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ConspectusAstatine (At) is the rarest on Earth of all naturally occurring elements, situated below iodine in the periodic table. While only short-lived isotopes (t1/2 ≤ 8.1 h) are known, 211At is the object of growing attention due to its emission of high-energy alpha particles. Such radiation is highly efficient to eradicate disseminated tumors, provided that the radionuclide is attached to a cancer-targeting molecule. The interest in applications of 211At in nuclear medicine translates into the increasing number of cyclotrons able to produce it. Yet, many challenges related to the minute amounts of available astatine are to be overcome in order to characterize its physical and chemical properties. This point is of paramount importance to develop synthetic strategies and solve the labeling instability in current approaches that limits the use of 211At-labeled radiopharmaceuticals. Despite its discovery in the 1940s, only the past decade has seen a significant rise in the understanding of astatine's basic chemical and radiochemical properties, thanks to the development of new analytical and computational tools.In this Account, we give a concise summary of recent advances in the determination of the physicochemical properties of astatine, putting in perspective the duality of this element which exhibits the characteristics both of a halogen and of a metal. Striking features were evidenced in the recent determination of its Pourbaix diagram such as the identification of stable cationic species, At+ and AtO+, contrasting with other halogens. Like metals, these species were shown to form complexes with anionic ligands and to exhibit a particular affinity for organic species bearing soft donor atoms. On the other hand, astatine shares many characteristics with other halogen elements. For instance, the At- species exists in water, but with the least range of EH-pH stability in the halogen series. Astatine can form molecular interactions through halogen bonding, and it was only recently identified as the strongest halogen-bond donor. This ability is nonetheless affected by relativistic effects, which translate to other peculiarities for this heavy element. For instance, the spin-orbit coupling boosts astatine's propensity to form charge-shift bonds, catching up with the behavior of the lightest halogens (fluorine, chlorine).All these new data have an impact on the development of radiolabeling strategies to turn 211At into radiopharmaceuticals. Inspired by the chemistry of iodine, the chemical approaches have sparsely evolved over the past decades and have long been limited to electrophilic halodemetalation reactions to form astatoaryl compounds. Conversely, recent developments have favored the use of the more stable At- species including the aromatic nucleophilic substitution with diaryliodonium salts or the copper-catalyzed halodeboronation of arylboron precursors. However, it is clear that new bonding modalities are necessary to improve the in vivo stability of 211At-labeled aryl compounds. The tools and data gathered over the past decade will contribute to instigate original strategies for overcoming the challenges offered by this enigmatic element. Alternatives to the C-At bond such as the B-At and the metal-At bonds are typical examples of exciting new axes of research.

International audience; Iodine and astatine radioisotopes are particularly attractive in nuclear medicine since their available isotopes cover all imaging and therapeutic modalities, from SPECT and PET imaging to beta, alpha and Auger electron therapy. Furthermore, their radiolabeling chemistry is highly versatile, being mainly based on covalent chemistry, unlike most other radionuclides that are metals. This makes them easily adaptable for the radiolabeling of a broad range of carrier compounds, from small molecules to large proteins. Iodine and astatine being both neighboring halogens, their radiolabeling chemistry is very similar. Knowledge on At is however limited given its low availability over the past decades and the facts that it exists only as short-lived isotopes, which has long hampered the study of its chemical properties. Nonetheless, recent research has highlighted features that distinguish it from its lighter halogen homologues and late developments open new perspectives with astatine radioisotopes to produce radiopharmaceuticals.In this chapter, the basics of iodine and astatine labeling chemistry are covered in parallel, starting with general principles and then detailing more specific applications and issue. In a first part the main production methods for the most relevant radionuclides, and the corresponding chemicals forms available for radiolabeling chemistry are presented. Radiolabeling reactions, which can be classified as electrophilic or nucleophilic, are introduced and their advantages and drawbacks are discussed. The second part introduces issues encountered in the specific case of proteins radiolabeling and the main strategies available. Finally, a third part discusses the stability issues encountered with iodine and especially At-labeled radiopharmaceuticals and the main approaches under investigation to improve it. The perspectives sections discuss the potential of iodine and astatine radioisotopes in the context of the development of the radiotheranostic modality.

International audience; In this report we describe the development of an alternative approach to arylstannane chemistry for radiolabeling antibodies with radioiodine or astatine based on aryliodonium salts precursors. Bifunctional aryliodonium salts were designed and tested for the synthesis of 125 I and 211 At labeled prosthetic groups for bioconjugation. The nature of the electron rich aryl group was varied and its impact on the regioselectivity of radiohalogenation was evaluated. Unexpectedly, whereas the 2-thienyl group provided the best regioselectivity towards the radioiodination of the aryl moiety of interest (98:2), it was less selective for astatination (87:13); the anisyl group providing the best regioselectivity in this case (94:6). Under optimized conditions, both radioiodination and astatination could be performed very efficiently in mild conditions (radiochemical yields > 85%). The ionic nature of the precursors was exploited to develop an efficient purification approach: the HPLC step that is usually necessary in conventionnal approaches to optimize removal of organotin toxic precursors and side products was replaced by a filtration through a silica cartridge with a significantly reduced loss of radiolabeled product. The purified radioiodinated and astatinated prosthetic groups were then conjugated efficiently to an anti-CD138 monoclonal antibody (75-80% conjugation yield). By using this novel and simple radiohalogenation procedure, higher overall radiochemical yields of astatination were obtained in comparison with the use of an arylstannane precursor and procedures of the litterature for labeling the same antibody. Overall, due to their simplicity of use and high robustness, these new precursors should simplify the labeling of proteins of interest with iodine and astatine radioisotopes for imaging and therapeutic applications.

