- Email: [email protected]
Bispidines as a platform for targeted multimodal imaging
632
Abstracts
N@C80 and irradiated at various fluxes for different lengths of time. Previous studies have indicated that fullerenes may not hold up resulting in leakage of the Lu from the fullerene. Fullerenes containing natural lutetium were irradiated in the reflector region of the MURR reactor. Samples were then dissolved using toluene and carbon disulfide and evaluated by TLC and HPLC to determine if the Lu was free or retained in the fullerene. Our preliminary results including evaluation by HPLC indicate a high retention of the Lu in the fullerene and that they may be a viable option for medical applications. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.130
70 Acyclic chelating ligands for PET imaging of tumor hypoxia with Ga-68 a,b
c
a
Caterina F. Ramogida , Cara L. Ferreira , Jacqueline F. Cawthray , Chris Orviga, Michael J. Adamb a
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver BC, V6T 1Z1 Canada b TRIUMF, 4004 Wesbrook Mall, Vancouver BC, V6T 2A3 Canada c Nordion, 4004 Wesbrook Mall, Vancouver BC, V6T 2A3 Canada Recently, our group has developed the linear N4O2 chelating ligand, H2dedpa that binds Ga3 + quickly and under mild conditions whilst exhibiting exceptional kinetic inertness in vitro – ideal properties to be incorporated into a 68Ga PET imaging agent [1]. Herein, we report nitroimidazole (NI) derivatives of H2dedpa to investigate specific targeting of hypoxic tumor cells, given that NI can be reduced and retained exclusively in hypoxic cells [2]. Nine N-alkylated-NI derivatives of H2dedpa and H2CHXdedpa (derivative with a chiral backbone) have been synthesized and screened for their ability to bind gallium. The compounds were radio-labeled with 67Ga and 68Ga, and show promising radiolabeling efficiencies (N95%) when labeled at 10− 5 M for 10 min at room temperature. Moreover, stability studies via apo-transferrin challenge assays show that the 67Ga-complexes exhibit exceptional stability (N97% intact) after two hours. In vitro cell uptake studies under hypoxia with two cancer cell lines are currently underway.
References [1] Boros E, et al. J Am Chem Soc 2010;132:15726–33. [2] Wilson WR, et al. Nat Rev Cancer 2011;11:393–410. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.022
71 Preparation of [45Ti] Ti-salan-dipic Gregory W. Severin, Andreas I. Jensen, Jesper Fonslet, Fedor Zhuravlev
45
Ti was prepared by proton irradiation of natSc foil followed by extraction onto a polystyrene-based diol-resin (RAPP polymers) after dissolution of the foil in 37% HCl. Synthesis proceeded on the column after quenching the residual acidity with pyridine. The ligands, salan and dipic, were added sequentially in pyridine, with the release of the final compound upon ligand exchange to dipic. [45Ti]Ti-salandipic was characterized by radio-TLC on silica in 1:1 ethylacetate: chloroform in comparison to the cold compound. This is a hydrolytically stable, cytotoxic, 45Ti compound. The solid-phase synthesis is robust, and provides opportunity for producing other 45Ti tracers. PET and radiotracer studies with [45Ti] Ti-salan-dipic and other Ti-based cytotoxic compounds will aid in mechanism determination, drug design, and eventually more effective treatment of cancer. Reference [1] Immel, et al. Chem Commun 2012;48:5790–2. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.107
72 Development of Ga-PpIX peptides as fluorescence/PET imaging probes Neha Sharmaa, Babak Behnam Azadb, Leonard G. Luyta,c a
The University of Western Ontario, London, Canada Johns Hopkins University c London Regional Cancer Program, London, Canada b
The use of gallium-68 for non-invasive PET imaging has gained much interest with the increasing availability of 68Ge/68Ga generators. Protoporphyrin IX (PpIX) was utilized for gallium coordination owing to its inherent fluorescence characteristics and suitable cavity size, allowing for fluorescence microscopy and PET imaging studies with a single structural manifold. PpIX was placed at the N-terminus of integrin targeting tripeptide RGD, through a short PEG linker [1]. Coordination with 69/71Ga provided a fluorescent analogue that exhibited significant uptake in the melanoma cell line MDA-MB-435, as indicated by fluorescence microscopy. Radiolabelling with 68Ga was carried out with a 33 ± 3% radiochemical yield (d.c.) and 97% radiochemical purity. Next, PpIX was placed at the C-terminus of the peptide ghrelin, which is the endogenous ligand for the growth hormone secretagogue receptor (GHSR1a), to form [Dpr3(octanoyl),Tyr8]-ghrelin(1–8)-PpIX and was subsequently coordinated to 69/71Ga. This PpIX-ghrelin analogue will permit in vitro evaluation via fluorescence microscopy (69/71Ga), as well as in vivo PET imaging (68Ga). This proof of concept study will validate the use of Ga-PpIX as a prosthetic group in peptide analogues, for dual modality optical/PET imaging of biological targets. Reference [1] Behnam Azad B, et al. Appl Radiat Isot 2012;70(3):505–11.
