["New Modalities in Cancer Imaging and Therapy" XVth edition of the workshop organized by the network "Tumor Targeting, Imaging, Radiotherapies" of the Cancéropôle Grand-Ouest, 5-8 October 2022, France]. / « New Modalities in Cancer Imaging and Therapy ¼ XVe édition de l'atelier organisé par le réseau « Vectorisation, Imagerie, Radiothérapies ¼ du Cancéropôle Grand-Ouest, 5­8 octobre 2022, Erquy, France.

The fifteenth edition of the international workshop organized by the "Tumour Targeting and Radiotherapies network" of the Cancéropôle Grand-Ouest focused on the latest advances in internal and external radiotherapy from different disciplinary angles: chemistry, biology, physics, and medicine. The workshop covered several deliberately diverse topics: the role of artificial intelligence, new tools for imaging and external radiotherapy, theranostic aspects, molecules and contrast agents, vectors for innovative combined therapies, and the use of alpha particles in therapy.

Preclinical Evaluation of a 64Cu-Based Theranostic Approach in a Murine Model of Multiple Myeloma.

Although the concept of theranostics is neither new nor exclusive to nuclear medicine, it is a particularly promising approach for the future of nuclear oncology. This approach is based on the use of molecules targeting specific biomarkers in the tumour or its microenvironment, associated with optimal radionuclides which, depending on their emission properties, allow the combination of diagnosis by molecular imaging and targeted radionuclide therapy (TRT). Copper-64 has suitable decay properties (both ß+ and ß- decays) for PET imaging and potentially for TRT, making it both an imaging and therapy agent. We developed and evaluated a theranostic approach using a copper-64 radiolabelled anti-CD138 antibody, [64Cu]Cu-TE1PA-9E7.4 in a MOPC315.BM mouse model of multiple myeloma. PET imaging using [64Cu]Cu-TE1PA-9E7.4 allows for high-resolution PET images. Dosimetric estimation from ex vivo biodistribution data revealed acceptable delivered doses to healthy organs and tissues, and a very encouraging tumour absorbed dose for TRT applications. Therapeutic efficacy resulting in delayed tumour growth and increased survival without inducing major or irreversible toxicity has been observed with 2 doses of 35 MBq administered at a 2-week interval. Repeated injections of [64Cu]Cu-TE1PA-9E7.4 are safe and can be effective for TRT application in this syngeneic preclinical model of MM.

["Adaptation of the tumour and its ecosystem to radiotherapies: Mechanisms, imaging and therapeutic approaches" XIVth edition of the workshop organised by the "Vectorisation, Imagerie, Radiothérapies" network of the Cancéropôle Grand-Ouest, 22-25 September 2021, Le Bono, France]. / « Adaptation of the tumour and its ecosystem to radiotherapies: Mechanisms, imaging and therapeutic approaches ¼ XIVe édition du workshop organisé par le réseau « Vectorisation, Imagerie, Radiothérapies ¼ du Cancéropôle Grand-Ouest, 22­25 septembre 2021, Le Bono, France.

The fourteenth edition of the workshop covered the latest advances in internal and external radiotherapy obtained through a better understanding of the adaptive capacity of the tumor and its microenvironment, from different disciplinary angles, chemistry, biology, physics, and medicine, paving the way for numerous technological innovations. The biological aspects and the contribution of imaging in monitoring and understanding the adaptation of tumors to radiotherapy were presented, before focusing on innovative radiotherapy strategies and machine learning and data-driven techniques. Finally, the challenges were explored in the radiobiology of targeted radionuclide therapy as well as data science and machine learning in radiomics.

Anti-Tumor Efficacy of PD-L1 Targeted Alpha-Particle Therapy in a Human Melanoma Xenograft Model.

