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Wang L, Zhang H, Huang W, Han Z, Xu H, Gu Y. Development of a novel EphA2-targeting radioligand for SPECT imaging in different tumor models. Eur J Med Chem 2024; 265:116105. [PMID: 38154255 DOI: 10.1016/j.ejmech.2023.116105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 12/21/2023] [Accepted: 12/25/2023] [Indexed: 12/30/2023]
Abstract
The erythropoietin-producing hepatoma A2 receptor (EphA2) is a tyrosine kinase, which is overexpressed in tumors while having lower expression in normal tissues, making it an excellent target for tumor diagnosis and treatment. Peptide radiotracers offer unique advantages in tumor diagnosis and therapy and have been approved for clinical use. In this study, a high-affinity EPHA2-targeted radiotracer, 99mTc-HYNIC-PEG4-EPH-3, was developed and designed based on linear peptides. 99mTc-HYNIC-PEG4-EPH-3 exhibited superior water solubility and stability. And 99mTc-HYNIC-PEG4-EPH-3 could specifically target EphA2-expressing tumors, particularly with a tumor-to-non-target (T/NT) ratio >4.7 excluding kidneys. As a result of excellent biodistribution and tumor targeting capability of 99mTc-HYNIC-PEG4-EPH-3, it might be a promising candidate drug for clinical diagnosis of EphA2-overexpressing tumors.
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Affiliation(s)
- Li Wang
- State Key Laboratory of Natural Medicine, Department of Biomedical Engineering, School of Engineering, China Pharmaceutical University, No. 24 Tongjia Lane, Gulou District, Nanjing, 211198, China
| | - Hao Zhang
- State Key Laboratory of Natural Medicine, Department of Biomedical Engineering, School of Engineering, China Pharmaceutical University, No. 24 Tongjia Lane, Gulou District, Nanjing, 211198, China
| | - Wenjing Huang
- State Key Laboratory of Natural Medicine, Department of Biomedical Engineering, School of Engineering, China Pharmaceutical University, No. 24 Tongjia Lane, Gulou District, Nanjing, 211198, China
| | - Zhihao Han
- State Key Laboratory of Natural Medicine, Department of Biomedical Engineering, School of Engineering, China Pharmaceutical University, No. 24 Tongjia Lane, Gulou District, Nanjing, 211198, China.
| | - Haoran Xu
- State Key Laboratory of Natural Medicine, Department of Biomedical Engineering, School of Engineering, China Pharmaceutical University, No. 24 Tongjia Lane, Gulou District, Nanjing, 211198, China.
| | - Yueqing Gu
- State Key Laboratory of Natural Medicine, Department of Biomedical Engineering, School of Engineering, China Pharmaceutical University, No. 24 Tongjia Lane, Gulou District, Nanjing, 211198, China.
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2
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Gan Q, Cui K, Cao Q, Zhang N, Yang MF, Yang X. Development of a 18F-Labeled Bicyclic Peptide Targeting EphA2 for Molecular Imaging of PSMA-Negative Prostate Cancer. J Med Chem 2023; 66:14623-14632. [PMID: 37908059 DOI: 10.1021/acs.jmedchem.3c01135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Although PSMA PET/CT imaging has great potential for noninvasively detecting prostate cancer (PCa), limitations exist for patients with low PSMA expression, caused by androgen deprivation treatment or neuroendocrine differentiation. Analysis of The Cancer Genome Atlas Prostate Adenocarcinoma (TCGA-PRAD) data found that erythropoietin-producing hepatocellular receptor A2 (EphA2), a receptor overexpressed in most PCa could be a potential target for PSMA-negative PCa. A fluorescent ligand ETF and a radiolabeled ligand [18F]AlF-ETN derived from a EphA2-targeting bicyclic peptide were synthesized and investigated. ETF could selectively stain and visualize the EphA2-positive but PSMA-negative PC3 cells, in complementary to the PSMA-targeting probe. PET/CT imaging and biodistribution experiments demonstrated that [18F]AlF-ETN specifically accumulated in PC3 tumors with a high contrast (tumor-to-muscle ratio: 21.29 ± 6.55). In conclusion, we have demonstrated the potential for using EphA2 to detect PSMA-negative PCa and developed a radiolabeled ligand [18F]AlF-ETN to specifically image EphA2 expressing PCa with high contrast.
