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Zou Y, Huang M, Hu M, Wang H, Chen W, Tian R. Radiopharmaceuticals Targeting Gastrin-Releasing Peptide Receptor for Diagnosis and Therapy of Prostate Cancer. Mol Pharm 2024; 21:4199-4216. [PMID: 39219355 DOI: 10.1021/acs.molpharmaceut.4c00066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
The high incidence and heavy disease burden of prostate cancer (PC) require accurate and comprehensive assessment for appropriate disease management. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) cannot detect PSMA-negative lesions, despite its key role in PC disease management. The overexpression of gastrin-releasing peptide receptor (GRPR) in PC lesions reportedly performs as a complementary target for the diagnosis and therapy of PC. Radiopharmaceuticals derived from the natural ligands of GRPR have been developed. These radiopharmaceuticals enable the visualization and quantification of GRPR within the body, which can be used for disease assessment and therapeutic guidance. Recently developed radiopharmaceuticals exhibit improved pharmacokinetic parameters without deterioration in affinity. Several heterodimers targeting GRPR have been constructed as alternatives because of their potential to detect tumor lesions with a low diagnostic efficiency of single target detection. Moreover, some GRPR-targeted radiopharmaceuticals have entered clinical trials for the initial staging or biochemical recurrence detection of PC to guide disease stratification and therapy, indicating considerable potential in PC disease management. Herein, we comprehensively summarize the progress of radiopharmaceuticals targeting GRPR. In particular, we discuss the impact of ligands, chelators, and linkers on the distribution of radiopharmaceuticals. Furthermore, we summarize a potential design scheme to facilitate the advancement of radiopharmaceuticals and, thus, prompt clinical translation.
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Affiliation(s)
- Yuheng Zou
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Mingxing Huang
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Mingxing Hu
- Department of Nuclear Medicine and Clinical Nuclear Medicine Research Lab, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Hui Wang
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Wei Chen
- Department of Nuclear Medicine and Clinical Nuclear Medicine Research Lab, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Rong Tian
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
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Kanellopoulos P, Mattsson A, Abouzayed A, Obeid K, Nock BA, Tolmachev V, Maina T, Orlova A. Preclinical evaluation of new GRPR-antagonists with improved metabolic stability for radiotheranostic use in oncology. EJNMMI Radiopharm Chem 2024; 9:13. [PMID: 38366299 PMCID: PMC10873254 DOI: 10.1186/s41181-024-00242-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 02/05/2024] [Indexed: 02/18/2024] Open
Abstract
BACKGROUND The gastrin-releasing peptide receptor (GRPR) has been extensively studied as a biomolecular target for peptide-based radiotheranostics. However, the lack of metabolic stability and the rapid clearance of peptide radioligands, including radiolabeled GRPR-antagonists, often impede clinical application. Aiming at circumventing these drawbacks, we have designed three new GRPR-antagonist radioligands using [99mTc]Tc-DB15 ([99mTc]Tc-N4-AMA-DIG-DPhe-Gln-Trp-Ala-Val-Sar-His-Leu-NHEt; AMA: p-aminomethylaniline; DIG: diglycolate) as a motif, due to its high GRPR-affinity and stability to neprilysin (NEP). The new analogues carry the DOTAGA-chelator (1,4,7,10-tetraazacyclododecane-1-glutaric acid-4,7,10-triacetic acid) through different linkers at the N-terminus to allow for labeling with the theranostic radionuclide pair In-111/Lu-177. After labeling with In-111 the following radioligands were evaluated: (i) [111In]In-AU-SAR-M1 ([111In]In-DOTAGA-AMA-DIG-DPhe-Gln-Trp-Ala-Val-Sar-His-Leu-NHEt), (ii) [111In]In-AU-SAR-M2 ([111In]In-[DOTAGA-Arg]AU-SAR-M1) and (iii) [111In]In-AU-SAR-M3 ([111In]In-[DOTAGA-DArg]AU-SAR-M1). RESULTS These radioligands were compared in a series of in vitro assays using prostate adenocarcinoma PC-3 cells and in murine models. They all displayed high and GRPR-specific uptake in PC-3 cells. Analysis of mice blood collected 5 min post-injection (pi) revealed similar or even higher metabolic stability of the new radioligands compared with [99mTc]Tc-DB15. The stability could be further increased when the mice were treated with Entresto® to in situ induce NEP-inhibition. In PC-3 xenograft-bearing mice, [111In]In-AU-SAR-M1 displayed the most favourable biodistribution profile, combining a good tumor retention with the highest tumor-to-organ ratios, with the kidneys as the dose-limiting organ. CONCLUSIONS These findings strongly point at AU-SAR-M1 as a promising radiotherapeutic candidate when labeled with Lu-177, or other medically appealing therapeutic radiometals, especially when combined with in situ NEP-inhibition. To this goal further investigations are currently pursued.
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Affiliation(s)
- Panagiotis Kanellopoulos
- Department of Medicinal Chemistry, Uppsala University, 75183, Uppsala, Sweden
- Molecular Radiopharmacy, INRaSTES, NCSR "Demokritos", 15341, Athens, Greece
| | - Adam Mattsson
- Department of Medicinal Chemistry, Uppsala University, 75183, Uppsala, Sweden
| | - Ayman Abouzayed
- Department of Medicinal Chemistry, Uppsala University, 75183, Uppsala, Sweden
| | - Karim Obeid
- Department of Medicinal Chemistry, Uppsala University, 75183, Uppsala, Sweden
| | - Berthold A Nock
- Molecular Radiopharmacy, INRaSTES, NCSR "Demokritos", 15341, Athens, Greece
| | - Vladimir Tolmachev
- Department of Immunology, Genetics and Pathology, Uppsala University, 75183, Uppsala, Sweden
| | - Theodosia Maina
- Molecular Radiopharmacy, INRaSTES, NCSR "Demokritos", 15341, Athens, Greece
| | - Anna Orlova
- Department of Medicinal Chemistry, Uppsala University, 75183, Uppsala, Sweden.
- Science for Life Laboratory, Uppsala University, 75237, Uppsala, Sweden.
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Nock BA, Kanellopoulos P, Joosten L, Mansi R, Maina T. Peptide Radioligands in Cancer Theranostics: Agonists and Antagonists. Pharmaceuticals (Basel) 2023; 16:ph16050674. [PMID: 37242457 DOI: 10.3390/ph16050674] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 04/25/2023] [Accepted: 04/27/2023] [Indexed: 05/28/2023] Open
Abstract
The clinical success of radiolabeled somatostatin analogs in the diagnosis and therapy-"theranostics"-of tumors expressing the somatostatin subtype 2 receptor (SST2R) has paved the way for the development of a broader panel of peptide radioligands targeting different human tumors. This approach relies on the overexpression of other receptor-targets in different cancer types. In recent years, a shift in paradigm from internalizing agonists to antagonists has occurred. Thus, SST2R-antagonist radioligands were first shown to accumulate more efficiently in tumor lesions and clear faster from the background in animal models and patients. The switch to receptor antagonists was soon adopted in the field of radiolabeled bombesin (BBN). Unlike the stable cyclic octapeptides used in the case of somatostatin, BBN-like peptides are linear, fast to biodegradable and elicit adverse effects in the body. Thus, the advent of BBN-like antagonists provided an elegant way to obtain effective and safe radiotheranostics. Likewise, the pursuit of gastrin and exendin antagonist-based radioligands is advancing with exciting new outcomes on the horizon. In the present review, we discuss these developments with a focus on clinical results, commenting on challenges and opportunities for personalized treatment of cancer patients by means of state-of-the-art antagonist-based radiopharmaceuticals.
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Affiliation(s)
- Berthold A Nock
- Molecular Radiopharmacy, INRaSTES, NCSR "Demokritos", 15310 Athens, Greece
| | | | - Lieke Joosten
- Department of Medical Imaging, Nuclear Medicine, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Rosalba Mansi
- Division of Radiopharmaceutical Chemistry, Clinic of Radiology and Nuclear Medicine, University Hospital Basel, 4031 Basel, Switzerland
| | - Theodosia Maina
- Molecular Radiopharmacy, INRaSTES, NCSR "Demokritos", 15310 Athens, Greece
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Günther T, Konrad M, Stopper L, Kunert JP, Fischer S, Beck R, Casini A, Wester HJ. Optimization of the Pharmacokinetic Profile of [ 99mTc]Tc-N 4-Bombesin Derivatives by Modification of the Pharmacophoric Gln-Trp Sequence. Pharmaceuticals (Basel) 2022; 15:ph15091133. [PMID: 36145354 PMCID: PMC9500665 DOI: 10.3390/ph15091133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/06/2022] [Accepted: 09/06/2022] [Indexed: 11/16/2022] Open
Abstract
Current radiolabeled gastrin-releasing peptide receptor (GRPR) ligands usually suffer from high accumulation in GRPR-positive organs (pancreas, stomach), limiting tumor-to-background contrast in the abdomen. In novel N4-bombesin derivatives this was addressed by substitutions at the Gln7-Trp8 site within the MJ9 peptide (H-Pip5-phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Sta13-Leu14-NH2) either by homoserine (Hse7), β-(3-benzothienyl) alanine (Bta8) or α-methyl tryptophan (α-Me-Trp8), with the aim of optimizing pharmacokinetics. We prepared and characterized the peptide conjugates 6-carboxy-1,4,8,11-tetraazaundecane (N4)-asp-MJ9, N4-asp-[Bta8]MJ9, N4-[Hse7]MJ9 and N4-[α-Me-Trp8]MJ9, and evaluated these compounds in vitro (GRPR affinity via IC50,inverse; internalization; lipophilicity via logD7.4) and in vivo (biodistribution and μSPECT/CT studies at 1 h post injection (p.i.) in PC-3 tumor-bearing CB17-SCID mice). 99mTc-labeling resulted in radiochemical yields (RCYs) > 95%. All 99mTc-labeled MJ9 analogues showed comparable or higher GRPR affinity than the external reference [99mTc]Tc-Demobesin 4. Receptor-bound fractions were noticeably higher than that of the reference. Despite a slightly enhanced lipophilicity, all novel MJ9 derivatives revealed improved in vivo pharmacokinetics compared to the reference. The Bta8-modified ligand revealed the most favorable tumor-to-abdomen contrast at 1 h p.i. Substitutions at the Gln7-Trp8 site within GRPR ligands hold great potential to modify pharmacokinetics for improved imaging.
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Mansi R, Nock BA, Dalm SU, Busstra MB, van Weerden WM, Maina T. Radiolabeled Bombesin Analogs. Cancers (Basel) 2021; 13:cancers13225766. [PMID: 34830920 PMCID: PMC8616220 DOI: 10.3390/cancers13225766] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/13/2021] [Accepted: 11/15/2021] [Indexed: 12/16/2022] Open
Abstract
Simple Summary Recent medical advancements have strived for a personalized medicine approach to patients, aimed at optimizing therapy outcomes with minimum toxicity. In this respect, nuclear medicine methodologies have been playing increasingly important roles. For example, the overexpression of peptide receptors, such as the gastrin-releasing peptide receptor (GRPR), on tumor cells as opposed to their lack of expression in healthy surrounding tissues can be elegantly exploited with the aid of “smart” peptide carriers, such as the analogs of the amphibian 14-peptide bombesin (BBN). These molecules can bring clinically attractive radionuclides to malignant lesions in prostate, breast, and other human cancers, sparing healthy tissues. Depending upon the radionuclide in question, diagnostic imaging with single-photon emission computed tomography (SPECT) or positron emission tomography (PET) has been pursued, identifying patients who are eligible for peptide radionuclide receptor therapy (PRRT) in an integrated “theranostic” approach. In the present review, we (i) discuss the major steps taken in the development of anti-GRPR theranostic radioligands, with a focus on those selected for clinical testing; (ii) comment on the present status in this field of research; and (iii) reflect on the current limitations as well as on new opportunities for their broader and more successful clinical applications. Abstract The gastrin-releasing peptide receptor (GRPR) is expressed in high numbers in a variety of human tumors, including the frequently occurring prostate and breast cancers, and therefore provides the rationale for directing diagnostic or therapeutic radionuclides on cancer lesions after administration of anti-GRPR peptide analogs. This concept has been initially explored with analogs of the frog 14-peptide bombesin, suitably modified at the N-terminus with a number of radiometal chelates. Radiotracers that were selected for clinical testing revealed inherent problems associated with these GRPR agonists, related to low metabolic stability, unfavorable abdominal accumulation, and adverse effects. A shift toward GRPR antagonists soon followed, with safer analogs becoming available, whereby, metabolic stability and background clearance issues were gradually improved. Clinical testing of three main major antagonist types led to promising outcomes, but at the same time brought to light several limitations of this concept, partly related to the variation of GRPR expression levels across cancer types, stages, previous treatments, and other factors. Currently, these parameters are being rigorously addressed by cell biologists, chemists, nuclear medicine physicians, and other discipline practitioners in a common effort to make available more effective and safe state-of-the-art molecular tools to combat GRPR-positive tumors. In the present review, we present the background, current status, and future perspectives of this endeavor.
