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Melendez-Alafort L, Ferro-Flores G, De Nardo L, Ocampo-García B, Bolzati C. Zirconium immune-complexes for PET molecular imaging: Current status and prospects. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.215005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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2
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Bubenshchikov VB, Larenkov AA. Chelating Agents for Zirconium-89 in the Synthesis of Radiopharmaceuticals: Current State and Prospects of Development. RUSS J COORD CHEM+ 2022. [DOI: 10.1134/s1070328422110021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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3
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Toporivska Y, Mular A, Piasta K, Ostrowska M, Illuminati D, Baldi A, Albanese V, Pacifico S, Fritsky IO, Remelli M, Guerrini R, Gumienna-Kontecka E. Thermodynamic Stability and Speciation of Ga(III) and Zr(IV) Complexes with High-Denticity Hydroxamate Chelators. Inorg Chem 2021; 60:13332-13347. [PMID: 34414758 PMCID: PMC8424644 DOI: 10.1021/acs.inorgchem.1c01622] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Increasing attention
has been recently devoted to 89Zr(IV) and 68Ga(III) radionuclides, due to their favorable
decay characteristics for positron emission tomography (PET). In the
present paper, a deep investigation is presented on Ga(III) and Zr(IV)
complexes with a series of tri-(H3L1, H3L3, H3L4 and desferrioxamine
E, DFOE) and tetrahydroxamate (H4L2) ligands. Herein, we describe the rational
design and synthesis of two cyclic complexing agents (H3L1 and H4L2) bearing three and four hydroxamate
chelating groups, respectively. The ligand structures allow us to
take advantage of the macrocyclic effect; the H4L2 chelator contains an additional side
amino group available for a possible further conjugation with a biomolecule.
The thermodynamic stability of Ga(III) and Zr(IV) complexes in solution
has been measured using a combination of potentiometric and pH-dependent
UV–vis titrations, on the basis of metal–metal competition.
The Zr(IV)-H4L2 complex
is characterized by one of the highest formation constants reported
to date for a tetrahydroxamate zirconium chelate (log β = 45.9,
pZr = 37.0), although the complex-stability increase derived from
the introduction of the fourth hydroxamate binding unit is lower than
that predicted by theoretical calculations. Solution studies on Ga(III)
complexes revealed that H3L1 and H4L2 are stronger chelators in comparison to DFOB. The complex stability
obtained with the new ligands is also compared with that previously
reported for other hydroxamate ligands. In addition to increasing
the library of the thermodynamic stability data of Ga(III) and Zr(IV)
complexes, the present work allows new insights into Ga(III) and Zr(IV)
coordination chemistry and thermodynamics and broadens the selection
of available chelators for 68Ga(III) and 89Zr(IV). Solution equilibria studies on Ga(III)
and Zr(IV) complexes
with a series of tri- and tetrahydroxamate ligands are presented.
For this purpose, the rational design and synthesis of two cyclic
complexing agents bearing three and four hydroxamate chelating groups
was performed. The thermodynamic and speciation studies allow a discussion
of the structure−complex stability dependence. The Zr(IV)-tetrahydroxamate
complex is characterized by one of the highest formation constants
reported to date for a hydroxamate zirconium chelator.
