Développement de nouveaux ligands pour l'imagerie phénotypique-TEP au cuivre-64 en cancérologie

Les techniques d'imagerie médicale morphologiques et métaboliques, utilisées pour le diagnostic ou la stadification en cancérologie, peuvent être peu contributives dans certains types de cancers. L'imagerie phénotypique-TEP est une modalité tierce basée sur le ciblage spécifique d'un biomarqueur tumoral ainsi que sur la tomographie par émission de positons. L'intérêt de cette modalité d'imagerie réside dans l'amélioration de la sensibilité et la spécificité diagnostique dans ces cancers difficiles à imager, ainsi que dans sa capacité à sélectionner les patients éligibles à une thérapie ciblée de même qu'à évaluer la réponse à ce type de traitements. Le cceutique administré consiste en un vecteur, de type anticorps monoclonal, marqué avec un radionucléide émetteur de positons, dont l'un des mieux adaptés actuellement est le cuivre-64. La problématique majeure des marquages au cuivre-64 est leur manque de stabilité in vivo. Les ligands macrocycliques bifonctionnels, mis à profit comme intermédiaires pour coupler le cuivre-64 au vecteur, forment en effet des complexes pouvant se dissocier in vivo, sous l'action de compétiteurs métalliques ou de certaines protéines physiologiques. Le développement de l'imagerie phénotypique-TEP au cuivre-64 repose donc en partie sur le design et l'évaluation de nouveaux ligands, à même de former des complexes plus inertes après leur administration chez l'homme. Ce travail présente le radiomarquage du cyclam monopicolinate (TE1PA) ainsi que les études réalisées in vitro et in vivo (chez la souris) ayant permis de montrer les propriétés très encourageantes de ce ligand pour de futures applications d'imagerie phénotypique.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF

ARRONAX Cyclotron: Setting up of In-HouseHospital Radiopharmacy

International audienceWhilst radiopharmaceuticals have an important role to play in both imaging and treatment of patients, most notably cancer patients, nuclear medicine and radiopharmacy are currently facing challenges to create innovative new drugs. Traditional radiopharmaceutical manufacture can be considered as either a routine hospital production or a large-scale industrial production. The gap between these two practices has meant that there is an inability to supply innovative radiopharmaceuticals for use at the local level for mono-or multicentric clinical trials with satisfactory quality and safety specifications. This article highlights the regulatory requirements in aseptic pharmaceutical processing and in nuclear medicine to be able to locally produce radiopharmaceuticals. We validate the proof-of-concept for an "in-house" hospital-based radiopharmacy including an on-site cyclotron, that can fulfill the conflicting requirements between radiation safety and aseptic processing. The ARRONAX in-house radiopharmacy is currently able to provide sterile and pyrogenic-free injectable radiopharmaceutical compounds for both industrial and institutional clinical trials

Focus on the Controversial Aspects of (64)Cu-ATSM in Tumoral Hypoxia Mapping by PET Imaging

International audienceMapping tumor hypoxia is a great challenge in positron emission tomography (PET) imaging as the precise functional information of the biological processes is needed for many effective therapeutic strategies. Tumor hypoxia has been widely reported as a poor prognostic indicator and is often associated with tumor aggressiveness, chemo- and radio-resistance. An accurate diagnosis of hypoxia is a challenge and is crucial for providing accurate treatment for patients' survival benefits. This challenge has led to the emergence of new and novel PET tracers for the functional and metabolic characterization of tumor hypoxia non-invasively. Among these tracers, copper semicarbazone compound [64Cu]-diacetyl-bis(N (4)-methylthiosemicarbazone) (=64Cu-ATSM) has been developed as a tracer for hypoxia imaging. This review focuses on 64Cu-ATSM PET imaging and the concept is presented in two sections. The first section describes its in vitro development and pre-clinical testing and particularly its affinity in different cell lines. The second section describes the controversial reports on its specificity for hypoxia imaging. The review concludes that 64Cu-ATSM - more than a hypoxic tracer, exhibits tracer accumulation in tumor, which is linked to the redox potential and reactive oxygen species. The authors concluded that 64Cu-ATSNM is a marker of over-reduced cell state and thus an indirect marker for hypoxia imaging. The affinity of 64Cu-ATSM for over-reduced cells was observed to be a complex phenomenon. And to provide a definitive and convincing mechanism, more in vivo studies are needed to prove the diagnostic utility of 64Cu-ATSM