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Affiliation(s)
- Rosalba Mansi
- Division of Radiopharmaceutical Chemistry, Clinic of Radiology and Nuclear Medicine University Hospital Basel, 4031 Basel, Switzerland;
| | - Berthold A. Nock
- Molecular Radiopharmacy, INRaSTES, NCSR “Demokritos”, 15310 Athens, Greece;
| | - Simone U. Dalm
- Erasmus Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands; (S.U.D.); (M.B.B.); (W.M.v.W.)
| | - Martijn B. Busstra
- Erasmus Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands; (S.U.D.); (M.B.B.); (W.M.v.W.)
| | - Wytske M. van Weerden
- Erasmus Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands; (S.U.D.); (M.B.B.); (W.M.v.W.)
| | - Theodosia Maina
- Molecular Radiopharmacy, INRaSTES, NCSR “Demokritos”, 15310 Athens, Greece;
- Correspondence: ; Tel.: +30-650-3908/3891
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Benard F, Bratanovic IJ. A Novel Radiotracer for Molecular Imaging and Therapy of Gastrin-Releasing Peptide Receptor Positive Prostate Cancer. J Nucl Med 2021; 63:424-430. [PMID: 34301778 DOI: 10.2967/jnumed.120.257758] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 06/06/2021] [Indexed: 11/16/2022] Open
Abstract
The gastrin-releasing peptide receptor (GRPR) is overexpressed in many solid malignancies, particularly in prostate and breast cancers, among others. We synthesized ProBOMB2, a novel bombesin derivative radiolabeled with 68Ga and 177Lu, and evaluated its ability to target GRPR in a preclinical model of human prostate cancer. Methods: ProBOMB2 was synthesized on solid phase using Fmoc chemistry. The chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid was coupled to the N-terminus and separated from the GRPR-targeting sequence by a cationic 4-amino-(1-carboxymethyl)-piperidine spacer. Binding affinity for both human and murine GRPR was determined using a cell-based competition assay, while a calcium efflux assay was used to measure the agonist/antagonist properties of the derivatives. ProBOMB2 was radiolabeled with 177Lu and 68Ga. SPECT and PET imaging, and biodistribution studies were conducted using a preclinical prostate cancer model of male immunocompromised mice bearing GRPR-positive PC-3 human prostate cancer xenografts. Results: Ga-ProBOMB2 and Lu-ProBOMB2 bound to PC-3 cells with a Ki of 4.58±0.67 and 7.29±1.73 nM, respectively. 68Ga-ProBOMB2 and 177Lu-ProBOMB2 were radiolabeled with a radiochemical purity greater than 95%. Both radiotracers were primarily excreted via the renal pathway. PET images of PC-3 tumor xenografts were visualized with excellent contrast at 1 h and 2 h post-injection (p.i.) with 68Ga-ProBOMB2, and very low off-target organ accumulation. 177Lu-ProBOMB2 enabled clear visualization of PC-3 tumor xenografts by SPECT imaging at 1 h, 4 h, and 24 h p.i. 177Lu-ProBOMB2 displayed higher tumor uptake than 68Ga-ProBOMB2 at 1 h p.i. 177Lu-ProBOMB2 tumor uptake at 1 h, 4 h, and 24 h p.i. was 14.9±3.1, 4.8±2.1, and 1.7±0.3 %ID/g, respectively. Conclusion: 68Ga-ProBOMB2 and 177Lu-ProBOMB2 are promising radiotracers with limited pancreas uptake, good tumor uptake, and favorable pharmacokinetics for imaging and therapy of GRPR-expressing tumors.
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Askari Rizvi SF, Zhang H. Emerging trends of receptor-mediated tumor targeting peptides: A review with perspective from molecular imaging modalities. Eur J Med Chem 2021; 221:113538. [PMID: 34022717 DOI: 10.1016/j.ejmech.2021.113538] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/06/2021] [Accepted: 05/07/2021] [Indexed: 01/10/2023]
Abstract
Natural peptides extracted from natural components such are known to have a relatively short in-vivo half-life and can readily metabolize by endo- and exo-peptidases. Fortunately, synthetic peptides can be easily manipulated to increase in-vivo stability, membrane permeability and target specificity with some well-known natural families. Many natural as well as synthetic peptides target to their endogenous receptors for diagnosis and therapeutic applications. In order to detect these peptides externally, they must be modified with radionuclides compatible with single photon emission computed tomography (SPECT) or positron emission tomography (PET). Although, these techniques mainly rely on physiological changes and have profound diagnostic strength over anatomical modalities such as MRI and CT. However, both SPECT and PET observed to possess lack of anatomical reference frame which is a key weakness of these techniques, and unfortunately, cannot be available freely in most clinical centres especially in under-developing countries. Hence, it is need of the time to design and develop economic, patient friendly and versatile strategies to grapple with existing problems without any hazardous side effects. Optical molecular imaging (OMI) has emerged as a novel technique in field of medical science using fluorescent probes as imaging modality and has ability to couple with organic drugs, small molecules, chemotherapeutics, DNA, RNA, anticancer peptide and protein without adding chelators as necessary for radionuclides. Furthermore, this review focuses on difference in imaging modalities and provides ample knowledge about reliable, economic and patient friendly optical imaging technique rather radionuclide-based imaging techniques.
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Affiliation(s)
- Syed Faheem Askari Rizvi
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, 730000, Gansu, PR China
| | - Haixia Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, 730000, Gansu, PR China.
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Mitran B, Tolmachev V, Orlova A. Radiolabeled GRPR Antagonists for Imaging of Disseminated Prostate Cancer - Influence of Labeling Chemistry on Targeting Properties. Curr Med Chem 2021; 27:7090-7111. [PMID: 32164503 DOI: 10.2174/0929867327666200312114902] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/31/2019] [Accepted: 01/10/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Radionuclide molecular imaging of Gastrin-Releasing Peptide Receptor (GRPR) expression promises unparalleled opportunities for visualizing subtle prostate tumors, which due to small size, adjacent benign tissue, or a challenging location would otherwise remain undetected by conventional imaging. Achieving high imaging contrast is essential for this purpose and the molecular design of any probe for molecular imaging of prostate cancer should be aimed at obtaining as high tumor-to-organ ratios as possible. OBJECTIVE This short review summarizes the key imaging modalities currently used in prostate cancer, with a special focus on radionuclide molecular imaging. Emphasis is laid mainly on the issue of radiometals labeling chemistry and its influence on the targeting properties and biodistribution of radiolabeled GRPR antagonists for imaging of disseminated prostate cancer. METHODS A comprehensive literature search of the PubMed/MEDLINE, and Scopus library databases was conducted to find relevant articles. RESULTS The combination of radionuclide, chelator and required labeling chemistry was shown to have a significant influence on the stability, binding affinity and internalization rate, off-target interaction with normal tissues and blood proteins, interaction with enzymes, activity uptake and retention in excretory organs and activity uptake in tumors of radiolabeled bombesin antagonistic analogues. CONCLUSION Labeling chemistry has a very strong impact on the biodistribution profile of GRPRtargeting peptide based imaging probes and needs to be considered when designing a targeting probe for high contrast molecular imaging. Taking into account the complexity of in vivo interactions, it is not currently possible to accurately predict the optimal labeling approach. Therefore, a detailed in vivo characterization and optimization is essential for the rational design of imaging agents.
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Affiliation(s)
- Bogdan Mitran
- Department of Medicianl Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala, Sweden
| | - Vladimir Tolmachev
- Department of Immunology, Genetics and Pathology, Faculty of Medicine, Uppsala University, Uppsala, Sweden
| | - Anna Orlova
- Department of Medicianl Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala, Sweden
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One Step Closer to Clinical Translation: Enhanced Tumor Targeting of [ 99mTc]Tc-DB4 and [ 111In]In-SG4 in Mice Treated with Entresto. Pharmaceutics 2020; 12:pharmaceutics12121145. [PMID: 33256013 PMCID: PMC7760338 DOI: 10.3390/pharmaceutics12121145] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 11/24/2020] [Accepted: 11/25/2020] [Indexed: 12/11/2022] Open
Abstract
Background: Peptide radioligands may serve as radionuclide carriers to tumor sites overexpressing their cognate receptor for diagnostic or therapeutic purposes. Treatment of mice with the neprilysin (NEP)-inhibitor phosphoramidon was previously shown to improve the metabolic stability and tumor uptake of biodegradable radiopeptides. Aiming to clinical translation of this methodology, we herein investigated the impact of the approved pill Entresto, releasing the potent NEP-inhibitor LBQ657 in vivo, on the stability and tumor uptake of two radiopeptides. Methods: The metabolic stability of [99mTc]Tc-DB4 (DB4, N4-Pro-Gln-Arg-Tyr-Gly-Asn-Gln-Trp-Ala-Val-Gly-His-Leu-Nle-NH2) and [111In]In-SG4 (SG4, DOTA-DGlu-Ala-Tyr-Gly-Trp-Nle-Asp-Phe-NH2) was tested in LBQ657/Entresto-treated mice vs. untreated controls. The uptake in gastrin-releasing peptide receptor (GRPR)-, or cholecystokinin subtype 2 receptor (CCK2R)-positive tumors respectively, was compared between LBQ657/Entresto-treated mice and untreated controls. Results: LBQ657/Entresto treatment induced marked stabilization of [99mTc] Tc-DB4 and [111In]In-SG4 in peripheral mice blood, resulting in equally enhanced tumor uptake at 4 h post-injection. Accordingly, the [99mTc]Tc-DB4 uptake of 7.13 ± 1.76%IA/g in PC-3 tumors increased to 16.17 ± 0.71/17.50 ± 3.70%IA/g (LBQ657/Entresto) and the [111In]In-SG4 uptake of 3.07 ± 0.87%IA/g in A431-CCK2R(+) tumors to 8.11 ± 1.45/9.61 ± 1.70%IA/g. Findings were visualized by SPECT/CT. Conclusions: This study has shown the efficacy of Entresto to notably improve the profile of [99mTc]Tc-DB4 and [111In]In-SG4 in mice, paving the way for clinical translation of this approach.
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Abbasi Gharibkandi N, Conlon JM, Hosseinimehr SJ. Strategies for improving stability and pharmacokinetic characteristics of radiolabeled peptides for imaging and therapy. Peptides 2020; 133:170385. [PMID: 32822772 DOI: 10.1016/j.peptides.2020.170385] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 08/13/2020] [Accepted: 08/13/2020] [Indexed: 02/07/2023]
Abstract
Tumor cells overexpress a variety of receptors that are emerging targets in cancer chemotherapy. Radiolabeled peptides with high affinity and selectivity for these overexpressed receptors have been designed for both imaging and therapy purposes. Such peptides display advantages such as high selectivity for tumor cells, rapid tumor tissue penetration, and rapid clearance from non-target tissues and the circulation. However, the very short in vivo half-life of radiolabeled peptides, arising from enzymatic degradation and/or efficient clearance by the kidney, limits their accumulation in tumors. This review presents various strategies that have been applied to extend the half-life extension and improve the pharmacokinetic characteristics of radiolabeled peptides. These include amino acid substitution, modification of the peptide termini, dimerization and multimerization of the peptide, cyclization, conjugation with polymers, sugars and albumin and use of peptidase inhibitors.
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Affiliation(s)
- Nasrin Abbasi Gharibkandi
- Department of Radiopharmacy, Faculty of Pharmacy, Pharmaceutical Sciences Research Center, Mazandaran University of Medical Sciences, Sari, Iran; Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - J Michael Conlon
- Diabetes Research Group, School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Northern Ireland, BT52 1SA, UK
| | - Seyed Jalal Hosseinimehr
- Department of Radiopharmacy, Faculty of Pharmacy, Pharmaceutical Sciences Research Center, Mazandaran University of Medical Sciences, Sari, Iran.
