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ABSTRACT: PURPOSE: Amyloid positron emission tomography (PET) is an important noninvasive method for detecting amyloid burden in Alzheimer's disease (AD) patients. As amyloid PET images have limited anatomical information, magnetic resonance (MR) imaging is usually acquired to perform reliable spatial normalization needed for large-scale analysis. This work proposed and evaluated the performance of new MR-free spatial normalization methods using a perfusion-like template for amyloid PET imaging. METHODS: Amyloid PET and MR images were collected in 35 subjects (cohort 1: 8 AD patients and 6 controls; cohort 2: 15 AD patients and 6 controls). Three ligand-related templates (AD, control, mixed group) and a perfusion-like template (pAV-45) from early time frames of amyloid PET images were constructed from cohort 1. The variations of (18)F-AV-45 standardized uptake value ratios (SUVRs) among AD patients, controls, and all subjects were tested with repeated two-way (template × brain region) analysis of variance (ANOVA) in cohort 2. (18)F-AV-45 SUVRs by region of interest analysis and voxelwise analysis between MR-based and MR-free approaches were compared and correlated to clinical and image parameters. Effect size (group mean SUVR difference between AD and control/standard deviation) was also evaluated for each template method. RESULTS: Significantly different (18)F-AV-45 SUVRs between MR-free spatial normalization and MR-based reference images were found among AD patients, controls, and all subjects by the effect of template and brain regions. The highest correlation (r=0.991) of (18)F-AV-45 SUVR to MR-based reference was found in the pAV-45 group. The SUVR percentage difference to MR-based reference showed the least variation and bias (control: -1.31±3.47 %; AD: -0.36±2.50 %) in the pAV-45 group as well. The voxelwise analysis showed the smallest t statistic value in pAV-45 followed by mixed, control, and AD groups when compared to MR-based reference images. Moreover, an overall larger effect size but compatible to that of MR-based reference result was observed in the pAV-45 group as compared to those of the other MR-free template. CONCLUSION: The novel MR-free template based on the early-phase perfusion images pAV-45 approach for amyloid imaging showed significantly better performance in quantitation accuracy, effect size, and stability when compared with other MR-free PET templates and thus has potential for large-scale clinical applications.
European Journal of Nuclear Medicine 02/2013; · 4.53 Impact Factor
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Kuo-Lun Huang,
Kun-Ju Lin,
Ing-Tsung Hsiao,
Hung-Chou Kuo,
Wen-Chuin Hsu,
Wen-Li Chuang, Mei-Ping Kung,
Shiaw-Pyng Wey,
Chia-Ju Hsieh,
Yau-Yau Wai,
Tzu-Chen Yen,
Chin-Chang Huang
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ABSTRACT: To compare the neocortical amyloid loads among cognitively normal (CN), amnestic mild cognitive impairment (aMCI), and Alzheimer's disease (AD) subjects with [(18)F]AV-45 positron emission tomography (PET).
[(18)F]AV-45 PET was performed in 11 CN, 13 aMCI, and 12 AD subjects to compare the cerebral cortex-to-whole cerebellum standard uptake value ratios (SUVRs) of global and individual volumes of interest (VOIs) cerebral cortex. The correlation between global cortical [(18)F]AV-45 SUVRs and Mini-Mental State Examination (MMSE) scores was analyzed.
The global cortical [(18)F]AV-45 SUVRs were significantly different among the CN (1.08±0.08), aMCI (1.27±0.06), and AD groups (1.34±0.13) (p = 0.0003) with amyloidosis positivity rates of 9%, 62%, and 92% in the three groups respectively. Compared to CN subjects, AD subjects had higher SUVRs in the global cortical, precuneus, frontal, parietal, occipital, temporal, and posterior cingulate areas; while aMCI subjects had higher values in the global cortical, precuneus, frontal, occipital and posterior cingulate areas. There were negative correlations of MMSE scores with SUVRs in the global cortical, precuneus, frontal, parietal, occipital, temporal, posterior cingulate and anterior cingulate areas on a combined subject pool of the three groups after age and education attainment adjustment.
Amyloid deposition occurs relatively early in precuneus, frontal and posterior cingulate in aMCI subjects. Higher [(18)F]AV-45 accumulation is present in parietal, occipital and temporal gyri in AD subjects compared to the aMCI group. Significant correlation between MMSE scores and [(18)F]AV-45 SUVRs can be observed among CN, aMCI and AD subjects.