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Affiliation(s)
- Qianqian Gan
- Department of Nuclear Medicine, Beijing Institute of Respiratory Medicine and Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Kai Cui
- Department of Nuclear Medicine, Peking University First Hospital, Beijing 100034, China
| | - Qi Cao
- Translational Cancer Research Center, Peking University First Hospital, Beijing 100034, China
| | - Ning Zhang
- Translational Cancer Research Center, Peking University First Hospital, Beijing 100034, China
- Yunnan Baiyao Group, Kunming 650000, China
| | - Min-Fu Yang
- Department of Nuclear Medicine, Beijing Institute of Respiratory Medicine and Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Xing Yang
- Department of Nuclear Medicine, Peking University First Hospital, Beijing 100034, China
- Yunnan Baiyao Group, Kunming 650000, China
- Laboratorial Center, Peking University First Hospital, Beijing 100034, China
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3
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Qu B, Han Y, Liang T, Zhang C, Hou G, Gao F. Evaluation of a novel EphA2 targeting peptide for triple negative breast cancer based on radionuclide molecular imaging. ARAB J CHEM 2022. [DOI: 10.1016/j.arabjc.2022.104211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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4
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Abstract
The increasing application of positron emission tomography (PET) in nuclear medicine has stimulated the extensive development of a multitude of novel and versatile techniques to introduce fluorine‐18, especially for the radiolabelling of biologically or pharmacologically active molecules. Taking into consideration that the introduction of fluorine‐18 (t1/2=109.8 min) mostly proceeds under harsh conditions, radiolabelling of such molecules represents a challenge and is of enormous interest. Ideally, it should proceed in a regioselective manner under mild physiological conditions, in an acceptable time span, with high yields and high specific activities. Special attention has been drawn to 2‐fluoroethyl and 3‐fluoropropyl groups, which are often the active sites of radiofluorinated compounds. Precursors containing an ammonium leaving group – such as a strained azetidinium or aziridinium moiety – can help to overcome these obstacles leading to a convenient and mild introduction of [18F]fluoride with high radiochemical yields.
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Affiliation(s)
- Falco Reissig
- Institut für Radiopharmazeutische Krebsforschung Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328, Dresden, Germany.,Fakultät Chemie und Lebensmittelchemie, Technische Universität Dresden, 01062, Dresden, Germany
| | - Constantin Mamat
- Institut für Radiopharmazeutische Krebsforschung Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328, Dresden, Germany.,Fakultät Chemie und Lebensmittelchemie, Technische Universität Dresden, 01062, Dresden, Germany
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Pretze M, Neuber C, Kinski E, Belter B, Köckerling M, Caflisch A, Steinbach J, Pietzsch J, Mamat C. Synthesis, radiolabelling and initial biological characterisation of 18F-labelled xanthine derivatives for PET imaging of Eph receptors. Org Biomol Chem 2020; 18:3104-3116. [PMID: 32253415 DOI: 10.1039/d0ob00391c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Eph receptor tyrosine kinases, particularly EphA2 and EphB4, represent promising candidates for molecular imaging due to their essential role in cancer progression and therapy resistance. Xanthine derivatives were identified to be potent Eph receptor inhibitors with IC50 values in the low nanomolar range (1-40 nm). These compounds occupy the hydrophobic pocket of the ATP-binding site in the kinase domain. Based on lead compound 1, we designed two fluorine-18-labelled receptor tyrosine kinase inhibitors ([18F]2/3) as potential tracers for positron emission tomography (PET). Docking into the ATP-binding site allowed us to find the best position for radiolabelling. The replacement of the methyl group at the uracil residue ([18F]3) rather than the methyl group of the phenoxy moiety ([18F]2) by a fluoropropyl group was predicted to preserve the affinity of the lead compound 1. Herein, we point out a synthesis route to [18F]2 and [18F]3 and the respective tosylate precursors as well as a labelling procedure to insert fluorine-18. After radiolabelling, both radiotracers were obtained in approximately 5% radiochemical yield with high radiochemical purity (>98%) and a molar activity of >10 GBq μmol-1. In line with the docking studies, first cell experiments revealed specific, time-dependent binding and uptake of [18F]3 to EphA2 and EphB4-overexpressing A375 human melanoma cells, whereas [18F]2 did not accumulate at these cells. Since both tracers [18F]3 and [18F]2 are stable in rat blood, the novel radiotracers might be suitable for in vivo molecular imaging of Eph receptors with PET.