International audience; 125I- and 211At-labeled azide and tetrazine (Tz) based prosthetic groups for bioorthogonal conjugation were designed and tested in a comparative study of five bioorthogonal systems. All five bioconjugation reactions conducted on a model clickable peptide led to quantitative yields within less than a minute to several hours depending on the system used. Transferability to the labeling of an IgG was demonstrated with one of the bioorthogonal system. This study provides several new alternatives to the conventional and suboptimal approach currently in use for radioiodination and astatination of biomolecules and should accelerate the development of new probes with these radionuclides for applications in nuclear imaging and targeted alpha-therapy.

In view of the excellent copper(ii) and 64-copper(ii) complexation of a TE1PA ligand, a monopicolinate cyclam, in both aqueous medium and in vivo, we looked for a way to make it bifunctional, while maintaining its chelating properties. Overcoming the already known drawback of grafting via its carboxyl group, which is essential to the overall properties of the ligand, a TE1PA bifunctional derivative bearing an additional isothiocyanate coupling function on a carbon atom of the macrocyclic ring was synthesized. This led to an architecture that is comparable to that of other commercially available bifunctional copper(ii) chelators such as p-SCN-Bn-DOTA already used in clinical trials for 64Cu-immuno-PET imaging. The C-functionalization of TE1PA on one carbon atom in the β-N position of the cyclam backbone was successfully achieved by adapting our patented methodology to the huge challenge, allowing the regiospecific mono-N-functionalization of the unsymmetrical ligand. The obtained ligand p-SCN-Bn-TE1PA was coupled to a 9E7.4 murine antibody (mAb), an IgG2a anti CD-138 for multiple myeloma (MM) targeting. The conjugation efficiency was assessed by looking at the 64Cu radiolabeling and the radiopharmaceutical 64Cu-9E7.4-p-SCN-Bn-TE1PA immunoreactivity, and in particular by comparing with 9E7.4-p-SCN-Bn-NOTA and 9E7.4-p-SCN-Bn-DOTA obtained from commercial and presumably highly efficient chelators NOTA and DOTA, respectively. The results are quite clear, showing that p-SCN-Bn-TE1PA has a coupling rate 5 times higher and an immunoreactivity 1.5 to 2 times greater than those of its two competitors. p-SCN-Bn-TE1PA also outperforms TE1PA conjugated via its carboxylic function on the same antibody. The first 64Cu-immuno-PET preclinical study in a syngeneic model of MM was performed, confirming the good in vivo properties of 64Cu-9E7.4-p-SCN-Bn-TE1PA for PET imaging, considering the high clearance even after 24 h and the particularly important tumor-to-liver ratio that was increasing at 48 h.

International audience; In view of the excellent copper(ii) and 64-copper(ii) complexation of a TE1PA ligand, a monopicolinate cyclam, in both aqueous medium and in vivo, we looked for a way to make it bifunctional, while maintaining its chelating properties. Overcoming the already known drawback of grafting via its carboxyl group, which is essential to the overall properties of the ligand, a TE1PA bifunctional derivative bearing an additional isothiocyanate coupling function on a carbon atom of the macrocyclic ring was synthesized. This led to an architecture that is comparable to that of other commercially available bifunctional copper(ii) chelators such as p-SCN-Bn-DOTA already used in clinical trials for 64Cu-immuno-PET imaging. The C-functionalization of TE1PA on one carbon atom in the β-N position of the cyclam backbone was successfully achieved by adapting our patented methodology to the huge challenge, allowing the regiospecific mono-N-functionalization of the unsymmetrical ligand. The obtained ligand p-SCN-Bn-TE1PA was coupled to a 9E7.4 murine antibody (mAb), an IgG2a anti CD-138 for multiple myeloma (MM) targeting. The conjugation efficiency was assessed by looking at the 64Cu radiolabeling and the radiopharmaceutical 64Cu-9E7.4-p-SCN-Bn-TE1PA immunoreactivity, and in particular by comparing with 9E7.4-p-SCN-Bn-NOTA and 9E7.4-p-SCN-Bn-DOTA obtained from commercial and presumably highly efficient chelators NOTA and DOTA, respectively. The results are quite clear, showing that p-SCN-Bn-TE1PA has a coupling rate 5 times higher and an immunoreactivity 1.5 to 2 times greater than those of its two competitors. p-SCN-Bn-TE1PA also outperforms TE1PA conjugated via its carboxylic function on the same antibody. The first 64Cu-immuno-PET preclinical study in a syngeneic model of MM was performed, confirming the good in vivo properties of 64Cu-9E7.4-p-SCN-Bn-TE1PA for PET imaging, considering the high clearance even after 24 h and the particularly important tumor-to-liver ratio that was increasing at 48 h.

