Development of PDT/PET theranostics: synthesis and biological evaluation of an ¹⁸F-radiolabeled water soluble porphyrin

Synthesis of the first water-soluble porphyrin radiolabeled with fluorine-18 is described: a new molecular theranostic agent which integrates the therapeutic selectivity of photodynamic therapy (PDT) with the imaging efficacy of positron emission tomography (PET). Generation of the theranostic was carried out through the conjugation of a cationic water-soluble porphyrin bearing an azide functionality to a fluorine-18 radiolabeled prosthetic bearing an alkyne functionality through click conjugation, with excellent yields obtained in both cold and hot synthesis. Biological evaluation of the synthesized structures shows the first example of an 18 F-radiolabeled porphyrin retaining photocytotoxicity following radiolabeling and demonstrable conjugate uptake and potential application as a radiotracer in vivo. The promising results gained from biological evaluation demonstrate the potential of this structure as a clinically relevant theranostic agent, offering exciting possibilities for the simultaneous imaging and photodynamic treatment of tumors

Automated sulfur-[18F]fluoride exchange radiolabelling of a prostate specific membrane antigen (PSMA) targeted ligand using the GE FASTlab™ cassette-based platform

Sulfur-[18F]fluoride exchange radiochemistry is a rapid and convenient method for incorporating fluorine-18 into biologically active molecules. We report a fully automated radiolabelling procedure for the synthesis of a [18F]SO3F-bearing prostate specific membrane antigen (PSMA) targeted ligand ([18F]5) using the GE FASTLab™ cassette-based platform in a 25.0 ± 2.6% radiochemical yield (decay corrected). Uptake in vitro and in vivo correlated with PSMA expression, and the radioligand exhibited favourable biodistribution and pharmacokinetic profiles

Chelator free gallium-68 radiolabelling of silica coated iron oxide nanorods via surface interactions

The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron–oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T₂ MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging

Structurally optimised BODIPY derivatives for imaging of mitochondrial dysfunction in cancer and heart cells

The structural features required for mitochondrial uptake of BODIPY-based optical imaging agents have been explored. The first derivatives of this class of dyes shown to have mitochondrial membrane potential-dependent uptake in both cancer and heart cells have been developed

64Cu PET Imaging of the CXCR4 Chemokine Receptor Using a Cross-Bridged Cyclam Bis-Tetraazamacrocyclic Antagonist

© 2020 by the Society of Nuclear Medicine and Molecular Imaging. Expression of the chemokine receptor chemokine C-X-C motif receptor 4 (CXCR4) plays an important role in cancer metastasis, in autoimmune diseases, and during stem cell-based repair processes after stroke and myocardial infarction. Previously reported PET imaging agents targeting CXCR4 suffer from either high nonspecific uptake or bind only to the human form of the receptor. The objective of this study was to develop a high-stability 64Cu-labeled small-molecule PET agent for imaging both human and murine CXCR4 chemokine receptors. Methods: Synthesis, radiochemistry, stability and radioligand binding assays were performed for the novel tracer 64Cu-CuCB-bicyclam. In vivo dynamic PET studies were performed on mice bearing U87 (CXCR4 low-expressing) and U87.CXCR4 (human-CXCR4 high-expressing) tumors. Biodistribution and receptor blocking studies were performed on CD1-IGS immunocompetent mice. CXCR4 expression on tumor and liver disaggregates was confirmed using a combination of immunohistochemistry, quantitative polymerase chain reaction, and Western blot. Results:64Cu-CuCB-bicyclam has a high affinity for both the human and the murine variants of the CXCR4 receptor (half-maximal inhibitory concentration, 8 nM [human]/2 nM [murine]) and can be obtained from the parent chelator that has low affinity. In vitro and in vivo studies demonstrate specific uptake in CXCR4-expressing cells that can be blocked by more than 90% using a higher-affinity antagonist, with limited uptake in non-CXCR4-expressing organs and high in vivo stability. The tracer was also able to selectively displace the CXCR4 antagonists AMD3100 and AMD3465 from the liver. Conclusion: The tetraazamacrocyclic small molecule 64Cu-CuCB-bicyclam has been shown to be an imaging agent for the CXCR4 receptor that is likely to be applicable across a range of species. It has high affinity and stability and is suitable for preclinical research in immunocompetent murine models

Conception, synthèse et évaluation pharmacologique d'inhibiteurs pseudopeptidiques de la farnésyltransférase, potentiellement utilisables dans le traitement du cancer

LILLE2-BU Santé-Recherche (593502101) / SudocSudocFranceF

Mono- and bis-alkylation of glyoxal-bridged tetraazamacrocycles using mechanochemistry