PLoS ONE 01/2013; 8(3):e58974. · 4.09 Impact Factor
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European Journal of Nuclear Medicine 05/2012; 39(9):1513. · 4.53 Impact Factor
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ABSTRACT: [¹⁸F]AV-133 is a novel PET tracer for targeting the vesicular monoamine transporter 2 (VMAT2). The aim of this study is to characterize and quantify the loss of monoamine neurons with [¹⁸F]AV-133 in the MPTP-lesioned PD mouse model using animal PET imaging and ex vivo quantitative autoradiography (QARG).
Optimal imaging time window of [¹⁸F]AV-133 was first determined in normal C57BL/6 mice (n = 3) with a 90-min dynamic scan. The reproducibility of [¹⁸F]AV-133 PET imaging was evaluated by performing a test-retest study within 1 week for the normal group (n = 6). For MPTP-lesioned studies, normal, and MPTP-treated [25 mg mg/kg once (Group A) and twice (Group B), respectively, daily for 5 days, i.p., groups of four normal and MPTP-treated] mice were used. PET imaging studies at baseline and at Day 4 post-MPTP injections were performed at the optimal time window after injection of 11.1 MBq [¹⁸F]AV-133. Specific uptake ratio (SUr) of [¹⁸F]AV-133 was calculated by [(target uptake-cerebellar uptake)/cerebellar uptake] with cerebellum as the reference region. Ex vitro QARG and immunohistochemistry (IHC) studies with tyrosine hydroxylase antibody were carried out to confirm the abundance of dopaminergic neurons.
The variability between [¹⁸F]AV-133 test-retest striatal SUr was 6.60 ± 3.61% with less than 5% standard deviation between animals (intervariability). The percentages of MPTP lesions were Group A 0.94 ± 0.29, -42.1% and Group B 0.65 ± 0.09, -60.4%. By QARG, specific binding of [¹⁸F]AV-133 was reduced relative to the control groups by 50.6% and 60.7% in striatum and by 30.6% and 46.4% in substantia nigra (Groups A and B, respectively). Relatively small [¹⁸F]AV-133 SUr decline was noted in the serotonin and norepinephrine-enriched regions (7.9% and 9.4% in mid-brain). Results obtained from IHC consistently confirmed the sensitivity and selectivity of dopaminergic neuron loss after MPTP treatment.
[¹⁸F]AV-133 PET SUr displayed a high test-retest stability. The SUr significantly declined in the caudate putamen but not in the hypothalamus and midbrain regions after MPTP treatment in the mouse brain. The results obtained for QARG and IHC were consistent and correlated well with the PET imaging studies. On the basis of these concordant results, we find that [¹⁸F]AV-133 should serve as a useful and reliable PET tracer for evaluating nigrostriatal degeneration.
Synapse 05/2012; 66(9):823-31. · 2.94 Impact Factor
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ABSTRACT: The formation and deposition of β-amyloid (Aβ) plaques are the earliest pathological changes in Alzheimer's disease (AD). Molecular imaging of Aβ plaques could serve as a surrogate marker in early diagnosis and neuropathogenesis studies of AD. Several radionuclide labeled ligands have recently been developed for noninvasive visualization of Aβ plaques in the brains of AD patients using single photon emission computed tomography or positron emission tomography (PET). There has been rapid progress in the field of imaging for plaque pathology. AV-45 was the first plaque imaging agent to enter multi-center, investigational new drug clinical trials in the US, and has now been studied in dozens of trials with more than 1,000 subjects ranging from cognitively normal individuals to those with AD dementia. "Imaging to autopsy" phase III studies further confirmed and validated the specific imaging signal correlated to the plaque burden in living subjects. With these promising and confirmed characteristics of AV-45, the Alzheimer's Disease Neuroimaging Initiative (ADNI) under common consensus decided on AV-45 as the emerging standard PET imaging agent for evaluating the progression of plaque pathology in patients with AD or mild cognition impairment, and even healthy controls. With the wide availability of AV-45 for plaque imaging, the ultimate goal of the ADNI is global clinical trials for disease detection and progression. This review presents recent experience with Aβ-targeting radiotracers at Chang Gung University and Chang Gung Memorial Hospital.