International audience

s of Annual Congress of the European Association of Nuclear Medicine October 13 – 17, 2018 Düsseldorf, Germany; International audience; Aim: Multiple myeloma is a B-cell malignancy of terminally differentiated plasma cells within the bone marrow. In spite of a very active search for new treatments, cure is almost never achieved. Alpha-radioimmunotherapy (RIT) is a new cancer treatment modality with tumour specific antibodies coupled to alpha particle-emitting radionuclides. CD138 (Syndecan-1) is found mainly in epithelial cells, but was shown to be expressed by most myeloma cells, both in human and in the mouse. The aim of the study was to evaluate the biodistribution, toxicity and efficacy of a rat Astatin-211-labelled anti-mouse CD138 antibody (211At-9E7.4) in a syngeneic mouse myeloma model. Materials and methods: C57BL/KaLwRij mice were grafted with 106 5T33 cells (murine myeloma cell line). Biodistribution was studied 15 min, 1h, 4h, 7h, 14h and 21h post-administration of 211At- 9E7.4 mAb. Toxicity (animal weight, blood cell counts and transaminase) and RIT efficacy were studied after a dose escalation using 370, 555, 740 and 1110 kBq of 211At-9E7.4 and two control groups 211At-IgG2a isotype control at 555 kBq or no treatment, 10 days after tumour engraftment. Results: Studies demonstrated a highly statistical survival benefit for the mice treated with 211At-9E7.4 at 555 kBq (p=0,0006) and 740 kBq (p

Radioimmunotherapy (RIT) has been developed for more than 30 years. Two products targeting the CD20 antigen are approved in the treatment of non-Hodgkin B-cell lymphoma (NHBL): iodine 131-tositumomab and yttrium 90-ibritumomab tiuxetan. RIT can be integrated in clinical practice for the treatment of patients with relapsed or refractory follicular lymphoma (FL) or as consolidation after induction chemotherapy. High-dose treatment, RIT in first-line treatment, fractionated RIT, and use of new humanized monoclonal antibodies (MAbs), in particular targeting CD22, showed promising results in NHBL. In other hemopathies, such as multiple myeloma, efficacy has been demonstrated in preclinical studies. In solid tumors, more resistant to radiation and less accessible to large molecules such as MAbs, clinical efficacy remains limited. However, pretargeting methods have shown clinical efficacy. Finally, new beta emitters such as lutetium 177, with better physical properties will further improve the safety of RIT and alpha emitters, such as bismuth 213 or astatine 211, offer the theoretical possibility to eradicate the last microscopic clusters of tumor cells, in the consolidation setting. Personalized treatments, based on quantitative positron emission tomography (PET), pre-therapeutic imaging, and dosimetry procedures, also could be applied to adapt injected activity to each patient.

The present invention concerns a method of synthesizing a iodo- or astatoarene comprising the reaction of a diaryliodonium compound with a iodide or astatide salt, respectively. The invention also relates to said iodo- or astatoarene and diaryliodonium compound as such. The invention also concerns a method of synthesizing a iodo- or astatolabelled biomolecule and/or vector using said iodo- or astatoarene.

International audience; Efficiency of ionic liquid supported organotin reagents in halodemetalation reaction has been investigated. High radiochemical yields of astatinated and iodinated compounds have been obtained using simple work-up procedure. This methodology represents a straightforward approach for the preparation of molecular imaging and therapy agents in nuclear medicine.

The aim of this study was to design liposomes as radioactivity carriers for pretargeted radioimmunotherapy with favorable pharmacokinetic parameters. To monitor the liposomes integrity in vivo, their surface was radiolabeled with indium-111 bound to DTPA-derivatized phosphatidylethanolamine (DSPE-DTPA) and the aqueous phase was labeled by using an original active loading technique of radioiodinated Bolton-Hunter reagent (BH) that reacts with pre-encapsulated arginine to form a positively charged conjugate ((125)I-BH-arginine). Different formulations of doubly radiolabeled liposomes were tested in vitro and in vivo to evaluate radiolabeling stability, integrity of the vesicles and their pharmacokinetics. Radiolabeling yields were high (surface >75%, encapsulation >60%) and stable (>85% after 24 h in serum 37 degrees C). In vivo, the pharmacokinetic behavior of doubly radiolabeled liposomes was strongly dependant on the formulation. Blood clearance of PEGylated liposomes (DSPC/Chol/DSPE-DTPA/DSPE-PEG5%) was 0.15 mL/h compared to a conventional formulation (DSPC/Chol/DSPE-DTPA: clearance 1.44 mL/h). Non-encapsulated BH-arginine conjugate was quickly eliminated in urine (clearance 6.04 mL/h). Blood kinetics of the two radionuclides were similar and radiochromatographic profiles of mice serum confirmed the integrity of circulating liposomes. The significant reduction of activity uptake in organs after liposome catabolism (liver and spleen), achieved by the rapid renal elimination of (125)I-BH-arginine, should bring significant improvements for targeted radionuclide therapy with sterically-stabilized liposomes.