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Affiliation(s)
- Yuliya Toporivska
- University of Wroclaw, Faculty of Chemistry, 14 F. Joliot-Curie, 50-383 Wrocław, Poland
| | - Andrzej Mular
- University of Wroclaw, Faculty of Chemistry, 14 F. Joliot-Curie, 50-383 Wrocław, Poland
| | - Karolina Piasta
- University of Wroclaw, Faculty of Chemistry, 14 F. Joliot-Curie, 50-383 Wrocław, Poland
| | - Małgorzata Ostrowska
- University of Wroclaw, Faculty of Chemistry, 14 F. Joliot-Curie, 50-383 Wrocław, Poland
| | - Davide Illuminati
- University of Ferrara, Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, 46 Via Luigi Borsari, 44121 Ferrara, Italy
| | - Andrea Baldi
- University of Ferrara, Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, 46 Via Luigi Borsari, 44121 Ferrara, Italy
| | - Valentina Albanese
- University of Ferrara, Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, 46 Via Luigi Borsari, 44121 Ferrara, Italy
| | - Salvatore Pacifico
- University of Ferrara, Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, 46 Via Luigi Borsari, 44121 Ferrara, Italy
| | - Igor O Fritsky
- Taras Shevchenko National University of Kyiv, Department of Chemistry, 64 Volodymyrska Str., 01601 Kyiv, Ukraine
| | - Maurizio Remelli
- University of Ferrara, Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, 46 Via Luigi Borsari, 44121 Ferrara, Italy
| | - Remo Guerrini
- University of Ferrara, Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, 46 Via Luigi Borsari, 44121 Ferrara, Italy
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4
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The Race for Hydroxamate-Based Zirconium-89 Chelators. Cancers (Basel) 2021; 13:cancers13174466. [PMID: 34503276 PMCID: PMC8431476 DOI: 10.3390/cancers13174466] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 08/30/2021] [Accepted: 08/31/2021] [Indexed: 12/18/2022] Open
Abstract
Simple Summary Chelators are small molecules that can form a complex with a metal ion by coordinating electron rich atoms from the chelator to the electron-poor cation. Bifunctionalization of the chelator allows for the coupling of the chelator to a vector, such as a biomolecule. Using this approach, radiolabeling of biomolecules with metallic radionuclides can be performed, enabling nuclear imaging studies for diagnosis and radiotherapy of diseases. In the case of positron emission tomography (PET) of radiolabeled antibodies, this approach is called immunoPET. In this review we focus on chelators using hydroxamate groups to coordinate the radionuclide zirconium-89 ([89Zr]Zr4+, denoted as 89Zr in the following). The most common chelator used in this context is desferrioxamine (DFO). However, preclinical studies indicate that the 89Zr-DFO complex is not stable enough in vivo, in particular when combined with biomolecules with slow pharmacokinetics (e.g., antibodies). Subsequently, new chelators with improved properties have been developed, of which some show promising potential. The progress is summarized in this review. Abstract Metallic radionuclides conjugated to biological vectors via an appropriate chelator are employed in nuclear medicine for the diagnosis (imaging) and radiotherapy of diseases. For the application of radiolabeled antibodies using positron emission tomography (immunoPET), zirconium-89 has gained increasing interest over the last decades as its physical properties (t1/2 = 78.4 h, 22.6% β+ decay) match well with the slow pharmacokinetics of antibodies (tbiol. = days to weeks) allowing for late time point imaging. The most commonly used chelator for 89Zr in this context is desferrioxamine (DFO). However, it has been shown in preclinical studies that the hexadentate DFO ligand does not provide 89Zr-complexes of sufficient stability in vivo and unspecific uptake of the osteophilic radiometal in bones is observed. For clinical applications, this might be of concern not only because of an unnecessary dose to the patient but also an increased background signal. As a consequence, next generation chelators based on hydroxamate scaffolds for more stable coordination of 89Zr have been developed by different research groups. In this review, we describe the progress in this research field until end of 2020, including promising examples of new candidates of chelators currently in advanced stages for clinical translation that outrun the performance of the current gold standard DFO.
