1
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Franchi S, Madabeni A, Tosato M, Gentile S, Asti M, Orian L, Di Marco V. Navigating through the coordination preferences of heavy alkaline earth metals: Laying the foundations for 223Ra- and 131/135mBa-based targeted alpha therapy and theranostics of cancer. J Inorg Biochem 2024; 256:112569. [PMID: 38701687 DOI: 10.1016/j.jinorgbio.2024.112569] [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] [Received: 02/26/2024] [Revised: 04/04/2024] [Accepted: 04/18/2024] [Indexed: 05/05/2024]
Abstract
The clinical success of [223Ra]RaCl2 (Xofigo®) for the palliative treatment of bone metastases in patients with prostate cancer has highlighted the therapeutic potential of α-particle emission. Expanding the applicability of radium-223 in Targeted Alpha Therapy of non-osseous tumors is followed up with significant interest, as it holds the potential to unveil novel treatment options in the comprehensive management of cancer. Moreover, the use of barium radionuclides, like barium-131 and -135m, is still unfamiliar in nuclear medicine applications, although they can be considered as radium-223 surrogates for imaging purposes. Enabling these applications requires the establishment of chelators able to form stable complexes with radium and barium radionuclides. Until now, only a limited number of ligands have been suggested and these molecules have been primarily inspired by existing structures known for their ability to complex large metal cations. However, a systematic inspection of chelators specifically tailored to Ra2+ and Ba2+ has yet to be conducted. This work delves into a comprehensive investigation of a series of small organic ligands, aiming to unveil the coordination preferences of both radium-223 and barium-131/135m. Electronic binding energies of both metal cations to each ligand were theoretically computed via Density Functional Theory calculations (COSMO-ZORA-PBE-D3/TZ2P), while thermodynamic stability constants were experimentally determined for Ba2+-ligand complexes by potentiometry, NMR and UV-Vis spectroscopies. The outcomes revealed malonate, 2-hydroxypyridine 1-oxide and picolinate as the most favorable building blocks to design multidentate chelators. These findings serve as foundation guidelines, propelling the development of cutting-edge radium-223- and barium-131/135m-based radiopharmaceuticals for Targeted Alpha Therapy and theranostics of cancer.
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Affiliation(s)
- Sara Franchi
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
| | - Andrea Madabeni
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
| | - Marianna Tosato
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy.
| | - Silvia Gentile
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
| | - Mattia Asti
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy.
| | - Laura Orian
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy; National Institute of Nuclear Physics, National Laboratories of Legnaro (INFN-LNL), 35020 Legnaro, Padova, Italy.
| | - Valerio Di Marco
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
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Tosato M, Randhawa P, Lazzari L, McNeil BL, Dalla Tiezza M, Zanoni G, Mancin F, Orian L, Ramogida CF, Di Marco V. Tuning the Softness of the Pendant Arms and the Polyazamacrocyclic Backbone to Chelate the 203Pb/ 212Pb Theranostic Pair. Inorg Chem 2024; 63:1745-1758. [PMID: 38230993 PMCID: PMC10828988 DOI: 10.1021/acs.inorgchem.3c02610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 12/18/2023] [Accepted: 12/20/2023] [Indexed: 01/18/2024]
Abstract
A series of macrocyclic ligands were considered for the chelation of Pb2+: 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), 1,7-bis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane-4,10-diacetic acid (DO2A2S), 1,5,9-tris[2-(methylsulfanyl)ethyl]-1,5,9-triazacyclododecane (TACD3S), 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetrazacyclotridecane (TRI4S), and 1,4,8,11-tetrakis[2-(methylsulfanyl)ethyl]-1,4,8,11-tetrazacyclotetradecane (TE4S). The equilibrium, the acid-mediated dissociation kinetics, and the structural properties of the Pb2+ complexes formed by these chelators were examined by UV-Visible and nuclear magnetic resonance (NMR) spectroscopies, combined with potentiometry and density functional theory (DFT) calculations. The obtained results indicated that DO4S, DO3S, DO3SAm, and DO2A2S were able to efficiently chelate Pb2+ and that the most suitable macrocyclic scaffold for Pb2+ is 1,4,7,10-tetrazacyclododecane. NMR