No effective therapy is currently available for the management of patients with metastases of most solid tumors. Thus, pretargeted radioimmunotherapy approaches have been developed that have shown promises. One of these techniques uses bispecific monoclonal antibody and radiolabeled bivalent haptens injected sequentially. In two clinical trials, 29 patients with advanced, progressive medullary thyroid carcinoma, as documented by short serum calcitonin doubling times, received an anti-carcinoembryonic antigen x anti-diethylenetriamine pentaacetic acid (DTPA)–indium) bispecific monoclonal antibody, followed four to five days later by an 131I-labeled bivalent hapten. Overall survival was significantly longer in high-risk, treated patients than in high-risk, untreated patients (110 versus 61 months; P < 0.030). Forty-seven percent of patients, defined as biologic responders by a more than 100% increase in calcitonin doubling time, experienced significantly longer survival than non-responders (159 versus 109 months; P < 0.035) and untreated patients (159 versus 61 months; P < 0.010). Toxicity was mainly hematologic and related to bone/bone-marrow tumor spread. Various multidisciplinary aspects of this long-term endeavor that resulted in long-term disease stabilization and a significantly longer survival in high-risk patients are described and discussed with respect to future directions of research on pretargeted radioimmunotherapy.

3'-Deoxy-3'-[18F]fluorothymidine ([18F]-FLT) has recently been described as a positron emission tomography (PET) radiopharmaceutical for visualizing cellular proliferation in vivo. All published radiosyntheses of [18F]-FLT provide crude products that must be purified before injection to human. This study describes a reliable purification procedure for [18F]-FLT. It is based on HPLC. In 17.9+/-0.5 min, pure [18F]-FLT is obtained that could be injected to human after a passage through a sterile 0.22 microm filter.

This letter reports a new labeling method of fucoidan and more precisely of its monomer, l -fucose. We studied the coupling processes of new aryliodide precursors to l -fucose in order to prepare the next step, that is, the fucoidan radiolabeling. The use of precursors containing hydrazide and hydroxylamines is an alternative procedure avoiding the use of toxic borohydride or organic borane used for reductive amination. These coupling reactions are efficient and stereoselective. They provide stable products.

International audience; Azamacrocyclic 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.

Two polyaminocarboxylic acid chelating agents were synthesized. Complexation properties regarding 111In and 153Sm, two radionuclides suitable for applications in immunoscintigraphy and radioimmunotherapy were investigated. The synthesis of aminodiacetic acid derivatives 7a and 7b involved preliminary stereoselective synthesis of the corresponding amines, cis and trans cyclopentane-1,2-diamines. 111In labelling confirmed the complexation abilities of the two ligands. An additional comparative study to probe the relationship between ligand structure and metal complex was performed with 153Sm.

Rationnel Les traitements du myelome multiple (MM), tels que la therapie a haute dose de melphalan, la transplantation allogenique, la transplantation autologue de cellules souches ou encore les regimes incorporant les nouveaux agents bortezomide, thalidomide et lenalidomide, augmentent sensiblement le taux de Reponse Complete (RC) associee a une survie plus longue des patients. Etant donne qu’aucun de ces traitements ne peut guerir le myelome, d’autres approches therapeutiques sont en cours de developpement. Au sein de ces approches, la radio-immunotherapie (RIT) peut etre une excellente alternative pour le traitement de la maladie residuelle. Les emetteurs alpha sont particulierement bien adaptes car la courte portee de ces particules permet une irradiation localisee des cellules tumorales dans la moelle osseuse et un effet cytotoxique sur les cellules isolees en raison du haut TEL de particules alpha. Enfin, l’antigene CD138 represente une bonne cible en raison de sa forte expression sur les cellules de myelome de 100 % des patients. Methode L’injection intraveineuse de 106 cellules 5T33 de myelome dans la souche de souris syngenique C57/Kalrwij entraine une invasion rapide de la moelle osseuse et une paralysie des membres inferieurs. L’evolution peut etre illustree par l’imagerie de bioluminescence de cellules 5T33 transfectees par la luciferase. La RIT a ete realisee 10 jours apres la greffe par injection IV d’un anticorps monoclonal 9E7.4 anti-CD138 murin radiomarque avec de l’astate-211. Une escalade de doses a ete realisee avec des activites de 370, 555, 740 et 1,11 kBq. Un comptage des cellules sanguines a ete effectue afin de surveiller la toxicite hematologique. Resultats Les groupes traites par 740 kBq d’astate-211 presentent une survie mediane superieure a 150 jours quand celle du groupe temoin non traite est de 43 jours. L’activite la plus elevee (1,11 kBq) a montre une forte toxicite a court terme, alors que l’activite la plus faible de 370 kBq donne des resultats semblables aux temoins. Avec des activites de 740 kBq, les souris presentaient une toxicite hematologique transitoire. Conclusion Cette etude demontre l’efficacite therapeutique prometteuse de l’anti-mCD138 marque par de l’astate-211 pour le traitement de la maladie residuelle dans le cas du MM, avec une toxicite hematologique moderee et transitoire.

Radioimmunotherapy (RIT) has been in use for more than 20 years and has progressed significantly with the discovery of new molecular targets, the development of new stable chelates, the humanization of monoclonal antibodies (mAbs), and the use of pretargeting techniques. Today, two products targeting the CD20 antigen are approved in the treatment of B cell lymphoma: 131I-tositumomab (Bexxar®) and 90Y-ibritumomab tiuxetan (Zevalin®). RIT can be integrated in clinical practice for treatment of patients with relapsed or refractory follicular lymphoma (FL) or as consolidation after induction chemotherapy in frontline treatment in FL patients. High-dose treatment, RIT as consolidation, RIT in first-line treatment, fractionated RIT, and use of new humanized mAbs, in particular targeting CD22, showed promising results in B cell lymphoma. In other hemopathies, such as multiple myeloma, efficacy has been demonstrated in preclinical studies. In solid tumors, more resistant to radiations and less accessible to large molecules such as mAbs, clinical efficacy remains limited. However, RIT used in minimal or small-size metastatic disease has shown promising clinical efficacy. Pretargeting approaches have been potential in increasing the therapeutic index of radiolabeled antibodies. Finally, new beta emitters such as lutetium-177 with better physical properties will further improve the safety of RIT. Moreover, alpha emitters such as bismuth-213 or astatine-211 offer the theoretical possibility to eradicate the last microscopic clusters of tumor cells, in the setting of consolidation. Personalized dosimetry protocols, particularly based on quantitative positron emission tomography (PET) imaging, should be developed to optimize injected activity.