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5
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Chomet M, van Dongen GAMS, Vugts DJ. State of the Art in Radiolabeling of Antibodies with Common and Uncommon Radiometals for Preclinical and Clinical Immuno-PET. Bioconjug Chem 2021; 32:1315-1330. [PMID: 33974403 PMCID: PMC8299458 DOI: 10.1021/acs.bioconjchem.1c00136] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Inert
and stable radiolabeling of monoclonal antibodies (mAb),
antibody fragments, or antibody mimetics with radiometals is a prerequisite
for immuno-PET. While radiolabeling is preferably fast, mild, efficient,
and reproducible, especially when applied for human use in a current
Good Manufacturing Practice compliant way, it is crucial that the
obtained radioimmunoconjugate is stable and shows preserved immunoreactivity
and in vivo behavior. Radiometals and chelators have
extensively been evaluated to come to the most ideal radiometal–chelator
pair for each type of antibody derivative. Although PET imaging of
antibodies is a relatively recent tool, applications with 89Zr, 64Cu, and 68Ga have greatly increased in
recent years, especially in the clinical setting, while other less
common radionuclides such as 52Mn, 86Y, 66Ga, and 44Sc, but also 18F as in [18F]AlF are emerging promising candidates for the radiolabeling
of antibodies. This review presents a state of the art overview of
the practical aspects of radiolabeling of antibodies, ranging from
fast kinetic affibodies and nanobodies to slow kinetic intact mAbs.
Herein, we focus on the most common approach which consists of first
modification of the antibody with a chelator, and after eventual storage
of the premodified molecule, radiolabeling as a second step. Other
approaches are possible but have been excluded from this review. The
review includes recent and representative examples from the literature
highlighting which radiometal–chelator–antibody combinations
are the most successful for in vivo application.
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Affiliation(s)
- Marion Chomet
- Amsterdam UMC, Vrije Universiteit Amsterdam, Radiology & Nuclear Medicine, Cancer Center Amsterdam, De Boelelaan 1117, Amsterdam 1081 HV, The Netherlands
| | - Guus A M S van Dongen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Radiology & Nuclear Medicine, Cancer Center Amsterdam, De Boelelaan 1117, Amsterdam 1081 HV, The Netherlands
| | - Danielle J Vugts
- Amsterdam UMC, Vrije Universiteit Amsterdam, Radiology & Nuclear Medicine, Cancer Center Amsterdam, De Boelelaan 1117, Amsterdam 1081 HV, The Netherlands
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6
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Yoon JK, Park BN, Ryu EK, An YS, Lee SJ. Current Perspectives on 89Zr-PET Imaging. Int J Mol Sci 2020; 21:ijms21124309. [PMID: 32560337 PMCID: PMC7352467 DOI: 10.3390/ijms21124309] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/13/2020] [Accepted: 06/15/2020] [Indexed: 12/14/2022] Open
Abstract
89Zr is an emerging radionuclide that plays an essential role in immuno-positron emission tomography (PET) imaging. The long half-life of 89Zr (t1/2 = 3.3 days) is favorable for evaluating the in vivo distribution of monoclonal antibodies. Thus, the use of 89Zr is promising for monitoring antibody-based cancer therapies. Immuno-PET combines the sensitivity of PET with the specificity of antibodies. A number of studies have been conducted to investigate the feasibility of 89Zr immuno-PET imaging for predicting the efficacy of radioimmunotherapy and antibody therapies, imaging target expression, detecting target-expressing tumors, and the monitoring of anti-cancer chemotherapies. In this review, we summarize the current status of PET imaging using 89Zr in both preclinical and clinical studies by highlighting the use of immuno-PET for the targets of high clinical relevance. We also present 89Zr-PET applications other than immuno-PET, such as nanoparticle imaging and cell tracking. Finally, we discuss the limitations and the ongoing research being performed to overcome the remaining hurdles.
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Affiliation(s)
- Joon-Kee Yoon
- Department of Nuclear Medicine & Molecular Imaging, Ajou University School of Medicine, Worldcup-ro 164, Suwon 16499, Korea; (B.-N.P.); (Y.-S.A.); (S.-J.L.)
- Correspondence: ; Tel.: +82-31-219-4303
| | - Bok-Nam Park
- Department of Nuclear Medicine & Molecular Imaging, Ajou University School of Medicine, Worldcup-ro 164, Suwon 16499, Korea; (B.-N.P.); (Y.-S.A.); (S.-J.L.)
| | - Eun-Kyoung Ryu
- Division of Magnetic Resonance, Korea Basic Science Institute, 162, Yeongudanji-ro, Cheongju 28119, Korea;
| | - Young-Sil An
- Department of Nuclear Medicine & Molecular Imaging, Ajou University School of Medicine, Worldcup-ro 164, Suwon 16499, Korea; (B.-N.P.); (Y.-S.A.); (S.-J.L.)
| | - Su-Jin Lee
- Department of Nuclear Medicine & Molecular Imaging, Ajou University School of Medicine, Worldcup-ro 164, Suwon 16499, Korea; (B.-N.P.); (Y.-S.A.); (S.-J.L.)
