H T Ravert

Johns Hopkins Medicine, Baltimore, MD, United States

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Publications (222)749.46 Total impact

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    ABSTRACT: INTRODUCTION: The alpha-7 nicotinic acetylcholine receptor (α7 nAChR) is key in brain communication and has been implicated in the pathophysiology of diseases of the central nervous system. A positron-emitting radioligand targeting the α7 nAChR would enable better understanding of a variety of neuropsychiatric illnesses, including schizophrenia and Alzheimer's disease, and could enhance the development of new drugs for these and other conditions. We describe our attempt to synthesize an α7 nAChR-selective radiotracer for positron emission tomography (PET). METHODS: We prepared the high-affinity (Kd=0.2 nM) α7 nAChR agonist, 5'-(2-[(18)F]fluorophenyl)spiro[1-azabicyclo-[2.2.2]octane]-3,2'-(3'H)furo[2,3-b]pyridine, [(18)F]AZ11637326, in two steps, a nucleophilic fluorination followed by decarbonylation. We studied [(18)F]AZ11637326 in rodents, including mice lacking α7 nAChR, and in non-human primates. RESULTS: [(18)F]AZ11637326 was synthesized in a non-decay-corrected radiochemical yield of 3% from the end of synthesis (90min) with a radiochemical purity >90% and average specific radioactivity of 140GBq/μmol (3,781mCi/μmol). Modest rodent brain uptake was observed (2-5% injected dose per gram of tissue, depending on specific activity), with studies comparing CD-1 and α7 nAChR null mice indicating an element of target-specific binding. Blocking studies in non-human primates did not reveal specific binding within the brain. CONCLUSION: Despite the high affinity and target selectivity of AZ11637326 for α7 nAChR in vitro and encouraging rodent studies, receptor-mediated binding could not be demonstrated in non-human primates. Further structural optimization of compounds of this class will be required for them to serve as suitable radiotracers for PET.
    Nuclear Medicine and Biology 05/2013; · 2.52 Impact Factor
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    ABSTRACT: To examine the association between regional brain uptake of a novel amyloid positron emission tomography (PET) tracer florbetapir F 18 ([(18)F]-AV-45) and cognitive performance in a pilot study. Cross-sectional comparison of [(18)F]-AV-45 in AD patients versus controls. Three specialty memory clinics. Eleven participants with probable Alzheimer disease (AD) by NINDS/ADRDA criteria and 15 healthy comparison (HC) participants. Participants underwent PET imaging following a 370 MBq (10 mCi) intravenous administration of [(18)F]-AV-45. Regional/cerebellar standardized uptake value ratios (SUVRs) were calculated. Cognition was assessed using Mini-Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), Wechsler Logical Memory IA (immediate recall) test (LMIA), and verbal category fluency. Greater [(18)F]-AV-45 SUVR was associated with poorer performance on all cognitive tests. In the HC group, occipital, parietal, precuneus, temporal, and cortical average SUVR was associated with greater ADAS-Cog, and greater anterior cingulate SUVR was associated with lower LMIA. Two HC participants had [(18)F]-AV-45 cortical/cerebellar SUVR greater than 1.5, one of whom had deficits in episodic recall and on follow-up met criteria for amnestic mild cognitive impairment. [(18)F]-AV-45 SUVR in several brain regions was associated with worse global cognitive performance particularly in HC, suggesting its potential as a marker of preclinical AD.
    The American journal of geriatric psychiatry: official journal of the American Association for Geriatric Psychiatry 03/2013; 21(3):272-8. · 3.35 Impact Factor
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    ABSTRACT: INTRODUCTION: α7-nicotinic acetylcholine receptor (α7-nAChR) is one of the major neuronal nAChR subtypes. α7-nAChR is involved in variety of neuronal processes and disorders including schizophrenia and Alzheimer's disease. A number of α7-nAChR PET radioligands have been developed, but a quality radiotracer remains to be discovered. METHODS: High binding affinity α7-nAChR ligands A-833834 and A-752274 were radiolabeled with (11)C. Baseline and blockade biodistribution studies in the mouse brain of [(11)C]A-833834 (5-(6-(5-[(11)C]methylhexahydropyrrolo[3,4-c]pyrrol-2(1H)-yl)pyridazin-3-yl)-1H-indole) and [(11)C]A-752274 (2-(6-[(11)C]methyl-3,6-diazabicyclo[3.2.0]heptan-3-yl)-7-(6-methyl-3,6-diazabicyclo[3.2.0]heptan-3-yl)-9H-fluoren-9-one) were performed. [(11)C]A-752274 was evaluated in a baseline baboon PET study. RESULTS: [(11)C]A-833834 and [(11)C]A-752274 were synthesized by radiomethylation of corresponding des-methyl precursors. The radioligands were prepared with radiochemical