PD-L1 (programmed death-ligand 1, B7-H1, CD274), the ligand for PD-1 inhibitory receptor, is expressed on various tumors, and its expression is correlated with a poor prognosis in melanoma. Anti-PD-L1 mAbs have been developed along with anti-CTLA-4 and anti-PD-1 antibodies for immune checkpoint inhibitor (ICI) therapy, and anti-PD-1 mAbs are now used as first line treatment in melanoma. However, many patients do not respond to ICI therapies, and therefore new treatment alternatives should be developed. Because of its expression on the tumor cells and on immunosuppressive cells within the tumor microenvironment, PD-L1 represents an interesting target for targeted alpha-particle therapy (TAT). We developed a TAT approach in a human melanoma xenograft model that stably expresses PD-L1 using a 213Bi-anti-human-PD-L1 mAb. Unlike treatment with unlabeled anti-human-PD-L1 mAb, TAT targeting PD-L1 significantly delayed melanoma tumor growth and improved animal survival. A slight decrease in platelets was observed, but no toxicity on red blood cells, bone marrow, liver or kidney was induced. Anti-tumor efficacy was associated with specific tumor targeting since no therapeutic effect was observed in animals bearing PD-L1 negative melanoma tumors. This study demonstrates that anti-PD-L1 antibodies may be used efficiently for TAT treatment in melanoma.

Cell Tracking in Cancer Immunotherapy.

The impressive development of cancer immunotherapy in the last few years originates from a more precise understanding of control mechanisms in the immune system leading to the discovery of new targets and new therapeutic tools. Since different stages of disease progression elicit different local and systemic inflammatory responses, the ability to longitudinally interrogate the migration and expansion of immune cells throughout the whole body will greatly facilitate disease characterization and guide selection of appropriate treatment regiments. While using radiolabeled white blood cells to detect inflammatory lesions has been a classical nuclear medicine technique for years, new non-invasive methods for monitoring the distribution and migration of biologically active cells in living organisms have emerged. They are designed to improve detection sensitivity and allow for a better preservation of cell activity and integrity. These methods include the monitoring of therapeutic cells but also of all cells related to a specific disease or therapeutic approach. Labeling of therapeutic cells for imaging may be performed in vitro, with some limitations on sensitivity and duration of observation. Alternatively, in vivo cell tracking may be performed by genetically engineering cells or mice so that may be revealed through imaging. In addition, SPECT or PET imaging based on monoclonal antibodies has been used to detect tumors in the human body for years. They may be used to detect and quantify the presence of specific cells within cancer lesions. These methods have been the object of several recent reviews that have concentrated on technical aspects, stressing the differences between direct and indirect labeling. They are briefly described here by distinguishing ex vivo (labeling cells with paramagnetic, radioactive, or fluorescent tracers) and in vivo (in vivo capture of injected radioactive, fluorescent or luminescent tracers, or by using labeled antibodies, ligands, or pre-targeted clickable substrates) imaging methods. This review focuses on cell tracking in specific therapeutic applications, namely cell therapy, and particularly CAR (Chimeric Antigen Receptor) T-cell therapy, which is a fast-growing research field with various therapeutic indications. The potential impact of imaging on the progress of these new therapeutic modalities is discussed.

What is the Best Radionuclide for Immuno-PET of Multiple Myeloma? A Comparison Study Between 89Zr- and 64Cu-Labeled Anti-CD138 in a Preclinical Syngeneic Model.

Although positron emission tomography (PET) imaging with 18-Fluorodeoxyglucose (18F-FDG) is a promising technique in multiple myeloma (MM), the development of other radiopharmaceuticals seems relevant. CD138 is currently used as a standard marker for the identification of myeloma cells and could be used in phenotype tumor imaging. In this study, we used an anti-CD138 murine antibody (9E7.4) radiolabeled with copper-64 (64Cu) or zirconium-89 (89Zr) and compared them in a syngeneic mouse model to select the optimal tracers for MM PET imaging. Then, 9E7.4 was conjugated to TE2A-benzyl isothiocyanate (TE2A) and desferrioxamine (DFO) chelators for 64Cu and 89Zr labeling, respectively. 64Cu-TE2A-9E7.4 and 89Zr-DFO-9E7.4 antibodies were evaluated by PET imaging and biodistribution studies in C57BL/KaLwRij mice bearing either 5T33-MM subcutaneous tumors or bone lesions and were compared to 18F-FDG-PET imaging. In biodistribution and PET studies, 64Cu-TE2A-9E7.4 and 89Zr-DFO-9E7.4 displayed comparable good tumor uptake of subcutaneous tumors. On the bone lesions, PET imaging with 64Cu-TE2A-9E7.4 and 89Zr-DFO-9E7.4 showed higher uptake than with 18F-FDG-PET. Comparison of both 9E7.4 conjugates revealed higher nonspecific bone uptakes of 89Zr-DFO-9E7.4 than 64Cu-TE2A-9E7.4. Because of free 89Zr's tropism for bone when using 89Zr-anti-CD138, 64Cu-anti-CD138 antibody had the most optimal tumor-to-nontarget tissue ratios for translation into humans as a specific new imaging radiopharmaceutical agent in MM.