spectroscopy gave insights into the solution structures of the Pb2+ complexes, and 1H-207Pb interactions confirmed the involvement of S and/or O donors in the metal coordination sphere. Highly fluxional solution behavior was discovered when Pb2+ was coordinated to symmetric ligands (i.e., DO4S and DO2A2S) while the introduction of structural asymmetry in DO3S and DO3SAm slowed down the intramolecular dynamics. The ligand ability to chelate [203Pb]Pb2+ under highly dilute reaction conditions was explored through radiolabeling experiments. While DO4S and DO3S possessed modest performance, DO3SAm and DO2A2S demonstrated high complexation efficiency under mild reaction conditions (pH = 7, 5 min reaction time). The [203Pb]Pb2+ complexes' integrity in human serum over 24 h was appreciably good for [203Pb][Pb(DO4S)]2+ (80 ± 5%) and excellent for [203Pb][Pb(DO3SAm)]2+ (93 ± 1%) and [203Pb][Pb(DO2A2S)] (94 ± 1%). These results reveal the promise of DO2A2S and DO3SAm as chelators in cutting-edge theranostic [203/212Pb]Pb2+ radiopharmaceuticals.
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Affiliation(s)
- Marianna Tosato
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
- Radiopharmaceutical
Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Parmissa Randhawa
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Luca Lazzari
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Brooke L. McNeil
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Marco Dalla Tiezza
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Giordano Zanoni
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Fabrizio Mancin
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Laura Orian
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Caterina F. Ramogida
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Valerio Di Marco
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
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3
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Tosato M, Franchi S, Dalla Tiezza M, Orian L, Gyr T, Alker A, Zanoni G, Pastore P, Andrighetto A, Köster U, Jensen M, Mäcke H, Asti M, Di Marco V. Tuning the Framework of Thioether-Functionalized Polyazamacrocycles: Searching for a Chelator for Theranostic Silver Radioisotopes. Inorg Chem 2023; 62:20777-20790. [PMID: 37768780 DOI: 10.1021/acs.inorgchem.3c02456] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Silver-111 is an attractive unconventional candidate for targeted cancer therapy as well as for single photon emission computed tomography and can be complemented by silver-103 for positron emission tomography noninvasive diagnostic procedures. However, the shortage of chelating agents capable of forming stable complexes tethered to tumor-seeking vectors has hindered their in vivo application so far. In this study, a comparative investigation of a series of sulfur-containing structural homologues, namely, 1,4,7-tris[2-(methylsulfanyl)ethyl)]-1,4,7-triazacyclononane (NO3S), 1,5,9-tris[2-(methylsulfanyl)ethyl]-1,5,9-triazacyclododecane (TACD3S), 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclotridecane (TRI4S), and 1,4,8,11-tetrakis[2-(methylsulfanyl)ethyl]-1,4,8,11-tetraazacyclotetradecane (TE4S) was conducted to appraise the influence of different polyazamacrocyclic backbones on Ag+ complexation. The performances of these macrocycles were also compared with those of the previously reported Ag+/[111Ag]Ag+-chelator 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S). Nuclear magnetic resonance data supported by density functional theory calculations and X-ray crystallographic results gave insights into the coordination environment of these complexes, suggesting that all of the donor atoms are generally involved in the metal coordination. However, the modifications of the macrocycle topology alter the dynamic binding of the pendant arms or the conformation of the ring around the metal center. Combined pH/pAg-potentiometric and spectroscopic experiments revealed that the 12-member N4 backbone of DO4S forms the most stable Ag+ complex while both the enlargement and the shrinkage of the macrocyclic frame dwindle the stability of the complexes. Radiolabeling experiments, conducted with reactor-produced [111Ag]Ag+, evidenced that the thermodynamic stability trend is reflected in the ligand's ability to incorporate the radioactive ion at high molar activity, even in the presence of a competing cation (Pd2+), as well as in the integrity of the corresponding complexes in human serum. As a consequence, DO4S proved to be the most favorable candidate for future in vivo applications.
