models of Cancer Translational Research Centre, The Peter MacCallum Cancer Centre, Victoria 3000, Australia
| | - Philip Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria 3052, Australia
| | - Peter D. Roselt
- Department of Radiopharmaceutical Sciences, Cancer Imaging, The Peter MacCallum Cancer Centre, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria 3010, Australia
| | - Mohammad B. Haskali
- Department of Radiopharmaceutical Sciences, Cancer Imaging, The Peter MacCallum Cancer Centre, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria 3010, Australia
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2
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Corlett A, Pinson JA, Rahimi MN, Zuylekom JV, Cullinane C, Blyth B, Thompson PE, Hutton CA, Roselt PD, Haskali MB. Development of Highly Potent Clinical Candidates for Theranostic Applications against Cholecystokinin-2 Receptor Positive Cancers. J Med Chem 2023; 66:10289-10303. [PMID: 37493526 DOI: 10.1021/acs.jmedchem.3c00377] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Peptide receptor radionuclide therapy (PRRT) is a promising form of systemic radiation therapy designed to eradicate cancer. Cholecystokinin-2 receptor (CCK2R) is an important molecular target that is highly expressed in a range of cancers. This study describes the synthesis and in vivo characterization of a novel series of 177Lu-labeled peptides ([177Lu]Lu-2b-4b) in comparison with the reference CCK2R-targeting peptide CP04 ([177Lu]Lu-1b). [177Lu]Lu-1b-4b showed high chemical purity (HPLC ≥ 94%), low Log D7.4 (-4.09 to -4.55) with strong binding affinity to CCK2R (KD 0.097-1.61 nM), and relatively high protein binding (55.6-80.2%) and internalization (40-67%). Biodistribution studies of the novel 177Lu-labeled peptides in tumors (AR42J and A431-CCK2R) showed uptake one- to eight-fold greater than the reference compound CP04 at 1, 24, and 48 h. Rapid clearance and high tumor uptake and retention were established for [177Lu]Lu-2b-4b, making these compounds excellent candidates for theranostic applications against CCK2R-expressing tumors.
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Affiliation(s)
- Alicia Corlett
- Department of Nuclear Medicine, The Royal Melbourne Hospital, Parkville, Victoria, 3000, Australia
| | - Jo-Anne Pinson
- The Radiopharmaceutical Research Laboratory, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Marwa N Rahimi
- The Radiopharmaceutical Research Laboratory, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Jessica Van Zuylekom
- Models of Cancer Translational Research Centre, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
| | - Carleen Cullinane
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
- The Centre for Molecular Imaging and Translational Research Laboratory, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
| | - Benjamin Blyth
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
- Models of Cancer Translational Research Centre, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
| | - Philip E Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria 3052, Australia
| | - Craig A Hutton
- School of Chemistry, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Peter D Roselt
- Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- The Radiopharmaceutical Research Laboratory, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
| | - Mohammad B Haskali
- Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- The Radiopharmaceutical Research Laboratory, The Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
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3
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Patamia V, Zagni C, Brullo I, Saccullo E, Coco A, Floresta G, Rescifina A. Computer-Assisted Design of Peptide-Based Radiotracers. Int J Mol Sci 2023; 24:ijms24076856. [PMID: 37047831 PMCID: PMC10095039 DOI: 10.3390/ijms24076856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 03/29/2023] [Accepted: 04/04/2023] [Indexed: 04/08/2023] Open
Abstract
In medical imaging, techniques such as magnetic resonance imaging, contrast-enhanced computerized tomography, positron emission tomography (PET), and single-photon emission computed tomography (SPECT) are extensively available and routinely used for disease diagnosis. PET probes with peptide-based targeting are typically composed of small peptides especially developed to have high affinity and specificity for a range of cellular and tissue targets. These probes’ key benefits include being less expensive than traditional antibody-based PET tracers and having an effective chemical modification process that allows them to be radiolabeled with almost any radionuclide, making them highly appealing for clinical usage. Currently, as with every pharmaceutical design, the use of in silico strategies is steadily growing in this field, even though it is not part of the standard toolkit used during radiopharmaceutical design. This review describes the recent applications of computational design approaches in the design of novel peptide-based radiopharmaceuticals.