Chang Gung medical journal 05/2012; 35(3):211-8.
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ABSTRACT: (18)F-Florbetapir (AV-45/Amyvid) is a novel positron emission tomography (PET) tracer for imaging plaque pathology in Alzheimer's disease (AD), while PET images of fluorodeoxyglucose (FDG) for cerebral glucose metabolism can provide complementary information to amyloid plaque images for diagnosis of AD. The goal of this preliminary study was to investigate the perfusion-like property of relative cerebral blood flow estimates (R(1)) and summed early-phase AV-45 images [perfusion AV-45 (pAV-45)] and optimize the early time frame for pAV-45.
Dynamic AV-45 PET scans (0-180 min) were performed in seven subjects. pAV-45, late-phase AV-45, and FDG images were spatially normalized to the Montreal Neurological Institute template aided by individual MRI images, and the corresponding standardized uptake value ratio (SUVR) was computed. The R(1) images were derived from a simplified reference tissue model. Correlations between regional and voxelwise R(1) and the corresponding FDG images were calculated. An optimization of time frames of pAV-45 was conducted in terms of correlation to FDG images. The optimal early time frame was validated in a separate cohort.
The regional distribution in the R(1) images correlated well (R = 0.91) to that of the FDG within subjects. Consistently high correlation was noted across a long range of time frames. The maximal correlation of pAV-45 to FDG SUVR of R = 0.95 was observed at the time frame of 1-6 min, while the peak correlation of R = 0.99 happened at 0-2 min between pAV-45 and R(1). A similar result was achieved in the validation cohort.
Preliminary results showed that the distribution patterns of R(1) and pAV-45 images are highly correlated with normalized FDG images, and the initial 5-min early time frame of 1-6 min is potentially useful in providing complementary FDG-like information to the amyloid plaque density by late-phase AV-45 images.
European Journal of Nuclear Medicine 01/2012; 39(4):613-20. · 4.53 Impact Factor
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ABSTRACT: The vesicular monoamine transporter type II (VMAT2) is highly expressed in pancreatic β-cells and thus has been proposed to be a potential target for measuring β-cell mass (BCM) by molecular imaging. Several tracers based on the TBZ backbone, including 9-fluoropropyl-(+)-dihydrotetrabenazine ([(18)F]AV-133), have shown some promising results as potential biomarkers for BCM despite a relatively high background signal in the pancreas. In the present study, we explore the background binding characteristics of [(18)F]AV-133 in rat pancreas.
Pancreatic exocrine cells and islet cells were isolated and purified from Sprague-Dawley rats. Membrane homogenates, prepared from both pancreatic exocrine and islet cells as well as from brain striatum regions, were used for in vitro binding studies of [(18)F]AV-133 under a selective masking condition. 1,3-Di-o-tolylguanidine (DTG), displaying high and roughly equal affinity for both sigma-1 and sigma-2 receptors, was chosen at 5 μM concentration for the masking/blocking studies.
[(18)F]AV-133 binding to rat striatum homogenates was not significantly altered by the presence of DTG. In contrast, [(18)F]AV-133 showed significant competition with DTG for binding sites in rat pancreatic exocrine homogenates as well as in rat islet cell homogenates. Importantly, in the presence of DTG, [(18)F]AV-133 showed a single high-affinity binding site on islet cell homogenates with a K(d) value of 3.8 nM which is consistent with the affinity reported previously for VMAT2 sites in rat pancreas.
[(18)F]AV-133, in addition to a high-affinity VMAT2 binding site, binds with low affinity (but high capacity) to sigma components that are present in the rat pancreas. Identification of the cause of background binding of [(18)F]AV-133 to rat pancreatic tissue may lead to improved methods for quantification.
Nuclear Medicine and Biology 10/2011; 38(7):1029-34. · 3.02 Impact Factor
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Kun-Ju Lin,
Wey-Yil Lin,
Chia-Ju Hsieh,
Yi-Hsin Weng,
Shiaw-Pyng Wey,
Chin-Song Lu,
Daniel Skovronsky,
Tzu-Chen Yen,
Chee-Jen Chang, Mei-Ping Kung,
Ing-Tsung Hsiao
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ABSTRACT: (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 the imaging time window for calculating standardized uptake value ratio (SUVR) with correlation to distribution volume ratio (DVR) and in differentiating PD from normal controls (NCs).