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Affiliation(s)
- Marc Pretze
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany. and Technische Universität Dresden, Fakultät Chemie und Lebensmittelchemie, D-01062 Dresden, Germany
| | - Christin Neuber
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany.
| | - Elisa Kinski
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany.
| | - Birgit Belter
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany.
| | - Martin Köckerling
- Universität Rostock, Institut für Chemie - Anorganische Festkörperchemie, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany
| | - Amedeo Caflisch
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Jörg Steinbach
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany. and Technische Universität Dresden, Fakultät Chemie und Lebensmittelchemie, D-01062 Dresden, Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany. and Technische Universität Dresden, Fakultät Chemie und Lebensmittelchemie, D-01062 Dresden, Germany
| | - Constantin Mamat
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany. and Technische Universität Dresden, Fakultät Chemie und Lebensmittelchemie, D-01062 Dresden, Germany
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7
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Pyo A, You SH, Sik Kim H, Young Kim J, Min JJ, Kim DY, Hong Y. Production of 64Cu-labeled monobody for imaging of human EphA2-expressing tumors. Bioorg Med Chem Lett 2020; 30:127262. [PMID: 32527560 DOI: 10.1016/j.bmcl.2020.127262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/20/2020] [Accepted: 05/11/2020] [Indexed: 10/24/2022]
Abstract
We previously reported on the monobody E1, which specifically targets the tumor marker hEphA2. In this study, we labeled NOTA-conjugated E1 with 64Cu (64Cu-NOTA-E1) and evaluated biologic characteristics. The uptake of 64Cu-NOTA-E1 in PC3 cells (a human prostate cancer cell line) with high expression of hEphA2 increased in a time-dependent manner. In PC3 xenograft mice, 64Cu-NOTA-E1 injected via the tail vein allowed visualization of tumors on positron emission tomography after 1 h and the highest uptake measured at 24 h post-injection. By contrast, the radioactivity of other tissues either did not increase or decreased over 24 h. This indicates that 64Cu-NOTA-E1 has high tumor uptake and retention, with rapid clearance, and low background values in other tissues. Therefore, 64Cu-NOTA-E1 should be suitable as a novel PET imaging agent for hEphA2-expressing tumors.
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Affiliation(s)
- Ayoung Pyo
- Department of Nuclear Medicine, Chonnam National University Medical School and Hwasun Hospital, Hwasun, Republic of Korea
| | - Sung-Hwan You
- Department of Nuclear Medicine, Chonnam National University Medical School and Hwasun Hospital, Hwasun, Republic of Korea
| | - Hyeon Sik Kim
- Medical Photonics Research Center, Korea Photonics Technology Institute, Gwangju, Republic of Korea
| | - Jung Young Kim
- Division of RI-Convergence Research, Korea Institute of Radiological and Medical Sciences, Seoul, Republic of Korea
| | - Jung-Joon Min
- Department of Nuclear Medicine, Chonnam National University Medical School and Hwasun Hospital, Hwasun, Republic of Korea
| | - Dong-Yeon Kim
- Department of Nuclear Medicine, Chonnam National University Medical School and Hwasun Hospital, Hwasun, Republic of Korea.
| | - Yeongjin Hong
- Department of Microbiology, Chonnam National University Medical School, Hwasun, Republic of Korea.
