We report the synthesis and evaluation of the first 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane-3,6,10,13-tetraacetic acid (PYTA) bifunctional chelators (BFCs) for 225Ac coordination. Methods: Three PYTA BFCs (PYTA-triacetate, PYTA-glutaric acid, and PYTA-pyridyl-ether) were synthesized. A comparative radiolabeling study with MACROPA, DOTA, and crown derivatives was performed. Conjugation to prostate-specific membrane antigen ligands and antibodies exemplified the applicability of these BFCs. Biodistribution and long-term stability of radiocomplexes were investigated in vivo. Results: PYTA derivatives demonstrated excellent radiochemical properties with quantitative radiolabeling under mild conditions (37 °C; low concentration) and exhibited prolonged in vitro stability. In vivo evaluation of radioimmunoconjugates confirmed the prolonged stability of PYTA conjugates, yielding results comparable to those seen with MACROPA, and revealed the instability of crown derivatives. Conclusion: PYTA emerges as a promising chelator for 225Ac, comparable to MACROPA, with the advantages of modular BFC synthesis.

We report the synthesis and evaluation of the first PYTA bifunctional chelators (BFCs) designed for actinium-225 coordination. Methods: Three PYTA bifunctional chelators, PY3A, PYTA-GA, and PYTA-PE, were synthesized. A comparative radiolabeling study with current gold standards, MacropaTM, DOTA and Crown derivatives, was performed. Conjugation to PSMA ligand and antibodies exemplified the applicability of the BFCs. In vivo evaluation investigated the biodistribution and long-term stability of radiocomplexes. Results: PYTA derivatives demonstrate excellent radiochemical properties with quantitative radiolabeling under smooth conditions (37°C, low concentration) and prolonged in vitro stability. In vivo evaluation of radioimmunoconjugates confirmed the prolonged stability of PYTA conjugates, yielding results comparable to Macropa™, while revealing clear instability of Crown derivative. Conclusion: These findings set PYTA as the next gold-standard chelator for actinium-225, comparable to Macropa™, with the advantages of easier bifunctional derivatives syntheses and greater versatility of radionuclides.

Molecular Radiotherapy (MRT) targeting SSTR2 or PSMA have proven to be highly efficient for the treatment of neuroendocrine or metastatic prostate cancer, respectively. Beyond the leading radiopharmaceutical molecules 177Lu-DOTATATE or 177Lu-PSMA-617, a variety of vectors (small molecules, peptides, panel of biologics) have been developed on the same targets in order to improve the biodistribution within the tumor, the blood clearance, the route of elimination or the dosimetry. The labeling of the targeting ligand, whatever its nature, is a crucial step as it may affect significantly the properties of the theranostic conjugate, i.e. its binding affinity, PK and biodistribution. The addition of linkers, such as albumin binding domain or PEG, and choice of chelating agents have a major impact on the chemical and biological properties of the vectors. Random or site-specific bioconjugation, click chemistry, also have to be considered in the early stage as the choice of the selected technology will modify your development plan and manufacturing. New ligands and biological platforms are now being developed based on this historical knowledge, improved Target Product Profiles are built to conduct optimal lead optimization of MRT. Herein, we will present our lead optimization and preclinical evaluation process to select efficiently good radiolabeled molecules and list the key parameters to be checked. To date, it remains hard to predict the behavior of the modified bioconjugated molecules, and versatile synthesis strategies are needed to screen various combinations of radiometal complexes, linker and conjugation function, in order to converge rapidly to the optimized bioconjugate. As an example, we will present a study case where the conjugation of various bifunctional chelating agents on a small NTS1 receptor antagonist resulted in drastically different in vivo behavior of the resulting 68Ga-labeled compounds. Once optimal in vivo tumor uptake has been achieved, preclinical evaluation requires the selection of appropriate and relevant models, driven by target expression, radioresistance, and potentially tumor immune infiltrate for combination studies with immunotherapies. The therapeutic evaluation should take into consideration the dose and specific activity, the tolerance of a model related to ionizing radiations and the scheduling of treatments (cumulated dose, fractionation). We will present our recent results which highlight the importance to optimize these parameters to improve the efficacy of MRT. Citation Format: Emma Renard, Olivier Raguin, Victor Goncalves, Celine Mothes, Mathieu Moreau, Claire Bernhard, Peggy Provent, Frederic Boschetti, Franck Denat, Fabrice Viviani, Cyril Berthet. Lead optimization of radiopharmaceuticals for molecular radiotherapy and preclinical evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1401.