Translational molecular imaging in exocrine pancreatic cancer.

Effective treatment for pancreatic cancer remains challenging, particularly the treatment of pancreatic ductal adenocarcinoma (PDAC), which makes up more than 95% of all pancreatic cancers. Late diagnosis and failure of chemotherapy and radiotherapy are all too common, and many patients die soon after diagnosis. Here, we make the case for the increased use of molecular imaging in PDAC preclinical research and in patient management.

Generation of fluorescently labeled tracers - which features influence the translational potential?

Given the increasing exploration of fluorescent tracers in the field of nuclear medicine, a need has risen for practical development guidelines that can help improve the translation aspects of fluorescent tracers. This editorial discusses the does and don'ts in developing fluorescence tracers. It has been put forward by the European Association of Nuclear Medicine (EANM) Translational Molecular Imaging & Therapy committee and has been approved by the EANM board.

Theranostic Approach for Metastatic Pigmented Melanoma Using ICF15002, a Multimodal Radiotracer for Both PET Imaging and Targeted Radionuclide Therapy.

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.

Pharmacokinetics and Dosimetry Studies for Optimization of Pretargeted Radioimmunotherapy in CEA-Expressing Advanced Lung Cancer Patients.

OBJECTIVES: A phase I pretargeted radioimmunotherapy trial (EudractCT 200800603096) was designed in patients with metastatic lung cancer expressing carcinoembryonic antigen (CEA) to optimize bispecific antibody and labeled peptide doses, as well as the delay between their injections. METHODS: Three cohorts of three patients received the anti-CEA × anti-histamine-succinyl-glycine (HSG)-humanized trivalent bispecific antibody (TF2) and the IMP288 bivalent HSG peptide. Patients underwent a pretherapeutic imaging session S1 (44 or 88 nmol/m(2) of TF2 followed by 4.4 nmol/m(2), 185 MBq, of (111)In-labeled IMP288) and, 1-2 weeks later, a therapy session S2 (240 or 480 nmol/m(2) of TF2 followed by 24 nmol/m(2), 1.1 GBq/m(2), of (177)Lu-labeled IMP288). The pretargeting delay was 24 or 48 h. The dose schedule was defined based on preclinical TF2 pharmacokinetic (PK) studies, on our previous clinical data using the previous anti-CEA-pretargeting system, and on clinical results observed in the first patients injected using the same system in Netherlands. RESULTS: TF2 PK was represented by a two-compartment model in which the central compartment volume (Vc) was linearly dependent on the patient's surface area. PK was remarkably similar, with a clearance of 0.33 ± 0.03 L/h/m(2). (111)In- and (177)Lu-IMP288 PK was also well represented by a two-compartment model. IMP288 PK was faster (clearance 1.4-3.3 L/h). The Vc was proportional to body surface area, and IMP288 clearance depended on the molar ratio of injected IMP288 to circulating TF2 at the time of IMP288 injection. Modeling of image quantification confirmed the dependence of IMP288 kinetics on circulating TF2, but tumor activity PK was variable. Organ-absorbed doses were not significantly different in the three cohorts, but the tumor dose was significantly higher with the higher molar doses of TF2 (p < 0.002). S1 imaging predicted absorbed doses calculated in S2. CONCLUSION: The best dosing parameters corresponded to the shorter pretargeting delay and to the highest TF2 molar doses. S1 imaging session accurately predicted PK as well as absorbed doses of S2, thus potentially allowing for patient selection and dose optimization. TRIAL REGISTRATION: ClinicalTrials.gov NCT01221675 (EudractCT 200800603096).

Synthesis, radiolabeling and preliminary in vivo evaluation of multimodal radiotracers for PET imaging and targeted radionuclide therapy of pigmented melanoma.