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7
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Alnahwi A, Ait-Mohand S, Dumulon-Perreault V, Dory YL, Guérin B. Promising Performance of 4HMS, a New Zirconium-89 Octadendate Chelator. ACS OMEGA 2020; 5:10731-10739. [PMID: 32455192 PMCID: PMC7240819 DOI: 10.1021/acsomega.0c00207] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/23/2020] [Indexed: 06/11/2023]
Abstract
Over the last decade, the interest in zirconium-89 (89Zr) as a positron-emitting radionuclide increased considerably because of its standardized production and its physical half-life (78.41 h), which matches the biological half-life of antibodies and its successful use in preclinical and clinical applications. So far, desferrioxamine (DFO), a commercially available chelator, has been mainly used as a bifunctional chelating system. However, there are some concerns regarding the in vivo stability of the [89Zr]Zr-DFO complex. In this study, we report the synthesis of an acyclic N-hydroxy-N-methyl succinamide-based chelator (4HMS) with 8 coordination sites and our first investigations into the use of this new chelator for 89Zr complexation. In vitro and in vivo comparative studies with [89Zr]Zr-4HMS and [89Zr]Zr-DFO are presented. The 4HMS chelator was synthesized in four steps starting with an excellent overall yield. Both chelators were quantitatively labeled with 89Zr within 5-10 min at pH 7 and room temperature; the molar activity of [89Zr]Zr-4HMS exceeded (>3 times) that of [89Zr]Zr-DFO. [89Zr]Zr-4HMS remained stable against transmetalation and transchelation and cleared from most tissues within 24 h. The kidney, liver, bone, and spleen uptakes were significantly low for this 89Zr-complex. Positron emission tomography images were in accordance with the results of the biodistribution in healthy mice. Based on DFT calculations, a rationale is provided for the high stability of 89Zr-4HMS. This makes 4HMS a promising chelator for future development of 89Zr-radiopharmaceuticals.
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Affiliation(s)
- Aiman
H. Alnahwi
- Department
of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health
Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Samia Ait-Mohand
- Department
of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health
Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Véronique Dumulon-Perreault
- Sherbrooke
Molecular Imaging Center (CIMS), CRCHUS, 3001, 12e Avenue Nord, Sherbrooke, Québec J1H 5N4, Canada
| | - Yves L. Dory
- Laboratoire
de Synthèse Supramoléculaire. Department of Chemistry,
Institut de Pharmacologie, Université
de Sherbooke, 3001, 12e
Avenue Nord, Sherbrooke, Québec J1H 5N4, Canada
| | - Brigitte Guérin
- Department
of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health
Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
- Sherbrooke
Molecular Imaging Center (CIMS), CRCHUS, 3001, 12e Avenue Nord, Sherbrooke, Québec J1H 5N4, Canada
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Abstract
Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.
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Affiliation(s)
- Weijun Wei
- Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
- Departments of Radiology and Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Room 7137, Madison, Wisconsin 53705, United States
| | - Zachary T Rosenkrans
- Department of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
| | - Jianjun Liu
- Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Gang Huang
- Department of Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
- Shanghai Key Laboratory of Molecular Imaging, Shanghai University of Medicine and Health Sciences, Shanghai 201318, China
| | - Quan-Yong Luo
- Department of Nuclear Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Weibo Cai
- Departments of Radiology and Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Room 7137, Madison, Wisconsin 53705, United States
- Department of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
- University of Wisconsin Carbone Cancer Center, Madison, Wisconsin 53705, United States
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9
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Rangger C, Haubner R. Radiolabelled Peptides for Positron Emission Tomography and Endoradiotherapy in Oncology. Pharmaceuticals (Basel) 2020; 13:E22. [PMID: 32019275 PMCID: PMC7169460 DOI: 10.3390/ph13020022] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/14/2020] [Accepted: 01/16/2020] [Indexed: 02/07/2023] Open
Abstract
This review deals with the development of peptide-based radiopharmaceuticals for the use with positron emission tomography and peptide receptor radiotherapy. It discusses the pros and cons of this class of radiopharmaceuticals as well as the different labelling strategies, and summarises approaches to optimise metabolic stability. Additionally, it presents different target structures and addresses corresponding tracers, which are already used in clinical routine or are being investigated in clinical trials.