The Hevesy Laboratory, Center for Nuclear Technologies, Technical University of Denmark We report the carrier-free radiochemical synthesis of a neutral, bio-active, titanium-45 complex, [45Ti]Ti-salan-dipic. In 2012, the Huhn group at Universität Konstanz reported the non-radioactive compound, Ti-salan-dipic, and demonstrated therapeutic efficacy in a xenograft cervical cancer mouse model as well as enhanced in-vitro cytotoxicity over several other titanium-based chemotherapeutics [1]. The mechanism of action for this class of therapeutics is under investigation and the determination of which will be aided by radiotracing and PET with 45Ti.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.124
73 Bispidines as a platform for targeted multimodal imaging Peter Combaa, Sebastian Hunoldtb, Michael Morgena, Jens Pietzschb, Jörg Steinbachb, Holger Stephanb, Martin Waltherb a
University of Heidelberg HZDR
b
Abstracts
Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable coordination compounds, in particular with first row transition metal ions. Considering multiple functionalization, bispidines are promising candidates for pharmaceutical targeting and multimodal imaging. Due to the formation of thermodynamically stable and kinetically inert CuII complexes, penta- and hexadentate bispidine ligands are well suited for 64Cu positron emission tomography imaging and radiotherapy (64Cu/67Cu). The bispidine scaffold paves the way for introducing further functionalities, such as targeting units and fluorescence labels, which broadens the scope regarding pharmaceutical targeting and dual labelling (PET and optical imaging). Several bispidine ligands have been developed in order to improve the radiopharmaceutical behavior as well as possibilities for further beneficial functionalization. Variable denticity (tetra-, penta- and hexadentate) with different donor groups, such as amino, amido, pyridine and/ or methoxypyridine functionalities allows for tuning properties such as complexation and lipophilicity. These ligands and the important properties of their CuII complexes, e.g., stabilities, ligand exchange kinetics, serum stability, partition coefficients ([64Cu]Cubispidine: n-octanol/water) and biodistribution studies will be reported.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.047
633
75 DOTHA2 and NOTHA2—New chelates for highly efficient 64 Cu radiolabeling S. Ait-Mohand, C. Denis, G. Tremblay, M. Paquette, B. Guérin Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke With the goal of identifying improved bifunctional chelates (BFCs) that stably complex with fast kinetics 64Cu, we have synthesized DOTHA2 and NOTHA2, two BFCs derived from polyazacycles and bearing methyl-hydroxamic acid pendant arms. Radiolabeling experiments were performed varying the pH and the counterion, and each chelate has been compared to currently used BFCs DOTA and NOTA with respect to radiolabeling efficiency and stability. DOTHA2 and NOTHA2 were prepared with great yields and ease of synthesis in solution and on solid phase. The novel BFCs offered very fast labeling kinetic at room temperature in a wide range of pH as compared to DOTA and NOTA. Specific activities of the radiolabeled-DOTHA2, NOTHA2 are excellent and the 64Cu-complexes are stable in mouse plasma and in vivo. Biodistribution and imaging experiments conducted in Balb/c mice showed low residual activity in various tissues and fast hepatic and renal clearance for the novel radiolabeled BFCs.