The coupling of radionuclides such as copper (67Cu and 64Cu) to antibodies by bifunctional chelating agents (or BCA) requires extremely high stability to avoid in vivo release of metal. Six copper(II) and five nickel(II) complexes with N2S2 tetradentate ligands were synthesised for potential medical applications, and stability studies were conducted. I.r and u.v.-vis. spectra provided structural data on the geometry of the complexes. The redox potentials obtained from cyclic voltammetry allowed us to estimate the stability constants of each complex and then select the more suitable ligand for future applications in radioimmunotherapy.

Immunotherapy with radiolabelled antibodies should allow fairly specific targeting of certain cancers. Although 153Sm possesses favourable radiophysical characteristics for such therapy, a lack of radiolabelling stability in vivo limits its application. Yet the use of phosphonic semi-rigid bifunctional chelating agents (BCA) can improve its stability. Syntheses of (1R*,2R*,4S*)-4-isothiocyanatocyclohexane-1,2-diamine-N,N,N′,N′-tetrakismethanephosphonic acid (4-ICMP) and (1R*,2R*,4S*)-4-isothiocyanatocyclohexane-1,2-diamine-N,N,N′,N′-tetrakisethanephosphonic acid (4-ICEP) are described in this paper. The complexing properties of these two compounds has been confirmed by labelling with 153Sm. A novel synthetic approach involving the introduction of methanephosphonic functions has also been developed.

Structural analyses of nickel and copper complexes obtained from N2S2 tetradentate ligands of the bis(enaminodithioester) type demonstrate the obtention of square planar complexes using the ligand derived from ethylenediamine (1a, 1b) while a flattened tetrahedral structure was obtained for the copper complex 2b using the ligand derived from 1,3-diaminopropan-2-ol. For complexes 1b and 2b, the bond lengths around the metal appear to be nearly unaffected by the nature of the ligand contrasted with the difference in the angles (shift from a square planar structure to a flattened tetrahedral one with increasing flexibility of the ligand). The kinetic and thermodynamic stabilities of the copper complexes 1b and 2b were roughly evaluated on the basis of transchelation experiments, competitive complexation experiments and electrochemical studies. Adaptation de ligands N2S2 tetradente′s en vue d'applications en me′decine nucle′aire: structure radiocristallographique de complexes de NiII et CuII et premiers re′sultats concernant leurs stabilite′s. L'e′tude structurale de complexes de nickel et de cuivre obtenus a partir de ligands N2S2 tetradente′s du type bis(e′naminodithioester) demontre l'obtention de complexes plan carre′ le′gerement de′forme′s lorsque l'on utilise des ligands de′rivant de l'e′thylenediamine (1a, 1b) alors que le complexe du cuivre 2b obtenu a partir d'un ligand de′rivant du 1,3-diaminopropan-2-ol pre′sente une structure de type te′traedre aplati. Pour les complexes du cuivre 1b et 2b, les longueurs de liaison autour du me′tal apparaissent peu affecte′es par la nature du ligand a la diffe′rence des angles (e′volution de plan carre′ vers te′traedre aplati lorsque le ligand devient plus flexible). Les stabilite′s cine′tiques et thermodynamiques des complexes du cuivre 1b et 2b ont e′te′ grossierement e′value′es a partir d'expe′riences de transche′lation et de complexation compe′titive ainsi que sur la base d'e′tudes e′lectrochimiques.

Introduction HTE1PA, 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 15min 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.

Introduction This paper proposes liposomes as a potential new tool for radioimmunotherapy in solid tumours with a two step targeting system. Tumour pretargeting is obtained by using a monoclonal bispecific antibody (BsmAb, anti CEA x anti-DTPA-In) and pegylated liposomes containing lipid-hapten (DSPE-DTPA-In or DSPE-PEG-DTPA-In). To optimise at the same time in vivo behaviour and specific targeting, the study focuses on the liposome formulation in order to determine more precisely the role of pegylation on both the blood half-life and the specific recognition with the BsmAb. Methods Different liposome formulations containing two PEG length (1000 and 2000) in varying amount (1.5–6 mol%) were prepared with DTPA directly coupled to DSPE or at the end of the PEG chain (DSPE-DTPA or DSPE-PEG-DTPA). Liposomes were immobilized on an L1 chip to measure by SPR (Surface Plasmon Resonance) the effect of pegylation on the BsmAb recognition of the DTPA-In hapten. Pharmacokinetic studies were performed in mice. Tumour targeting was studied in nude mice xenografted with human colorectal adenocarcinoma cells that express CEA, and doubly radiolabelled liposomes (with 111In and 125I) injected 24 h after the BsmAb. Results The best in vitro apparent dissociation constant was obtained with liposomes bearing DTPA at the end of the PEG chain (KD = 6.3 nM), which showed significant specific tumour uptake after BsmAb injection (8.6 ± 2.4% ID/g at 24 h versus 4.5 ± 0.5%ID/g for passive targeting, α = 0.01). All tumour/organ ratios were superior to 1 at 24 h for this formulation, except for the spleen. Conclusion The feasibility of specific tumour targeting in mice with a BsmAb and radiolabelled liposomes was demonstrated and the interest of SPR to predict their targeting performance in vivo was highlighted. This original and new approach provides promising prospects for the radioimmunotherapy of solid tumours.

