Abstract:
INTRODUCTION:The tricyclic indole compound, [(18)F]GE-180 has been previously identified as a promising positron emission tomography (PET) imaging agent of the translocator protein (TSPO) with the potential to aid in the diagnosis, prognosis and therapy monitoring of degenerative neuroinflammatory conditions such as multiple sclerosis. [(18)F]GE-180 was first identified and evaluated as a racemate, but subsequent evaluations of the resolved enantiomers have shown that the S-enantiomer has a higher affinity for TSPO and an improved in vivo biodistribution performance, in terms of higher uptake in specific brain regions and good clearance (as described previously). Here we describe the additional biological evaluations carried out to confirm the improved performance of the S-enantiomer and including experiments which have demonstrated the stability of the chiral centre to chemical and biological factors. MATERIALS AND METHODS:GE-180 and the corresponding radiolabelling precursor were separated into single enantiomers using semi-preparative chiral supercritical fluid chromatography (SFC). A detailed comparison of the individual enantiomers and the racemate was carried out in a number of biological studies. TSPO binding affinity was assessed using a radioligand binding assay. Incubation with rat hepatic S9 fractions was used to monitor metabolic stability. In vivo biodistribution studies up to 60 min post injection (PI) in naïve rats were carried out to monitor uptake and clearance. Achiral and chiral in vivo metabolite detection methods were developed to assess the presence of metabolite/s in plasma and brain samples, with the chiral method also determining potential racemisation at the chiral centre. RESULTS:Evaluation of the chiral stability of the two enantiomers to metabolism by rat S9 fractions, showed no racemisation of enantiomers. There were notable differences in the biodistribution between the racemate and the R- and S-enantiomers. All compounds had similar initial brain uptake between 0.99 and 1.01% injected dose (id) at 2 min PI, with S-[(18)F]GE-180 showing significantly greater retention than the R-enantiomer at 10 and 30 min PI (P<0.05). S-[(18)F]GE-180 uptake to the TSPO-expressing olfactory bulbs was 0.45% id (SD ± 0.17) at 30 min PI in comparison to RS-[(18)F]GE-180 or R-[(18)F]GE-180 levels of 0.41% id ± 0.09 and 0.23% id ± 0.02 respectively, at the same timepoint (P > 0.05). The signal-to-noise ratio (ratio olfactory bulb to striata binding) were similar for both RS-[(18)F]GE-180 and S-[(18)F]GE-180 (3.2 and 3.4 respectively). Initial uptake to the lungs (an organ with high TSPO expression) was more than 3-fold greater with S-[(18)F]GE-180 than R-[(18)F]GE-180, and significantly higher at 10 and 30 min PI (P < 0.05). Furthermore lung uptake of S-[(18)F]GE-180 at 2 and 10 min PI was also significant when compared to the racemate (P < 0.05). The majority of the radioactivity in the rat brain following administration of RS-[(18)F]GE-180 or S-[(18)F]GE-180 was due to the presence of the parent compound (91% ± 1.5 and 94% ± 2.0 of total radioactivity at 60 min PI respectively). In contrast at 60 min PI for the plasma samples, the parent compounds accounted for only 28% ± 1.2 and 21% ± 4.6 of total radioactivity for RS-[(18)F]GE-180 and S-[(18)F]GE-180 respectively. Chiral assessment confirmed that the S-enantiomer was chirally stable in vivo, with no stereochemical conversion in brain and plasma samples up to 60 min PI. CONCLUSIONS:Developing racemic radiotracers, as for racemic therapeutics, is a considerable challenge due to differences of the enantiomers in pharmacokinetics, efficacy and potential toxicity. We have shown that the enantiomers of the promising racemic PET ligand [(18)F]GE-180 do not share identical performance, with S-[(18)F]GE-180 demonstrating higher TSPO affinity, higher brain uptake and better retention to the high TSPO-expressing lungs. Furthermore, S-[(18)F]GE-180 has also been shown to be enantiomerically stable in vivo, with no observed conversation of the eutomer to the distomer. As a single enantiomer, S-[(18)F]GE-180 retains the beneficial characteristics of the racemate and is a promising imaging agent for imaging neuroinflammation in vivo.
