INTRODUCTION:this study investigates the production of Lead-203 (203Pb) using a deuteron beam and demonstrates its application with DOTATATE for diagnostic imaging of neuroendocrine tumours (NETs) thanks to its γ-ray emissions well-suited for SPECT imaging. 203Pb presents a high potential in nuclear medicine, as it is the imaging counterpart of part of Lead-212 (212Pb), a radionuclide with an alpha-emitting decay chain used for targeted alpha therapy. METHODS:Enriched Thallium-205 (205Tl) was electrodeposited onto a gold substrate using a custom-made PEEK cell, with a platinum rod as the auxiliary electrode. The electrodeposition was conducted at a controlled temperature and stirring speed, with reverse pulse potentials applied to obtain a smooth and dense deposit. The 205Tl deposit was then irradiated with deuteron beams at 31 MeV to produce 203Pb. Chemical separation was performed using two columns containing Pb resin. The first column (150 mg resin) was used to remove 205Tl for further recycling and the second column (60 mg resin) was employed to obtain 203Pb in 1 M ammonium acetate at pH 5 ensuring high purity and specific activity. Radiolabelling of DOTATATE with 203Pb was conducted in a modified acetate buffer, and the radiochemical purity and stability were assessed using HPLC and TLC. The stability of [203Pb]Pb-DOTATATE was evaluated over a period of up to 120 h. RESULTS:the electrodeposition process, conducted over 8 h, yielded a reproducible 205Tl deposit with an average thickness of 37.7 ± 3.2 μm, which remained stable during irradiation. The chemical separation process achieved a 203Pb purity exceeding 99 % in 1 M ammonium acetate at pH 5, with a specific activity surpassing 3783 TBq/g for an integrated beam current of 175 μAh at calibration time (EOB + 32 h). The radiochemical separation yield during the process was 80.5 %. Radiolabelling of DOTATATE with 203Pb showed a high radiochemical purity (99.1 %) and a stability over 96 h, demonstrating the feasibility of using [203Pb]Pb-DOTATATE for clinical applications. CONCLUSION:Our results support the use of 203Pb produced using deuteron beam as valuable tools in the advancement of personalized nuclear medicine therapies. The high purity and specific activity of 203Pb, achieved through dual Pb resin purification process, along with its effective radiolabelling with DOTATATE at high yield and long stability, underscore its potential for clinical use in diagnostic imaging, especially in neuroendocrine tumours.

The development of 64Cu-based immuno-PET radiotracers requires the use of copper-specific bifunctional chelators (BFCs) that contain functional groups allowing both convenient bioconjugation and stable copper complexes to limit in vivo bioreduction, transmetallation and/or transchelation. The excellent in vivo kinetic inertness of the pentaazamacrocyclic [64Cu]Cu-15-5 complex prompted us to investigate its potential for the 64Cu-labelling of monoclonal antibodies (mAbs), compared with the well-known NODAGA and DOTA chelators. To this end, three NODAGA, DOTA and 15-5-derived BFCs, containing a pendant azadibenzocyclooctyne moiety, were synthesised and a robust methodology was determined to form covalent bonds between them and azide-functionalised trastuzumab, an anti-HER2 mAb, using strain-promoted azide-alkyne cycloaddition. Unlike the DOTA derivative, the NODAGA- and 15-5-mAb conjugates were radiolabelled with 64Cu, obtaining excellent radiochemical yields, under mild conditions. Although all the radioimmunoconjugates showed excellent stability in PBS or mouse serum, [64Cu]Cu-15-5- and [64Cu]Cu-NODAGA-trastuzumab presented higher resistance to transchelation when challenged by EDTA. Finally, the immunoreactive fraction of the radioimmunoconjugates (88–94%) was determined in HER-2 positive BT474 human breast cancer cells, confirming that the bioconjugation and radiolabelling processes implemented had no significant impact on antigen recognition.

Characterization of [3H]-Mel and [3H]-Mel-QA

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Whilst 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.