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Affiliation(s)
- Vincenzo Patamia
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Chiara Zagni
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Ilaria Brullo
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Erika Saccullo
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Alessandro Coco
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Giuseppe Floresta
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Antonio Rescifina
- Dipartimento di Scienze del Farmaco e della Salute, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
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4
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Yang K, Jin H, Gao X, Wang GC, Zhang GQ. Elucidating the molecular determinants in the process of gastrin C-terminal pentapeptide amide end activating cholecystokinin 2 receptor by Gaussian accelerated molecular dynamics simulations. Front Pharmacol 2023; 13:1054575. [PMID: 36756145 PMCID: PMC9899899 DOI: 10.3389/fphar.2022.1054575] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 12/02/2022] [Indexed: 01/24/2023] Open
Abstract
Gastrin plays important role in stimulating the initiation and development of many gastrointestinal diseases through interacting with the cholecystokinin 2 receptor (CCK2R). The smallest bioactive unit of gastrin activating CCK2R is the C-terminal tetrapeptide capped with an indispensable amide end. Understanding the mechanism of this smallest bioactive unit interacting with CCK2R on a molecular basis could provide significant insights for designing CCK2R antagonists, which can be used to treat gastrin-related diseases. To this end, we performed extensive Gaussian accelerated molecular dynamics simulations to investigate the interaction between gastrin C-terminal pentapeptide capped with/without amide end and CCK2R. The amide cap influences the binding modes of the pentapeptide with CCK2R by weakening the electrostatic attractions between the C-terminus of the pentapeptide and basic residues near the extracellular domain in CCK2R. The C-terminus with the amide cap penetrates into the transmembrane domain of CCK2R while floating at the extracellular domain without the amide cap. Different binding modes induced different conformational dynamics of CCK2R. Residue pairs in CCK2R had stronger correlated motions when binding with the amidated pentapeptide. Key residues and interactions important for CCK2R binding with the amidated pentagastrin were also identified. Our results provide molecular insights into the determinants of the bioactive unit of gastrin activating CCK2R, which would be of great help for the design of CCK2R antagonists.
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Affiliation(s)
- Kecheng Yang
- National Supercomputing Center in Zhengzhou, Zhengzhou University, Zhengzhou, China,*Correspondence: Kecheng Yang,
| | - Huiyuan Jin
- School of International Studies, Zhengzhou University, Zhengzhou, China
| | - Xu Gao
- National Supercomputing Center in Zhengzhou, Zhengzhou University, Zhengzhou, China
| | - Gang-Cheng Wang
- Department of General Surgery, Affiliated Cancer Hospitalof Zhengzhou University, Henan Cancer Hospital, Zhengzhou, China
| | - Guo-Qiang Zhang
- Department of General Surgery, Affiliated Cancer Hospitalof Zhengzhou University, Henan Cancer Hospital, Zhengzhou, China
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5
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Kleynhans J, Kruger HG, Cloete T, Zeevaart JR, Ebenhan T. In Silico Modelling in the Development of Novel Radiolabelled Peptide Probes. Curr Med Chem 2020; 27:7048-7063. [DOI: 10.2174/0929867327666200504082256] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 01/28/2020] [Accepted: 02/19/2020] [Indexed: 12/11/2022]
Abstract
This review describes the usefulness of in silico design approaches in the design of
new radiopharmaceuticals, especially peptide-based radiotracers (including peptidomimetics).