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Affiliation(s)
| | - Roland Haubner
- Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria;
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10
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Abstract
The thermodynamic stability of a metal-ligand complex, as measured by the formation constant (log β), is one of the most important parameters that determines metal ion selectivity and potential applications in, for example, radiopharmaceutical science. The stable coordination chemistry of radioactive 89Zr4+ in an aqueous environment is of paramount importance when developing positron-emitting radiotracers based on proteins (usually antibodies) for use with positron emission tomography. Desferrioxamine B (DFO) remains the chelate of choice for clinical applications of 89Zr-labeled proteins, but the coordination of DFO to Zr4+ ions is suboptimal. Many alternative ligands have been reported, but the challenges in measuring very high log β values with metal ions such as Zr4+ that tend to hydrolyze mean that accurate thermodynamic data are scarce. In this work, density functional theory (DFT) calculations were used to predict the reaction energetics for metal ion complexation. Computed values of pseudoformation constants (log β') are correlated with experimental data and showed an excellent linear relationship (R2 = 0.97). The model was then used to estimate the absolute and relative formation constants of 23 different Zr4+ complexes using a total of 17 different ligands, including many of the alternative bifunctional chelates that have been reported recently for use in 89Zr4+ radiochemistry. In addition, detailed computational studies were performed on the geometric isomerism and hydration state of Zr-desferrioxamine. Collectively, the results offer new insights into Zr4+ coordination chemistry that will help guide the synthesis of future ligands. The computational model developed here is straightforward and reproducible and can be readily applied in the design of other metal coordination compounds.
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Affiliation(s)
- Jason P Holland
- University of Zurich , Department of Chemistry , Winterthurerstrasse 190 , CH-8057 Zurich , Switzerland
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11
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Buchwalder C, Jaraquemada-Peláez MDG, Rousseau J, Merkens H, Rodríguez-Rodríguez C, Orvig C, Bénard F, Schaffer P, Saatchi K, Häfeli UO. Evaluation of the Tetrakis(3-Hydroxy-4-Pyridinone) Ligand THPN with Zirconium(IV): Thermodynamic Solution Studies, Bifunctionalization, and in Vivo Assessment of Macromolecular 89Zr-THPN-Conjugates. Inorg Chem 2019; 58:14667-14681. [DOI: 10.1021/acs.inorgchem.9b02350] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christian Buchwalder
- University of British Columbia, Faculty of Pharmaceutical Sciences, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | | | - Julie Rousseau
- BC Cancer Agency, Department of Functional Imaging, 600 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | - Helen Merkens
- BC Cancer Agency, Department of Functional Imaging, 600 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | - Cristina Rodríguez-Rodríguez
- University of British Columbia, Faculty of Pharmaceutical Sciences, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
- University of British Columbia, Department of Physics & Astronomy, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
| | - Chris Orvig
- Medicinal Inorganic Chemistry Group, University of British Columbia, Department of Chemistry, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - François Bénard
- BC Cancer Agency, Department of Functional Imaging, 600 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | - Paul Schaffer
- TRIUMF, Life Sciences Division, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada
| | - Katayoun Saatchi
- University of British Columbia, Faculty of Pharmaceutical Sciences, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Urs O. Häfeli
- University of British Columbia, Faculty of Pharmaceutical Sciences, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
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