Antibodies directed against CD22 have been used in radioimmunotherapy (RIT) clinical trials to treat patients with diffuse large B-cell lymphoma (DLBCL) with promising results. However, relevant preclinical models are needed to facilitate the evaluation and optimization of new protocols. Spontaneous DLBCL in dogs is a tumor model that may help accelerate the development of new methodologies and therapeutic strategies for RIT targeting CD22. Seven murine monoclonal antibodies specific for canine CD22 were produced by the hybridoma method and characterized. The antibodies' affinity and epitopic maps, their internalization capability and usefulness for diagnosis in immunohistochemistry were determined. Biodistribution and PET imaging on a mouse xenogeneic model of dog DLBCL was used to choose the most promising antibody for our purposes. PET-CT results confirmed biodistribution study observations and allowed tumor localization. The selected antibody, 10C6, was successfully used on a dog with spontaneous DLBCL for SPECT-CT imaging in the context of disease staging, validating its efficacy for diagnosis and the feasibility of future RIT assays. This first attempt at phenotypic imaging on dogs paves the way to implementing quantitative imaging methodologies that would be transposable to humans in a theranostic approach. Taking into account the feedback of existing human radioimmunotherapy clinical trials targeting CD22, animal trials are planned to investigate protocol improvements that are difficult to consider in humans due to ethical concerns.

Glioblastoma is the most common malignant adult brain tumor and has a very poor patient prognosis. The mean survival for highly proliferative glioblastoma is only 10 to 14 months despite an aggressive current therapeutic approach known as Stupp’s protocol, which consists of debulking surgery followed by radiotherapy and chemotherapy. Despite several clinical trials using anti-angiogenic targeted therapies, glioblastoma medical care remains without major progress in the last decade. Recent progress in nuclear medicine, has been mainly driven by advances in biotechnologies such as radioimmunotherapy, radiopeptide therapy, and radionanoparticles, and these bring a new promising arsenal for glioblastoma therapy. For therapeutic purposes, nuclear medicine practitioners classically use β− particle emitters like 131I, 90Y, 186/188Re, or 177Lu. In the glioblastoma field, these radioisotopes are coupled with nanoparticles, monoclonal antibodies, or peptides. These radiopharmaceutical compounds have resulted in a stabilization and/or improvement of the neurological status with only transient side effects. In nuclear medicine, the glioblastoma-localized and targeted internal radiotherapy proof-of-concept stage has been successfully demonstrated using β− emitting isotopes. Similarly, α particle emitters like 213Bi, 211At, or 225Ac appear to be an innovative and interesting alternative. Indeed, α particles deliver a high proportion of their energy inside or at close proximity to the targeted cells (within a few micrometers from the emission point versus several millimeters for β− particles). This physical property is based on particle–matter interaction differences and results in α particles being highly efficient in killing tumor cells with minimal irradiation of healthy tissues and permits targeting of isolated tumor cells. The first clinical trials confirmed this idea and showed good therapeutic efficacy and less side effects, thus opening a new and promising era for glioblastoma medical care using α therapy. The objective of this literature review is focused on the developing field of nuclear medicine and aims to describe the various parameters such as targets, vectors, isotopes, or injection route (systemic and local) in relation to the clinical and preclinical results in glioblastoma pathology.

Background Diacetyl-bis(N4-methylthiosemicarbazone), labeled with 64Cu ( 64 Cu-ATSM) has been suggested as a promising tracer for imaging hypoxia. However, various controversial studies highlighted potential pitfalls that may disable its use as a selective hypoxic marker. They also highlighted that the results may be tumor location dependent. Here, we first analyzed uptake of Cu-ATSM and its less lipophilic counterpart Cu-Cl 2 in the tumor over time in an orthotopic glioblastoma model. An in vitro study was also conducted to investigate the hypoxia-dependent copper uptake in tumor cells. We then further performed a comprehensive ex vivo study to compare 64 Cu uptake to hypoxic markers, specific cellular reactions, and also transporter expression. Methods μPET was performed 14 days ( 18 F-FMISO), 15 days ( 64 Cu-ATSM and 64 Cu-Cl2), and 16 days ( 64 Cu-ATSM and 64 Cu-Cl 2 ) after C6 cell inoculation. Thereafter, the brains were withdrawn for further autoradiography and immunohistochemistry. C6 cells were also grown in hypoxic workstation to analyze cellular uptake of Cu complexes in different oxygen levels. Results In vivo results showed that Cu-ASTM and Cu-Cl2 accumulated in hypoxic areas of the tumors. Cu-ATSM also stained, to a lesser extent, non-hypoxic regions, such as regions of astrogliosis, with high expression of copper transporters and in particular DMT-1 and CTR1, and also characterized by the expression of elevated astrogliosis. In vitro results show that 64Cu-ATSM showed an increase in the uptake only in severe hypoxia at 0.5 and 0.2% of oxygen while for 64 Cu-Cl2, the cell retention was significantly increased at 5% and 1% of oxygen with no significant rise at lower oxygen percentages. Conclusion In the present study, we show that Cu-complexes undoubtedly accumulate in hypoxic areas of the tumors. This uptake may be the reflection of a direct dependency to a redox metabolism and also a reflection of hypoxic-induced overexpression of transporters. We also show that Cu-ATSM also stained non-hypoxic regions such as astrogliosis.