74 [64Cu]Cu-CryptTM – A novel cryptate for copper-64? Christian Foerstera, James C. Knighta, Melinda Wuesta, Brendan Rowanb, Suzanne E. Lapic, Angelo J. Amorosob, Peter G. Edwardsb, Frank Wuesta a
University of Alberta Cardiff University of Wales c Washington University School of Medicine b
Objective: Radiopharmaceutical evaluation of novel cryptand CryptTM for labeling with 64Cu. Methods: Stability of [64Cu]Cu-CryptTM was assessed in vitro by challenging experiments using competitive chelators EDTA and NOTA. Radiopharmacological profile of [64Cu]Cu-CryptTM was evaluated by dynamic PET studies in EMT6-tumor bearing Balb/C mice. The current “gold standard” for kinetically inert 64Cu-cryptates [64Cu]Cu-DiAmSar was prepared and used as internal reference for in vitro and in vivo studies. Results: Radiochemical yields of N95% were achieved by mixing CryptTM (0.25 nmol/μL) and [64Cu]Cu(OAc)2 (4.1 ± 0.5 MBq/μL) for 60 min at 37 °C. EDTA and NOTA clearly demonstrated kinetically- and thermodynamically-driven trans-chelation. Dynamic PET studies showed fast blood clearance for [64Cu]Cu-CryptTM and [64Cu]Cu-DiAmSar. [64Cu]CuCryptTM was predominantly eliminated hepatobiliary. Uptake of [64Cu]Cu-CryptTM in EMT6 tumors resulted in an SUV 0.40 ± 0.03 which was higher compared to muscle (SUV 0.16 ± 0.02 (n = 3) 60 min p.i.). Conclusion: Radiopharmacological evaluation of [64Cu]Cu-CryptTM revealed insufficient kinetic stability for in vivo applications. However, the facile synthetic access and its favorable 64Cu-labeling properties warrant further investigation of related derivatives possessing a tripyridyl/tri-amine donor group set to allow the formation of more kinetically inert 64Cu-cryptates.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.127
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.029
76 Kinetic inertness evaluation of copper complexes using gel electrophoresis techniques Manja Kubeil, Kristof Zarschler, Jörg Steinbach, Holger Stephan Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research The development of highly stable radiocopper complexes is one major challenge that seeks to further improve radiopharmaceuticals for medicinal applications. In many cases, radiocopper complexes suffer the fate of dissociation in vivo which is contributed to loss of the radionuclide resulting amongst others in an unspecific accumulation in non-target tissues and thus in poor target-to-background ratios. The kinetic lability has been addressed as major issue for transchelation or dissociation in vivo. Valuable information of kinetic inertness can be derived from non-physiological and non-radiotracer conditions e.g., ligand or metal ion challenge experiments, acidassisted dissociation studies. Serum stability experiments are more suitable, since they are associated with in vivo conditions. Usually, the method of choice to measure the kinetic inertness involves a time-consuming radio-HPLC procedure. In contrast, we describe two reliable in vitro assays using standard gel electrophoresis techniques which provide a timesaving work-flow for measuring simultaneously a variety of copper-containing chelates. With this procedure, different radiocopper chelates can be evaluated and compared concerning their kinetic inertness using protein challenge assays. Moreover, both experiments are transferable not only to newly
Abstracts
N@C80 and irradiated at various fluxes for different lengths of time. Previous studies have indicated that fullerenes may not hold up resulting in leakage of the Lu from the fullerene. Fullerenes containing natural lutetium were irradiated in the reflector region of the MURR reactor. Samples were then dissolved using toluene and carbon disulfide and evaluated by TLC and HPLC to determine if the Lu was free or retained in the fullerene. Our preliminary results including evaluation by HPLC indicate a high retention of the Lu in the fullerene and that they may be a viable option for medical applications. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.130
70 Acyclic chelating ligands for PET imaging of tumor hypoxia with Ga-68 a,b
c
a
Caterina F. Ramogida , Cara L. Ferreira , Jacqueline F. Cawthray , Chris Orviga, Michael J. Adamb a
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver BC, V6T 1Z1 Canada b TRIUMF, 4004 Wesbrook Mall, Vancouver BC, V6T 2A3 Canada c Nordion, 4004 Wesbrook Mall, Vancouver BC, V6T 2A3 Canada Recently, our group has developed the linear N4O2 chelating ligand, H2dedpa that binds Ga3 + quickly and under mild conditions whilst exhibiting exceptional kinetic inertness in vitro – ideal properties to be incorporated into a 68Ga PET imaging agent [1]. Herein, we report nitroimidazole (NI) derivatives of H2dedpa to investigate specific targeting of hypoxic tumor cells, given that NI can be reduced and retained exclusively in hypoxic cells [2]. Nine N-alkylated-NI derivatives of H2dedpa and H2CHXdedpa (derivative with a chiral backbone) have been synthesized and screened for their ability to bind gallium. The compounds were radio-labeled with 67Ga and 68Ga, and show promising radiolabeling efficiencies (N95%) when labeled at 10− 5 M for 10 min at room temperature. Moreover, stability studies via apo-transferrin challenge assays show that the 67Ga-complexes exhibit exceptional stability (N97% intact) after two hours. In vitro cell uptake studies under hypoxia with two cancer cell lines are currently underway.