Ultrasmall polyaminocarboxylate-coated gold nanoparticles (NPs), Au@DTDTPA and Au@TADOTAGA, that have been recently developed exhibit a promising potential for image-guided radiotherapy. In order to render the radiosensitizing effect of these gold nanoparticles even more efficient, the study of their localization in cells is required to better understand the relation between the radiosensitizing properties of the agents and their localization in cells and in tumors. To achieve this goal, post-functionalization of Au@DTDTPA nanoparticles by near-infrared (NIF) organic dyes (aminated derivative of cyanine 5, Cy5-NH2) was performed. The immobilization of organic Cy5-NH2 dyes onto the gold nanoparticles confers to these radiosensitizers fluorescence properties which can be exploited for monitoring their internalization in cancerous cells, for determining their localization in cells by fluorescence microscopy (a common and powerful imaging tool in biology), and for following up on their accumulation in tumors after intravenous injection.

A novel trifunctional imaging probe containing a chelator of radiometal for PET, a NIR heptamethine cyanine dye, and a bioconjugatable handle, has been grafted onto AGuIX® nanoparticles via a Michael addition reaction. The resulting functionalized nanoparticles have been fully characterized, radiolabelled with 64Cu, and evaluated in a mice TSA tumor model using multimodal (PET/MRI/optical) imaging.

An efficient route has been developed for the synthesis of multifunctional tetraazacycloalkanes (in particular 1,4,7,10-tetraazacyclotridecane) incorporating an aminomethyl pendant arm on the carbon skeleton. Starting from the appropriate C-functionalized bisaminal-protected intermediate, the target macrocycles were easily obtained by means of a step-by-step introduction of the desired functional groups onto the free primary amine group, followed by deprotection of the bisaminal intermediates. This straightforward and versatile synthetic approach paves the way for the design of a new family of multifunctional chelators.

Ultrasmall silica nanoparticles (NPs), having hydrodynamic diameters under 10 nm are promising inorganic platforms for imaging and therapeutic applications in medicine. Herein is described a new way for synthesizing such kind of NPs in a one-pot scalable protocol. These NPs bear DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) ligands on their surface that can chelate different metals suitable for a wide variety of biomedical applications. By varying the ratio of the precursors, the hydrodynamic diameters of the particles can be controlled over the range of 3 to 15 nm. The resulting NPs have been characterized extensively by complementary techniques like dynamic light scattering (DLS), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), mass spectrometry (MS), phosphorescence titration, photophysical measurements, relaxometry and elemental analysis to elucidate their structures. Chelation of gadolinium (Gd) allowed its use as an effective intravenous contrast agent in MRI and was illustrated in mice bearing colorectal CT26 tumors. The new particle appears to sufficiently accumulate in the tumors and efficiently clear out of animal bodies through kidneys. This new synthesis is an original, time/material-saving and very flexible process that can be applied for creating versatile ultrasmall multifunctional nanomedicines.

Multimodal nanoprobes are highly demanded for biomedical imaging applications to enhance the reliability of the diagnostic results. Among different types of nano-objects, ultrasmall silica gadolinium nanoparticle (SiGdNP) appears as a safe, effective, and versatile platform for this purpose. In this study, a new method to functionalize SiGdNP based on silane chemistry has been reported. Two types of chelating silanes (APTES-DOTAGA and APTES-NODAGA) have been synthesized and grafted on SiGdNP by a simple one-step protocol. This functionalization strategy requires no other reactants or catalyzers and does not compromise the ultrasmall size of the particles. NODAGA-functionalized particle has been labeled with 64Cu isotope and injected intravenously to mice bearing TS/A carcinoma tumor for biodistribution study to demonstrate its potential as a bimodal MRI/PET imaging agent. A fully integrated MRI/PET system was used to simultaneously monitor the distribution of the particle. The results showed that the functionalized particle maintained properties of a renal clearable NP which could rapidly escape through kidneys and had low retention in other organs, especially liver, even though its accumulation in the tumor was modest.