PURPOSE Dosimetry for melanoma-targeted radionuclide therapy (TRT) with [131 I]ICF01012, a melanin ligand, has been previously evaluated in mice bearing melanomas. In this study, activity distribution and dosimetry are performed on healthy rabbits (Fauve de Bourgogne) using SPECT-CT imaging and ex vivo measurements. MATERIAL AND METHODS Ex vivo biodistribution (i.v. injection: 370 kBq/kg, n = 2 per point) is performed on blood, eyes, brain, lung, liver, kidneys, heart, stomach, and spleen. Dosimetry calculations follow the MIRD formalism: S values are calculated from CT images using the GATE Monte Carlo platform and activity distributions are obtained from SPECT-CT imaging (i.v. injection: 37 MBq/kg n = 3 per point). A specific study is presented to assess dose to human retina. RESULTS Time-integrated activities based on SPECT-CT are in accordance with ex vivo measurements except for spleen. Doses to liver and eyes are the most significant, with respectively, 6.38 ± 0.50 Gy/GBq (evaluated through SPECT-CT imaging) and 45.8 ± 7.9 Gy/GBq (evaluated through ex vivo measurements). Characterization of ocular [131 I]ICF01012 biodistribution in rabbits and quantification of melanin allowed to assess a dose of 3.07 ± 0.70 Gy/GBq to human retina. CONCLUSION This study sustains [131 I]ICF01012 as a good candidate for melanoma TRT and open perspectives for personalized dosimetry calculation during phase I clinical transfer.

Mapping 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.

PURPOSE: This work reports, in melanoma models, the theranostic potential of ICF15002 as a single fluorinated and iodinated melanin-targeting compound. METHODS: Studies were conducted in the murine syngeneic B16BL6 model and in the A375 and SK-MEL-3 human xenografts. ICF15002 was radiolabeled with fluorine-18 for positron emission tomography (PET) imaging and biodistribution, with iodine-125 for metabolism study, and iodine-131 for targeted radionuclide therapy (TRT). TRT efficacy was assessed by tumor volume measurement, with mechanistics and dosimetry parameters being determined in the B16BL6 model. Intracellular localization of ICF15002 was characterized by secondary ion mass spectrometry (SIMS). RESULTS: PET imaging with [18F]ICF15002 evidenced tumoral uptake of 14.33±2.11%ID/g and 4.87±0.93%ID/g in pigmented B16BL6 and SK-MEL-3 models, respectively, at 1 hour post inoculation. No accumulation was observed in the unpigmented A375 melanoma. SIMS demonstrated colocalization of ICF15002 signal with melanin polymers in melanosomes of the B16BL6 tumors. TRT with two doses of 20 MBq [131I]ICF15002 delivered an absorbed dose of 102.3 Gy to B16BL6 tumors, leading to a significant tumor growth inhibition [doubling time (DT) of 2.9±0.5 days in treated vs 1.8±0.3 in controls] and a prolonged median survival (27 days vs 21 in controls). P53S15 phosphorylation and P21 induction were associated with a G2/M blockage, suggesting mitotic catastrophe. In the human SK-MEL-3 model, three doses of 25 MBq led also to a DT increase (26.5±7.8 days vs 11.0±3.8 in controls) and improved median survival (111 days vs 74 in controls). CONCLUSION: Results demonstrate that ICF15002 fulfills suitable properties for bimodal imaging/TRT management of patients with pigmented melanoma.