Although not part of the standard arsenal utilized during radiopharmaceutical design, the use
of in silico strategies is steadily increasing in the field of radiochemistry as it contributes to a
more rational and scientific approach. The development of new peptide-based radiopharmaceuticals
as well as a short introduction to suitable computational approaches are provided in
this review. The first section comprises a concise overview of the three most useful computeraided
drug design strategies used, namely i) a Ligand-based Approach (LBDD) using pharmacophore
modelling, ii) a Structure-based Design Approach (SBDD) using molecular docking
strategies and iii) Absorption-Distribution-Metabolism-Excretion-Toxicity (ADMET)
predictions. The second section summarizes the challenges connected to these computer-aided
techniques and discusses successful applications of in silico radiopharmaceutical design in
peptide-based radiopharmaceutical development, thereby improving the clinical procedure in
Nuclear Medicine. Finally, the advances and future potential of in silico modelling as a design
strategy is highlighted.
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Affiliation(s)
- Janke Kleynhans
- Nuclear Medicine Research Infrastructure (NuMeRI) NPC, Pelindaba 0420, South Africa
| | | | - Theunis Cloete
- Center of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom 2520, South Africa
| | - Jan Rijn Zeevaart
- Nuclear Medicine Research Infrastructure (NuMeRI) NPC, Pelindaba 0420, South Africa
| | - Thomas Ebenhan
- Nuclear Medicine Research Infrastructure (NuMeRI) NPC, Pelindaba 0420, South Africa
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6
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Childs MD, Luyt LG. A Decade's Progress in the Development of Molecular Imaging Agents Targeting the Growth Hormone Secretagogue Receptor. Mol Imaging 2020; 19:1536012120952623. [PMID: 33104445 PMCID: PMC8865914 DOI: 10.1177/1536012120952623] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The growth hormone secretagogue receptor 1a (GHSR), also called the ghrelin receptor, is a G protein-coupled receptor known to play an important metabolic role in the regulation of various physiological processes, including energy expenditure, growth hormone secretion, and cell proliferation. This receptor has been implicated in numerous health issues including obesity, gastrointestinal disorders, type II diabetes, and regulation of body weight in patients with Prader-Willi syndrome, and there has been growing interest in studying its mechanism of behavior to unlock further applications of GHSR-targeted therapeutics. In addition, the GHSR is expressed in various types of cancer including prostate, breast, and testicular cancers, while aberrant expression has been reported in cardiac disease. Targeted molecular imaging of the GHSR could provide insights into its role in biological processes related to these disease states. Over the past decade, imaging probes targeting this receptor have been discovered for the imaging modalities PET, SPECT, and optical imaging. High-affinity analogues of ghrelin, the endogenous ligand for the GHSR, as well as small molecule inhibitors have been developed and evaluated both in vitro and in pre-clinical models. This review provides a comprehensive overview of the molecular imaging agents targeting the GHSR reported to the end of 2019.
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Affiliation(s)
- Marina D Childs
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada
| | - Leonard G Luyt
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada.,Lawson Health Research Institute, London, Ontario, Canada.,Department of Oncology, University of Western Ontario, London, Ontario, Canada.,Department of Medical Imaging, University of Western Ontario, London, Ontario, Canada
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7
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Grob NM, Häussinger D, Deupi X, Schibli R, Behe M, Mindt TL. Triazolo-Peptidomimetics: Novel Radiolabeled Minigastrin Analogs for Improved Tumor Targeting. J Med Chem 2020; 63:4484-4495. [PMID: 32302139 DOI: 10.1021/acs.jmedchem.9b01936] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
MG11 is a truncated analog of minigastrin, a peptide with high affinity and specificity toward the cholecystokinin-2 receptor (CCK2R), which is overexpressed by different tumors. Thus, radiolabeled MG11 derivatives have great potential for use in cancer diagnosis and therapy. A drawback of MG11 is its fast degradation by proteases, leading to moderate tumor uptake in vivo. We introduced 1,4-disubstituted 1,2,3-triazoles as metabolically stable bioisosteres to replace labile amide bonds of the peptide. The "triazole scan" yielded peptidomimetics with improved resistance to enzymatic degradation and/or enhanced affinity toward the CCK2R. Remarkably, our lead compound achieved a 10-fold increase in receptor affinity, resulting in a 2.6-fold improved tumor uptake in vivo. Modeling of the ligand-CCK2R complex suggests that an additional cation-π interaction of the aromatic triazole moiety with the Arg356 residue of the receptor is accountable for these observations. We show for the first time that the amide-to-triazole substitution strategy offers new opportunities in drug development that go beyond the metabolic stabilization of bioactive peptides.