Improvement of the Targeting of Radiolabeled and Functionalized Liposomes with a Two-Step System Using a Bispecific Monoclonal Antibody (Anti-CEA × Anti-DTPA–In)

International audienceThis study proposes liposomes as a new tool for pretargeted radioimmunotherapy (RIT) in solid tumors. Tumor pretargeting is obtained by using a bispecific monoclonal antibody [BsmAb, anti-CEA × anti-DTPA-indium complex (DTPA-In)] and pegylated radioactive liposomes containing a lipid-hapten conjugate (DSPE-PEG-DTPA-In). In this work, the immunospecificity of tumor targeting is demonstrated both in vitro by fluorescence microscopy and in vivo by biodistribution studies.METHODS: Carcinoembryonic antigen (CEA)-expressing cells (LS174T) were used either in cell culture or as xenografts in nude mice. Doubly fluorescent liposomes or doubly radiolabeled liposomes were, respectively, used for in vitro and in vivo studies. In each case, a tracer of the lipid bilayer [rhodamine or indium-111 ((111)In)] and a tracer of the aqueous phase [fluorescein or iodine-125 ((125)I)] were present. The targeting of liposomes was assessed with BsmAb for active targeting or without for passive targeting.RESULTS: Data obtained with the lipid bilayer tracer showed a fluorescent signal on cell membranes two to three times higher for active than for passive targeting. This immunospecificity was confirmed in vivo with tumor uptake of 7.5 ± 2.4% ID/g (percentage of injected dose per gram of tissue) for active targeting versus 4.5 ± 0.45% ID/g for passive targeting (p = 0.03). Regarding the aqueous phase tracer, results are slightly more contrasted. In vitro, the fluorescent tracer seems to be released in the extracellular matrix, which can be correlated with the in vivo data. Indeed, the tumor uptake of (125)I is lower than that of (111)In: 5.1 ± 2.5% ID/g for active targeting and 2.7 ± 0.6% ID/g for passive targeting, but resulted in more favorable tumor/organs ratios.CONCLUSION: This work demonstrated the tumor targeting immunospecificity of DSPE-PEG-DTPA-In liposomes by two different methods. This original and new approach suggests the potential of immunospecific targeting liposomes for the RIT of solid tumors

Radioimmunoconjugates for treating cancer: recent advances and current opportunities

International audienceIntroduction: Radioimmunoconjugates have been used for 30 years to diagnose and treat cancer. For many years, the use of these therapeutic tools has been limited to haematological disorders, such as non-Hodgkin's lymphoma, given that they have only had a moderate effect on solid tumours. Areas covered: Recently, several strategies have revived the potential therapeutic application for radioimmunoconjugates. In this review, the authors review the advances in immunological engineering to develop new tools like monoclonal antibodies and their derivatives. Then, the authors summarize the development of radionuclides, the use of recombinant antibodies, pretargeting approaches, and dose fractionation techniques, providing opportunities for both therapeutic and diagnostic applications. Expert opinion: Radioimmunoconjugates used in nuclear medicine have entered a new era of development. These advances give rise to a variety of opportunities in the management of various cancers, where the radiolabelled antibodies may be particularly useful in immuno-specific phenotypic imaging e.g. companion diagnostics. Concerning therapeutic applications, radioimmunoconjugates have demonstrated their efficacy in the treatment of both haematological malignancies and solid tumours. Recent procedural developments are of great interest in optimising oncological targeted therapies. In the field of cancer theranostics, we believe that radioimmunoconjugated compounds are likely to play a large part in near future. ARTICLE HISTOR

Monopicolinate-dipicolyl Derivative of Triazacyclononane for Stable Complexation of Cu 2+ and 64 Cu 2+