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Rezazadeh F, Karoubian S, Abediankenari S, Sadeghzadeh N, Jandaghi M, Rasuli S. The Effects of the Spacer on Radiochemical and Biological Properties of New Radiolabeled Bombesin(7-14) Derivative. Curr Radiopharm 2020; 13:149-158. [PMID: 32497000 DOI: 10.2174/1874471013666200604175905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/07/2020] [Accepted: 05/13/2020] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The aim of this study was to develop 99mTc-[HYNIC-X-D-Phe13]-BBN(7-14)NH2 derivatives using two different tripeptidic spacer groups (X=GGG and X=SSS) in order to improve its pharmacokinetics, in vitro stability, specific binding, and affinity. BACKGROUND Bombesin (BBN), a 14-aminoacid amphibian peptide homolog of mammalian gastrinreleasing peptide (GRP), has demonstrated the ability to bind with high affinity and specificity to GRP receptor, which is overexpressed on a variety of human cancers. METHODS Peptide conjugates labeled with 99mTc using tricine-EDDA and radiochemical purity was assessed by TLC and HPLC. The stability of radio conjugates was evaluated in the presence of saline and human serum. Affinity, internalization, and also dissociation Constant was evaluated using MDAMB- 231 and PC-3 cell line. Biodistribution study was performed in BALB/C mice. RESULTS Labeling yield of ˃95% was obtained. The change introduced in the BBN sequence increased plasma stability. In vitro blocking studies showed that binding and internalization of both radiolabeled peptides are mediated by their receptors on the surface of MDA-MB-231 and PC-3 cells. Biodistribution results demonstrated a rapid blood clearance, with predominantly renal excretion. Specific binding in GRP receptor-positive tissues, such as pancreas was confirmed with a blocking study. CONCLUSION The introduction of the spacer sequence between chelator and BBN(7-14) led to improved bidistribution. Analog with tri-Gly spacer is the more promising radiopeptide for targeting GRP receptors than Ser conjugates. Therefore, these analogs can be considered as a candidate for the identification of bombesin-positive tumors.
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Affiliation(s)
- Farzaneh Rezazadeh
- Faculty of Pharmacy, Department of Radiopharmacy, Mazandaran University of Medical Sciences, Sari, Iran,Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Sara Karoubian
- Faculty of Pharmacy, Department of Radiopharmacy, Mazandaran University of Medical Sciences, Sari, Iran,Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Saied Abediankenari
- Immunogenetics Research Center, Mazandaran University of Medical Sciences, Sari, Iran
| | - Nourollah Sadeghzadeh
- Faculty of Pharmacy, Department of Radiopharmacy, Mazandaran University of Medical Sciences, Sari, Iran
| | - Manouchehr Jandaghi
- Faculty of Pharmacy, Department of Radiopharmacy, Mazandaran University of Medical Sciences, Sari, Iran,Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Shayan Rasuli
- Faculty of Pharmacy, Department of Radiopharmacy, Mazandaran University of Medical Sciences, Sari, Iran,Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
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12
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Structural modifications of amino acid sequences of radiolabeled peptides for targeted tumor imaging. Bioorg Chem 2020; 99:103802. [DOI: 10.1016/j.bioorg.2020.103802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 03/19/2020] [Accepted: 03/25/2020] [Indexed: 12/18/2022]
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13
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Ermert J, Benešová M, Hugenberg V, Gupta V, Spahn I, Pietzsch HJ, Liolios C, Kopka K. Radiopharmaceutical Sciences. Clin Nucl Med 2020. [DOI: 10.1007/978-3-030-39457-8_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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14
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Abstract
Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., 99mTc, 123I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.
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15
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Hoppenz P, Els‐Heindl S, Beck‐Sickinger AG. Identification and stabilization of a highly selective gastrin‐releasing peptide receptor agonist. J Pept Sci 2019; 25:e3224. [DOI: 10.1002/psc.3224] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 09/24/2019] [Accepted: 09/25/2019] [Indexed: 12/20/2022]
Affiliation(s)
- Paul Hoppenz
- Institute of BiochemistryLeipzig University Leipzig Germany
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16
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Stability Evaluation and Stabilization of a Gastrin-Releasing Peptide Receptor (GRPR) Targeting Imaging Pharmaceutical. Molecules 2019; 24:molecules24162878. [PMID: 31398865 PMCID: PMC6720803 DOI: 10.3390/molecules24162878] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 07/24/2019] [Accepted: 08/06/2019] [Indexed: 01/15/2023] Open
Abstract
The prostate-specific membrane antigen (PSMA) and gastrin-releasing peptide receptor (GRPR) are identified as important targets on prostate cancer. Receptor-targeting radiolabeled imaging pharmaceuticals with high affinity and specificity are useful in studying and monitoring biological processes and responses. Two potential imaging pharmaceuticals, AMBA agonist (where AMBA = DO3A-CH2CO-G-[4-aminobenzyl]- Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH2) and RM1 antagonist (where RM1 = DO3A-CH2CO-G-[4-aminobenzyl]-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2), have demonstrated high binding affinity (IC50) to GRP receptors and high tumor uptake. Antagonists, despite the poor tumor cell internalization properties, can show clearer images and pharmacokinetic profiles by virtue of their higher tumor uptake in animal models compared to agonists. For characterization, development, and translation of a potential imaging pharmaceutical into the clinic, it must be evaluated in a series of tests, including in vitro cell binding assays, in vitro buffer and serum stability studies, the biodistribution of the radiolabeled material, and finally imaging studies in preclinical animal models. Data related to acetate buffer, mouse, canine, and human sera stability of 177Lu-labeled RM1 are presented here and compared with the acetate buffer and sera stability data of AMBA agonist. The samples of 177Lu-labeled RM1 with a high radioconcentration degrade faster than low-radioconcentration samples upon storage at 2–8 °C. Addition of stabilizers, ascorbic acid and gentisic acid, improve the stability of 177Lu-labeled RM1 significantly with gentisic acid being more efficient than ascorbic acid as a stabilizer. The degradation kinetics of 177Lu-labeled AMBA and RM1 in sera follow the order (fastest to slowest): mouse > canine > human sera. Finally, 177Lu-labeled RM1 antagonist is slower to degrade in mouse, canine, and human sera than 177Lu-labeled AMBA agonist, further suggesting that an antagonist is a more promising candidate than agonist for the positron emission tomography (PET) imaging and therapy of prostate cancer patients.
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17
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Oroujeni M, Abouzayed A, Lundmark F, Mitran B, Orlova A, Tolmachev V, Rosenström U. Evaluation of Tumor-Targeting Properties of an Antagonistic Bombesin Analogue RM26 Conjugated with a Non-Residualizing Radioiodine Label Comparison with a Radiometal-Labelled Counterpart. Pharmaceutics 2019; 11:pharmaceutics11080380. [PMID: 31382362 PMCID: PMC6724035 DOI: 10.3390/pharmaceutics11080380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 07/16/2019] [Accepted: 07/24/2019] [Indexed: 12/24/2022] Open
Abstract
Radiolabelled antagonistic bombesin analogues are successfully used for targeting of gastrin-releasing peptide receptors (GRPR) that are overexpressed in prostate cancer. Internalization of antagonistic bombesin analogues is slow. We hypothesized that the use of a non-residualizing radioiodine label might not affect the tumour uptake but would reduce the retention in normal organs, where radiopharmaceutical would be internalized. To test this hypothesis, tyrosine was conjugated via diethylene glycol linker to N-terminus of an antagonistic bombesin analogue RM26 to form Tyr-PEG2-RM26. [111In]In-DOTA-PEG2-RM26 was used as a control with a residualizing label. Tyr-PEG2-RM26 was labelled with 125I with 95% radiochemical purity and retained binding specificity to GRPR. The IC50 values for Tyr-PEG2-RM26 and DOTA-PEG2-RM26 were 1.7 ± 0.3 nM and 3.3 ± 0.5 nM, respectively. The cellular processing of [125I]I-Tyr-PEG2-RM26 by PC-3 cells showed unusually fast internalization. Biodistribution showed that uptake in pancreas and tumour was GRPR-specific for both radioconjugates. Blood clearance of [125I]I-Tyr-PEG2-RM26 was appreciably slower and activity accumulation in all organs was significantly higher than for [111In]In-DOTA-PEG2-RM26. Tumor uptake of [111In]In-DOTA-PEG2-RM26 was significantly higher than for [125I]I-Tyr-PEG2-RM26, resulting in higher tumour-to-organ ratio for [111In]In-DOTA-PEG2-RM26 at studied time points. Incorporation of amino acids with hydrophilic side-chains next to tyrosine might overcome the problems associated with the use of tyrosine as a prosthetic group for radioiodination.
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Affiliation(s)
- Maryam Oroujeni
- Department of Immunology, Genetics and Pathology, Uppsala University, SE-751 85 Uppsala, Sweden
| | - Ayman Abouzayed
- Department of Medicinal Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Fanny Lundmark
- Department of Medicinal Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Bogdan Mitran
- Department of Medicinal Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Anna Orlova
- Department of Medicinal Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
- Science for Life Laboratory, Uppsala University, SE-750 03 Uppsala, Sweden
| | - Vladimir Tolmachev
- Department of Immunology, Genetics and Pathology, Uppsala University, SE-751 85 Uppsala, Sweden.
| | - Ulrika Rosenström
- Department of Medicinal Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
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18
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Farzipour S, Hosseinimehr SJ. Correlation between in vitro and in vivo Data of Radiolabeled Peptide for Tumor Targeting. Mini Rev Med Chem 2019; 19:950-960. [DOI: 10.2174/1389557519666190304120011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 12/28/2018] [Accepted: 02/22/2019] [Indexed: 12/12/2022]
Abstract
Tumor-targeting peptides have been generally developed for the overexpression of tumor specific receptors in cancer cells. The use of specific radiolabeled peptide allows tumor visualization by single photon emission computed tomography (SPECT) and positron emission tomography (PET) tools. The high affinity and specific binding of radiolabeled peptide are focusing on tumoral receptors. The character of the peptide itself, in particular, its complex molecular structure and behaviors influence on its specific interaction with receptors which are overexpressed in tumor. This review summarizes various strategies which are applied for the expansion of radiolabeled peptides for tumor targeting based on in vitro and in vivo specific tumor data and then their data were compared to find any correlation between these experiments. With a careful look at previous studies, it can be found that in vitro unblock-block ratio was unable to correlate the tumor to muscle ratio and the success of radiolabeled peptide for in vivo tumor targeting. The introduction of modifiers’ approaches, nature of peptides, and type of chelators and co-ligands have mixed effect on the in vitro and in vivo specificity of radiolabeled peptides.
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Affiliation(s)
- Soghra Farzipour
- Department of Radiopharmacy, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran
| | - Seyed Jalal Hosseinimehr
- Department of Radiopharmacy, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran
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19
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Zhang J, Singh A, Kulkarni HR, Schuchardt C, Müller D, Wester HJ, Maina T, Rösch F, van der Meulen NP, Müller C, Mäcke H, Baum RP. From Bench to Bedside-The Bad Berka Experience With First-in-Human Studies. Semin Nucl Med 2019; 49:422-437. [PMID: 31470935 DOI: 10.1053/j.semnuclmed.2019.06.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Precision oncology is being driven by rapid advances in novel diagnostics and therapeutic interventions, with treatments targeted to the needs of individual patients on the basis of genetic, biomarker, phenotypic, or psychosocial characteristics that distinguish a given patient from other patients with similar clinical presentations. Inherent in the theranostics paradigm is the assumption that diagnostic test results can precisely determine whether an individual is likely to benefit from a specific treatment. As part and integral in the current era of precision oncology, theranostics in the context of nuclear medicine aims to identify the appropriate molecular targets in neoplasms (diagnostic tool), so that the optimal ligands and radionuclides (therapeutic tool) with favorable labeling chemistry can be selected for personalized management of a specific disease, taking into consideration the specific patient, and subsequently monitor treatment response. Over the past two decades, the use of gallium-68 labeled peptides for somatostatin receptor (SSTR)-targeted PET/CT (or PET/MRI) imaging followed by lutetium-177 and yttrium-90 labeled SSTR-agonist for peptide receptor radionuclide therapy has demonstrated remarkable success in the management of neuroendocrine neoplasms, and paved the way to other indications of theranostics. Rapid advances are being made in the development of other peptide-based radiopharmaceuticals, small molecular-weight ligands and with newer radioisotopes with more favorable kinetics, potentially useful for theranostics strategies for the clinical application. The present review features the Bad Berka experience with first-in-human studies of new radiopharmaceuticals, for example, prostate-specific membrane antigen ligand, gastrin-releasing peptide receptor, neurotensin receptor 1 ligand, novel SSTR-targeting peptides and nonpeptide, and bone-seeking radiopharmaceuticals. Also new radioisotopes, for example, actinium (225Ac), copper (64Cu), scandium (44Sc), and terbium (152Tb/161Tb) will be discussed briefly demonstrating the development from basic science to precision oncology in the clinical setting.