This study was conducted during the development of innovative treatment targeting the microenvironment of chondrosarcoma. In this context, MMP inhibitors were conjugated with a quaternary ammonium (QA) function as a targeting ligand to proteoglycans of chondrosarcoma extracellular matrix. Here we report the proof of concept of this strategy applied to the MMP13 inhibitor, doxycycline (Dox).

With the recent interest on the theranostic approach, there has been a renewed interest for alternative radionuclides in nuclear medicine. They can be produced using common production routes, i.e., using protons accelerated by biomedical cyclotrons or neutrons produced in research reactors. However, in some cases, it can be more valuable to use deuterons as projectiles. In the case of Cu-64, smaller quantities of the expensive target material, Ni-64, are used with deuterons as compared with protons for the same produced activity. For the Sc-44m/Sc-44g generator, deuterons afford a higher Sc-44m production yield than with protons. Finally, in the case of Re-186g, deuterons lead to a production yield five times higher than protons. These three examples show that it is of interest to consider not only protons or neutrons but also deuterons to produce alternative radionuclides.

Le 99mTc-NTP 15-5, grâce à sa fonction ammonium quaternaire chargée positivement, est un traceur ciblant les protéoglycanes chargés négativement situés dans la matrice extracellulaire cartilagineuse. Nous retraçons ici les différentes étapes précliniques ayant conduit à la preuve de concept dans les pathologies cartilagineuses dégénératives et tumorales telles que le chondrosarcome. Le 99mTc-NTP 15-5 pourrait s’avérer à terme être un traceur compagnon pertinent pour l’évaluation des pathologies articulaires. Son transfert clinique est initié. La pertinence du radiotraceur 99mTc-NTP 15-5 a été évaluée, chez l’animal, pour l’imagerie du cartilage sain et de ses pathologies : (i) arthrose expérimentale par méniscectomie unilatérale médiale chez le cobaye ; (ii) défects ostéochondraux ; (iii) chondrosarcome primitif de grade II ; (iv) récidive locale du chondrosarcome après curetage. Les potentialités de fixation du 99mTc-NTP 15-5 au cartilage humain ont également été évaluées avec succès par imagerie TEMP/TDM après incubation ex vivo de spécimens articulaires humains. La pertinence de l’imagerie 99mTc-NTP 15-5 pour le suivi de traitement a également été évaluée dans le modèle de chondrosarcome (traitement zolédronate). Les résultats ont montré l’intérêt du 99mTc-NTP 15-5 comme traceur du cartilage, avec une accumulation sélective à l’origine d’un excellent contraste en imagerie. In vivo, des modifications de fixation du traceur ont été corrélées aux remaniements des protéoglycanes liés aux processus physiopathologiques. Dans le chondrosarcome, la fixation du traceur s’est révélée étroitement liée au développement tumoral dans les modèles primitifs, récidive post-curetage et dans le modèle traité. Cachin et al. ont démontré l’excellente spécificité du 99mTc NTP 15-5 pour une fixation ex vivo au cartilage humain avec un ratio cartilage sur corticale osseuse de 4,57 ± 3,07 en 99mTc-NTP 15-5 versus 0,71 ± 0,31 en 99mTc-HDMP. Dans la perspective d’un transfert clinique, une trousse de marquage a été conçue. Pour l’arthrose, une étude préclinique est en cours pour définir la place du 99mTc-NTP 15-5 dans le suivi par imagerie des nouvelles thérapeutiques structuromodulatrices (DMOAD). Dans le chondrosarcome, une étude « first in human » est planifiée. Collaboration avec le CHU Gabriel-Montpied (Pr. Boisgard et Soubrier), partenariat avec Cyclopharma. Soutiens : AVIESAN/ITMO TS, PRTK Inca/DGOS, ANR, CPER.