Thirteen (18)F-AV-133 positron emission tomography studies were conducted on four NCs (age, 62.3±4.9 years) and nine PD patients (age, 60.8±6.0 years) with Hoehn and Yahr stages 2 to 3. Dynamic images were acquired within 180 min (0-30, 50-140 and 160-180 min) and were rearranged into 14 of 10-min scans. The contralateral striatum was defined as the opposite striatum to the predominantly affected limbs. Volumes of interest (VOIs) of bilateral putamen, caudate nuclei and occipital cortex (OC; as the reference region) were delineated from individual magnetic resonance imaging. SUVRs of striatum to OC were computed from 14 dynamic image sets. The DVRs were computed from Logan graphic analysis by using OC as the input. The performance of SUVR was evaluated based on the correlation of SUVR at each time window to DVR, as well as the Cohen effect size (group mean SUVR difference between PD and NC/standard deviation).
(18)F-AV-133 uptake decreased in PD subjects at bilateral striatum especially at contralateral side with posterior putamen predominant as compared with NC. Consistent higher correlations of SUVRs to DVR for all VOIs were observed at later time window and reached to its maximal value of 0.9917 at 90-100 min. The group mean SUVR differences between NC and PD subjects increased and reached relatively stable values after 90 min. The effect sizes for all VOIs were stable across different time window and with the largest value around 90~120 min.
The scanning time of 90-100 min for (18)F-AV-133 is considered as the optimal time window for summed uptake measurements in terms of SUVRs' correlation to DVRs, differential power, stability and clinical feasibility across and between NC and PD patients.
Nuclear Medicine and Biology 08/2011; 38(8):1149-55. · 3.02 Impact Factor
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ABSTRACT: We report herein the Good Manufacturing Practice (GMP)-compliant automated synthesis of (18)F-labeled styrylpyridine, AV-45 (Florbetapir), a novel tracer for positron emission tomography (PET) imaging of beta-amyloid (Abeta) plaques in the brain of Alzheimer's disease patients. [(18)F]AV-45 was prepared in 105 min using a tosylate precursor with Sumitomo modules for radiosynthesis under GMP-compliant conditions. The overall yield was 25.4+/-7.7% with a final radiochemical purity of 95.3+/-2.2% (n=19). The specific activity of [(18)F]AV-45 reached as high as 470+/-135 TBq/mmol (n=19). The present studies show that [(18)F]AV-45 can be manufactured under GMP-compliant conditions and could be widely available for routine clinical use.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 12/2010; 68(12):2293-7. · 1.09 Impact Factor
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ABSTRACT: Sigma-2 receptors represent an endogenous marker for proliferation in solid tumors. The high affinity, high selectivity sigma(2) receptor ligand N-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-2-(2-fluoroethoxy)-5-iodo-3-methoxybenzamide (3) was separately radiolabeled with F-18 and I-125. The radiolabeling yield was 30% and 70% for [(18)F]3 and [(125)I]3, respectively. Studies of [(125)I]3 using murine 66 breast tumor membrane homogenates and evaluation of [(18)F]3 and [(125)I]3 in 66 tumor-bearing mice indicate that this ligand has potential as a PET or a SPECT probe for imaging sigma(2) receptors in breast cancer.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 12/2010; 68(12):2268-73. · 1.09 Impact Factor
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ABSTRACT: Vesicular monoamine transporter 2 (VMAT2) is highly expressed in the endocrine cells and brain. We investigated the biodistribution and radiation dosimetry of (2R,3R,11bR)-9-(3-(18)F-fluoropropoxy)-3-isobutyl-10-methoxy-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinolin-2-ol ((18)F-FP-(+)-dihydrotetrabenazine [DTBZ] or (18)F-AV-133), a potential VMAT2 imaging agent showing encouraging results in humans, to facilitate its future clinical use.
Nine healthy human subjects (mean age +/- SD, 58.6 +/- 4.2 y) were enrolled for the whole-body PET scan. Serial images were acquired for 3 h immediately after a bolus injection of 390.7 +/- 22.9 MBq of (18)F-AV-133 per individual. The source organs were delineated on PET/CT images. The OLINDA/EXM application was used to determine the equivalent dose for individual organs.