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Affiliation(s)
- Jingjing Zhang
- THERANOSTICS Center for Molecular Radiotherapy and Precision Oncology, Zentralklinik Bad Berka, Bad Berka, Germany
| | - Aviral Singh
- THERANOSTICS Center for Molecular Radiotherapy and Precision Oncology, Zentralklinik Bad Berka, Bad Berka, Germany
| | - Harshad R Kulkarni
- THERANOSTICS Center for Molecular Radiotherapy and Precision Oncology, Zentralklinik Bad Berka, Bad Berka, Germany
| | - Christiane Schuchardt
- THERANOSTICS Center for Molecular Radiotherapy and Precision Oncology, Zentralklinik Bad Berka, Bad Berka, Germany
| | - Dirk Müller
- THERANOSTICS Center for Molecular Radiotherapy and Precision Oncology, Zentralklinik Bad Berka, Bad Berka, Germany
| | - Hans-J Wester
- Institute for Radiopharmaceutical Chemistry, Technische Universität München, Garching, Germany
| | - Theodosia Maina
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Athens, Greece
| | - Frank Rösch
- Institute of Nuclear Chemistry, Johannes Gutenberg-University, Mainz, Germany
| | - Nicholas P van der Meulen
- Center for Radiopharmaceutical Sciences, ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland; (
- )Laboratory of Radiochemistry, Paul Scherrer Institute, Villigen, Switzerland
| | - Cristina Müller
- Center for Radiopharmaceutical Sciences, ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland
| | - Helmut Mäcke
- Department of Nuclear Medicine, University Hospital of Freiburg, Freiburg, Germany
| | - Richard P Baum
- THERANOSTICS Center for Molecular Radiotherapy and Precision Oncology, Zentralklinik Bad Berka, Bad Berka, Germany.
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20
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The effect of Longan Arillus extract on enhancing oral absorption of bioactive peptides derived from defatted walnut meal hydrolysates. J Funct Foods 2019. [DOI: 10.1016/j.jff.2019.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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21
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Kaloudi A, Lymperis E, Kanellopoulos P, Waser B, de Jong M, Krenning EP, Reubi JC, Nock BA, Maina T. Localization of 99mTc-GRP Analogs in GRPR-Expressing Tumors: Effects of Peptide Length and Neprilysin Inhibition on Biological Responses. Pharmaceuticals (Basel) 2019; 12:ph12010042. [PMID: 30897789 PMCID: PMC6469168 DOI: 10.3390/ph12010042] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 03/16/2019] [Accepted: 03/18/2019] [Indexed: 02/06/2023] Open
Abstract
The overexpression of gastrin-releasing peptide receptors (GRPRs) in frequently occurring human tumors has provided the opportunity to use bombesin (BBN) analogs as radionuclide carriers to cancer sites for diagnostic and therapeutic purposes. We have been alternatively exploring human GRP motifs of higher GRPR selectivity compared to frog BBN sequences aiming to improve pharmacokinetic profiles. In the present study, we compared two differently truncated human endogenous GRP motifs: GRP(14–27) and GRP(18–27). An acyclic tetraamine was coupled at the N-terminus to allow for stable binding of the SPECT radionuclide 99mTc. Their biological profiles were compared in PC-3 cells and in mice without or with coinjection of phosphoramidon (PA) to induce transient neprilysin (NEP) inhibition in vivo. The two 99mTc-N4-GRP(14/18–27) radioligands displayed similar biological behavior in mice. Coinjection of PA exerted a profound effect on in vivo stability and translated into notably improved radiolabel localization in PC-3 experimental tumors. Hence, this study has shown that promising 99mTc-radiotracers for SPECT imaging may indeed derive from human GRP sequences. Radiotracer bioavailability was found to be of major significance. It could be improved during in situ NEP inhibition resulting in drastically enhanced uptake in GRPR-expressing lesions.
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Affiliation(s)
- Aikaterini Kaloudi
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", 15310 Athens, Greece.
| | - Emmanouil Lymperis
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", 15310 Athens, Greece.
| | | | - Beatrice Waser
- Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland.
| | - Marion de Jong
- Department of Radiology & Nuclear Medicine Erasmus MC, 3015 CN Rotterdam, The Netherlands.
| | - Eric P Krenning
- Cytrotron Rotterdam BV, Erasmus MC, 3015 CN Rotterdam, The Netherlands.
| | - Jean Claude Reubi
- Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland.
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", 15310 Athens, Greece.
| | - Theodosia Maina
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", 15310 Athens, Greece.
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22
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De K, Mukherjee D, Sinha S, Ganguly S. HYNIC and DOMA conjugated radiolabeled bombesin analogs as receptor-targeted probes for scintigraphic detection of breast tumor. EJNMMI Res 2019; 9:25. [PMID: 30887136 PMCID: PMC6423188 DOI: 10.1186/s13550-019-0493-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 02/21/2019] [Indexed: 12/21/2022] Open
Abstract
Background Among the many peptide receptor systems, gastrin-releasing-peptide (GRP) receptors, the mammalian equivalent of bombesin (BN) receptors, are potential targets for diagnosis and therapy of breast tumors due to their overexpression in various frequently occurring human cancers. The aim of this study was to synthesize and comparative evaluation of 99mTc-labeled new BN peptide analogs. Four new BN analogs, HYNIC-Asp[PheNle]BN(7-14)NH2, BN1; HYNIC-Pro-Asp[TyrMet]BN(7-14)NH2, BN2; HYNIC-Asp-Asn[Lys-CHAla-Nle]BN(7-14)NH2, BN3; and DOMA-GABA[Pro-Tyr-Nle]BN(7-14)NH2, BN4 were synthesized and biologically evaluated for targeted imaging of GRP receptor-positive breast-tumors. Methods Solid-phase synthesis using Fmoc-chemistry was adopted for the synthesis of peptides. BN1–BN4 analogs were better over the standard Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH2 (BNS). Lipophilicity, serum stability, internalization, and binding affinity studies were carried out using 99mTc-labeled analogs. Biodistribution and imaging analyses were performed on MDA-MB-231 cell-induced tumor-bearing mice. BN-analogs induced angiogenesis; tumor formation and GRP-receptor-expression were confirmed by histology and immunohistochemistry analyses of tumor sections and important tissue sections. Results All the analogs displayed ≥ 97% purity after the HPLC purification. BN-peptide-conjugates exhibited high serum stability and significant binding affinity to GRP-positive tumor; rapid internalization/externalization in/from MDA-MB-231 cells were noticed for the BN analogs. BN4 and BN3 exhibited higher binding affinity, stability than BN1 and BN2. Highly specific in vivo uptakes to the tumor were clearly visualized by scintigraphy; rapid excretion from non-target tissues via kidneys suggests a higher tumor-to-background ratio. BN4, among all the analogs, stimulates the expression of angiogenic markers to a maximum. Conclusion Considering its most improved pharmacological characteristics, BN4 is thus considered as most promising probes for early non-invasive diagnosis of GRP receptor-positive breast tumors. Electronic supplementary material The online version of this article (10.1186/s13550-019-0493-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kakali De
- Infectious Diseases and Immunology Division (Nuclear Medicine Laboratory), CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, West Bengal, 700032, India.
| | - Dibyanti Mukherjee
- Infectious Diseases and Immunology Division (Nuclear Medicine Laboratory), CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, West Bengal, 700032, India
| | - Samarendu Sinha
- Regional Radiation Medicine Center, Thakurpukur Cancer Research Center and Welfare Home Campus, Kolkata, West Bengal, 700 060, India
| | - Shantanu Ganguly
- Regional Radiation Medicine Center, Thakurpukur Cancer Research Center and Welfare Home Campus, Kolkata, West Bengal, 700 060, India
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Zhuo L, Yang X, Liao W, Wang J, Wang H, Lv M, Wang G, Song H, Feng Y, Chen Y, Wei H, Yang Y, Zhao P. Comparative cell uptake study of FITC-/177Lu-labeled RM26 monomer, dimer and trimer on PC-3: improving binding affinity of gastrin releasing peptide receptor (GRPR) antagonist via bivalency/trivalency. J Radioanal Nucl Chem 2019. [DOI: 10.1007/s10967-018-6396-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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24
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Baratto L, Jadvar H, Iagaru A. Prostate Cancer Theranostics Targeting Gastrin-Releasing Peptide Receptors. Mol Imaging Biol 2019; 20:501-509. [PMID: 29256046 DOI: 10.1007/s11307-017-1151-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Gastrin-releasing peptide receptors (GRPRs), part of the bombesin (BBN) family, are aberrantly overexpressed in many cancers, including those of the breast, prostate, pancreas, and lung, and therefore present an attractive target for cancer diagnosis and therapy. Different bombesin analogs have been radiolabeled and used for imaging diagnosis, staging, evaluation of biochemical recurrence, and assessment of metastatic disease in patients with prostate cancer. Recently, interest has shifted from BBN-like receptor agonists to antagonists, because the latter does not induce adverse effects and demonstrate superior in vivo pharmacokinetics. We review the preclinical and clinical literatures on the use of GRPRs as targets for imaging and therapy of prostate cancer, with a focus on the newer developments and theranostic potential of GRPR peptides.
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Affiliation(s)
- Lucia Baratto
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Hossein Jadvar
- Department of Radiology, University of Southern California, 2250 Alcazar Street, CSC 102, Los Angeles, CA, 90033, USA.
| | - Andrei Iagaru
- Department of Radiology, Stanford University, Stanford, CA, USA
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25
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Rezazadeh F, Sadeghzadeh N. Tumor targeting with 99m Tc radiolabeled peptides: Clinical application and recent development. Chem Biol Drug Des 2018; 93:205-221. [PMID: 30299570 DOI: 10.1111/cbdd.13413] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 08/19/2018] [Accepted: 09/23/2018] [Indexed: 01/16/2023]
Abstract
Targeting overexpressed receptors on the cancer cells with radiolabeled peptides has become very important in nuclear oncology in the recent years. Peptides are small and have easy preparation and easy radiolabeling protocol with no side-effect and toxicity. These properties made them a valuable tool for tumor targeting. Based on the successful imaging of neuroendocrine tumors with 111 In-octreotide, other receptor-targeting peptides such as bombesin (BBN), cholecystokinin/gastrin analogues, neurotensin analogues, glucagon-like peptide-1, and RGD peptides are currently under development or undergoing clinical trials. The most frequently used radionuclides for tumor imaging are 99m Tc and 111 In for single-photon emission computed tomography and 68 Ga and 18 F for positron emission tomography imaging. This review presents some of the 99m Tc-labeled peptides, with regard to their potential for radionuclide imaging of tumors in clinical and preclinical application.
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Affiliation(s)
- Farzaneh Rezazadeh
- Department of Radiopharmacy, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran.,Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Nourollah Sadeghzadeh
- Department of Radiopharmacy, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran
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26
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Lymperis E, Kaloudi A, Sallegger W, Bakker IL, Krenning EP, de Jong M, Maina T, Nock BA. Radiometal-Dependent Biological Profile of the Radiolabeled Gastrin-Releasing Peptide Receptor Antagonist SB3 in Cancer Theranostics: Metabolic and Biodistribution Patterns Defined by Neprilysin. Bioconjug Chem 2018; 29:1774-1784. [PMID: 29664606 DOI: 10.1021/acs.bioconjchem.8b00225] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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 68Ga-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 switching 68Ga to 111In/177Lu-label on the biological properties of resulting radiopeptides. Notably, the bioavailability of 111In/177Lu-SB3 in mice drastically deteriorated compared with metabolically robust 68Ga-SB3, and as a result led to poorer 111In/177Lu-SB3 uptake in GRPR-positive PC-3 xenografts. The peptide cleavage sites were identified by chromatographic comparison of blood samples from mice intravenously receiving 111In/177Lu-SB3 with each of newly synthesized 111In/177Lu-SB3-fragments. Coinjection of the radioconjugates with the neprilysin (NEP)-inhibitor phosphoramidon led to full stabilization of 111In/177Lu-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 indistinguishable 68Ga/111In/177Lu-SB3 profiles in mice emphasizing the theranostic prospects of SB3 for clinical use.