Melanin pigment represents an attractive target to address specific treatment to melanoma cells, such as cytotoxic radionuclides. However, less than half of the patients have pigmented metastases. Hence, specific marker is required to stratify this patient population before proceeding with melanin-targeted radionuclide therapy. In such a context, we developed fluorinated analogues of a previously studied melanin-targeting ligand, N-(2-diethylaminoethyl)-6-iodoquinoxaline-2-carboxamide (ICF01012). These latter can be labeled either with (18)F or (131)I/(125)I for positron emission tomography imaging (melanin-positive patient selection) and targeted radionuclide therapy purposes. Here we describe the syntheses, radiosyntheses and preclinical evaluations on melanoma-bearing mice model of several iodo- and fluoro(hetero)aromatic derivatives of the ICF01012 scaffold. After preliminary planar gamma scintigraphic and positron emission tomography imaging evaluations, [(125)I]- and [(18)F]-N-[2-(diethylamino)ethyl]-4-fluoro-3-iodobenzamides ([(125)I]4, [(18)F]4) were found to be chemically and biologically stable with quite similar tumor uptakes at 1 h p.i. (9.7 ± 2.6% ID/g and 6.8 ± 1.9% ID/g, respectively).

Development and Preliminary Evaluation of TFIB, a New Bimodal Prosthetic Group for Bioactive Molecule Labeling.

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 αvß3 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.

[¹²³I]ICF01012 melanoma imaging and [¹³¹I]ICF01012 dosimetry allow adapted internal targeted radiotherapy in preclinical melanoma models.

BACKGROUND: Melanin-targeting radiotracers are interesting tools for imaging and treatment of pigmented melanoma metastases. However, variation of the pigment concentration may alter the efficiency of such targeting. OBJECTIVES: A clear assessment of both tumor melanin status and dosimetry are therefore prerequisites for internal radiotherapy of disseminated melanoma. MATERIALS & METHODS: The melanin tracer ICF01012 was labelled with iodine-123 for melanoma imaging in pigmented murine B16F0 and human SK-Mel 3 melanomas. RESULTS: In vivo imaging showed that the uptake of [(123)I]ICF01012 to melanomas correlated significantly with melanin content. Schedule treatment of 3 × 25 MBq [(131)I]ICF01012 significantly reduced SK-Mel 3 tumor growth and significantly increased the median survival in treated mice. For this protocol, the calculated delivered dose was 53.2 Gy. CONCLUSION: Radio-iodinated ICF01012 is a good candidate for both imaging and therapeutic purposes for patients with metastatic pigmented melanomas.

Differential dopamine receptor occupancy underlies L-DOPA-induced dyskinesia in a rat model of Parkinson's disease.

Dyskinesia is a major side effect of an otherwise effective L-DOPA treatment in Parkinson's patients. The prevailing view for the underlying presynaptic mechanism of L-DOPA-induced dyskinesia (LID) suggests that surges in dopamine (DA) via uncontrolled release from serotonergic terminals results in abnormally high level of extracellular striatal dopamine. Here we used high-sensitivity online microdialysis and PET imaging techniques to directly investigate DA release properties from serotonergic terminals both in the parkinsonian striatum and after neuronal transplantation in 6-OHDA lesioned rats. Although L-DOPA administration resulted in a drift in extracellular DA levels, we found no evidence for abnormally high striatal DA release from serotonin neurons. The extracellular concentration of DA remained at or below levels detected in the intact striatum. Instead, our results showed that an inefficient release pool of DA associated with low D2 receptor binding remained unchanged. Taken together, these findings suggest that differential DA receptor activation rather than excessive release could be the underlying mechanism explaining LID seen in this model. Our data have important implications for development of drugs targeting the serotonergic system to reduce DA release to manage dyskinesia in patients with Parkinson's disease.

Synthesis, radiofluorination, and in vivo evaluation of novel fluorinated and iodinated radiotracers for PET imaging and targeted radionuclide therapy of melanoma.