The radiotracer did not show any noticeable adverse effects for the 9 subjects examined. The radioactivity uptake in the brain was the highest at 7.5% +/- 0.6% injected dose at 10 min after injection. High absorbed doses were found in the pancreas, liver, and upper large intestine wall. The highest-dosed organ, which received 153.3 +/- 23.8 microGy/MBq, was the pancreas. The effective dose equivalent and effective dose for (18)F-AV-133 were 36.5 +/- 2.8 and 27.8 +/- 2.5 microSv/MBq, respectively. These values are comparable to those reported for any other (18)F-labeled radiopharmaceutical.
(18)F-AV-133 is safe, with appropriate biodistribution and radiation dosimetry for imaging VMAT2 sites in humans.
Journal of Nuclear Medicine 09/2010; 51(9):1480-5. · 6.38 Impact Factor
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ABSTRACT: The vesicular monoamine transporter type 2 (VMAT2) is highly expressed in pancreatic beta-cells and thus has been proposed to be a potential target for measuring beta-cell mass (BCM) by molecular imaging. C-11- and F-18-labeled tetrabenazine derivatives targeting VMAT2 have shown some promising results as potential biomarkers for BCM. In the present study, we examined the binding characteristics of 9-fluoropropyl-(+)-dihydrotetrabenzazine ([(18)F]AV-133), a potential PET tracer for BCM imaging, in rat pancreas and rat brain.
Pancreatic exocrine cells and pancreatic islet cells were isolated and purified from Sprague-Dawley rats. Membrane homogenates, prepared from both pancreatic exocrine and islet cells as well as from brain striatum and hypothalamus regions, were used for in vitro binding studies. In vitro and ex vivo autoradiography studies with [(18)F]AV-133 were performed on rat brain and rat pancreas sections. Immunohistochemistry studies were performed to confirm the distribution of VMAT2 on islet beta-cells.
Excellent binding affinities of [(18)F]AV-133 were observed in rat striatum and hypothalamus homogenates with K(d) values of 0.19 and 0.25 nM, respectively. In contrast to single-site binding observed in rat striatum homogenates, rat islet cell homogenates showed two saturable binding sites (site A: K(d)=6.76 nM, B(max)=60 fmol/mg protein; site B: K(d)=241 nM, B(max)=1500 fmol/mg protein). Rat exocrine pancreas homogenates showed only a single low-affinity binding site (K(d)=209 nM), which was similar to site B in islet cells. In vitro autoradiography of [(18)F]AV-133 using frozen sections of rat pancreas showed specific labeling of islets, as evidenced by co-localization with anti-insulin antibody. Ex vivo VMAT2 pancreatic autoradiography in the rat, however, was not successful, in contrast to the excellent ex vivo autoradiography of VMAT2 binding sites in the brain. In vivo/ex vivo islet labeling may be complicated by the presence of the low-affinity/high-capacity site B binding in rat pancreas.
[(18)F]AV-133 is an excellent imaging agent for mapping VMAT2 sites in rat brain and specifically binds rat islet cells in vitro and postmortem. Additional optimization may be required to achieve ex vivo islet beta-cell labeling in rats.
Nuclear Medicine and Biology 05/2010; 37(4):413-9. · 3.02 Impact Factor
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Kun-Ju Lin,
Wen-Chuin Hsu,
Ing-Tsung Hsiao,
Shiaw-Pyng Wey,
Lee-Way Jin,
Daniel Skovronsky,
Yau-Yau Wai,
Hsiu-Ping Chang,
Chuan-Wei Lo,
Cheng Hsiang Yao,
Tzu-Chen Yen, Mei-Ping Kung
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ABSTRACT: The compound (E)-4-(2-(6-(2-(2-(2-(18)F-fluoroethoxy)ethoxy)ethoxy) pyridin-3-yl)vinyl)-N-methylbenzenamine ([(18)F]AV-45) is a novel radiopharmaceutical capable of selectively binding to beta-amyloid (A beta) plaques. This pilot study reports the safety, biodistribution, and radiation dosimetry of [(18)F]AV-45 in human subjects.
In vitro autoradiography and fluorescent staining of postmortem brain tissue from patients with Alzheimer's disease (AD) and cognitively healthy subjects were performed to assess the specificity of the tracer. Biodistribution was assessed in three healthy elderly subjects (mean age: 60.0+/-5.2 years) who underwent 3-h whole-body positron emission tomography (PET)/computed tomographic (CT) scans after a bolus injection of 381.9+/-13.9 MBq of [(18)F]AV-45. Another six subjects (three AD patients and three healthy controls, mean age: 67.7+/-13.6 years) underwent brain PET studies. Source organs were delineated on PET/CT. All subjects underwent magnetic resonance imaging (MRI) for obtaining structural information.