journal_name
Nucl Med Bioljournal_title
Nuclear medicine and biologyauthors
Chau WF,Black AM,Clarke A,Durrant C,Gausemel I,Khan I,Mantzilas D,Oulie I,Rogstad A,Trigg W,Jones PAdoi
10.1016/j.nucmedbio.2015.05.004subject
Has Abstractpub_date
2015-09-01 00:00:00pages
711-9issue
9eissn
0969-8051issn
1872-9614pii
S0969-8051(15)00090-6journal_volume
42pub_type
杂志文章abstract:INTRODUCTION:We synthesized and evaluated (64)Cu-labeled tetraiodothyroacetic acid (tetrac)-conjugated liposomes for PET imaging of tumor angiogenesis, because tetrac inhibits angiogenesis via integrin αVβ3. METHODS:Tetrac-PEG-DSPE and DOTA-PEG-DSPE were synthesized and formulated with other lipids into liposomes. The...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2013.08.003
更新日期:2013-11-01 00:00:00
abstract::The niobium-90 radioisotope ((90)Nb) holds considerable promise for use in immuno-PET, due to its decay parameters (t½ = 14.6h, positron yield=53%, Eß(+)(mean) = 0.35 MeV and Eß(+)(max) = 1.5 MeV). In particular, (90)Nb appears well suited to detect in vivo the pharmacokinetics of large targeting vectors (50-150 kDa)....
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2014.06.006
更新日期:2014-10-01 00:00:00
abstract:INTRODUCTION:Nuclear and optical imaging are complementary in many aspects and there would be many advantages when optical imaging probes are prepared using radionuclides rather than classic fluorophores, and when nuclear and optical dual images are obtained using single imaging probe. METHODS:The luminescence intensi...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2010.09.003
更新日期:2011-04-01 00:00:00
abstract::We have synthesized three different PET ligands to investigate the physiological function of metabotropic glutamate subtype 5 receptors (mGluR5) in vivo: 2-[(11)C]methyl-6-(2-phenylethynyl)pyridine ([(11)C]MPEP), 2-(2-(3-[(11)C]methoxyphenyl)ethynyl)pyridine ([(11)C]M-MPEP) and 2-(2-(5-[(11)C]methoxypyridin-3-yl)ethyn...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2005.05.004
更新日期:2005-08-01 00:00:00
abstract::We present a method for estimating 99mTc-MAG3 clearance from both a single injection and two blood samples that is valid for both adults and children. It was obtained by fitting a scaled two-compartment model (having only two adjustable parameters) to adult and pediatric data from multiple centers. ...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/0969-8051(94)00076-v
更新日期:1995-01-01 00:00:00
abstract:INTRODUCTION:The commercially available 68Ge/68Ga generators are generally used in clinical context in conjunction with automated or semi-automated modules for the syntheses of 68Ga radiopharmaceuticals. It is desirable to develop strategies for the formulation of 68Ga-radiopharmaceuticals without use of such expensive...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2016.11.006
更新日期:2017-03-01 00:00:00
abstract:INTRODUCTION:As the use of metallic radionuclides increases, so does the demand for a simple production method. In this study, we demonstrated an in situ target processing concept for automated metallic radionuclide production without the use of any robotic device. METHODS:An alumina ceramic vessel for a vertical irra...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2012.05.010
更新日期:2012-11-01 00:00:00
abstract:INTRODUCTION:Several psychiatric and neurodegenerative diseases are associated with malfunction of brain norepinephrine transporter (NET). However, current clinical evaluations of NET function are limited by the lack of sufficiently sensitive methods of detection. To this end, we have synthesized exo-3-[(6-[18F]fluoro-...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2017.10.005
更新日期:2018-01-01 00:00:00
abstract:INTRODUCTION:After its intravenous injection, [18F]fluorocholine is oxidized by choline-oxidase into its main plasma metabolite, [18F]fluorobetaine. If PET kinetic modeling quantification of [18F]fluorocholine uptake is intended, the plasma input time-activity-curve of the parent tracer must be obtained, i.e., the frac...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2019.08.003