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8
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Neuber C, Belter B, Mamat C, Pietzsch J. Radiopharmacologist's and Radiochemist's View on Targeting the Eph/Ephrin Receptor Tyrosine Kinase System. ACS Omega 2020; 5:16318-16331. [PMID: 32685795 PMCID: PMC7364440 DOI: 10.1021/acsomega.0c01058] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 05/25/2020] [Indexed: 05/06/2023]
Abstract
In the past decade, there have been extensive efforts to open up the Eph/ephrin subfamily of the receptor tyrosine kinase family for diagnostic and therapeutic applications. Besides classical pharmaceutical developments, which focus either on drugs targeting the extracellular ligand binding domains or on the intracellular tyrosine kinase domains of these receptors, there also have been first radiopharmaceutical approaches. Here the focus is on the development of specific and selective probes for molecular imaging, particularly by means of positron emission tomography, and the functional characterization of the Eph/ephrin subfamily in certain target tissues. The aim of this mini-review is to summarize the different approaches toward Eph-targeting radiotracers by using antibodies, peptides, and small molecules and to discuss their radiopharmacological characterization. With regard to the small molecules, further considerations will focus on the design and synthesis of nonradioactive reference compounds and precursors as well as on radiolabeling strategies.
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Affiliation(s)
- Christin Neuber
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Institute of Radiopharmaceutical Cancer
Research, Department of Radiopharmaceutical
and Chemical Biology, 01328 Dresden, Germany
| | - Birgit Belter
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Institute of Radiopharmaceutical Cancer
Research, Department of Radiopharmaceutical
and Chemical Biology, 01328 Dresden, Germany
| | - Constantin Mamat
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Institute of Radiopharmaceutical Cancer
Research, Department of Radionuclide Theragnostics, 01328 Dresden, Germany
- Technische
Universität Dresden, School of Science,
Faculty of Chemistry and Food Chemistry, 01062 Dresden, Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Institute of Radiopharmaceutical Cancer
Research, Department of Radiopharmaceutical
and Chemical Biology, 01328 Dresden, Germany
- Technische
Universität Dresden, School of Science,
Faculty of Chemistry and Food Chemistry, 01062 Dresden, Germany
- E-mail:
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9
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Wiemer J, Steinbach J, Pietzsch J, Mamat C. Preparation of a novel radiotracer targeting the EphB4 receptor via radiofluorination using spiro azetidinium salts as precursor. J Labelled Comp Radiopharm 2017; 60:489-498. [DOI: 10.1002/jlcr.3526] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 05/10/2017] [Accepted: 05/29/2017] [Indexed: 12/26/2022]
Affiliation(s)
- Jens Wiemer
- Institut für Radiopharmazeutische Krebsforschung; Helmholtz-Zentrum Dresden-Rossendorf; Dresden Germany
| | - Jörg Steinbach
- Institut für Radiopharmazeutische Krebsforschung; Helmholtz-Zentrum Dresden-Rossendorf; Dresden Germany
- Fachbereich Chemie und Lebensmittelchemie; Technische Universität Dresden; Dresden Germany
| | - Jens Pietzsch
- Institut für Radiopharmazeutische Krebsforschung; Helmholtz-Zentrum Dresden-Rossendorf; Dresden Germany
- Fachbereich Chemie und Lebensmittelchemie; Technische Universität Dresden; Dresden Germany
| | - Constantin Mamat
- Institut für Radiopharmazeutische Krebsforschung; Helmholtz-Zentrum Dresden-Rossendorf; Dresden Germany
- Fachbereich Chemie und Lebensmittelchemie; Technische Universität Dresden; Dresden Germany
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10
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Abstract
Click chemistry is an approach that uses efficient and reliable reactions, such as Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), to bind two molecular building blocks. CuAAC has broad applications in medicinal chemistry and other fields of chemistry. This review describes the general features and applications of CuAAC in solid-phase synthesis (CuAAC-SP), highlighting the suitability of this kind of reaction for peptides, nucleotides, small molecules, supramolecular structures, and polymers, among others. This versatile reaction is expected to become pivotal for meeting future challenges in solid-phase chemistry.