References [1] Boros E, et al. J Am Chem Soc 2010;132:15726–33. [2] Wilson WR, et al. Nat Rev Cancer 2011;11:393–410. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.022
71 Preparation of [45Ti] Ti-salan-dipic Gregory W. Severin, Andreas I. Jensen, Jesper Fonslet, Fedor Zhuravlev
45
Ti was prepared by proton irradiation of natSc foil followed by extraction onto a polystyrene-based diol-resin (RAPP polymers) after dissolution of the foil in 37% HCl. Synthesis proceeded on the column after quenching the residual acidity with pyridine. The ligands, salan and dipic, were added sequentially in pyridine, with the release of the final compound upon ligand exchange to dipic. [45Ti]Ti-salandipic was characterized by radio-TLC on silica in 1:1 ethylacetate: chloroform in comparison to the cold compound. This is a hydrolytically stable, cytotoxic, 45Ti compound. The solid-phase synthesis is robust, and provides opportunity for producing other 45Ti tracers. PET and radiotracer studies with [45Ti] Ti-salan-dipic and other Ti-based cytotoxic compounds will aid in mechanism determination, drug design, and eventually more effective treatment of cancer. Reference [1] Immel, et al. Chem Commun 2012;48:5790–2. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.107
72 Development of Ga-PpIX peptides as fluorescence/PET imaging probes Neha Sharmaa, Babak Behnam Azadb, Leonard G. Luyta,c a
The University of Western Ontario, London, Canada Johns Hopkins University c London Regional Cancer Program, London, Canada b
The use of gallium-68 for non-invasive PET imaging has gained much interest with the increasing availability of 68Ge/68Ga generators. Protoporphyrin IX (PpIX) was utilized for gallium coordination owing to its inherent fluorescence characteristics and suitable cavity size, allowing for fluorescence microscopy and PET imaging studies with a single structural manifold. PpIX was placed at the N-terminus of integrin targeting tripeptide RGD, through a short PEG linker [1]. Coordination with 69/71Ga provided a fluorescent analogue that exhibited significant uptake in the melanoma cell line MDA-MB-435, as indicated by fluorescence microscopy. Radiolabelling with 68Ga was carried out with a 33 ± 3% radiochemical yield (d.c.) and 97% radiochemical purity. Next, PpIX was placed at the C-terminus of the peptide ghrelin, which is the endogenous ligand for the growth hormone secretagogue receptor (GHSR1a), to form [Dpr3(octanoyl),Tyr8]-ghrelin(1–8)-PpIX and was subsequently coordinated to 69/71Ga. This PpIX-ghrelin analogue will permit in vitro evaluation via fluorescence microscopy (69/71Ga), as well as in vivo PET imaging (68Ga). This proof of concept study will validate the use of Ga-PpIX as a prosthetic group in peptide analogues, for dual modality optical/PET imaging of biological targets. Reference [1] Behnam Azad B, et al. Appl Radiat Isot 2012;70(3):505–11.
The Hevesy Laboratory, Center for Nuclear Technologies, Technical University of Denmark We report the carrier-free radiochemical synthesis of a neutral, bio-active, titanium-45 complex, [45Ti]Ti-salan-dipic. In 2012, the Huhn group at Universität Konstanz reported the non-radioactive compound, Ti-salan-dipic, and demonstrated therapeutic efficacy in a xenograft cervical cancer mouse model as well as enhanced in-vitro cytotoxicity over several other titanium-based chemotherapeutics [1]. The mechanism of action for this class of therapeutics is under investigation and the determination of which will be aided by radiotracing and PET with 45Ti.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.124
73 Bispidines as a platform for targeted multimodal imaging Peter Combaa, Sebastian Hunoldtb, Michael Morgena, Jens Pietzschb, Jörg Steinbachb, Holger Stephanb, Martin Waltherb a
University of Heidelberg HZDR
b
Abstracts
Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable coordination compounds, in particular with first row transition metal ions. Considering multiple functionalization, bispidines are promising candidates for pharmaceutical targeting and multimodal imaging. Due to the formation of thermodynamically stable and kinetically inert CuII complexes, penta- and hexadentate bispidine ligands are well suited for 64Cu positron emission tomography imaging and radiotherapy (64Cu/67Cu). The bispidine scaffold paves the way for introducing further functionalities, such as targeting units and fluorescence labels, which broadens the scope regarding pharmaceutical targeting and dual labelling (PET and optical imaging). Several bispidine ligands have been developed in order to improve the radiopharmaceutical behavior as well as possibilities for further beneficial functionalization. Variable denticity (tetra-, penta- and hexadentate) with different donor groups, such as amino, amido, pyridine and/ or methoxypyridine functionalities allows for tuning properties such as complexation and lipophilicity. These ligands and the important properties of their CuII complexes, e.g., stabilities, ligand exchange kinetics, serum stability, partition coefficients ([64Cu]Cubispidine: n-octanol/water) and biodistribution studies will be reported.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.047
633
75 DOTHA2 and NOTHA2—New chelates for highly efficient 64 Cu radiolabeling S. Ait-Mohand, C. Denis, G. Tremblay, M. Paquette, B. Guérin Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke With the goal of identifying improved bifunctional chelates (BFCs) that stably complex with fast kinetics 64Cu, we have synthesized DOTHA2 and NOTHA2, two BFCs derived from polyazacycles and bearing methyl-hydroxamic acid pendant arms. Radiolabeling experiments were performed varying the pH and the counterion, and each chelate has been compared to currently used BFCs DOTA and NOTA with respect to radiolabeling efficiency and stability. DOTHA2 and NOTHA2 were prepared with great yields and ease of synthesis in solution and on solid phase. The novel BFCs offered very fast labeling kinetic at room temperature in a wide range of pH as compared to DOTA and NOTA. Specific activities of the radiolabeled-DOTHA2, NOTHA2 are excellent and the 64Cu-complexes are stable in mouse plasma and in vivo. Biodistribution and imaging experiments conducted in Balb/c mice showed low residual activity in various tissues and fast hepatic and renal clearance for the novel radiolabeled BFCs.