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Affiliation(s)
- Marianna Tosato
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy
| | - Sara Franchi
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Marco Dalla Tiezza
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Laura Orian
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Thomas Gyr
- Division of Radiopharmaceutical Chemistry, Clinic of Radiology and Nuclear Medicine, University Hospital Basel, 4058 Basel, Switzerland
| | - André Alker
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel F. Hoffmann-La Roche, 4058 Basel, Switzerland
| | - Giordano Zanoni
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Paolo Pastore
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Alberto Andrighetto
- Italian Institute of Nuclear Physics, Legnaro National Laboratories, 35020 Legnaro, Padova, Italy
| | - Ulli Köster
- Institut Laue-Langevin, 38042 Grenoble, France
| | - Mikael Jensen
- The Hevesy Laboratory, Department Health Technology, Technical University of Denmark, 4000 Roskilde, Denmark
| | - Helmut Mäcke
- Department of Nuclear Medicine, University Hospital Freiburg, D-79106 Freiburg, Germany
| | - Mattia Asti
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy
| | - Valerio Di Marco
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
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4
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Tosato M, Franchi S, Isse AA, Del Vecchio A, Zanoni G, Alker A, Asti M, Gyr T, Di Marco V, Mäcke H. Is Smaller Better? Cu 2+/Cu + Coordination Chemistry and Copper-64 Radiochemical Investigation of a 1,4,7-Triazacyclononane-Based Sulfur-Rich Chelator. Inorg Chem 2023; 62:20621-20633. [PMID: 37115633 PMCID: PMC10731632 DOI: 10.1021/acs.inorgchem.3c00621] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Indexed: 04/29/2023]
Abstract
The biologically triggered reduction of Cu2+ to Cu+ has been postulated as a possible in vivo decomplexation pathway in 64/67Cu-based radiopharmaceuticals. In an attempt to hinder this phenomenon, we have previously developed a family of S-containing polyazamacrocycles based on 12-, 13-, or 14-membered tetraaza rings able to stabilize both oxidation states. However, despite the high thermodynamic stability of the resulting Cu2+/+ complexes, a marked [64Cu]Cu2+ release was detected in human serum, likely as a result of the partially saturated coordination sphere around the copper center. In the present work, a new hexadentate macrocyclic ligand, 1,4,7-tris[2-(methylsulfanyl)ethyl)]-1,4,7-triazacyclononane (NO3S), was synthesized by hypothesizing that a smaller macrocyclic backbone could thwart the observed demetalation by fully encapsulating the copper ion. To unveil the role of the S donors in the metal binding, the corresponding alkyl analogue 1,4,7-tris-n-butyl-1,4,7-triazacyclononane (TACN-n-Bu) was considered as comparison. The acid-base properties of the free ligands and the kinetic, thermodynamic, and structural properties of their Cu2+ and Cu+ complexes were investigated in solution and solid (crystal) states through a combination of spectroscopic and electrochemical techniques. The formation of two stable mononuclear species was detected in aqueous solution for both ligands. The pCu2+ value for NO3S at physiological pH was 6 orders of magnitude higher than that computed for TACN-n-Bu, pointing out the significant stabilizing contribution arising from the Cu2+-S interactions. In both the solid state and solution, Cu2+ was fully embedded in the ligand cleft in a hexacoordinated N3S3 environment. Furthermore, NO3S exhibited a remarkable ability to form a stable complex with Cu+ through the involvement of all of the donors in the coordination sphere. Radiolabeling studies evidenced an excellent affinity of NO3S toward [64Cu]Cu2+, as quantitative incorporation was achieved at high apparent molar activity (∼10 MBq/nmol) and under mild conditions (ambient temperature, neutral pH, 10 min reaction time). Human serum stability assays revealed an increased stability of [64Cu][Cu(NO3S)]2+ when compared to the corresponding complexes formed by 12-, 13-, or 14-membered tetraaza rings.