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Affiliation(s)
- Emmanouil Lymperis
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-15310 Athens , Greece
| | - Aikaterini Kaloudi
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-15310 Athens , Greece
| | | | - Ingrid L Bakker
- Department of Radiology & Nuclear Medicine , Erasmus MC , 3015 CN Rotterdam , The Netherlands
| | - Eric P Krenning
- Cyclotron Rotterdam BV , Erasmus MC , 3015 CE Rotterdam , The Netherlands
| | - Marion de Jong
- Department of Radiology & Nuclear Medicine , Erasmus MC , 3015 CN Rotterdam , The Netherlands
| | - Theodosia Maina
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-15310 Athens , Greece
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-15310 Athens , Greece
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Evaluation of new 99mTc-labeled HYNIC-bombesin analogue for prostate cancer imaging. J Radioanal Nucl Chem 2018. [DOI: 10.1007/s10967-018-5819-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Nock BA, Charalambidis D, Sallegger W, Waser B, Mansi R, Nicolas GP, Ketani E, Nikolopoulou A, Fani M, Reubi JC, Maina T. New Gastrin Releasing Peptide Receptor-Directed [ 99mTc]Demobesin 1 Mimics: Synthesis and Comparative Evaluation. J Med Chem 2018. [PMID: 29517903 DOI: 10.1021/acs.jmedchem.8b00177] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have previously reported on the gastrin releasing peptide receptor (GRPR) antagonist [99mTc]1, ([99mTc]demobesin 1, 99mTc-[N4'-diglycolate-dPhe6,Leu-NHEt13]BBN(6-13)). [99mTc]1 has shown superior biological profile compared to analogous agonist-based 99mTc-radioligands. We herein present a small library of [99mTc]1 mimics generated after structural modifications in (a) the linker ([99mTc]2, [99mTc]3, [99mTc]4), (b) the peptide chain ([99mTc]5, [99mTc]6), and (c) the C-terminus ([99mTc]7 or [99mTc]8). The effects of above modifications on the biological properties of analogs were studied in PC-3 cells and tumor-bearing SCID mice. All analogs showed subnanomolar affinity for the human GRPR, while most receptor-affine 4 and 8 behaved as potent GRPR antagonists in a functional internalization assay. In mice bearing PC-3 tumors, [99mTc]1-[99mTc]6 exhibited GRPR-specific tumor uptake, rapidly clearing from normal tissues. [99mTc]4 displayed the highest tumor uptake (28.8 ± 4.1%ID/g at 1 h pi), which remained high even after 24 h pi (16.3 ± 1.8%ID/g), well surpassing that of [99mTc]1 (5.4 ± 0.7%ID/g at 24 h pi).
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Affiliation(s)
- Berthold A Nock
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-153 10 Athens , Greece
| | - David Charalambidis
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-153 10 Athens , Greece
| | | | - Beatrice Waser
- Cell Biology and Experimental Cancer Research, Institute of Pathology , University of Berne , CH-3010 Berne , Switzerland
| | | | | | - Eleni Ketani
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-153 10 Athens , Greece
| | - Anastasia Nikolopoulou
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-153 10 Athens , Greece
| | | | - Jean-Claude Reubi
- Cell Biology and Experimental Cancer Research, Institute of Pathology , University of Berne , CH-3010 Berne , Switzerland
| | - Theodosia Maina
- Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-153 10 Athens , Greece
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Peptide-Based Radiopharmaceuticals for Molecular Imaging of Prostate Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1096:135-158. [DOI: 10.1007/978-3-319-99286-0_8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Khan M, Huang T, Lin CY, Wu J, Fan BM, Bian ZX. Exploiting cancer's phenotypic guise against itself: targeting ectopically expressed peptide G-protein coupled receptors for lung cancer therapy. Oncotarget 2017; 8:104615-104637. [PMID: 29262666 PMCID: PMC5732832 DOI: 10.18632/oncotarget.18403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 05/23/2017] [Indexed: 02/07/2023] Open
Abstract
Lung cancer, claiming millions of lives annually, has the highest mortality rate worldwide. This advocates the development of novel cancer therapies that are highly toxic for cancer cells but negligibly toxic for healthy cells. One of the effective treatments is targeting overexpressed surface receptors of cancer cells with receptor-specific drugs. The receptors-in-focus in the current review are the G-protein coupled receptors (GPCRs), which are often overexpressed in various types of tumors. The peptide subfamily of GPCRs is the pivot of the current article owing to the high affinity and specificity to and of their cognate peptide ligands, and the proven efficacy of peptide-based therapeutics. The article summarizes various ectopically expressed peptide GPCRs in lung cancer, namely, Cholecystokinin-B/Gastrin receptor, the Bombesin receptor family, Bradykinin B1 and B2 receptors, Arginine vasopressin receptors 1a, 1b and 2, and the Somatostatin receptor type 2. The autocrine growth and pro-proliferative pathways they mediate, and the distinct tumor-inhibitory effects of somatostatin receptors are then discussed. The next section covers how these pathways may be influenced or 'corrected' through therapeutics (involving agonists and antagonists) targeting the overexpressed peptide GPCRs. The review proceeds on to Nano-scaled delivery platforms, which enclose chemotherapeutic agents and are decorated with peptide ligands on their external surface, as an effective means of targeting cancer cells. We conclude that targeting these overexpressed peptide GPCRs is potentially evolving as a highly promising form of lung cancer therapy.
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Affiliation(s)
- Mahjabin Khan
- Laboratory of Brain-Gut Research, School of Chinese Medicine, Hong Kong Baptist University, HKSAR, Kowloon Tong, P.R. China
| | - Tao Huang
- Laboratory of Brain-Gut Research, School of Chinese Medicine, Hong Kong Baptist University, HKSAR, Kowloon Tong, P.R. China
| | - Cheng-Yuan Lin
- Laboratory of Brain-Gut Research, School of Chinese Medicine, Hong Kong Baptist University, HKSAR, Kowloon Tong, P.R. China
- YMU-HKBU Joint Laboratory of Traditional Natural Medicine, Yunnan Minzu University, Kunming, P.R. China
| | - Jiang Wu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, P. R. China
| | - Bao-Min Fan
- YMU-HKBU Joint Laboratory of Traditional Natural Medicine, Yunnan Minzu University, Kunming, P.R. China
| | - Zhao-Xiang Bian
- Laboratory of Brain-Gut Research, School of Chinese Medicine, Hong Kong Baptist University, HKSAR, Kowloon Tong, P.R. China
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Ayati N, Lee ST, Zakavi R, Pathmaraj K, Al-Qatawna L, Poon A, Scott AM. Long-Acting Somatostatin Analog Therapy Differentially Alters 68Ga-DOTATATE Uptake in Normal Tissues Compared with Primary Tumors and Metastatic Lesions. J Nucl Med 2017; 59:223-227. [PMID: 28729431 DOI: 10.2967/jnumed.117.192203] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 06/28/2017] [Indexed: 12/17/2022] Open
Abstract
Synthetic somatostatin analogs have been posed as a potential source of error in somatostatin receptor imaging through interference with tumor detection; however, experimental models and clinical studies have shown a complex mechanism of the effect of octreotide on tumors. The aim of this study was to assess whether 68Ga-DOTATATE uptake before treatment with long-acting somatostatin analogs differs from that after treatment. Methods: Thirty patients (15 men; age [mean ± SD], 64.6 ± 13.4 y) who had intermediately differentiated to well-differentiated neuroendocrine tumors and who underwent 68Ga-DOTATATE PET/CT scanning before and after receiving long-acting repeatable octreotide (Sandostatin LAR) were included in the study. The SUVmax and SUVmean of healthy target organs, residual primary tumor, and up to 5 lesions with the highest SUVmax in each organ were compared before and after octreotide treatment. Results: The mean time interval between the 2 68Ga-DOTATATE studies was 9.6 ± 7.2 mo, and the mean time gap between the last Sandostatin LAR injection and the second 68Ga-DOTATATE study was 25.1 ± 14.8 d. The pretreatment mean SUVmax and SUVmean were both significantly higher in the thyroid, liver, and spleen (P < 0.05) than the values measured after the administration of Sandostatin LAR. No significant differences were found among the uptake indices for residual primary tumor or any metastatic lesions in the liver, bone, lung, or lymph nodes before and after Sandostatin LAR administration (P > 0.05). Conclusion: Long-acting octreotide treatment diminished 68Ga-DOTATATE uptake in the liver, spleen, and thyroid but did not compromise tracer uptake in residual primary tumor and metastatic lesions. These findings have a direct impact on the interpretation of 68Ga-DOTATATE PET/CT scans.
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Affiliation(s)
- Narjess Ayati
- Nuclear Medicine Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Sze Ting Lee
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Victoria, Australia
| | - Rasoul Zakavi
- Nuclear Medicine Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Kunthi Pathmaraj
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Victoria, Australia
| | - Louai Al-Qatawna
- Nuclear Medicine and Cyclotron Unit, King Hussein Medical Center, Jordanian Royal Medical Services, Amman, Jordan
| | - Aurora Poon
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Victoria, Australia
| | - Andrew M Scott
- Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, Victoria, Australia .,Olivia Newton-John Cancer Research Institute, and School of Cancer Medicine, La Trobe University, Melbourne, Australia; and.,Department of Medicine, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia
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Maina T, Nock BA, Kulkarni H, Singh A, Baum RP. Theranostic Prospects of Gastrin-Releasing Peptide Receptor–Radioantagonists in Oncology. PET Clin 2017; 12:297-309. [DOI: 10.1016/j.cpet.2017.02.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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33
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Maina T, Kaloudi A, Valverde IE, Mindt TL, Nock BA. Amide-to-triazole switch vs. in vivo NEP-inhibition approaches to promote radiopeptide targeting of GRPR-positive tumors. Nucl Med Biol 2017. [PMID: 28636973 DOI: 10.1016/j.nucmedbio.2017.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Radiolabeled bombesin (BBN)-analogs have been proposed for diagnosis and therapy of gastrin-releasing peptide receptor (GRPR)-expressing tumors, such as prostate, breast and lung cancer. Metabolic stability represents a crucial factor for the success of this approach by ensuring sufficient delivery of circulating radioligand to tumor sites. The amide-to-triazole switch on the backbone of DOTA-PEG4-[Nle14]BBN(7-14) (1) was reported to improve the in vitro stability of resulting 177Lu-radioligands. On the other hand, in-situ inhibition of neutral endopeptidase (NEP) by coinjection of phosphoramidon (PA) was shown to significantly improve the in vivo stability and tumor uptake of biodegradable radiopeptides. We herein compare the impact of the two methods on the bioavailability and localization of 177Lu-DOTA-PEG4-[Nle14]BBN(7-14) analogs in GRPR-positive tumors in mice. METHODS The 1,4-disubstituted [1-3]-triazole was used to replace one (2: Gly11-His12; 3: Ala9-Val10) or two (4: Ala9-Val10 and Gly11-His12) peptide bonds in 1 (reference) and all compounds were labeled with 177Lu. Each of [177Lu]1-[177Lu]4 was injected without (control) or with PA in healthy mice. Blood samples collected 5min post-injection (pi) were analyzed by HPLC. Biodistribution of [177Lu]1-[177Lu]4 was conducted in SCID mice bearing human prostate adenocarcinoma PC-3 xenografts at 4h pi. Groups of 4 animals were injected with radioligand, alone (controls), or with coinjection of PA, or of a mixture of PA and excess and [Tyr4]BBN to determine GRPR-specificity of uptake (Block). RESULTS The in vivo stability of the radioligands was: [177Lu]1 (25% intact), [177Lu]2 (45% intact), [177Lu]3 (30% intact) and [177Lu]4 (40% intact). By PA-coinjection these values notably increased to 90%-93%. Moreover, treatment with PA induced an impressive and GRPR-specific uptake of all radioligands in the PC-3 xenografts at 4h pi: [177Lu]1: 4.7±0.4 to 24.8±4.9%ID/g; [177Lu]2: 8.3±1.2 to 26.0±1.1%ID/g; [177Lu]3: 6.6±0.4 to 21.3±4.4%ID/g; and [177Lu]4: 4.8±1.6 to 13.7±3.8%ID/g. CONCLUSIONS This study has shown that amide-to-triazole substitutions in 177Lu-DOTA-PEG4-[Nle14]BBN(7-14) induced minor effects on bioavailability and tumor uptake in mice models, whereas in-situ NEP-inhibition(s) by PA impressively improved in vivo profiles.