更新日期:2019-01-01 00:00:00
abstract:UNLABELLED:Several radiopharmaceuticals and imaging techniques are proposed for breast cancer imaging. Since limited data are available of the uptake of SPECT and PET radiopharmaceuticals in malignant breast tumors and their metastases the aim of this study was to compare the uptake values and to correlate these data w...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(02)00342-6
更新日期:2002-11-01 00:00:00
abstract:INTRODUCTION:[(18)F]Nifene is a novel radiotracer specific to the nicotinic acetylcholine α4β2 receptor class. In preparation for using this tracer in humans we have performed whole-body PET studies in mice to evaluate the in vivo biodistribution and dosimetry of [(18)F]Nifene. METHODS:Seven BALB/c mice (3 males, 4 fe...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2012.11.004
更新日期:2013-02-01 00:00:00
abstract:INTRODUCTION:Fatty acid amide hydrolase (FAAH) is the enzyme responsible for metabolising the endogenous cannabinoid, anandamide, and thus represents an important target for molecular imaging. To date, no radiotracer has been shown to be useful for imaging of FAAH using either positron emission tomography (PET) or sing...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2010.08.001
更新日期:2011-02-01 00:00:00
abstract:INTRODUCTION:Our objective was to evaluate the effect of epidermal growth factor receptor(s) (EGFR) density on the importation and nuclear localization of 111In-labeled diethylenetriaminepentaacetic acid human epidermal growth factor ([111In]DTPA-hEGF) in breast cancer (BC) cells in vitro and in tumor xenografts and no...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2007.06.010
更新日期:2007-11-01 00:00:00
abstract:UNLABELLED:The radiolabelled bombesin analogue AMBA shows high potential for diagnosis and treatment of prostate and breast cancer, but the influence of different chelators, which differ in terms of radiochemical reactivity and stability, have not been explored so far. In order to find the best suitable chelator for la...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2013.08.010
更新日期:2014-01-01 00:00:00
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journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2007.10.007
更新日期:2008-02-01 00:00:00
abstract::Positron-emission tomography (PET) provides potential in neuropsychiatric drug development by expanding knowledge of drug action in the living human brain and reducing time consumption and costs. The 5-hydroxytryptamine(1A) (5-HT(1A)) receptor is of central interest as a target for the treatment of anxiety, depression...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(00)00121-9
更新日期:2000-07-01 00:00:00
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journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2006.06.006
更新日期:2006-08-01 00:00:00
abstract::Rhenium-186 (Re-186) hydroxyethylidene diphosphonate (HEDP) has been shown to localize in metastatic foci within bone in a manner similar to Tc-99m bone-seeking agents. Usually, in the preparation of diagnostic Tc-99m radiopharmaceuticals, the concentration of Tc is at trace level (10(-8) M). However, large amounts of...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(99)00007-4
更新日期:1999-05-01 00:00:00
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journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/0969-8051(95)02011-x
更新日期:1996-01-01 00:00:00
abstract::The imaging of apoptosis represents an attractive diagnostic goal in the area of tumor therapy, degenerative diseases and organ transplantation. Since caspases play a key role during the early period of the intracellular signal cascade of cells undergoing apoptosis we considered benzyloxycarbonyl-Val-Ala-DL-Asp(O-meth...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(01)00247-5
更新日期:2001-10-01 00:00:00