In vitro autoradiography revealed exquisitely high specific binding of [(18)F]AV-45 to postmortem AD brain sections, but not to the control sections. There were no serious adverse events throughout the study period. The peak uptake of the tracer in the brain was 5.12+/-0.41% of the injected dose. The highest absorbed organ dose was to the gallbladder wall (184.7+/-78.6 microGy/MBq, 4.8 h voiding interval). The effective dose equivalent and effective dose values for [(18)F]AV-45 were 33.8+/-3.4 microSv/MBq and 19.3+/-1.3 microSv/MBq, respectively.
[(18)F]AV-45 binds specifically to A beta in vitro, and is a safe PET tracer for studying A beta distribution in human brain. The dosimetry is suitable for clinical and research application.
Nuclear Medicine and Biology 05/2010; 37(4):497-508. · 3.02 Impact Factor
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ABSTRACT: A facile synthesis of six 4-iodophenyl tagged sphingosine (SP) derivatives bearing alkyl chain lengths from 6 to 13 is described. The key steps for the assembly of these molecules, 5a-f, are Suzuki-Miyaura cross-coupling and cross-metathesis reactions. The feasibility of radiolabeling was demonstrated by synthesizing two (125)I labeled compounds, [(125)I]5c and [(125)I]5e. In vitro enzyme assays indicated that the molecules, 5c-e, are potent inhibitors. Thus, they deserve further evaluation as potential radioactive probes for tumor imaging.
Bioorganic & medicinal chemistry letters 08/2009; 19(13):3382-5. · 2.65 Impact Factor
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ABSTRACT: Recently, the feasibility of detecting amyloid plaques in the living brain by positron emission tomography (PET) imaging has been successfully demonstrated. As such, imaging beta-amyloid (A beta) plaques in the brain may further advance the differential diagnosis of the disease and allow clinicians to measure the effectiveness of therapeutic drugs aimed at lowering plaques in the brain. We report herein the preclinical validation of a potential (18)F-labeled biphenylalkyne, AV-138, as a preliminary step toward developing the imaging agent for patients suspected of having Alzheimer's disease.
In vitro binding was carried out in the homogenates prepared from postmortem AD brains with [(125)I]IMPY as the radioligand. [(18)F]AV-138 was successfully prepared using a tosylate precursor and Sumitomo modules for radiosynthesis. Similarly, specific binding of [(18)F]AV-138 (0.02-0.05 nM) to homogenates, prepared from gray and white matters of pooled AD patients and control subjects, was performed. Specific binding to A beta plaques was measured by autoradiography in AD brain sections (n=11), and the same brain sections were fluorescently stained with thioflavin-S (TF-S). Images of both radiolabeling and fluorescent staining of plaques obtained by a phosphor imager were used for correlation image analysis.
As expected, AV-138 displayed a high binding affinity (K(i)=2.4+/-0.7 nM) in AD gray matter homogenates (due to its high level of A beta plaque accumulation). Specific binding can be clearly measured in the AD gray matter homogenates, but not in the AD white matters. Control brain homogenates, due to a lack of A beta plaques, also showed no specific binding. Furthermore, in vitro autoradiography of postmortem AD brain sections showed that the high binding signal of [(18)F]AV-138 was specifically due to A beta plaques. Fluorescent staining of plaques with TF-S correlated well with the radiolabeling of [(18)F]AV-138 in AD brain sections (r>0.90).
Taken together, these preliminary results strongly suggest that [(18)F]AV-138 is potentially useful for imaging A beta plaques in the living human brain.