Abstract To date, surgery remains the only option for the treatment of chondrosarcoma, which is radio- and chemoresistant due in part to its large extracellular matrix (ECM) and poor vascularity. In case of unresectable locally advanced or metastatic diseases with a poor prognosis, improving the management of chondrosarcoma still remains a challenge. Our team developed an attractive approach of improvement of the therapeutic index of chemotherapy by targeting proteoglycan (PG)-rich tissues using a quaternary ammonium (QA) function conjugated to melphalan (Mel). First of all, we demonstrated the crucial role of the QA carrier for binding to aggrecan by surface plasmon resonance. In the orthotopic model of Swarm rat chondrosarcoma, an in vivo biodistribution study of Mel and its QA derivative (Mel-QA), radiolabeled with tritium, showed rapid radioactivity accumulation in healthy cartilaginous tissues and tumor after [3H]-Mel-QA injection. The higher T/M ratio of the QA derivative suggests some advantage of QA-active targeting of chondrosarcoma. The antitumoral effects were characterized by tumor volume assessment, in vivo 99mTc-NTP 15-5 scintigraphic imaging of PGs, 1H-HRMAS NMR spectroscopy, and histology. The conjugation of a QA function to Mel did not hamper its in vivo efficiency and strongly improved the tolerability of Mel leading to a significant decrease of side effects (hematologic analyses and body weight monitoring). Thus, QA conjugation leads to a significant improvement of the therapeutic index, which is essential in oncology and enable repeated cycles of chemotherapy in patients with chondrosarcoma. Mol Cancer Ther; 15(11); 2575–85. ©2016 AACR.

The new readily available prosthetic group, tetrafluorophenyl 4-fluoro-3-iodobenzoate (TFIB), designed for both molecular imaging and targeted radionuclide therapy purposes was radiolabeled either with fluorine or iodine radionuclides with excellent radiochemical yields and purities. These radiolabeled tags were conjugated to N,N-diethylethylenediamine to give melanin-targeting radiotracers [ (125) I]9 and [ (18) F]9, which were successfully evaluated by PET and gamma scintigraphic imaging in B16F0 pigmented melanoma-bearing C57BL/6J mice. Then, radiolabeled [ (125) I]/[ (18) F]TFIB was used to tag tumor-targeting peptides (i.e., PEG3[c(RGDyK)]2 and NDP-MSH targeting αvβ3 integrin and MC1R receptors, respectively) in mild conditions and with good radiochemical yields (47-83% d.c.) and purities (>99%). The resulting radiolabeled peptides were assessed both in vitro and by PET imaging in animal models.

The cartilage-targeting strategy is based on the strong affinity of quaternary ammonium (QA) functions for cartilage proteoglycans. We use a bifunctional agent containing QA moiety and a polyazamacrocycle structure able to complex technetium-99m. (99m)Tc-NTP 15-5 was selected for its high stability and its high affinity for proteoglycans in vivo. Labeling conditions of NTP 15-5 were optimized, and a lyophilized kit was developed for radiolabeling of (99m)Tc-NTP 15-5 (radiochemical yields 94.6±1.8%). (99m)Tc-NTP 15-5 was stable and resulted in favorable biological evaluations.

This study determined, using the intraarticular complete Freund adjuvant arthritis mice model, whether the radiotracer Tc-99m-N-(triethyl-ammonium)- 3-propyl-[15] ane-N5 ((99)mTc-NTP 15-5) targeting proteoglycans has a pathophysiologic validity for in vivo imaging of rheumatoid arthritis (RA) and its response to chronic nonsteroidal antiinflammatory drugs. Methods: We investigated the time course of cartilage remodeling by Tc-99m-NTP 15-5 scintigraphy, bone damages by Tc-99m-hydroxymethylene diphosphonate imaging, inflammation by F-18-FDG PET, and joint proteoglycan content and pain behavior in animals, without and with meloxicam treatment. Paw circumference, thermal pain behavior, and histology as well as proteoglycan content of the whole joint were determined. Results: Tc-99m-NTP 15-5 showed specific tracer accumulation within RA joints, with a significant increase in scintigraphic ratio observed in RA versus shams from day 3 to day 28. F-18-FDG evidenced uptake in RA joints from day 15 to day 29. Animals treated with meloxicam (5 mg/kg) exhibited a dose-dependent decrease in both Tc-99m-NTP 15-5 and F-18-FDG uptake ratios versus saline-treated animals. Tc-99m-hydroxymethylene diphosphonate bone scans were only positive at day 14 in RA versus shams, with a significant effect of meloxicam. An increase in proteoglycans of RA joint and thermal pain behavior were observed and were dose-dependently reduced by meloxicam. Conclusion: These experimental results bring data in favor of the Tc-99m-NTP 15-5 radiotracer for assessing, in vivo, cartilage remodeling in RA that could be used to monitor therapy.