AGuIX® are sub-5 nm nanoparticles made of a polysiloxane matrix and gadolinium chelates. This nanoparticle has been recently accepted in clinical trials in association with radiotherapy. This review will summarize the principal preclinical results that have led to first in man administration. No evidence of toxicity has been observed during regulatory toxicity tests on two animal species (rodents and monkeys). Biodistributions on different animal models have shown passive uptake in tumours due to enhanced permeability and retention effect combined with renal elimination of the nanoparticles after intravenous administration. High radiosensitizing effect has been observed with different types of irradiations in vitro and in vivo on a large number of cancer types (brain, lung, melanoma, head and neck…). The review concludes with the second generation of AGuIX nanoparticles and the first preliminary results on human.

We report herein an efficient and general method for the synthesis of new bismacrocyclic compounds, structural analogues of biscyclam AMD3100, in which the two macrocycles are linked together through carbon atoms of the cycles. Several representatives of this new class of biscyclic derivatives were prepared by reacting C-aminomethyl-13aneN4 with aromatic dialdehydes. Preliminary in vitro studies were performed to evaluate the affinity of these compounds towards the co-receptor CXCR4.

Univ. Bourgogne Franche-Comté, AgroSup D France. E-mail: nicolas.sok@agrosupdijon.fr Institut de Chimie Moléculaire de l'Univers Bourgogne Franche-Comté, 9 Avenue Alain S franck.denat@u-bourgogne.fr INSERM UMR 866, UFR des Sciences de Dijon, France Centre Hospitalier Universitaire, Dijon, Fra Chematech S.A., 2 Rue Pauline Kergomard, † Electronic supplementary information ( and 1476683. For ESI and crystallographic see DOI: 10.1039/c7ra04218c Cite this: RSC Adv., 2017, 7, 28291

(76) Inventors: Frederic Boschetti, Dijon (FR); Franck Denat, Dijon (FR); Roger Guilard, Dijon (FR); Henry Ledon, Versailles (FR); Herve Chollet, Dijon (FR); Jean-Louis Babouhot, Dijon (FR) Correspondence Address: YOUNG & THOMPSON 745 SOUTH 23RD STREET 2ND FLOOR ARLINGTON, VA 2.2202 (21) Appl. No.: 10/490,948 (22) PCT Filed: Sep. 27, 2002 (86) PCT No.: PCT/FR02/03319 (30) Foreign Application Priority Data Sep. 28, 2001 (FR)............................................ O1/12550

The introduction of one or two nitriles on the bridge of reinforced cyclams paves the way for the synthesis of new bifunctional chelating agents. X-ray structures of the chelators and of two copper complexes are reported.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The new ligand L was prepared and features a 13-membered tetraaza macrocyclic ring with a 1,8-naphthalimide fluorophore appended to a C atom of its backbone. The protonation constants of L as well as its complexation constants with Zn2+ ions were determined in 1:1 water/methanol solutions by potentiometric titrations. Fluorimetric pH titrations were performed with L alone and L in the presence of Zn2+ ions (1:1), and the species distributions (%) versus pH were compared. A window-shaped fluorescence trend was observed with pH for the L/Zn2+ system, which behaves as an off–on–off pH sensor. The on window is centred in the 6.5–7.5 pH range, in correspondence with the formation of [ZnL]2+. The ligand L also works as a sensor for Zn2+ ions in this pH window, which includes the physiological pH value (7.4). Accordingly, L was used as a probe for the visualization of the Zn2+ pools in Saccharomyces cerevisiae yeast cells at pH 7.4 and has the additional ability to distinguish between living and dead cells.