Our project deals with a multimodal approach using a single fluorinated and iodinated melanin-targeting structure and offering both imaging (positron emission tomography (PET)/fluorine-18) and treatment (targeted radionuclide therapy/iodine-131) of melanoma. Six 6-iodoquinoxaline-2-carboxamide derivatives with various side chains bearing fluorine were synthesized and radiofluorinated, and their in vivo biodistribution was studied by PET imaging in B16Bl6 primary melanoma-bearing mice. Among this series, [(18)F]8 emerged as the most promising compound. [(18)F]8 was obtained by a fully automated radiosynthesis process within 57 min with an overall radiochemical yield of 21%, decay-corrected. PET imaging of [(18)F]8 demonstrated very encouraging results as early as 1 h postinjection with high tumor uptake (14.33% ± 2.11% ID/g), high contrast (11.04 ± 2.87 tumor-to-muscle ratio), and favorable clearance properties. These results, associated with the previously reported pharmacokinetic properties and dosimetry of 8, make it a potential agent for both PET imaging and targeted radionuclide therapy of melanoma.

Synthesis, radioiodination and in vivo screening of novel potent iodinated and fluorinated radiotracers as melanoma imaging and therapeutic probes.

In order to develop new iodinated and fluorinated matched-pair radiotracers for Single-Photon Emission Computed Tomography (SPECT)/Positron Emission Tomography (PET) imaging and targeted radionuclide therapy of melanoma, we successfully synthesized and radiolabelled with iodine-125 seven new derivatives, starting from our previously described lead structure 3. The relevance of these radiotracers for gamma scintigraphic imaging of melanoma in rodent was assessed. The tumoural radioactivity uptake was most often high and specific even at early time points (12.1-18.3% ID/g at 3 h p.i. for [(125)I]39-42) and a fast clearance from the non-target organs was observed. Also, calculated effective doses that could be delivered to tumours when using corresponding [(131)I]-labelled analogues were generally higher than 100 cGy/MBq injected (98.9-150.5 cGy/MBq for [(131)I]39-42). These results make compounds 39-42 suitable candidates for (i) PET imaging of melanoma after labelling with fluorine-18 and (ii) targeted radionuclide therapy of disseminated melanoma after labelling with iodine-131.

Early detection and longitudinal monitoring of experimental primary and disseminated melanoma using [¹°F]ICF01006, a highly promising melanoma PET tracer.

PURPOSE: Here, we report a new and rapid radiosynthesis of (18)F-N-[2-(diethylamino)ethyl]-6-fluoro-pyridine-3-carboxamide ([(18)F]ICF01006), a molecule with a high specificity for melanotic tissue, and its evaluation in a murine model for early specific detection of pigmented primary and disseminated melanoma. METHODS: [(18)F]ICF01006 was synthesized using a new one-step bromine-for-fluorine nucleophilic heteroaromatic substitution. Melanoma models were induced by subcutaneous (primary tumour) or intravenous (lung colonies) injection of B16BL6 melanoma cells in C57BL/6J mice. The relevance and sensitivity of positron emission tomography (PET) imaging using [(18)F]ICF01006 were evaluated at different stages of tumoural growth and compared to (18)F-fluorodeoxyglucose ([(18)F]FDG). RESULTS: The fully automated radiosynthesis of [(18)F]ICF01006 led to a radiochemical yield of 61 % and a radiochemical purity >99 % (specific activity 70-80 GBq/µmol; total synthesis time 42 min). Tumours were visualized before they were palpable as early as 1 h post-injection with [(18)F]ICF01006 tumoural uptake of 1.64 ± 0.57, 3.40 ± 1.47 and 11.44 ± 2.67 percentage of injected dose per gram of tissue (%ID/g) at days 3, 5 and 14, respectively. [(18)F]ICF01006 PET imaging also allowed detection of melanoma pulmonary colonies from day 9 after tumour cell inoculation, with a lung radiotracer accumulation correlated with melanoma invasion. At day 21, radioactivity uptake in lungs reached a value of 5.23 ± 2.08 %ID/g (versus 0.41 ± 0.90 %ID/g in control mice). In the two models, comparison with [(18)F]FDG showed that both radiotracers were able to detect melanoma lesions, but [(18)F]ICF01006 was superior in terms of contrast and specificity. CONCLUSION: Our promising results provide further preclinical data, reinforcing the excellent potential of [(18)F]ICF01006 PET imaging for early specific diagnosis and follow-up of melanin-positive disseminated melanoma.