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Affiliation(s)
- Theodosia Maina
- Molecular Radiopharmacy, INRASTES, National Center for Scientific Research "Demokritos", Athens, Greece
| | - Aikaterini Kaloudi
- Molecular Radiopharmacy, INRASTES, National Center for Scientific Research "Demokritos", Athens, Greece
| | - Ibai E Valverde
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR 6302 CNRS-UBFC, Université de Bourgogne Franche-Comté, Dijon, France
| | - Thomas L Mindt
- Department of Biomedical Imaging and Image Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria; Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Vienna, Austria.
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES, National Center for Scientific Research "Demokritos", Athens, Greece.
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Charron CL, Hickey JL, Nsiama TK, Cruickshank DR, Turnbull WL, Luyt LG. Molecular imaging probes derived from natural peptides. Nat Prod Rep 2017; 33:761-800. [PMID: 26911790 DOI: 10.1039/c5np00083a] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Covering: up to the end of 2015.Peptides are naturally occurring compounds that play an important role in all living systems and are responsible for a range of essential functions. Peptide receptors have been implicated in disease states such as oncology, metabolic disorders and cardiovascular disease. Therefore, natural peptides have been exploited as diagnostic and therapeutic agents due to the unique target specificity for their endogenous receptors. This review discusses a variety of natural peptides highlighting their discovery, endogenous receptors, as well as their derivatization to create molecular imaging agents, with an emphasis on the design of radiolabelled peptides. This review also highlights methods for discovering new and novel peptides when knowledge of specific targets and endogenous ligands are not available.
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Affiliation(s)
- C L Charron
- Department of Chemistry, The University of Western Ontario, London, Canada.
| | - J L Hickey
- Department of Chemistry, The University of Western Ontario, London, Canada.
| | - T K Nsiama
- London Regional Cancer Program, Lawson Health Research Institute, London, Canada
| | - D R Cruickshank
- Department of Chemistry, The University of Western Ontario, London, Canada.
| | - W L Turnbull
- Department of Chemistry, The University of Western Ontario, London, Canada.
| | - L G Luyt
- Department of Chemistry, The University of Western Ontario, London, Canada. and Departments of Oncology and Medical Imaging, The University of Western Ontario, London, Canada and London Regional Cancer Program, Lawson Health Research Institute, London, Canada
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Maina T, Nock BA. From Bench to Bed: New Gastrin-Releasing Peptide Receptor-Directed Radioligands and Their Use in Prostate Cancer. PET Clin 2017; 12:205-217. [PMID: 28267454 DOI: 10.1016/j.cpet.2016.12.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Gastrin-releasing peptide receptors (GRPRs) are overexpressed in prostate and breast cancer, and are therefore attractive molecular targets for diagnosis and therapy with radiolabeled GRPR-directed peptide probes. The amphibian tetradecapeptide bombesin or the mammalian gastrin-releasing peptide and neuromedin C have been modified with a variety of chelators. As a result, labeling with radiometals attractive for SPECT or PET imaging and for radionuclide therapy has led to the development of peptide radioligands suitable for in vivo targeting of prostate cancer. A shift of paradigm from internalizing GRPR-agonists to antagonists has occurred owing to the higher biosafety and superior pharmacokinetics of radioantagonists.
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Affiliation(s)
- Theodosia Maina
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Agia Paraskevi, Attikis, Athens 15310, Greece.
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Agia Paraskevi, Attikis, Athens 15310, Greece
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Feng Y, Phelps TE, Carroll V, Gallazzi F, Sieckman G, Hoffman TJ, Barnes CL, Ketring AR, Hennkens HM, Jurisson SS. Chemistry and radiochemistry of As, Re and Rh isotopes relevant to radiopharmaceutical applications: high specific activity radionuclides for imaging and treatment. Dalton Trans 2017; 46:14677-14690. [DOI: 10.1039/c7dt02407j] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Advances in production, separation, target recovery, and chelation chemistry of high specific activity radionuclides will promote new theranostic agent development.
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Affiliation(s)
- Yutian Feng
- Department of Chemistry
- University of Missouri
- Columbia
- USA
| | - Tim E. Phelps
- Department of Chemistry
- University of Missouri
- Columbia
- USA
| | | | - Fabio Gallazzi
- Structural Biology Core
- University of Missouri
- Columbia
- USA
| | - Gary Sieckman
- Research Division
- Harry S. Truman Memorial Veterans’ Hospital
- Columbia
- USA
| | | | | | - Alan R. Ketring
- University of Missouri Research Reactor Center (MURR)
- University of Missouri
- Columbia
- USA
| | - Heather M. Hennkens
- University of Missouri Research Reactor Center (MURR)
- University of Missouri
- Columbia
- USA
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Römhild K, Fischer CA, Mindt TL. Glycated 99m Tc-Tricarbonyl-Labeled Peptide Conjugates for Tumor Targeting by "Click-to-Chelate". ChemMedChem 2016; 12:66-74. [PMID: 27902882 DOI: 10.1002/cmdc.201600485] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 10/25/2016] [Indexed: 12/29/2022]
Abstract
Attaching polar pharmacological modifiers to molecular imaging probes is a common strategy to modulate their pharmacokinetic profiles to improve such parameters as the clearance rate of radiotracers and/or metabolites, and to enhance signal-to-background ratios. We combined the tumor-targeting peptide sequence of bombesin (BBN) with glucuronic acid and the single-photon emission computed tomography (SPECT) radionuclide 99m Tc by the "click-to-chelate" methodology. The 99m Tc-tricarbonyl-labeled glucuronated BBN conjugate was compared with a reference compound lacking the carbohydrate. The radiolabeled conjugates displayed similar characteristics in vitro (cell internalization, receptor affinity), but the hydrophilicity of the glycated version was significantly increased. While the tumor uptake of the two radioconjugates in xenografted mice was similar, the glycated peptide exhibited unexpected higher uptake in organs of the hepatobiliary excretion pathway than the more lipophilic reference compound. Control experiments suggest that this may be the result of unspecific accumulation of metabolites in which the glucuronic acid moiety does not act as an innocent pharmacological modifier.
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Affiliation(s)
- Karolin Römhild
- Division of Radiopharmaceutical Chemistry, University of Basel, Petersgraben 4, 4031, Basel, Switzerland
| | - Christiane A Fischer
- Division of Radiopharmaceutical Chemistry, University of Basel, Petersgraben 4, 4031, Basel, Switzerland
| | - Thomas L Mindt
- Division of Radiopharmaceutical Chemistry, University of Basel, Petersgraben 4, 4031, Basel, Switzerland.,Institute of Pharmaceutical Sciences, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland.,Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
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Popp I, Del Pozzo L, Waser B, Reubi JC, Meyer PT, Maecke HR, Gourni E. Approaches to improve metabolic stability of a statine-based GRP receptor antagonist. Nucl Med Biol 2016; 45:22-29. [PMID: 27865999 DOI: 10.1016/j.nucmedbio.2016.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 10/05/2016] [Accepted: 11/01/2016] [Indexed: 02/08/2023]
Abstract
The bombesin receptor family, in particular the gastrin-releasing peptide receptor (GRPr), is an attractive target in the field of nuclear oncology due to the high density of these receptors on the cell surface of several human tumors. The successful clinical implementation of 64Cu-CB-TE2A-AR06, 68Ga-RM2 and 68Ga-NODAGA-MJ9, prompted us to continue the development of GRPr-antagonists. The aim of the present study was to assess if N-terminal modulations of the statine-based GRPr-antagonist influence the binding affinity, the pharmacokinetic performance and the in vivo metabolic stability. METHODS The GRPr-antagonist (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) was functionalized with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) via the spacer 4-amino-1-carboxymethyl-piperidine (Pip) and the amino acid N-Methyl-β-Ala, to obtain NMe-RM2 and labeled with 68Ga and 177Lu. The GRPr affinity of the corresponding metalloconjugates determined using [125I-Tyr4]-BN as radioligand. In vitro evaluation included internalization studies using PC3 cells. The 68Ga-conjugate was evaluated in PC3 xenografts by biodistribution and PET studies, while investigations on the metabolic stability and plasma protein binding were performed. RESULTS The half maximum inhibitory concentrations (IC50) of the metalloconjugates, using [125I-Tyr4]-BN, are in the low nanomolar range. PC3-cell culture binding studies of both metallated NMe-RM2 and RM2 show high GRPr-bound activity and low internalization. Metabolic studies showed that 68Ga-NMe-RM2 and 68Ga-RM2 are being cleaved in a similar fashion into three metabolites, with a good proportion of about 50% of the remaining blood activity at 15min post injection (p.i.) being represented by the intact radiotracer. 68Ga-NMe-RM2 was shown to target specifically PC3 xenografts, with high and sustained tumor uptake of about 13% IA/g within a time frame of 3h. The PET images clearly visualized the tumor. CONCLUSIONS The relatively high percentage of the remaining intact radiotracer in blood 15min post injection sufficiently enables in vivo targeting of GRPr positive tumors, finding which has been also shown in clinical trials.
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Affiliation(s)
- Ilinca Popp
- Department of Nuclear Medicine, University Hospital Freiburg, Germany
| | - Luigi Del Pozzo
- Department of Nuclear Medicine, University Hospital Freiburg, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany; German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Beatrice Waser
- Department of Pathology, University Hospital Bern, Bern, Switzerland
| | - Jean Claude Reubi
- Department of Pathology, University Hospital Bern, Bern, Switzerland
| | - Philipp T Meyer
- Department of Nuclear Medicine, University Hospital Freiburg, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany; German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Helmut R Maecke
- Department of Nuclear Medicine, University Hospital Freiburg, Germany
| | - Eleni Gourni
- Department of Nuclear Medicine, University Hospital Freiburg, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany; German Cancer Research Center (DKFZ), Heidelberg, Germany,.
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van der Kroon I, Joosten L, Nock BA, Maina T, Boerman OC, Brom M, Gotthardt M. Improved Quantification of the Beta Cell Mass after Pancreas Visualization with 99mTc-demobesin-4 and Beta Cell Imaging with 111In-exendin-3 in Rodents. Mol Pharm 2016; 13:3478-3483. [PMID: 27537699 DOI: 10.1021/acs.molpharmaceut.6b00495] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
OBJECTIVE Accurate assessment of the 111In-exendin-3 uptake within the pancreas requires exact delineation of the pancreas, which is highly challenging by MRI and CT in rodents. In this study, the pancreatic tracer 99mTc-demobesin-4 was evaluated for accurate delineation of the pancreas to be able to accurately quantify 111In-exendin-3 uptake within the pancreas. METHODS Healthy and alloxan-induced diabetic Brown Norway rats were injected with the pancreatic tracer 99mTc-demobesin-4 ([99mTc-N4-Pro1,Tyr4,Nle14]bombesin) and the beta cell tracer 111In-exendin-3 ([111In-DTPA-Lys40]exendin-3). After dual isotope acquisition of SPECT images, 99mTc-demobesin-4 was used to define a volume of interest for the pancreas in SPECT images subsequently the 111In-exendin-3 uptake within this region was quantified. Furthermore, biodistribution and autoradiography were performed in order to gain insight in the distribution of both tracers in the animals. RESULTS 99mTc-demobesin-4 showed high accumulation in the pancreas. The uptake was highly homogeneous throughout the pancreas, independent of diabetic status, as demonstrated by autoradiography, whereas 111In-exendin-3 only accumulates in the islets of Langerhans. Quantification of both ex vivo and in vivo SPECT images resulted in an excellent linear correlation between the pancreatic uptake, determined with ex vivo counting and 111In-exendin-3 uptake, determined from the quantitative analysis of the SPECT images (Pearson r = 0.97, Pearson r = 0.92). CONCLUSION 99mTc-demobesin-4 shows high accumulation in the pancreas of rats. It is a suitable tracer for accurate delineation of the pancreas and can be conveniently used for simultaneous acquisition with 111In labeled exendin-3. This method provides a straightforward, reliable, and objective method for preclinical beta cell mass (BCM) quantification with 111In-exendin-3.