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Affiliation(s)
- Vida Castro
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology 08028-Barcelona, Spain
- CIBER-BBN, Networking Centre on Bioengineering, Biomaterials and Nanomedicine, 08028-Barcelona, Spain
| | - Hortensia Rodríguez
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology 08028-Barcelona, Spain
- CIBER-BBN, Networking Centre on Bioengineering, Biomaterials and Nanomedicine, 08028-Barcelona, Spain
- School
of Chemistry, Yachay Tech, Yachay City of Knowledge, Urcuqui, Ecuador
| | - Fernando Albericio
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology 08028-Barcelona, Spain
- CIBER-BBN, Networking Centre on Bioengineering, Biomaterials and Nanomedicine, 08028-Barcelona, Spain
- Department
of Organic Chemistry, University of Barcelona, 08028-Barcelona, Spain
- School of Chemistry & Physics, University of KwaZulu-Natal, 4001-Durban, South Africa
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Ebert K, Wiemer J, Caballero J, Köckerling M, Steinbach J, Pietzsch J, Mamat C. Development of indazolylpyrimidine derivatives as high-affine EphB4 receptor ligands and potential PET radiotracers. Bioorg Med Chem 2015; 23:6025-35. [PMID: 26189032 DOI: 10.1016/j.bmc.2015.06.040] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 01/06/2023]
Abstract
Due to their essential role in the pathogenesis of cancer, members of the Eph (erythropoietin-producing hepatoma cell line-A2) receptor tyrosine kinase family represent promising candidates for molecular imaging. Thus, the development and preparation of novel radiotracers for the noninvasive imaging of the EphB4 receptor via positron emission tomography (PET) is described. First in silico investigations with the indazolylpyrimidine lead compound which is known to be highly affine to EphB4 were executed to identify favorable labeling positions for an introduction of fluorine-18 to retain the affinity. Based on this, reference compounds as well as precursors were developed and labeled with carbon-11 and fluorine-18, respectively. For this purpose, a protecting group strategy essentially had to be generated to prevent unwanted methylation and to enable the introduction of fluorine-18. Further, a convenient radiolabeling strategy using [(11)C]methyl iodide was established which afforded the isotopically labeled radiotracer in 30-35% RCY (d.c.) which is identical with the original inhibitor molecule. A spiro ammonium precursor was prepared for radiolabeling with fluorine-18. Unfortunately, the labeling did not lead to the desired (18)F-radiotracer under the chosen conditions.
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Affiliation(s)
- Kristin Ebert
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - Jens Wiemer
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - Julio Caballero
- Universidad de Talca, Centro de Bioinformática y Simulación Molecular, 2 Norte 685, Casilla 721, Talca, Chile
| | - Martin Köckerling
- Universität Rostock, Institut für Chemie, Anorganische Festkörperchemie, Albert-Einstein-Straße 3a, D-18057 Rostock, Germany
| | - Jörg Steinbach
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany; TU Dresden, Fachbereich Chemie und Lebensmittelchemie, D-01062 Dresden, Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany; TU Dresden, Fachbereich Chemie und Lebensmittelchemie, D-01062 Dresden, Germany
| | - Constantin Mamat
- Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany; TU Dresden, Fachbereich Chemie und Lebensmittelchemie, D-01062 Dresden, Germany.
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12
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Abstract
Eph receptor tyrosine kinases and ephrin ligands constitute an important cell communication system that controls development, tissue homeostasis and many pathological processes. Various Eph receptors/ephrins are present in essentially all cell types and their expression is often dysregulated by injury and disease. Thus, the 14 Eph receptors are attracting increasing attention as a major class of potential drug targets. In particular, agents that bind to the extracellular ephrin-binding pocket of these receptors show promise for medical applications. This pocket comprises a broad and shallow groove surrounded by several flexible loops, which makes peptides particularly suitable to target it with high affinity and selectivity. Accordingly, a number of peptides that bind to Eph receptors with micromolar affinity have been identified using phage display and other approaches. These peptides are generally antagonists that inhibit ephrin binding and Eph receptor/ ephrin signaling, but some are agonists mimicking ephrin-induced Eph receptor activation. Importantly, some of the peptides are exquisitely selective for single Eph receptors. Most identified peptides are linear, but recently the considerable advantages of cyclic scaffolds have been recognized, particularly in light of potential optimization towards drug leads. To date, peptide improvements have yielded derivatives with low nanomolar Eph receptor binding affinity, high resistance to plasma proteases and/or long in vivo half-life, exemplifying the merits of peptides for Eph receptor targeting. Besides their modulation of Eph receptor/ephrin function, peptides can also serve to deliver conjugated imaging and therapeutic agents or various types of nanoparticles to tumors and other diseased tissues presenting target Eph receptors.
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Affiliation(s)
| | - Elena B Pasquale
- Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.
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