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Affiliation(s)
- Marianna Tosato
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Sara Franchi
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | | | | | - Giordano Zanoni
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - André Alker
- Roche
Pharmaceutical Research and Early Development, Roche Innovation Center Basel F. Hoffmann-La Roche, 4058 Basel, Switzerland
| | - Mattia Asti
- Radiopharmaceutical
Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy
| | - Thomas Gyr
- Division
of Radiopharmaceutical Chemistry, Clinic of Radiology and Nuclear
Medicine, University Hospital Basel, 4031 Basel, Switzerland
| | - Valerio Di Marco
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Helmut Mäcke
- Department
of Nuclear Medicine, University Hospital
Freiburg, D-79106 Freiburg, Germany
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5
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Tosato M, Asti M, Di Marco V, Jensen ML, Schell J, Dang TT, Köster U, Jensen M, Hemmingsen L. Towards in vivo applications of 111Ag perturbed angular correlation of γ-rays (PAC) spectroscopy. Appl Radiat Isot 2022; 190:110508. [DOI: 10.1016/j.apradiso.2022.110508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 10/04/2022] [Accepted: 10/05/2022] [Indexed: 11/27/2022]
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6
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Chelation of Theranostic Copper Radioisotopes with S-Rich Macrocycles: From Radiolabelling of Copper-64 to In Vivo Investigation. Molecules 2022; 27:molecules27134158. [PMID: 35807404 PMCID: PMC9268100 DOI: 10.3390/molecules27134158] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 12/10/2022] Open
Abstract
Copper radioisotopes are generally employed for cancer imaging and therapy when firmly coordinated via a chelating agent coupled to a tumor-seeking vector. However, the biologically triggered Cu2+-Cu+ redox switching may constrain the in vivo integrity of the resulting complex, leading to demetallation processes. This unsought pathway is expected to be hindered by chelators bearing N, O, and S donors which appropriately complements the borderline-hard and soft nature of Cu2+ and Cu+. In this work, the labelling performances of a series of S-rich polyazamacrocyclic chelators with [64Cu]Cu2+ and the stability of the [64Cu]Cu-complexes thereof were evaluated. Among the chelators considered, the best results were obtained with 1,7-bis [2-(methylsulfanyl)ethyl]-4,10,diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S). DO2A2S was labelled at high molar activities in mild reaction conditions, and its [64Cu]Cu2+ complex showed excellent integrity in human serum over 24 h. Biodistribution studies in BALB/c nude mice performed with [64Cu][Cu(DO2A2S)] revealed a behavior similar to other [64Cu]Cu-labelled cyclen derivatives characterized by high liver and kidney uptake, which could either be ascribed to transchelation phenomena or metabolic processing of the intact complex.
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Tosato M, Lazzari L, Marco VD. Revisiting Lead(II)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic Acid Coordination Chemistry in Aqueous Solutions: Evidence of an Underestimated Thermodynamic Stability. ACS OMEGA 2022; 7:15596-15602. [PMID: 35571797 PMCID: PMC9096932 DOI: 10.1021/acsomega.2c00387] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 04/11/2022] [Indexed: 06/15/2023]
Abstract
The complexes formed between Pb2+ and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) were reinvestigated in aqueous solutions using a combination of pH potentiometry, UV-vis spectroscopy, and NMR spectroscopy. The thermodynamic data were supported by kinetics assays. Differently protonated complexes, i.e., [PbH3L]+, [PbH2L], [PbHL]-, and [PbL]2-, were detected, and the corresponding stability constants (logβ) at T = 298 K and I = 0.1 M NaCl were 33.1 ± 0.2, 32.00 ± 0.06, 29.28 ± 0.06, and 25.3 ± 0.1, respectively. Results differed significantly from those previously reported by Chaves et al. (Talanta1992, 39, 249) and Pippin et al. (Inorg. Chim. Acta1995, 239, 43) in both the speciation and the overall complex stability; the latter in particular was found to be remarkably higher. The work disclosed herein provides revised data on the Pb2+-DOTA complexes, which should be used as a new stability benchmark during the development of lead chelators.