International audience; The 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 determined

Anti-CEA F(ab')2 monoclonal antibody fragments [F6 MAb F(ab')2] were conjugated to two bifunctional semi-rigid chelating agents derived from trans-1,2-diaminocyclohexane tetraacetic acid (CDTA), the monolithium salt of N-[methyl(2-isothiocyanatoethyl)carbamide] trans-1,2-diaminocyclohexane-N,N',N'-triacetic acid (SCN), and 4 isothiocyanato-trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (4-ICE) and labelled with 111In to obtain IIIIn-labelled-F6 MAb F(ab')2 conjugates (111In-F6-SCN and 111In-F6-4-ICE respectively). Biodistribution in mice and clinical studies were undertaken to assess the potential of these two ligands in the detection of colorectal adenocarcinoma recurrences and metastases in humans. Toxicity studies were carried out on guinea pigs and Swiss mice injected with a dose proportionally 100 times greater than that used in human studies. Clinical studies were performed in patients with clinically and/or biologically suspected adenocarcinoma recurrences. No immunoconjugate-induced toxicity was found. The biodistribution studies in mice gave better visualization of tumour sites with 111In-F6-SCN and 111In-F6-4-ICE than with 111In-F6-DTPA. Ten patients were included in the clinical protocol. 111In-F6-SCN and 111In-F6-4-ICE effectively visualized adenocarcinoma recurrences. However, in this small series, 111In-F6-4-ICE performed somewhat better than 111In-F6-SCN. The present study has demonstrated the potential of new bifunctional semi-rigid chelating agents coupled to antibody and labelled with 111In to localize recurrences (especially in liver) in humans using a one-step targeting method.

A novel bifunctional chelating agent for samarium complexation has been synthesised in eight steps. A novel synthetic approach involving the introduction of methanephosphonic functions has been developed. The complexing properties of this compound has also been confirmed by labelling with 153 Sm.

International audience; 211At is a promising radionuclide for a-particle therapy of cancers. Its physical characteristics make this radio-nuclide particularly interesting to consider when bound to cancer-targeting biomolecules for the treatment of microscopic tumors. 211At is produced by cyclotron irradiation of 209 Bi with a-particles accelerated at *28 MeV and can be obtained in high radionuclidic purity after isolation from the target. Its chemistry resembles iodine, but there is also a tendency to behave as a metalloid. However, the chemical behavior of astatine has not yet been clearly established, primarily due to the lack of any stable isotopes of this element, which precludes the use of conventional analytical techniques for its characterization. There are also only a limited number of research centers that have been able to produce this element in sufficient amounts to carry out extensive investigations. Despite these difficulties, chemical reactions typically used with iodine can be performed, and a number of biomolecules of interest have been labeled with 211At. However, most of these compounds exhibit unacceptable instability in vivo due to the weakness of the astatine-biomolecule bond. Nonetheless, several compounds have shown high potential for the treatment of cancers in vitro and in several animal models, thus providing a promising basis that has allowed initiation of the first two clinical studies.

International audience; Aryliodonium salts have become precursors of choice for the synthesis of 18 F-labeled tracers for nuclear imaging. However, little is known on the reactivity of these compounds with heavy halides, that is, radioiodide and asta-tide, at the radiotracer scale. In the first comparative study of radiohalogenation of aryliodonium salts with 125 I À and 211 At À , initial experiments on a model compound highlight the higher reactivity of astatide compared to iodide, which could not be anticipated from the trends previously observed within the halogen series. Kinetic studies indicate a significant difference in activation energy (E a = 23.5 and 17.1 kcal mol À1 with 125 I À and 211 At À , respectively). Quantum chemical calculations suggest that astatination occurs via the monomeric form of an iodonium complex whereas iodi-nation occurs via a heterodimeric iodonium intermediate. The good to excellent regioselectivity of halogenation and high yields achieved with diversely substituted aryliodonium salts indicate that this class of compounds is a promising alternative to the stannane chemistry currently used for heavy radiohalogen labeling of tracers in nuclear medicine.

This study describes a simple, efficient synthesis pathway from trans-1,2-diaminocyclohexane that provides access to a new class of semi-rigid polyamine, polycarboxylic, and polyphosphonic ligands. The key steps in synthesis were the functionalisation (with an appropriate branching group) of a bisphosphonate diaminocyclohexane derivative and the introduction of methanephosphonic functions by a rarely used method.