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Affiliation(s)
- Inge van der Kroon
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Lieke Joosten
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES, NCSR Demokritos, GR-153 10 Agia Paraskevi, Attikis, Athens, Greece
| | - Theodosia Maina
- Molecular Radiopharmacy, INRASTES, NCSR Demokritos, GR-153 10 Agia Paraskevi, Attikis, Athens, Greece
| | - Otto C Boerman
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Maarten Brom
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Martin Gotthardt
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , PO Box 9101, 6500 HB Nijmegen, The Netherlands
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Nock BA, Kaloudi A, Lymperis E, Giarika A, Kulkarni HR, Klette I, Singh A, Krenning EP, de Jong M, Maina T, Baum RP. Theranostic Perspectives in Prostate Cancer with the Gastrin-Releasing Peptide Receptor Antagonist NeoBOMB1: Preclinical and First Clinical Results. J Nucl Med 2016; 58:75-80. [DOI: 10.2967/jnumed.116.178889] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 07/13/2016] [Indexed: 12/22/2022] Open
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Valverde IE, Vomstein S, Mindt TL. Toward the Optimization of Bombesin-Based Radiotracers for Tumor Targeting. J Med Chem 2016; 59:3867-77. [PMID: 27054526 DOI: 10.1021/acs.jmedchem.6b00025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The peptide bombesin (BBN) is a peptide with high affinity for the gastrin-releasing peptide receptor (GRPr), a receptor that is overexpressed by, for example, breast and prostate cancers. Thus, GRPr agonists can be used as cancer-targeting vectors to shuttle diagnostic and therapeutic agents into tumor cells. With the aim of optimizing the tumor targeting properties of a radiolabeled [Nle(14)]BBN(7-14) moiety, novel BBN(7-14)- and BBN(6-14)-based radioconjugates were synthesized, labeled with Lu-177, and fully evaluated in vitro and in vivo. The effect of residue and backbone modification on several parameters such as the internalization of the radiolabeled peptides into PC3 and AR42J tumor cells, their affinity toward the human GRPr, metabolic stability in blood plasma, and biodistribution in mice bearing GRPr-expressing PC3 xenografts was studied. As a result of our investigations, a novel radiolabeled GRPr agonist with a high tumor uptake and a high tumor-to-kidney ratio was identified.
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Affiliation(s)
- Ibai E Valverde
- Division of Radiopharmaceutical Chemistry, University of Basel Hospital , Petersgraben 4, 4031 Basel, Switzerland
| | - Sandra Vomstein
- Division of Radiopharmaceutical Chemistry, University of Basel Hospital , Petersgraben 4, 4031 Basel, Switzerland
| | - Thomas L Mindt
- Division of Radiopharmaceutical Chemistry, University of Basel Hospital , Petersgraben 4, 4031 Basel, Switzerland.,Ludwig Boltzmann Institute for Applied Diagnostics, General Hospital of Vienna , Währinger Gürtel 18-20, A-1090 Vienna, Austria
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Maina T, Bergsma H, Kulkarni HR, Mueller D, Charalambidis D, Krenning EP, Nock BA, de Jong M, Baum RP. Preclinical and first clinical experience with the gastrin-releasing peptide receptor-antagonist [⁶⁸Ga]SB3 and PET/CT. Eur J Nucl Med Mol Imaging 2015; 43:964-973. [PMID: 26631238 DOI: 10.1007/s00259-015-3232-1] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 10/15/2015] [Indexed: 01/07/2023]
Abstract
PURPOSE Gastrin-releasing peptide receptors (GRPR) represent attractive targets for tumor diagnosis and therapy because of their overexpression in major human cancers. Internalizing GRPR agonists were initially proposed for prolonged lesion retention, but a shift of paradigm to GRPR antagonists has recently been made. Surprisingly, radioantagonists, such as [(99m)Tc]DB1 ((99m)Tc-N4'-DPhe(6),Leu-NHEt(13)]BBN(6-13)), displayed better pharmacokinetics than radioagonists, in addition to their higher inherent biosafety. We introduce here [(68)Ga]SB3, a [(99m)Tc]DB1 mimic-carrying, instead of the (99m)Tc-binding tetraamine, the chelator DOTA for labeling with the PET radiometal (68)Ga. METHODS Competition binding assays of SB3 and [(nat)Ga]SB3 were conducted against [(125)I-Tyr(4)]BBN in PC-3 cell membranes. Blood samples collected 5 min postinjection (pi) of the [(67)Ga]SB3 surrogate in mice were analyzed using high-performance liquid chromatography (HPLC) for degradation products. Likewise, biodistribution was performed after injection of [(67)Ga]SB3 (37 kBq, 100 μL, 10 pmol peptide) in severe combined immunodeficiency (SCID) mice bearing PC-3 xenografts. Eventually, [(68)Ga]SB3 (283 ± 91 MBq, 23 ± 7 nmol) was injected into 17 patients with breast (8) and prostate (9) cancer. All patients had disseminated disease and had received previous therapies. PET/CT fusion images were acquired 60-115 min pi. RESULTS SB3 and [(nat)Ga]SB3 bound to the human GRPR with high affinity (IC50: 4.6 ± 0.5 nM and 1.5 ± 0.3 nM, respectively). [(67)Ga]SB3 displayed good in vivo stability (>85 % intact at 5 min pi). [(67)Ga]SB3 showed high, GRPR-specific and prolonged retention in PC-3 xenografts (33.1 ± 3.9%ID/g at 1 h pi - 27.0 ± 0.9%ID/g at 24 h pi), but much faster clearance from the GRPR-rich pancreas (≈160%ID/g at 1 h pi to <17%ID/g at 24 h pi) in mice. In patients, [(68)Ga]SB3 elicited no adverse effects and clearly visualized cancer lesions. Thus, 4 out of 8 (50 %) breast cancer and 5 out of 9 (55 %) prostate cancer patients showed pathological uptake on PET/CT with [(68)Ga]SB3. CONCLUSION [(67)Ga]SB3 showed excellent pharmacokinetics in PC-3 tumor-bearing mice, while [(68)Ga]SB3 PET/CT visualized lesions in about 50 % of patients with advanced and metastasized prostate and breast cancer. We expect imaging with [(68)Ga]SB3 to be superior in patients with primary breast or prostate cancer.
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Affiliation(s)
- Theodosia Maina
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Ag. Paraskevi Attikis, 15310, Athens, Greece.
| | - Hendrik Bergsma
- Department of Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands
| | - Harshad R Kulkarni
- Molecular Radiotherapy and Molecular Imaging, Zentralklinik, Bad Berka, Germany
| | - Dirk Mueller
- Molecular Radiotherapy and Molecular Imaging, Zentralklinik, Bad Berka, Germany
| | - David Charalambidis
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Ag. Paraskevi Attikis, 15310, Athens, Greece
| | - Eric P Krenning
- Department of Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Ag. Paraskevi Attikis, 15310, Athens, Greece
| | - Marion de Jong
- Department of Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands.,Department of Radiology, Erasmus MC, Rotterdam, The Netherlands
| | - Richard P Baum
- Molecular Radiotherapy and Molecular Imaging, Zentralklinik, Bad Berka, Germany
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Valverde IE, Vomstein S, Fischer CA, Mascarin A, Mindt TL. Probing the Backbone Function of Tumor Targeting Peptides by an Amide-to-Triazole Substitution Strategy. J Med Chem 2015; 58:7475-84. [DOI: 10.1021/acs.jmedchem.5b00994] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Ibai E. Valverde
- Division
of Radiopharmaceutical Chemistry, University of Basel Hospital, Petersgraben
4, 4031 Basel, Switzerland
| | - Sandra Vomstein
- Division
of Radiopharmaceutical Chemistry, University of Basel Hospital, Petersgraben
4, 4031 Basel, Switzerland
| | - Christiane A. Fischer
- Division
of Radiopharmaceutical Chemistry, University of Basel Hospital, Petersgraben
4, 4031 Basel, Switzerland
| | - Alba Mascarin
- Division
of Radiopharmaceutical Chemistry, University of Basel Hospital, Petersgraben
4, 4031 Basel, Switzerland
| | - Thomas L. Mindt
- Division
of Radiopharmaceutical Chemistry, University of Basel Hospital, Petersgraben
4, 4031 Basel, Switzerland
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Pandey U, Mukherjee A, Jindal A, Gamre N, Korde A, Ram R, Sarma HD, Dash A. Preparation and evaluation of a single vial AMBA kit for 68Ga labeling with potential for imaging of GRP receptor-positive cancers. J Radioanal Nucl Chem 2015. [DOI: 10.1007/s10967-015-4290-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Carlucci G, Kuipers A, Ananias HJK, de Paula Faria D, Dierckx RAJO, Helfrich W, Rink R, Moll GN, de Jong IJ, Elsinga PH. GRPR-selective PET imaging of prostate cancer using [(18)F]-lanthionine-bombesin analogs. Peptides 2015; 67:45-54. [PMID: 25797109 DOI: 10.1016/j.peptides.2015.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 03/02/2015] [Accepted: 03/09/2015] [Indexed: 01/20/2023]
Abstract
The gastrin-releasing peptide receptor (GRPR) is overexpressed in a variety of human malignancies, including prostate cancer. Bombesin (BBN) is a 14 amino acids peptide that selectively binds to GRPR. In this study, we developed two novel Al(18)F-labeled lanthionine-stabilized BBN analogs, designated Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN, for positron emission tomography (PET) imaging of GRPR expression using xenograft prostate cancer models. (Methyl)lanthionine-stabilized 4,7-lanthionine-BBN and 2,6-lanthionine-BBN analogs were conjugated with a NOTA chelator and radiolabeled with Al(18)F using the aluminum fluoride strategy. Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN was labeled with Al(18)F with good radiochemical yield and specific activity>30 GBq/μmol for both radiotracers. The logD values measured for Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN were -2.14 ± 0.14 and -2.34 ± 0.15, respectively. In athymic nude PC-3 xenografts, at 120 min post injection (p.i.), the uptake of Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN in prostate cancer (PC-3) mouse models was 0.82 ± 0.23% ID/g and 1.40 ± 0.81% ID/g, respectively. An excess of unlabeled ɛ-aminocaproic acid-BBN(7-14) (300-fold) was co-injected to assess GRPR binding specificity. Tumor uptake of Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN in PC-3 tumors was evaluated by microPET (μPET) imaging at 30, 60 and 120 min p.i. Blocking studies showed decreased uptake in PC-3 bearing mice. Stabilized 4,7-lanthionine-BBN and 2,6-lanthionine-BBN peptides were rapidly and successfully labeled with (18)F. Both tracers may have potential for GRPR-positive tumor imaging.
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Affiliation(s)
- G Carlucci
- Department of Urology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - A Kuipers
- Lanthio Pharma, Groningen, The Netherlands
| | - H J K Ananias
- Department of Urology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - D de Paula Faria
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - R A J O Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - W Helfrich
- Surgical Research Laboratory, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - R Rink
- Lanthio Pharma, Groningen, The Netherlands
| | - G N Moll
- Lanthio Pharma, Groningen, The Netherlands; Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - I J de Jong
- Department of Urology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - P H Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
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Mansi R, Abiraj K, Wang X, Tamma ML, Gourni E, Cescato R, Berndt S, Reubi JC, Maecke HR. Evaluation of three different families of bombesin receptor radioantagonists for targeted imaging and therapy of gastrin releasing peptide receptor (GRP-R) positive tumors. J Med Chem 2014; 58:682-91. [PMID: 25474596 DOI: 10.1021/jm5012066] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two new classes of radiolabeled GRP receptor antagonists are studied and compared with the well-established statine-based receptor antagonist DOTA-4-amino-1-carboxymethylpiperidine-d-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 (RM2, 1; DOTA:1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid; Sta:(3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid). The bombesin-based pseudopeptide DOTA-4-amino-1-carboxymethylpiperidine-d-Phe-Gln-Trp-Ala-Val-Gly-His-Leuψ(CHOH-CH2)-(CH2)2-CH3 (RM7, 2), and the methyl ester DOTA-4-amino-1-carboxymethylpiperidine-d-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-OCH3 (ARBA05, 3) analogues are labeled with (111)In and evaluated in vitro in PC-3 cell line and in vivo in PC-3 tumor-bearing nude mice. Antagonist potency was assessed by immunofluorescence-based receptor internalization and Ca(2+) mobilization assays. The conjugates showed good binding affinity, the IC50 value of 2 (3.2 ± 1.8 nM) being 2 and 10 times lower than 1 and 3. Compared to (111)In-1, (111)In-2 showed higher uptake in target tissues such as pancreas (1.5 ± 0.5%IA/g and 39.8 ± 9.3%IA/g at 4 h, respectively), whereas the compounds had similar tumor uptake (11.5 ± 2.4%IA/g and 11.8 ± 3.9%IA/g at 4h, respectively). The displacement of the radioligand in vivo was different in different receptor positive organs and depended on the displacing peptide.