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Affiliation(s)
- Nathalie M Grob
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zürich, Switzerland
| | - Daniel Häussinger
- Department of Chemistry, University of Basel, 4056 Basel, Switzerland
| | - Xavier Deupi
- Condensed Matter Theory Group, Laboratory for Scientific Computing and Modelling, Paul Scherrer Institute, 5232 Villigen, Switzerland.,Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Roger Schibli
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zürich, Switzerland.,Center for Radiopharmaceutical Sciences, Division of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Martin Behe
- Center for Radiopharmaceutical Sciences, Division of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Thomas L Mindt
- Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, 1090 Vienna, Austria.,Department of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, 1090 Vienna, Austria.,Department of Biomedical Imaging and Image Guided Therapy, Medical University of Vienna, 1090 Vienna, Austria
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8
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Ritler A, Shoshan MS, Deupi X, Wilhelm P, Schibli R, Wennemers H, Béhé M. Elucidating the Structure-Activity Relationship of the Pentaglutamic Acid Sequence of Minigastrin with Cholecystokinin Receptor Subtype 2. Bioconjug Chem 2019; 30:657-666. [PMID: 30608664 DOI: 10.1021/acs.bioconjchem.8b00849] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Derivatized minigastrin analogues make up a promising class of candidates for targeting cholecystokinin receptor subtype 2 (CCK2R), which is overexpressed on cancer cells of various neuroendocrine tumors. The pentaglutamic acid sequence of minigastrin influences its biological properties. In particular, it plays a crucial role in the kidney reuptake mechanism. However, the importance of the binding affinity and interaction of this region with the receptor on a molecular level remains unclear. To elucidate its structure-activity relationship with CCK2R, we replaced this sequence with various linkers differing in their amount of anionic charge, structural characteristics, and flexibility. Specifically, a flexible aliphatic linker, a linker with only three d-Glu residues, and a structured linker with four adjacent β3-glutamic acid residues were evaluated and compared to the lead compound PP-F11N (DOTA-[d-Glu1-6,Nle11]gastrin-13). 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was conjugated to the minigastrin derivatives, which allowed radiolabeling with Lutetium-177. The levels of In vitro internalization into MZ-CRC1 cells and in vivo tumor uptake as well as human blood plasma stability increased in the following order: aliphatic linker < three d-Glu < (β3-Glu)4 < (d-Glu)6. The in vitro and in vivo behavior was therefore significantly improved with anionic charges. Computational modeling of a CCK2 receptor-ligand complex revealed ionic interactions between cationic residues (Arg and His) of the receptor and anionic residues of the ligand in the linker.
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Affiliation(s)
- Andreas Ritler
- Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Organic Chemistry (LOC) , ETH , CH-8093 Zurich , Switzerland.,Department of Chemistry and Applied Biosciences (D-CHAB), Institute of Pharmaceutical Sciences (IPW) , ETH , CH-8093 Zurich , Switzerland.,Research Department of Biology and Chemistry, Center for Radiopharmaceutical Sciences (CRS) , Paul Scherrer Institute , CH-5232 Villigen , Switzerland
| | - Michal S Shoshan
- Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Organic Chemistry (LOC) , ETH , CH-8093 Zurich , Switzerland
| | - Xavier Deupi
- Laboratory of Biomolecular Research and Condensed Matter Theory Group , Paul Scherrer Institute , CH-5232 Villigen , Switzerland
| | - Patrick Wilhelm
- Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Organic Chemistry (LOC) , ETH , CH-8093 Zurich , Switzerland
| | - Roger Schibli
- Department of Chemistry and Applied Biosciences (D-CHAB), Institute of Pharmaceutical Sciences (IPW) , ETH , CH-8093 Zurich , Switzerland.,Research Department of Biology and Chemistry, Center for Radiopharmaceutical Sciences (CRS) , Paul Scherrer Institute , CH-5232 Villigen , Switzerland