Radiolabeled antibodies were studied first for tumor detection by single-photon imaging, but FDG PET stopped these developments. In the meantime, radiolabeled antibodies were shown to be effective in the treatment of lymphoma. Radiolabeling techniques are well established and radiolabeled antibodies are a clinical and commercial reality that deserves further studies to advance their application in earlier phase of the diseases and to test combination and adjuvant therapies including radiolabeled antibodies in hematological diseases. In solid tumors, more resistant to radiations and less accessible to large molecules such as antibodies, clinical efficacy remains limited. However, radiolabeled antibodies used in minimal or small-size metastatic disease have shown promising clinical efficacy. In the adjuvant setting, ongoing clinical trials show impressive increase in survival in otherwise unmanageable tumors. New technologies are being developed over the years: recombinant antibodies and pretargeting approaches have shown potential in increasing the therapeutic index of radiolabeled antibodies. In several cases, clinical trials have confirmed preclinical studies. Finally, new radionuclides, such as lutetium-177, with better physical properties will further improve the safety of radioimmunotherapy. Alpha particle and Auger electron emitters offer the theoretical possibility to kill isolated tumor cells and microscopic clusters of tumor cells, opening the perspective of killing the last tumor cell, which is the ultimate challenge in cancer therapy. Preliminary preclinical and preliminary clinical results confirm the feasibility of this approach.

Radiolabeled antibodies were studied first for tumor detection by single-photon imaging, but FDG PET stopped these developments. In the meantime, radiolabeled antibodies were shown to be effective in the treatment of lymphoma. Radiolabeling techniques are well established and radiolabeled antibodies are a clinical and commercial reality that deserves further studies to advance their application in earlier phase of the diseases and to test combination and adjuvant therapies including radiolabeled antibodies in hematological diseases. In solid tumors, more resistant to radiations and less accessible to large molecules such as antibodies, clinical efficacy remains limited. However, radiolabeled antibodies used in minimal or small-size metastatic disease have shown promising clinical efficacy. In the adjuvant setting, ongoing clinical trials show impressive increase in survival in otherwise unmanageable tumors. New technologies are being developed over the years: recombinant antibodies and pretargeting approaches have shown potential in increasing the therapeutic index of radiolabeled antibodies. In several cases, clinical trials have confirmed preclinical studies. Finally, new radionuclides, such as lutetium-177, with better physical properties will further improve the safety of radioimmunotherapy. Alpha particle and Auger electron emitters offer the theoretical possibility to kill isolated tumor cells and microscopic clusters of tumor cells, opening the perspective of killing the last tumor cell, which is the ultimate challenge in cancer therapy. Preliminary preclinical and preliminary clinical results confirm the feasibility of this approach.

We report the synthesis of a new diethylenetriaminepentaacetic acid (DTPA) analogue, Ph-DTPA, possessing an aromatic rigid skeleton. This precursor of a bifunctional chelating agent was synthesized by elaboration of the intermediate N-(o-aminophenyl)ethylenediamine and obtained in five steps with an overall yield of 42%. Preliminary complexation studies between Ph-DTPA and 153Sm has been carried out.

International audience; Targeted PEGylated liposomes could increase the amount of drugs or radionuclides delivered to tumor cells. They show favorable stability and pharmacokinetics, but steric hindrance of the PEG chains can block the binding of the targeting moiety. Here, specific interactions between an antihapten antibody (clone 734, specific for the DTPA-indium complex) and DTPA-indium-tagged liposomes were characterized by surface plasmon resonance (SPR). Non-PEGylated liposomes fused on CM5 chips whereas PEGylated liposomes did not. By contrast, both PEGylated and non-PEGylated liposomes attached to L1 chips without fusion. SPR binding kinetics showed that, in the absence of PEG, the antibody binds the hapten at the surface of lipid bilayers with the affinity of the soluble hapten. The incorporation of PEGylated lipids hinders antibody binding to extents depending on PEGylated lipid fraction and PEG molecular weight. SPR on immobilized liposomes thus appears as a useful technique to optimize formulations of liposomes for targeted therapy.

The five linker-containing immunoconjugates described in the preceding paper were labeled with 111In and tested for their biodistribution, pharmacokinetics and immunoscintigraphic imaging properties in tumor-xenografted nude mice. The results were compared with DTPADA and CDTAMA for reference. Results showed that, for immunoscintigraphy, the derivatives in decreasing order of effectiveness were: aliphatic (tumor/liver > 4.5 and tumor/kidney > 6.5 at 96 h), thioether (tumor/liver > 3 and tumor/kidney > 1.2 at 24 h), ethylene glycol succinate (tumor/liver > 1.7 and tumor/kidney > 0.5 at 24 h) and disulfide (tumor/liver > 0.5 and tumor/kidney > 0.6 at 96 h). Pharmacokinetic results were complementary with those of the biodistribution studies and provide a basis for the study of in vivo metabolic mechanisms of linker-immunoconjugates. Indium-111-labeled linker-immunoconjugates appear promising for tumor imaging with better contrast than what is obtained with the use of the conventional 111In-DTPA dianhydride chelate.

The purpose of this study was to synthesize new bifunctional linker-chelating agents for the modification of the in vivo distribution of 111 In-labeled antibodies. A general simple synthetic method of preparing cyclohexyl EDTA (CDTA) derivatives containing a linker/spacer group is described. Linkers prepared included a diester, a six carbon aliphatic chain, two thioethers and a disulfide group. The CDTA-linker compounds were coupled to F(Ab′) 2 fragments of anti-carcinoembryonic antigen monoclonal antibody and labeled with 111 In with good retention of immunoreactivity.