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Affiliation(s)
- Rosalba Mansi
- Division of Radiological Chemistry, University Hospital Basel , Petersgraben 4, CH-4031 Basel, Switzerland
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Lim JC, Cho EH, Kim JJ, Choi SM, Lee SY, Nam SS, Park UJ, Park SH. Biological evaluation of (177)Lu-labeled DOTA-Ala(SO3H)-Aminooctanoyl-Gln-Trp-Ala-Val-N methyl Gly-His-Statine-Leu-NH2 for gastrin-releasing peptide receptor-positive prostate tumor targeting. Nucl Med Biol 2014; 42:131-6. [PMID: 25457455 DOI: 10.1016/j.nucmedbio.2014.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 10/07/2014] [Accepted: 10/09/2014] [Indexed: 12/22/2022]
Abstract
Bombesin binds with selectivity and high affinity to a Gastrin-releasing peptide receptor (GRPR), which is highly overexpressed in prostate cancer cells. The present study describes the in vitro and in vivo biological characteristics of DOTA-Ala(SO3H)-Aminooctanoyl-Gln-Trp-Ala-Val-N methyl Gly-His-Statine-Leu-NH2 (DOTA-sBBNA), an antagonist analogue of bombesin peptide for the targeting of GRPR. DOTA-sBBNA was synthesized and labeled with (177)Lu as previously published. A saturation assay on PC-3 human prostate cancer cells revealed that the Kd value of the radiolabeled peptide was 1.88 nM with a maximum binding capacity (Bmax) of 289.3 fmol/10(6) cells. The radio-peptide slowly internalized, and 24.4±0.5% of the total binding was internalized in 4hr. Biodistribution studies were conducted in healthy and PC-3 xenografted balb/c mice, which showed high uptake and retention of tumor-associated radioactivity in PC-3 xenografted mice. The tumor-to-blood ratio was 126.02±9.36 at 1.5hr p.i., and was increased to 216.33±61.58 at 24hr p.i., which means that the radiolabeled peptide was highly accumulated in a tumor and rapidly cleared from the blood pool. The GRPR is also over-expressed in Korean prostate cancer patients. These results suggest that this (177)Lu-labeled peptide has promising characteristics for application in nuclear medicine, namely for the diagnosis and treatment of GRPR over-expressing prostate tumors.
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Affiliation(s)
- Jae Cheong Lim
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea; Bio-therapy Human Resources Center, Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Republic of Korea.
| | - Eun Ha Cho
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Jin Joo Kim
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Sang Mu Choi
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - So young Lee
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Sung Soo Nam
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Ul Jae Park
- Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
| | - Soo Hyun Park
- Bio-therapy Human Resources Center, Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Republic of Korea.
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Stott Reynolds TJ, Schehr R, Liu D, Xu J, Miao Y, Hoffman TJ, Rold TL, Lewis MR, Smith CJ. Characterization and evaluation of DOTA-conjugated Bombesin/RGD-antagonists for prostate cancer tumor imaging and therapy. Nucl Med Biol 2014; 42:99-108. [PMID: 25459113 DOI: 10.1016/j.nucmedbio.2014.10.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 09/30/2014] [Accepted: 10/06/2014] [Indexed: 12/18/2022]
Abstract
INTRODUCTION Here we present the metallation, characterization, in vivo and in vitro evaluations of dual-targeting, peptide-based radiopharmaceuticals with utility for imaging and potentially treating prostate tumors by virtue of their ability to target the αVβ3 integrin or the gastrin releasing peptide receptor (GRPr). METHODS [RGD-Glu-6Ahx-RM2] (RGD: Arg-Gly-Asp; Glu: glutamic acid; 6-Ahx: 6-amino hexanoic acid; RM2: (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2)) was conjugated to a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) bifunctional chelator (BFCA) purified via reversed-phase high-performance liquid chromatography (RP-HPLC), characterized by electrospray ionization-mass spectrometry (ESI-MS), and radiolabeled with (111)In or (177)Lu. Natural-metallated compounds were assessed for binding affinity for the αVβ3 integrin or GRPr in human glioblastoma U87-MG and prostate PC-3 cell lines and stability prior to in vivo evaluation in normal CF-1 mice and SCID mice xenografted with PC-3 cells. RESULTS Competitive displacement binding assays with PC-3 and U87-MG cells revealed high to moderate binding affinity for the GRPr or the αVβ3 integrin (IC50 range of 5.39±1.37 nM to 9.26±0.00 nM in PC-3 cells, and a range of 255±47 nM to 321±85 nM in U87-MG cells). Biodistribution studies indicated high tumor uptake in PC-3 tumor-bearing mice (average of 7.40±0.53% ID/g at 1h post-intravenous injection) and prolonged retention of tracer (mean of 4.41±0.91% ID/g at 24h post-intravenous injection). Blocking assays corroborated the specificity of radioconjugates for each target. Micro-single photon emission computed tomography (microSPECT) confirmed favorable radiouptake profiles in xenografted mice at 20h post-injection. CONCLUSIONS [RGD-Glu-[(111)In-DO3A]-6-Ahx-RM2] and [RGD-Glu-[(177)Lu- DO3A]-6-Ahx-RM2] show favorable pharmacokinetic and radiouptake profiles, meriting continued evaluation for molecular imaging in murine U87-MG/PC-3 xenograft models and radiotherapy studies with (177)Lu and (90)Y conjugates. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE These heterovalent, peptide-targeting ligands perform comparably with many mono- and multivalent conjugates with the potential benefit of increased sensitivity for detecting cancer cells exhibiting differential expression of target receptors.
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Affiliation(s)
- Tamila J Stott Reynolds
- Research Division, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri, United States, 65201; Department of Veterinary Pathobiology, Comparative Medicine Program, University of Missouri College of Veterinary Medicine, Columbia, MO, United States, 65211.
| | - Rebecca Schehr
- Veterinary Research Scholars Program, University of Missouri College of Veterinary Medicine, Columbia, MO, United States, 65211
| | - Dijie Liu
- Research Division, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri, United States, 65201; Department of Radiology, University of Missouri School of Medicine, Columbia, MO, United States, 65211
| | - Jingli Xu
- College of Pharmacy, University of New Mexico, Albuquerque, NM, United States, 87131
| | - Yubin Miao
- College of Pharmacy, University of New Mexico, Albuquerque, NM, United States, 87131; Cancer Research and Treatment Center, University of New Mexico, Albuquerque, NM, United States, 87131; Department of Dermatology, University of New Mexico, Albuquerque, NM, United States, 87131
| | - Timothy J Hoffman
- Research Division, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri, United States, 65201; Department of Internal Medicine, University of Missouri School of Medicine, Columbia, MO, United States, 65211; Department of Chemistry, University of Missouri, Columbia, MO, United States, 65211
| | - Tammy L Rold
- Research Division, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri, United States, 65201; Department of Internal Medicine, University of Missouri School of Medicine, Columbia, MO, United States, 65211
| | - Michael R Lewis
- Research Division, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri, United States, 65201; Department of Radiology, University of Missouri School of Medicine, Columbia, MO, United States, 65211
| | - Charles J Smith
- Research Division, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri, United States, 65201; Department of Radiology, University of Missouri School of Medicine, Columbia, MO, United States, 65211; University of Missouri Research Reactor Center, University of Missouri, Columbia, MO, United States, 65211.
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Gourni E, Mansi R, Jamous M, Waser B, Smerling C, Burian A, Buchegger F, Reubi JC, Maecke HR. N-Terminal Modifications Improve the Receptor Affinity and Pharmacokinetics of Radiolabeled Peptidic Gastrin-Releasing Peptide Receptor Antagonists: Examples of 68Ga- and 64Cu-Labeled Peptides for PET Imaging. J Nucl Med 2014; 55:1719-25. [DOI: 10.2967/jnumed.114.141242] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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Varasteh Z, Rosenström U, Velikyan I, Mitran B, Altai M, Honarvar H, Rosestedt M, Lindeberg G, Sörensen J, Larhed M, Tolmachev V, Orlova A. The effect of mini-PEG-based spacer length on binding and pharmacokinetic properties of a 68Ga-labeled NOTA-conjugated antagonistic analog of bombesin. Molecules 2014; 19:10455-72. [PMID: 25036155 PMCID: PMC6270800 DOI: 10.3390/molecules190710455] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 07/10/2014] [Accepted: 07/11/2014] [Indexed: 11/25/2022] Open
Abstract
The overexpression of gastrin-releasing peptide receptor (GRPR) in cancer can be used for peptide-receptor mediated radionuclide imaging and therapy. We have previously shown that an antagonist analog of bombesin RM26 conjugated to 1,4,7-triazacyclononane-N,N',N''-triacetic acid (NOTA) via a diethyleneglycol (PEG2) spacer (NOTA-PEG2-RM26) and labeled with 68Ga can be used for imaging of GRPR-expressing tumors. In this study, we evaluated if a variation of mini-PEG spacer length can be used for optimization of targeting properties of the NOTA-conjugated RM26. A series of analogs with different PEG-length (n = 2, 3, 4, 6) was synthesized, radiolabeled and evaluated in vitro and in vivo. The IC50 values of natGa-NOTA-PEGn-RM26 (n = 2, 3, 4, 6) were 3.1 ± 0.2, 3.9 ± 0.3, 5.4 ± 0.4 and 5.8 ± 0.3 nM, respectively. In normal mice all conjugates demonstrated similar biodistribution pattern, however 68Ga-NOTA-PEG3-RM26 showed lower liver uptake. Biodistribution of 68Ga-NOTA-PEG3-RM26 was evaluated in nude mice bearing PC-3 (prostate cancer) and BT-474 (breast cancer) xenografts. High uptake in tumors (4.6 ± 0.6%ID/g and 2.8 ± 0.4%ID/g for PC-3 and BT-474 xenografts, respectively) and high tumor-to-background ratios (tumor/blood of 44 ± 12 and 42 ± 5 for PC-3 and BT-474 xenografts, respectively) were found already at 2 h p.i. of 68Ga-NOTA-PEG3-RM26. Results of this study suggest that variation in the length of the PEG spacer can be used for optimization of targeting properties of peptide-chelator conjugates. However, the influence of the mini-PEG length on biodistribution is minor when di-, tri-, tetra- and hexaethylene glycol are compared.
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Affiliation(s)
- Zohreh Varasteh
- Preclinical PET Platform, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
| | - Ulrika Rosenström
- Organic Pharmaceutical Chemistry, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
| | - Irina Velikyan
- Preclinical PET Platform, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
| | - Bogdan Mitran
- Preclinical PET Platform, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
| | - Mohamed Altai
- Biomedical Radiation Sciences, Department of Radiology, Oncology and Radiation Sciences, Faculty of Medicine, Uppsala University, Uppsala SE-751 85, Sweden
| | - Hadis Honarvar
- Biomedical Radiation Sciences, Department of Radiology, Oncology and Radiation Sciences, Faculty of Medicine, Uppsala University, Uppsala SE-751 85, Sweden
| | - Maria Rosestedt
- Preclinical PET Platform, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
| | - Gunnar Lindeberg
- Organic Pharmaceutical Chemistry, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
| | - Jens Sörensen
- Biomedical Radiation Sciences, Department of Radiology, Oncology and Radiation Sciences, Faculty of Medicine, Uppsala University, Uppsala SE-751 85, Sweden
| | - Mats Larhed
- Department of Medicinal Chemistry, Science for Life Laboratory, BMC, Uppsala University, Uppsala SE-751 23, Sweden
| | - Vladimir Tolmachev
- Biomedical Radiation Sciences, Department of Radiology, Oncology and Radiation Sciences, Faculty of Medicine, Uppsala University, Uppsala SE-751 85, Sweden.
| | - Anna Orlova
- Preclinical PET Platform, Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala University, Uppsala SE-751 23, Sweden
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