Nuclear Medicine and Biology 05/2009; 36(4):411-7. · 3.02 Impact Factor
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Hank F Kung,
Brian P Lieberman,
Zhi-Ping Zhuang,
Shunichi Oya, Mei-Ping Kung,
Seok Rye Choi,
Karl Poessl,
Eric Blankemeyer,
Catherine Hou,
Daniel Skovronsky,
Michael Kilbourn
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ABSTRACT: Development of imaging agents for pancreatic beta cell mass may provide tools for studying insulin-secreting beta cells and their relationship with diabetes mellitus. In this paper, a new imaging agent, [(18)F](+)-2-oxiranyl-3-isobutyl-9-(3-fluoropropoxy)-10-methoxy-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinoline [(18)F](+)4, which displays properties targeting vesicular monoamine transporter 2 (VMAT2) binding sites of beta cells in the pancreas, was evaluated as a positron emission tomography (PET) agent for estimating beta cell mass in vivo. The hydrolyzable epoxide group of (+)4 may provide a mechanism for shifting biodistribution from liver to kidney, thus reducing the background signal.
Both (18)F- and (19)F-labeled (+) and (-) isomers of 4 were synthesized and evaluated. Organ distribution was carried out in normal rats. Uptake of [(18)F](+)4 in pancreas of normal rats was measured and correlated with blocking studies using competing drugs, (+)dihydrotetrabenazine [(+)-DTBZ] or 9-fluoropropyl-(+)dihydro tetrabenazine [FP-(+)-DTBZ, (+)2].
In vitro binding study of VMAT2 using rat brain striatum showed a K(i) value of 0.08 and 0.15 nM for the (+)4 and (+/-)4, respectively. The in vivo biodistribution of [(18)F](+)4 in rats showed the highest uptake in the pancreas (2.68 %ID/g at 60 min postinjection). In vivo competition experiments with cold FP-(+)-DTBZ, (+)2, (3.5 mg/kg, 5 min iv pretreatment) led to a significant reduction of pancreas uptake (85% blockade at 60 min). The inactive isomer [(18)F](-)4 showed significantly lower pancreas uptake (0.22 %ID/g at 30 min postinjection). Animal PET imaging studies of [(18)F](+)4 in normal rats demonstrated an avid pancreatic uptake in rats.
The preliminary results suggest that the epoxide, [(18)F](+)4, is highly selective in binding to VMAT2 and it has an excellent uptake in the pancreas of rats. The liver uptake was significantly reduced through the use of the epoxide group. Therefore, it may be potentially useful for imaging beta cell mass in the pancreas.
Nuclear Medicine and Biology 12/2008; 35(8):825-37. · 3.02 Impact Factor
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ABSTRACT: Two new phenylacetylene derivatives, 5-((4-(2-(2-(2-fluoroethoxy)ethoxy)ethoxy)phenyl)ethynyl)indoline 8 and 5-((4-(2-(2-(2-fluoroethoxy)ethoxy)ethoxy)phenyl)ethynyl)-1H-indole 14, targeting beta-amyloid (Abeta) plaques have been prepared. In vitro binding carried out in tissue homogenates prepared from postmortem AD brains with [(125)I]IMPY (6-iodo-2-(4'-dimethylamino-)phenyl-imidazo[1,2-a]pyridine) as the radioligand indicated good binding affinities (K(i)=4.0 and 1.5nM for 8 and 14, respectively). Brain penetration of the corresponding radiofluorinated ligands, evaluated in the normal mice, showed good initial brain penetration (4.50 and 2.43% ID/g (injected dose/gram) for [(18)F]8 and [(18)F]14 at 2min after injection) with moderate to low washout rates from the brain (1.71% ID/g at 2h and 2.10% ID/g at 3h, respectively). Autoradiography and homogenate binding studies demonstrated the high specific binding of [(18)F]14 to the Abeta plaques; however, [(18)F]8 showed low specific binding. These preliminary results identified that indolylphenylacetylene, 14, may be a good lead for further structural modification to develop a useful Abeta plaque imaging agent.
Bioorganic & medicinal chemistry letters 10/2008; 18(17):4823-7. · 2.65 Impact Factor
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ABSTRACT: Recent studies on gene expression of beta-cell mass (BCM) in the pancreas showed that vesicular monoamine transporter 2 (VMAT2) is highly expressed in the BCM (mainly in the islets of Langerhans). Imaging pancreatic BCM may provide an important tool for understanding the relationship between loss of insulin-secreting beta-cells and onset of diabetes mellitus. In this article, 9-fluoropropyl-(+)-dihydrotetrabenazine (FP-(+)-DTBZ), which is a VMAT2 imaging agent, was evaluated as a PET agent for estimating BCM in vivo.