CXCR4 is a G protein-coupled receptor (GPCR), which is overexpressed in numerous diseases, particularly in multiple cancers. Therefore, this receptor represents a valuable target for imaging and therapeutic purposes. Among the different approaches, which were developed for CXCR4 imaging, a CXCR4 antagonist biscyclam system (AMD3100, also called Mozobil), currently used in the clinic for the mobilization of hematopoietic stem cells, was radiolabeled with different radiometals such as (62)Zn, (64)Cu, (67)Ga, or (99m)Tc. However, cyclam is not an ideal chelator for most of these radiometals, and could lead to the release of the radionuclide in vivo. In the current study, a new family of CXCR4 imaging agents is presented, in which AMD3100 is used as a carrier for specific delivery of an imaging reporter, i.e., a (68)Ga complex for PET imaging. AMD3100 was functionalized on the phenyl moiety with different linkers, either ethylenediamine or diamino-polyethylene glycol 3 (PEG3). The resulting AMD3100 analogues were further coupled with two different chelators, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or 1,4,7-triazacyclononane-1-glutaric acid-4,7-acetic acid (NODAGA). Five potential CXCR4 targeting agents were obtained. The derived AMD3100-based ligands were labeled with (68)Ga, highlighting the influence of the spacer nature on the (68)Ga-labeling yield. The lipophilic character of the different systems was also investigated, as well as their affinity for the CXCR4 receptor. The most promising compound was further evaluated in vivo in H69 tumor xenografts by biodistribution and PET imaging studies, validating the proof of principle of our concept.

Owing to their large range of properties which can be accurately tuned by the chemical composition, the shape and the dimensions, multifunctional nanoparticles appear as promising candidates for imageguided therapy. For achieving this goal, we developed the synthesis of gold nanoparticles which are designed for combining multimodal imaging (magnetic resonance imaging (MRI), scintigraphy (SPECT), ultrasound imaging (echography) and X-ray imaging) and radiotherapy [1-5]. Ultrasmall gold nanoparticles were synthesized by reducing gold salt in presence of various highly hydrophilic dithiolated polyaminocarboxylate ligands (linear (DTDTPA) and macrocyclic (TADOTA, TADOTAGA) ligands). They are composed of a gold core (mean diameter of ~ 2.5 nm) encapsulated within an organic shell of ligands (DTDTPA, TADOTA or TADOTAGA). The gold core is expected to provide a strong X-ray absorption whereas the ligands of the organic shell were chosen for their propensity to entrap gadolinium ions (for MRI) and radionuclides (for SPECT). Since the passive accumulation of the gold nanoparticles in the tumor depends on the nature of the ligands, the possibility to follow up the gadolinium chelate-coated gold nanoparticles by MRI is therefore very useful for determining the most opportune delay between intravenous injection and irradiation. Owing to the radiosensitizing effect of the gold core, the combination of microbeam radiation therapy (MRT) and gold nanoparticles based MRI contrast agents led to a great increase in lifespan of the 9L gliosarcoma-bearing rats in comparison to non-treated animals and animals treated only by MRT [5]. Finally, this study demonstrated that gadolinium chelate-coated gold nanoparticles exhibit a real potential for image-guided microbeam radiation therapy.

CXCR4 is a target of growing interest for the development of new therapeutic drugs and imaging agents as its role in multiple disease states has been demonstrated. AMD3100, a CXCR4 chemokine receptor antagonist that is in current clinical use as a haematopoietic stem cell mobilising drug, has been widely studied for its anti-HIV properties, potential to inhibit metastatic spread of certain cancers and, more recently, its ability to chelate radiometals for nuclear imaging. In this study, AMD3100 is functionalised on the phenyl moiety to investigate the influence of the structural modification on the anti-HIV-1 properties and receptor affinity in competition with anti-CXCR4 monoclonal antibodies and the natural ligand for CXCR4, CXCL12. The effect of complexation of nickel(II) in the cyclam cavities has been investigated. Two amino derivatives were obtained and are suitable intermediates for conjugation reactions to obtain CXCR4 molecular imaging agents. A fluorescent probe (BODIPY) and a precursor for (18)F (positron emitting isotope) radiolabelling were conjugated to validate this route to new CXCR4 imaging agents.