Glyoxal-bridged bisaminal tetraazamacrocyclic derivatives of 1,4,7,10-tetraazacyclododecane (cyclen) and 1,4,8,11-tetraazacyclotetradecane (cyclam) can be N-functionalized to incorporate coordinating groups or for conjugation to biomolecules. Herein, we present an improved N-functionalization methodology using mechanochemistry which reduces reaction times in comparison with conventional synthetic routes. A range of six alkyl halides were reacted with cyclen and cyclam bisaminal derivatives in various ratios to form mono- and bis-functionalized quaternary ammonium salts. Cross-bridged cyclam, a key intermediate for CB-TE2A, a commonly used chelator in positron emission tomography medical imaging with 64 Cu, has been synthesized using nonconventional synthetic methodologies (grinding and microwave heating) with intermediates characterized by 2D NMR and single crystal XRD. The overall synthesis time of CB-TE2A from cyclam could be shortened to 5 days from the 35 days required for the conventional synthesis

o-BF3-Phosphonium pincer moieties in the design of delocalized lipophilic cation based tracers for PET imaging of mitochondrial function

International audienceObjectives: Delocalized lipophilic cations, such as triphenylphosphonium (TPP), are able to cross cell membranes and are known to accumulate in the mitochondria in a membrane potential (MMP) dependent manner. MMP is a reliable indicator of mitochondrial and, consequently, cell and tissue function, hence MMP dependent uptake radiotracers are of interest in cardiac and tumour imaging. Conventional C-18F radiofluorination methods require strict aprotic conditions and heating, moreover, C-18F fluorinated tracers may suffer from metabolic defluorination reducing the quality of the images. The objective of this study was to investigate a suitability of o-B[18F]F3-phosphonium pincer moiety, easily accessible via radiofluorination of boronic ester precursors in aqueous mixtures to give high stability, for use as MMP dependent tracers.Methods: Required boronic ester precursors and cold 19F-fluorine labelled reference compounds 1-4 (Fig. 1) were prepared and purified following modified published synthetic protocols. Radiofluorination was carried out in a 0.2 mg scale with carrier added 18F-fluoride at 55oC in 30 min in 20% acetonitrile / water mixture acidified by addition of concentrated hydrochloric acid. LogD7.4 values were determined via the shake flask method. Stability in human serum was assessed using radio-HPLC analysis. The isolated mitochondria uptake assay was performed on freshly isolated mitochondria from Sprague-Dawley rat heart tissue. Cell uptake of the tracer was measured in normal H9c2 cardiac and U87 tumour cells in presence and absence of a membrane depolarizing agent 2-[2-(3-chlorophenyl)hydrazineylyidene]propanedinitrile (CCCP). PET/CT imaging and biodistribution studies were performed in CD-1 nude mice bearing U87 tumour xenografts. Overall charge distributions were calculated using fully optimised geometries at TPSS-D3/def2-TZVPP theory level. 18FHTP (6-18F-fluorohexyltriphenylphosphonium) was prepared in an original one step radiolabelling procedure from an iodinated precursor and was used to validate all assays and as a benchmark for the novel tracers.Results: 18FHTP and 18F-1-4 were obtained in 20-25% decay corrected radiochemical yields within 60 min from the end of bombardment. The LogD7.4 values ranged between 1.78±0.06 (18FHTP and 18F-2) and 0.52±0.01 (18F-1), with 0.88±0.09 and 1.11±0.08 for 18F-3 and 18F-4, respectively. All radiotracers showed 蠅 95% stability in human serum for 3 h. Tracers 18FHTP and 18F-2 showed a comparable MMP dependent uptake in isolated mitochondria (~8%), with the uptake of 18F-3 and 18F-4 below 4% and MMP independent, indicating the importance of the lipophilicity. U87 cell uptake of all tracers was low and MMP independent (~ 0.1% and 1% for 18FHTP and 18F-1-4 respectively). 18F-2 showed the highest and the only MMP dependent cell uptake from the series of new compounds(~ 4% vs ~7% observed for 18FHTP). None of BF3 group containing tracers showed any cardiac or tumour uptake in vivo. Overall charge distribution analysis in a computational study revealed a localised positive charge at the boron atom with partial negative charges carried by fluorine atoms or an ipso carbon of one of the unsubstituted phenyl rings.Conclusion: A series of o-BF3 substituted triphenylphosphonium tracers were successfully synthesized and radiolabelled with fluorine-18. A preliminary in vitro investigation confirmed the importance of the lipophilicity for mitochondrial uptake of the tracer, however, this was not sufficient to ensure cell membrane transport and consequent in vivo localization. The comparison of overall charge distribution maps suggests that addition of a BF3 group introduces a localized charge which is not compensated for by the charge of phosphonium and cannot be delocalised into the phenyl rings