International audienceThe synthesis and characterization of Hno1pa2py, a new tacn-based ligand, is reported. The complexation process with Cu2+ was proved to be very fast even in acidic medium. Potentiometric titrations allowed us to establish that Hno1pa2py exhibits an overall low basicity as well as a high selectivity for Cu2+ over Zn2+ cations. The copper(II) complex was synthesized and characterized using UV–vis and EPR spectroscopies and density functional theory (DFT) calculations. The studies clearly showed that the [Cu(no1pa2py)]+ complex is present in solution as a mixture of two isomers in which the ligand is coordinated to the metal center using a N5O donor set with the metal center in a distorted octahedral geometry. The very high kinetic inertness of the [Cu(no1pa2py)]+ complex was demonstrated by using acid-assisted dissociation assays as well as cyclic voltammetry. Preliminary investigations of 64Cu complexation were performed to validate the potential use of such chelating agent for further application in nuclear medicine. The X-ray crystal structures of copper(II) complexes of L1, the ester derivative of Hno1pa2py, have been determine

Radiolabeling of HTE1PA: A new monopicolinate cyclam derivative for Cu-64 phenotypic imaging. In vitro and in vivo stability studies in mice

International audienceHTE1PA, a monopicolinate-N-alkylated cyclam-based ligand has previously demonstrated fast complexation process, high kinetic inertness and important thermodynamic and electrochemical stability with respect to natural copper. In this work we first developed a new synthetic route to obtain HTE1PA in good yields. Then, we investigated HTE1PA chelation properties towards copper-64 and assessed in vitro and in vivo stability of the resulting compound.METHODS:Radiolabeling of HTE1PA with copper-64 was tested at different ligand concentrations in ammonium acetate medium. In vitro stability study was carried out by incubating [(64)Cu]TE1PA complex in human serum at both 37°C and 4°C; chromatographic controls were performed over 24h. Biodistribution, pharmacokinetic and hepatic metabolism of [(64)Cu]TE1PA were conducted in BALC/c mice in comparison with [(64)Cu]acetate and [(64)Cu]DOTA, used as a reference ligand.RESULTS:The promising results obtained for natural copper complexation were confirmed. HTE1PA was quantitatively radiolabeled in 15 min at room temperature. The resulting complex showed high serum stability. [(64)Cu]TE1PA induced a significant uptake in the liver and kidneys at early biodistribution time point. Nevertheless, a high speed wash out was observed at 24h leading to significantly lower uptake into the liver compared to [(64)Cu]DOTA. The metabolism study was consistent with a high resistance to transchelation as the initial uptake into liver matches with the intact form of [(64)Cu]TE1PA.CONCLUSION:Despite the partial elimination of HTE1PA - as copper-64 complex - through the hepatic route, its high selectivity for copper and its resistance to transchelation make it a promising ligand for antibody radiolabeling with either copper-64 or copper-67

New synthesis of phenyl-isothiocyanate C-functionalised cyclams. Bioconjugation and 64 Cu phenotypic PET imaging studies of multiple myeloma with the te2a derivative †

