[Show abstract][Hide abstract] ABSTRACT: Positron emission tomography (PET) can be used to monitor in vivo translocator protein (TSPO) expression by using specific radioligands. Recently, several [11C]PK11195 analogues have been synthesized to improve binding stability and brain availability. [18F]VC701 was synthesized and validated in CD healthy rats by biodistribution and inhibition analysis. Imaging studies were also conducted on animals injected unilaterally in the striatum with quinolinic acid (QA) to evaluate the TSPO ligand uptake in a neuroinflammation/neurodegenerative model. [18F]VC701 was synthesized with a good chemical and radiochemical purity and specific activity higher than 37 GBq/μmol. Kinetic studies performed on healthy animals showed the highest tracer biodistribution in TSPO-rich organs, and preadministration of cold PK11195 caused an overall radioactivity reduction. Metabolism studies showed the absence of radiometabolites in the rat brain of QA lesioned rats, and biodistribution analysis revealed a progressive increase in radioactivity ratios (lesioned to nonlesioned striatum) during time, reaching an approximate value of 5 4 hours after tracer injection. These results encourage further evaluation of this TSPO radioligand in other models of central and peripheral diseases.
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
Hypoxic regions are present in different types of cancer and are a negative prognostic factor for disease progression and response to therapy. (18)F-fluoroazomycin-arabinofuranoside ((18)F-FAZA) and (64)Cu-diacetyl-bis(N4-methylthiosemicarbazone) ((64)Cu-ATSM) have been widely used to visualize hypoxic regions in preclinical and clinical studies. Although both these radioligands have high signal-to-noise ratios, (64)Cu-ATSM may be suitable for use in in vivo imaging and as a radiotherapeutic agent. Despite encouraging results suggesting that it may have a role as a prognostic tracer, (64)Cu-ATSM was recently shown to display cell line-dependent kinetics of oxygen-dependent uptake. We set out to evaluate the kinetics of (64)Cu-ATSM distribution in different cancer models, using (18)F-FAZA as the gold standard.
(18)F-FAZA and (64)Cu-ATSM uptake were compared ex vivo using dual-tracer autoradiography and in vivo using PET in different xenograft mouse models (FaDu, EMT-6, and PC-3). (18)F-FAZA uptake was compared with (64)Cu-ATSM uptake in PET studies acquired at early (2 h after injection) and delayed time points (24 h after injection). To evaluate the presence of hypoxia and copper pumps, the tumors from animals submitted to PET were harvested and analyzed by an immunohistochemical technique, using antibodies against carbonic anhydrase IX (CAIX) and copper pumps (Ctr1 and ATP7B).
(64)Cu-ATSM showed a higher tumor-to-muscle ratio than did (18)F-FAZA. In the FaDu mouse model, radioactivity distribution profiles were overlapping irrespective of the hypoxic agent injected or the time of (64)Cu acquisition. Conversely, in the EMT-6 and PC-3 models there was little similarity between the early and delayed (64)Cu-ATSM images, and both the radiotracers showed a heterogeneous distribution. The microscopic analysis revealed that (18)F-FAZA-positive areas were also positive for CAIX immunostaining whereas immunolocalization for copper pumps in the 3 models was not related to radioactivity distribution.
The results of this study confirm the cell-dependent distribution and retention kinetics of (64)Cu-ATSM and underline the need for proper validation of animal models and PET acquisition protocols before exploration of any new clinical applications.
Journal of Nuclear Medicine 05/2013; 54(7). DOI:10.2967/jnumed.112.111120 · 6.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The quinoline nucleus of the previously described 4-phenylquinoline-3-carboxamides NK(1) receptor ligands 7 has been transformed into either substituted or azole-(i.e., triazole or tetrazole) fused pyridine moieties of compounds 9 and 10, respectively, in order to obtain NK(1) receptor ligands showing lower molecular weight or higher hydrophilicity. The program of molecular manipulations produced NK(1) receptor ligands showing affinity in the nanomolar range. In particular, 4-methyl-1-piperazinyl derivative 9j showed an IC(50) value of 4.8 nM and was proved to behave as a NK(1) antagonist blocking Sar(9)-SP-sulfone induced proliferation and migration of microvascular endothelial cells. Therefore, compound 9j has been labeled with [(11)C]CH(3)I (t(1/2)=20.4 min, β(+)=99.8%) starting from the corresponding des-methyl precursor 9i using with a radiochemical yield of about 10% (not decay corrected) and a specific radioactivity>1 Ci/μmol in order to be used as a radiotracer in next PET studies.
[Show abstract][Hide abstract] ABSTRACT: (60)Cu and (64)Cu are useful radioisotopes for positron emission tomography (PET) radiopharmaceuticals and may be used for the preparation of promising agents for diagnosis and radiotherapy. In this study, the production and purification of (60/64)Cu starting from (60/64)Ni using a new automated system, namely Alceo, is described. A dynamic process for electrodeposition and dissolution of (60/64)Ni/(60/64)Cu was developed. Preliminary production yields of (60)Cu and (64)Cu were 400 and 300mCi, respectively. (64)Cu was used to radiolabel the hypoxia detection tracer ATSM with a specific activity of 2.2+/-1.3Ci/micromol.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 09/2009; 68(1):5-13. DOI:10.1016/j.apradiso.2009.08.010 · 1.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Standards and des-methyl precursors of (R)- and (S)-thionisoxetine, potent and selective norepinephrine reuptake inhibitors, were synthesized and radiolabeled with carbon-11. Both enantiomers of the N-methyl-3-(2-thiomethylphenoxy)-3-phenylpropanamine and the 3-(2-thiomethylphenoxy)-3-phenylpropylamine were obtained via multi-step syntheses, while the radiosyntheses were carried out using [11C]CH3I. The radiochemical yields were 26%, decay corrected and the specific radioactivity ranging from 2 to 3 Ci/micromol. The HPLC analyses were performed using a chiral column: during the radiolabeling, no racemization occurred and the isomers were synthesized with high enantiomeric purity.