Organ biodistribution after an intravenous injection of (18)F-FP-(+)-DTBZ (active isomer) and (18)F-FP-(-)-DTBZ (inactive isomer) was evaluated in normal rats. The specificity of uptake of (18)F-FP-(+)-DTBZ was assessed by a pretreatment (3.8 mg of (+)-DTBZ per kilogram and 3.5 mg of FP-(+)-DTBZ per kilogram, intravenously, 5 min prior) or coadministration (2 mg of (+)-DTBZ per kilogram). PET studies were performed in normal rats.
The in vivo biodistribution of (18)F-FP-(+)-DTBZ in rats showed the highest uptake in the pancreas (5% dose/g at 30 min after injection), whereas (18)F-FP-(-)-DTBZ showed a very low pancreas uptake. Rats pretreated with FP-(+)-DTBZ displayed a 78% blockade of pancreas uptake. PET studies in normal rats demonstrated an avid pancreas uptake of (18)F-FP-(+)-DTBZ.
The preliminary data obtained with (18)F-FP-(+)-DTBZ suggest that this fluorinated derivative of DTBZ shows good pancreas specificity and has the potential to be useful for quantitative measurement of VMAT2 binding sites reflecting BCM in the pancreas.
Journal of Nuclear Medicine 08/2008; 49(7):1171-6. · 6.38 Impact Factor
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ABSTRACT: Through the development and application of a unique approach for producing Re-metallopeptides, a new class of peptide-derived probes that are designed to target beta-amyloid plaques was developed. Derivatives of a class of beta-breaker peptides having the core sequence lvffa or affvl (lower case letters represent D-amino acids) and the single amino acid chelate quinoline (SAACQ) ligand which can bind Re and (99m)Tc were prepared on an automated peptide synthesizer. Both monomeric and dimeric peptides were synthesized in modest to good yields where in select examples a biotin-containing amino acid derivative was included to act as a linker point for further conjugation to carrier proteins. The Re complexes for all reported peptides were prepared similarly and screened for their ability to inhibit fibrillogenesis. Two of the reported compounds showed excellent inhibitory properties (8a: 40 +/- 5% amyloid formation versus control; 16: 40 +/- 4%) and warrant further investigation. For one of these leads, the (99m)Tc analogue was synthesized and the product showed high stability toward histidine and cysteine challenges, making it a viable candidate for in vivo biodistribution studies.
Bioconjugate Chemistry 06/2008; 19(5):1087-94. · 4.93 Impact Factor
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ABSTRACT: A new (18)F ligand, 2-(2'-((dimethylamino)methyl)-4'-(3-[(18)F]fluoropropoxy)-phenylthio)benzenamine ([(18)F]1), for positron emission tomography (PET) imaging of serotonin transporters (SERT) was evaluated.
Binding affinity was determined through in vitro binding assays with LLC-PK1 cells overexpressing SERT, NET or DAT (LLC-SERT, LLC-NET and LLC-DAT) and with rat cortical homogenates. Localization and selectivity of [(18)F]1 binding in vivo were evaluated by biodistribution, autoradiography and A-PET imaging studies in rats.
This compound displayed excellent binding affinity for SERT in vitro with K(i)=0.33 and 0.24 nM in LLC-SERT and rat cortical homogenates, respectively. Biodistribution studies with [(18)F]1 showed good brain uptake (1.61% dose/g at 2 min postinjection), high uptake into the hypothalamus (1.22% dose/g at 30 min) and a high target-to-nontarget (hypothalamus to cerebellum) ratio of 9.66 at 180 min postinjection. Pretreatment with a SERT selective inhibitor considerably inhibited [(18)F]1 binding in biodistribution studies. Ex vivo autoradiography reveals [(18)F]1 localization to brain regions with high SERT density, and this binding was blocked by pretreatment with SERT selective inhibitors. Small animal PET (A-PET) imaging in rats provided clear images of tracer localization in the thalamus, midbrain and striatum. In A-PET chasing experiments, injecting a SERT selective inhibitor 75 min post-tracer injection causes a dramatic reduction in regional radioactivity and the target-to-nontarget ratio.
The results of the biological studies and the ease of radiosynthesis with moderately good radiochemical yield (RCY=10-35%) make [(18)F]1 an excellent candidate for SERT PET imaging.
Nuclear Medicine and Biology 06/2008; 35(4):447-58. · 3.02 Impact Factor