abstract:UNLABELLED:In recent years, several PET and SPECT studies have shown loss of striatal dopamine transporter (DAT) binding in amphetamine (AMPH) users. However, the use of DAT SPECT tracers to detect AMPH-induced changes in DAT binding has not been validated. We therefore examined if repeated administration of D-AMPH or ...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2005.12.007
更新日期:2006-04-01 00:00:00
abstract::Positron emission tomography (PET), which requires a compound labeled with a positron emitter radioisotope as an imaging probe, is one of the most useful and valuable imaging modalities in molecular imaging. It has several advantages over other imaging modalities, particularly in sensitive and quantitative investigati...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2011.07.005
更新日期:2012-01-01 00:00:00
abstract:INTRODUCTION:We measured the tiagabine-induced enhancement of the GABAA receptor's affinity for benzodiazepine ligands ("GABA shift") using [18F]flumazenil (FMZ) PET with preclinical application of bolus plus constant infusion (B/I). Differences in quantified results of [18F]FMZ binding were compared to that of [18F]FM...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2016.11.003
更新日期:2017-02-01 00:00:00
abstract::We evaluated 99mTc-labeled mercaptoacetyltriglycine (99mTc-MAG3)-biocytin as a hepatobiliary imaging agent in the absence and presence of bilirubin in mice. We then compared its pharmacokinetic parameters; peak liver/heart activity ratio (rmax) and half clearance time (HCT) with those of 99mTc-labeled diisopropyl-imin...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(98)00077-8
更新日期:1999-01-01 00:00:00
abstract:UNLABELLED:(18)F-9-fluoropropyl-(+)-dihydrotetrabenazine ((18)F-AV-133) is a novel positron emission tomography tracer for imaging the vesicular monoamine transporter II in dopaminergic neuron degeneration, which might be indicative for Parkinson's disease (PD) and other parkinsonism. Studies were performed to optimize...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2011.05.010
更新日期:2011-11-01 00:00:00
abstract::Dual probe microdialysis was employed in intact rat brain to investigate the effect of intrastriatal perfusion with selective dopamine D1 and D2 receptor agonists and with c-fos antisense oligonucleotide on (a) local GABA release in the striatum; (b) the internal segment of the globus pallidus and the substantia nigra...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(98)00066-3
更新日期:1998-11-01 00:00:00
abstract::The application of radionuclide-labeled biomolecules such as monoclonal antibodies or antibody fragments for imaging purposes is called immunoscintigraphy. More specifically, when the nuclides used are positron emitters, such as zirconium-89, the technique is referred to as immuno-PET. Currently, there is an urgent ne...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2016.02.003
更新日期:2016-05-01 00:00:00
abstract:OBJECTIVE:The goal of this study was to measure functional and structural aspects of local neuroinflammation induced by intracerebral injection of lipopolysaccharide (LPS) in rats using TSPO microPET imaging with [(18)F]DPA-714, magnetic resonance imaging (MRI), in vitro autoradiography and immunohistochemistry (IHC) i...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/j.nucmedbio.2015.06.010
更新日期:2015-10-01 00:00:00
abstract::A simple, rapid, and reproducible micromethod for quantification of sulfhydryl (SH) groups generated after reduction of monoclonal antibody (MAb) disulfide bonds with 2-mercaptoethanol (2-ME) is described. The number of SH groups per molecule of antibody in the 2-ME and in the other reducing agents was calculated from...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/0969-8051(96)00028-5
更新日期:1996-07-01 00:00:00
abstract::We describe the synthesis of 2'-[(18)F]fluoroflumazenil (FFMZ), which differs from the typically used [(18)F]fluoroethylflumazenil (FEFMZ) for benzodiazepine receptor imaging. For one-pot one-step labeling, the precursors, 2'-tosyloxyflumazenil (TFMZ) and 2'-mesyloxyflumazenil (MFMZ), were synthesized in three steps. ...
journal_title:Nuclear medicine and biology
pub_type: 杂志文章
doi:10.1016/s0969-8051(03)00030-1
更新日期:2003-07-01 00:00:00