International audienceAzamacrocyclic bifunctional chelating agents (BCAs) are essential for the development of radiopharma-ceuticals in nuclear medicine and we wish to prove that their bioconjugation by a function present on a carbon atom of the macrocyclic skeleton is a solution of choice to maintain their in vivo inertness. Based on our very recent methodology using a bisaminal template and selective N-alkylation approach, a new synthesis of conjugable C-functionalised teta, te2a and cb-te2a has been developed. These chelators have indeed a growing interest in nuclear medicine for positron emission tomography (PET) and radio-immunotherapy (RIT) where they show in several cases better complexation properties than dota or dota-like macrocycles, especially with 64 Cu or 67 Cu radioisotopes. Chelators are bearing an isothiocyanate grafting function introduced by C-alkylation to avoid as much as possible a critical decrease of their che-lating properties. The synthesis is very efficient and yields the targeted ligands, teta-Ph-NCS, te2a-Ph-NCS and cb-te2a-Ph-NCS without fastidious work-up and could be easily extended to other cyclam based-BCAs. The newly synthetised te2a-Ph-NCS has been conjugated to an anti mCD138 monoclonal antibody (mAb) to evaluate its in vivo behavior and potentiality as BCA and to explore a first attempt of PET-phenotypic imaging in multiple myeloma (MM). Mass spectrometry analysis of the immunoconjugate showed that up to 4 chelates were conjugated per 9E7.4 mAb. The radiolabeling yield and specific activity post-purification of the bioconjugate 9E7.4-CSN-Ph-te2a were 95 ± 2.8% and 188 ± 27 MBq mg −1 respectively and the immunoreactivity of 64 Cu-9E7.4-CSN-Ph-te2a was 81 ± 7%. Animal experiments were carried out on 5T33-Luc(+) tumor bearing mice, either in subcutaneous or orthotopic. To achieve PET imaging, mice were injected with 64 Cu-9E7.4-CNS-Ph-te2a and acquisitions were conducted 2 and 20 h post-injection (PI). A millimetric bone uptake was localised in a sacroiliac of a MM orthotopic tumor. Nonspecific uptakes were observed at 2 h PI but, unlike for the tumor, a significant decrease was observed at 20 h PI which improves the contrast of the images

Cyclam te1pa for 64 Cu PET imaging. Bioconjugation to antibody, radiolabeling and preclinical application in xenografted colorectal cancer

International audiencete1pa is a monopicolinate cyclam previously presented as a better 64 Cu chelator than dota, nota and other chelators with an improved biodistribution and in vivo resistance to transchelation. This study aimed to determine whether te1pa could improve the in vivo stability of 64 Cu chelation concerning radioimmunoconjugates in order to obtain better contrast in PET imaging. te1pa was activated on its remaining acid function to obtain a N-hydroxysulfosuccinimide ester and was then conjugated to the F6 mouse IgG1a (F6 mAb), directed against CEA (carcinoembryonic antigen), leading to the F6-te1pa immunoconjugate. F6-te1pa was compared to F6–C-dota, i.e. F6 mAb conjugated with a C-functionalized dota which is the only chelator used nowadays in preclinical trials for 64 Cu PET imaging. Immunoconjugates were radiolabeled with 64 Cu showing an equivalent conjugation rate of 1 ligand per mAb. The study of the complexation kinetics highlighted a relatively fast process and 64 Cu–F6-te1pa, exhibiting a specific activity of 69.3 AE 28.9 MBq mg À1 , was proved to be inert since only 4.3% of radioactivity was transchelated from the ligand to EDTA (50 000 equiv., overnight) used as a competitor. All these results are comparable with C-functionalized dota. However, in vivo studies carried out in LS174T tumor-bearing nude mice showed a limited transchelation of superoxide dismutase (SOD) into the liver; 1.6% for 64 Cu–F6-te1pa after 24 h post-injection, compared to 4.3% for 64 Cu–F6–C-dota. The uptake of 64 Cu–F6-te1pa in tumors and radioactivity distribution in organs after 24 and 48 h was satisfactory and equivalent to various standards presented in the literature. Finally, PET-phenotypic images obtained with 64 Cu–F6-te1pa at 24 h post-injection showed an excellent contrast between tumors and the healthy tissues around, which agrees well with the results of the biodistribution. The usefulness of te1pa for PET phenotypic imaging using 64 Cu has been validated. The synthesis of a bifunctional derivative of te1pa will be the next step of this work to keep the ligand properties intact

5-ALA induced PpIX fluorescence guided surgery of gliomas: comparison of expert and machine learning based models

International audienceGliomas are diffuse brain tumors still hardly curable due to the difficulties to identify margins. 5-ALA induced PpIX fluorescence measurements enable to gain in sensitivity but are still limited to discriminate margin from healthy tissue. In this fluorescence spectroscopic study, we compare an expert-based model assuming that two states of PpIX contribute to total fluorescence and machine learning-based models. We show that machine learning retrieves the main features identified by the expert approach. We also show that machine learning approach slightly overpasses expert-based model for the identification of healthy tissues. These results might help to improve fluorescence-guided resection of gliomas by discriminating healthy tissues from tumor margins