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Tosato M, Pelosato M, Franchi S, Isse AA, May NV, Zanoni G, Mancin F, Pastore P, Badocco D, Asti M, Di Marco V. When ring makes the difference: coordination properties of Cu 2+/Cu + complexes with sulfur-pendant polyazamacrocycles for radiopharmaceutical applications. NEW J CHEM 2022. [DOI: 10.1039/d2nj01032a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Cu2+/+ complexes formed by sulfur-containing polyazamacrocycles were studied in aqueous solution using potentiometry, UV-Vis, NMR, EPR, and cyclic voltammetry.
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Affiliation(s)
- Marianna Tosato
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Matteo Pelosato
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Sara Franchi
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | | | - Nóra Veronica May
- Centre for Structural Science, Research Centre for Natural Sciences, 1117 Budapest, Hungary
| | - Giordano Zanoni
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Fabrizio Mancin
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Paolo Pastore
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Denis Badocco
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Mattia Asti
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS di Reggio Emilia, 42122 Reggio Emilia, Italy
| | - Valerio Di Marco
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
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Tosato M, Dalla Tiezza M, May NV, Isse AA, Nardella S, Orian L, Verona M, Vaccarin C, Alker A, Mäcke H, Pastore P, Di Marco V. Copper Coordination Chemistry of Sulfur Pendant Cyclen Derivatives: An Attempt to Hinder the Reductive-Induced Demetalation in 64/67Cu Radiopharmaceuticals. Inorg Chem 2021; 60:11530-11547. [PMID: 34279088 PMCID: PMC8389837 DOI: 10.1021/acs.inorgchem.1c01550] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The Cu2+ complexes formed by a series of cyclen derivatives bearing sulfur pendant arms, 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), and 1,7-bis[2-(methylsulfanyl)ethyl]-4,10-diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S), were studied in aqueous solution at 25 °C from thermodynamic and structural points of view to evaluate their potential as chelators for copper radioisotopes. UV-vis spectrophotometric out-of-cell titrations under strongly acidic conditions, direct in-cell UV-vis titrations, potentiometric measurements at pH >4, and spectrophotometric Ag+-Cu2+ competition experiments were performed to evaluate the stoichiometry and stability constants of the Cu2+ complexes. A highly stable 1:1 metal-to-ligand complex (CuL) was found in solution at all pH values for all chelators, and for DO2A2S, protonated species were also detected under acidic conditions. The structures of the Cu2+ complexes in aqueous solution were investigated by UV-vis and electron paramagnetic resonance (EPR), and the results were supported by relativistic density functional theory (DFT) calculations. Isomers were detected that differed from their coordination modes. Crystals of [Cu(DO4S)(NO3)]·NO3 and [Cu(DO2A2S)] suitable for X-ray diffraction were obtained. Cyclic voltammetry (CV) experiments highlighted the remarkable stability of the copper complexes with reference to dissociation upon reduction from Cu2+ to Cu+ on the CV time scale. The Cu+ complexes were generated in situ by electrolysis and examined by NMR spectroscopy. DFT calculations gave further structural insights. These results demonstrate that the investigated sulfur-containing chelators are promising candidates for application in copper-based radiopharmaceuticals. In this connection, the high stability of both Cu2+ and Cu+ complexes can represent a key parameter for avoiding in vivo demetalation after bioinduced reduction to Cu+, often observed for other well-known chelators that can stabilize only Cu2+.