| | - Helma Wennemers
- Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Organic Chemistry (LOC) , ETH , CH-8093 Zurich , Switzerland
| | - Martin Béhé
- Research Department of Biology and Chemistry, Center for Radiopharmaceutical Sciences (CRS) , Paul Scherrer Institute , CH-5232 Villigen , Switzerland
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9
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Klingler M, Summer D, Rangger C, Haubner R, Foster J, Sosabowski J, Decristoforo C, Virgolini I, von Guggenberg E. DOTA-MGS5, a New Cholecystokinin-2 Receptor-Targeting Peptide Analog with an Optimized Targeting Profile for Theranostic Use. J Nucl Med 2018; 60:1010-1016. [PMID: 30530828 DOI: 10.2967/jnumed.118.221283] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 11/13/2018] [Indexed: 12/25/2022] Open
Abstract
Molecular imaging and targeted radiotherapy with radiolabeled cholecystokinin-2 receptor (CCK2R) targeting peptide probes holds high promise to improve the clinical management of patients with metastatic medullary thyroid carcinoma and other CCK2R-expressing malignancies. Low stability and suboptimal targeting of currently available radiolabeled peptide analogs has prompted us to seek new stabilization strategies. In this study, we present a new minigastrin analog with site-specific C-terminal modifications showing a highly optimized targeting profile. Methods: DOTA-D-Glu-Ala-Tyr-Gly-Trp-(N-Me)Nle-Asp-1-Nal-NH2 (DOTA-MGS5) radiolabeled with 111In, 68Ga, and 177Lu was evaluated in extensive in vitro stability studies. For 177Lu-DOTA-MGS5, additional metabolic studies were performed on BALB/c mice. Receptor affinity and cell uptake were studied in A431 human epidermoid carcinoma cells transfected with human CCK2R (A431-CCK2R), as well as the same cell line transfected with the empty vector (A431-mock). A431-CCK2R/A431-mock xenografted athymic BALB/c nude mice were used for biodistribution studies and small-animal SPECT/CT. Results: DOTA-MGS5 radiolabeled with 111In and 177Lu showed a highly increased stability against enzymatic degradation in different media up to 24 h of incubation. Similar results were observed for 68Ga-DOTA-MGS5 incubated up to 4 h. In the blood of mice injected with 177Lu-DOTA-MGS5, at least 70% intact radiopeptide was detected up to 1 h after injection. The unlabeled peptide and the complexes with the natural isotopes showed retained receptor affinity, and the radiopeptides showed unexpectedly high cell uptake in A431-CCK2R cells (>60% at 4 h). Regardless of the radiometal used for labeling, impressively high uptake in A431-CCK2R xenografts was found (∼20% injected activity/g 1-4 h after injection), whereas the uptake in A431-mock xenografts was negligible. Low background activity and favorable tumor-to-kidney ratios (4-6) allowed for high image contrast in small-animal SPECT/CT. Conclusion: The excellent targeting properties of DOTA-MGS5 support future clinical studies evaluating the diagnostic and therapeutic potential in patients with progressive or metastatic medullary thyroid carcinoma, as well as other advanced-stage CCK2R-expressing malignancies.
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Affiliation(s)
- Maximilian Klingler
- Department of Nuclear Medicine, Medical University of Innsbruck, Innsbruck, Austria; and
| | - Dominik Summer
- Department of Nuclear Medicine, Medical University of Innsbruck, Innsbruck, Austria; and
| | - Christine Rangger
- Department of Nuclear Medicine, Medical University of Innsbruck, Innsbruck, Austria; and
| | - Roland Haubner
- Department of Nuclear Medicine, Medical University of Innsbruck, Innsbruck, Austria; and
| | - Julie Foster
- Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Jane Sosabowski
- Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Clemens Decristoforo
- Department of Nuclear Medicine, Medical University of Innsbruck, Innsbruck, Austria; and
| | - Irene Virgolini
- Department of Nuclear Medicine, Medical University of Innsbruck, Innsbruck, Austria; and
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