74 [64Cu]Cu-CryptTM – A novel cryptate for copper-64? Christian Foerstera, James C. Knighta, Melinda Wuesta, Brendan Rowanb, Suzanne E. Lapic, Angelo J. Amorosob, Peter G. Edwardsb, Frank Wuesta a
University of Alberta Cardiff University of Wales c Washington University School of Medicine b
Objective: Radiopharmaceutical evaluation of novel cryptand CryptTM for labeling with 64Cu. Methods: Stability of [64Cu]Cu-CryptTM was assessed in vitro by challenging experiments using competitive chelators EDTA and NOTA. Radiopharmacological profile of [64Cu]Cu-CryptTM was evaluated by dynamic PET studies in EMT6-tumor bearing Balb/C mice. The current “gold standard” for kinetically inert 64Cu-cryptates [64Cu]Cu-DiAmSar was prepared and used as internal reference for in vitro and in vivo studies. Results: Radiochemical yields of N95% were achieved by mixing CryptTM (0.25 nmol/μL) and [64Cu]Cu(OAc)2 (4.1 ± 0.5 MBq/μL) for 60 min at 37 °C. EDTA and NOTA clearly demonstrated kinetically- and thermodynamically-driven trans-chelation. Dynamic PET studies showed fast blood clearance for [64Cu]Cu-CryptTM and [64Cu]Cu-DiAmSar. [64Cu]CuCryptTM was predominantly eliminated hepatobiliary. Uptake of [64Cu]Cu-CryptTM in EMT6 tumors resulted in an SUV 0.40 ± 0.03 which was higher compared to muscle (SUV 0.16 ± 0.02 (n = 3) 60 min p.i.). Conclusion: Radiopharmacological evaluation of [64Cu]Cu-CryptTM revealed insufficient kinetic stability for in vivo applications. However, the facile synthetic access and its favorable 64Cu-labeling properties warrant further investigation of related derivatives possessing a tripyridyl/tri-amine donor group set to allow the formation of more kinetically inert 64Cu-cryptates.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.127
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.029
76 Kinetic inertness evaluation of copper complexes using gel electrophoresis techniques Manja Kubeil, Kristof Zarschler, Jörg Steinbach, Holger Stephan Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research The development of highly stable radiocopper complexes is one major challenge that seeks to further improve radiopharmaceuticals for medicinal applications. In many cases, radiocopper complexes suffer the fate of dissociation in vivo which is contributed to loss of the radionuclide resulting amongst others in an unspecific accumulation in non-target tissues and thus in poor target-to-background ratios. The kinetic lability has been addressed as major issue for transchelation or dissociation in vivo. Valuable information of kinetic inertness can be derived from non-physiological and non-radiotracer conditions e.g., ligand or metal ion challenge experiments, acidassisted dissociation studies. Serum stability experiments are more suitable, since they are associated with in vivo conditions. Usually, the method of choice to measure the kinetic inertness involves a time-consuming radio-HPLC procedure. In contrast, we describe two reliable in vitro assays using standard gel electrophoresis techniques which provide a timesaving work-flow for measuring simultaneously a variety of copper-containing chelates. With this procedure, different radiocopper chelates can be evaluated and compared concerning their kinetic inertness using protein challenge assays. Moreover, both experiments are transferable not only to newly