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Affiliation(s)
- Marianna Tosato
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Marco Dalla Tiezza
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Nóra V May
- Centre for Structural Science, Research Centre for Natural Sciences, Magyar tudósok Körútja 2, 1117 Budapest, Hungary
| | - Abdirisak Ahmed Isse
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Sonia Nardella
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy.,Department of Pharmaceutical Sciences, University of Padova, via Marzolo 8, 35131 Padova, Italy
| | - Laura Orian
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Marco Verona
- Department of Pharmaceutical Sciences, University of Padova, via Marzolo 8, 35131 Padova, Italy
| | - Christian Vaccarin
- Department of Pharmaceutical Sciences, University of Padova, via Marzolo 8, 35131 Padova, Italy
| | - André Alker
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel F. Hoffmann-La Roche, Grenzacherstrasse 124, 4058 Basel, Switzerland
| | - Helmut Mäcke
- Department of Nuclear Medicine, University Hospital Freiburg, Hugstetterstrasse 55, D-79106 Freiburg, Germany
| | - Paolo Pastore
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Valerio Di Marco
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
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Tosato M, Asti M, Dalla Tiezza M, Orian L, Häussinger D, Vogel R, Köster U, Jensen M, Andrighetto A, Pastore P, Marco VD. Highly Stable Silver(I) Complexes with Cyclen-Based Ligands Bearing Sulfide Arms: A Step Toward Silver-111 Labeled Radiopharmaceuticals. Inorg Chem 2020; 59:10907-10919. [PMID: 32658468 PMCID: PMC8009516 DOI: 10.1021/acs.inorgchem.0c01405] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
With a half-life of 7.45 days, silver-111 (βmax 1.04 MeV, Eγ 245.4 keV [Iγ 1.24%], Eγ 342.1 keV [Iγ 6.7%]) is a promising candidate for targeted cancer therapy with β- emitters as well as for associated SPECT imaging. For its clinical use, the development of suitable ligands that form sufficiently stable Ag+-complexes in vivo is required. In this work, the following sulfur-containing derivatives of tetraazacyclododecane (cyclen) have been considered as potential chelators for silver-111: 1,4,7,10-tetrakis(2-(methylsulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane (DO4S), (2S,5S,8S,11S)-2,5,8,11-tetramethyl-1,4,7,10-tetrakis(2-(methylsulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane (DO4S4Me), 1,4,7-tris(2-(methylsulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris(2-(methylsulfanyl)ethyl)-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), and 1,7-bis(2-(methylsulfanyl)ethyl)-4,10,diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S). Natural Ag+ was used in pH/Ag-potentiometric and UV-vis spectrophotometric studies to determine the metal speciation existing in aqueous NaNO3 0.15 M at 25 °C and the equilibrium constants of the complexes, whereas NMR and DFT calculations gave structural insights. Overall results indicated that sulfide pendant arms coordinate Ag+ allowing the formation of very stable complexes, both at acidic and physiological pH. Furthermore, radiolabeling, stability in saline phosphate buffer, and metal-competition experiments using the two ligands forming the strongest complexes, DO4S and DO4S4Me, were carried out with [111Ag]Ag+ and promising results were obtained.
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Affiliation(s)
- Marianna Tosato
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Mattia Asti
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS di Reggio Emilia, Viale Risorgimento 80, 42122 Reggio Emilia, Italy
| | - Marco Dalla Tiezza
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Laura Orian
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Daniel Häussinger
- Department of Chemistry, University of Basel, St. Johannsring 19, 4056, Basel, Switzerland
| | - Raphael Vogel
- Department of Chemistry, University of Basel, St. Johannsring 19, 4056, Basel, Switzerland
| | - Ulli Köster
- Institut Laue-Langevin, 71 avenue des Martyrs CS 20156, 38042 Grenoble Cedex 9, France
| | - Mikael Jensen
- The Hevesy Laboratory, Department Health Technology, Technical University of Denmark (DTU), Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Alberto Andrighetto
- Italian Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell'Università 2, 35020 Legnaro (Padova), Italy
| | - Paolo Pastore
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Valerio Di Marco
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
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