Two polyaminocarboxylic acid chelating agents were synthesized. Complexation properties regarding 111In and 153Sm, two radionuclides suitable for applications in immunoscintigraphy and radioimmunotherapy were investigated. The synthesis of aminodiacetic acid derivatives 7a and 7b involved preliminary stereoselective synthesis of the corresponding amines, cis and trans cyclopentane-1,2-diamines. 111In labelling confirmed the complexation abilities of the two ligands. An additional comparative study to probe the relationship between ligand structure and metal complex was performed with 153Sm.

Polylysine-based chelating polymers were used for site-specific modification of anti-CEA mAb Fab' fragments via their SH group distal to the antigen-binding site of the antibody molecule. Conjugation was performed using chain-terminal (pyridyldithio)propionate or 4-(p-maleimidophenyl)butyrate moieties to form reducible (S-S) or stable (S-C) bonds between a polymer and Fab' molecule, respectively. One S-S conjugate (S-S9) and two different S-C conjugates (S-C3 and S-C9) were prepared using 3- and 9-kDa molecular weight polymers. No significant loss of immunoreactivity was observed in solid-phase immunoassay, 90-95% of 111In-labeled conjugates being bound to CEA-coated Sepharose beads. After labeling with 111In, the conjugates had a specific radioactivity of 90-120 microCi/micrograms. Injected in nude mice bearing LS 174T carcinoma, the conjugates produced different biodistribution patterns. S-S9 was practically unable to accumulate in tumor and produced very rapid blood clearance of radioactivity and high uptake of radioactivity in liver, spleen, and especially kidneys (225% ID/g 24 h postinjection). S-C3 and S-C9 produced practically the same blood clearances (much slower than that of S-S9) and significant tumor uptake (9-10% ID/g at 24 h). S-C3 gave significantly lower radioactivity in spleen, skin, and bones, and cleared more rapidly from liver and kidneys. Renal uptake for S-C3 and S-C9 was rather high (45% ID/g at 24 h), but much lower than for S-S9.

A novel bifunctional chelating agent for actinium was synthesized in eight steps. Bimolecular cyclization between an iminodiester and a polyamine was achieved through the action of a molar equivalent of sodium methoxide.

Astatine-211, a most promising α-particle emitter for targeted radiotherapy, is generally obtained by high-temperature distillation. However, a liquid-liquid extraction procedure (wet extraction) has also been described. The purpose of this study was to develop and optimize the labelling of the stannylated-activated ester N-hydroxysuccinimidyl-meta-trimethylstannylbenzoate ester (MeSTB) with astatine-211 extracted in di-isopropylether (DIPE) in the presence of the oxidant N-chlorosuccinimide (NCS). The effect of final volume, incubation duration and NCS amounts on radiolabelling yield was studied. The best yields (85-90%) of N-hydroxysuccinimidyl-meta-[(211)At]astatobenzoate ester (SAB) were obtained with 20 nmol of MeSTB, 100 nmol of NCS in 120 µL of DIPE after 15 min. The astatine-211-labelled-activated ester was then used to radiolabel a monoclonal antibody (mAb). The labelling yield was 20-25% and the radiochemical purity was 97-99%. These results show that mAbs may be efficiently labelled with astatine-211 obtained by wet extraction, a fully automatable technique that may prove to be a useful alternative to dry distillation for high activity labelling of radiopharmaceuticals. Copyright © 2008 John Wiley & Sons, Ltd.

Correction for ‘New synthesis of phenyl-isothiocyanate C-functionalised cyclams. Bioconjugation and 64Cu phenotypic PET imaging studies of multiple myeloma with the te2a derivative’ by Zakaria Halime et al., Org. Biomol. Chem., 2015, 13, 11302–11314.

International audience; AIM: Radioimmunotherapy is limited in some cases by the low radioactive doses delivered to tumor cells by antibodies or pretargeted haptens. In order to increase this dose, lipidic nanocapsules (LNC) with a hydrophobic core are proposed as radionuclide vectors that could be targeted to cancer cells by a bispecific anti-tumor x anti-hapten antibody after incorporation of different haptens in the nanocapsule membrane. METHODS: To bind different radionuclides to the nanocapsules, several bifunctional chelating agents (BCA) were used to form stable complexes with the radionuclides. Some of them are hydrophilic for LNC shell while others are lipophilic to radiolabel the core. Poly(ethylene glycols) (PEG) were used to increase the residence time in blood. Since PEG can modify haptens recognition by the bispecific antibody and radiolabeling efficiency, haptens, BCA or Bolton-Hunter reagent (BH) were attached to the PEG extremity to optimize accessibility. Specific constructs (DSPE-PEG-haptens, DSPE-PEG-BCA, and DSPE-PEG-BH) were synthesized to develop these new radiolabeled vector formulations. Large amounts of PEG have been introduced by a postinsertion method without important change in nanocapsule size and properties. The nanocapsule core was radiolabeled with a lipophilic [(99m)Tc]SSS complex. RESULTS: Serum stability studies showed that this (99m)Tc-labeling method was efficient for at least 20 h. Concerning the nanocapsule surface, several methods have been performed for (111)In-labeling by using DSPE-PEG-DTPA and for (125)I-labeling with DSPE-PEG-BH. CONCLUSIONS: The nanocapsules labeling feasibility with a variety of radionuclides and their stability were demonstrated in this paper.