yield of 12%-32%, high specific radioactivity (330-403GBq/μmol) and radiochemical purity>95%. Dissection studies with [(11)C]A-833834 demonstrated low specific α7-nAChR binding in the mouse brain. [(11)C]A-752274 specifically (~50%) labeled α7-nAChR in the mouse thalamus. However, [(11)CA-752274 exhibited low brain uptake in baboon (%SUV<100). CONCLUSION: Two novel α7-nAChR ligands radioligands were synthesized and studied in animals. Specific binding of [(11)C]A-833834 in the mouse brain is low due to the insufficient binding affinity of the radioligand. The very high binding affinity [(11)C]A-752274 exhibited good specific binding in the α7-nAChR-rich mouse brain regions. The low uptake of [(11)C]A-752274 in the baboon brain is due to its high hydrophilicity, rapid metabolism or other properties. Future development of α7-nAChR PET radioligands will be based on compounds with high binding affinities and good blood-brain barrier permeability.
    Nuclear Medicine and Biology 01/2013; · 2.52 Impact Factor
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    ABSTRACT: Prior studies using positron emission tomography (PET) or single-photon emission computed tomography techniques have reported inconsistent findings regarding differences between patients with restless legs syndrome (RLS) and control patients in the striatal dopamine-2 receptor (D2R) binding potentials (BP). D2R-BP does reflect receptor-ligand interactions such as receptor affinity (K(d)) and density (β(max)) or neurotransmitter synaptic concentrations. Thus, differences in D2R-BP reflect changes in these primary factors. PET techniques are currently available to estimate D2R β(max) and K(d). Separate morning and evening PET scans were performed. The D2R-BP were measured in basal ganglia using [(11)C]raclopride. Academic medical center. Thirty-one patients with primary RLS and 36 age- and sex-matched control patients completed the study. Patients with RLS had lower D2R-BP in putamen and caudate but not the ventral striatum. A subgroups analysis of those RLS patients who had not previously taken dopaminergic medications continued to show a significantly lower D2R-BP in the posterior putamen. D2R-BP did not differ between night and day for either group. D2R β(max) and K(d) did not differ significantly between patients with RLS and control patients but did show a strong and significant increase at night in the ventral striatum. Primary and secondary clinical measures of disease status failed to show any relation to D2R in any brain region. Given the lack of any difference in either β(max) or K(d) and the prior studies supporting an increase in presynaptic dopaminergic activity, the current changes found in D2R-BP likely reflect an increase in synaptic dopamine. CITATION: Earley CJ; Kuwabara H; Wong DF; Gamaldo C; Salas RE; Brašić JR; Ravert HT; Dannals RF; Allen RP. Increased synaptic dopamine in the putamen in restless legs syndrome. SLEEP 2013;36(1):51-57.
    Sleep 01/2013; 36(1):51-7. · 5.10 Impact Factor
  • Mitochondrion 09/2012; 12(5):569. · 4.03 Impact Factor
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    ABSTRACT: The radiosynthesis and in vivo evaluation of 5-(5-(6-[(11)C]methyl-3,6-diazabicyclo[3.2.0]heptan-3-yl)pyridin-2-yl)-1H-indole [(11)C]rac-(1), a potential PET tracer for α7 nicotinic acetylcholine receptors (α7-nAChR), are described. Syntheses of the nonradioactive standard rac-1 and corresponding desmethyl precursor 7 were achieved in several reaction steps. Radiomethylation of 7 with [(11)C]CH(3)I afforded [(11)C]rac-1 in an average radiochemical yield of 30 ± 5% (n=5) with high radiochemical purity and an average specific radioactivity of 444 ± 74 GBq/μmol (n=5). The total synthesis time was 30 min from end-of-bombardment. Biodistribution studies in mice showed that [(11)C]rac-1 penetrates the blood-brain barrier and specifically labels neuronal α7-nAChRs.
    Bioorganic & medicinal chemistry 05/2012; 20(12):3698-702. · 2.82 Impact Factor
  • Hayden T Ravert, Daniel P Holt, Robert F Dannals
    01/2012: pages 139-154;
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    ABSTRACT: There are only 2 currently available radioligands, 2-(18)F-FA and 6-(18)F-FA, for quantitative PET of the main cerebral subtype of nicotinic acetylcholine receptors (α4β2-nAChRs) in humans. Both exhibit slow distribution kinetics in the brain and require several hours for PET imaging. This makes PET of nAChRs with these radioligands logistically difficult and a serious burden for human subjects. The main purpose of this study was to preclinically evaluate (-)-2-(6-(18)F-fluoro-2,3'-bipyridin-5'-yl)-7-methyl-7-azabicyclo[2.2.1]heptane ((18)F-AZAN), our new radiolabeled antagonist of α4β2-nAChRs, that has high binding potential and rapid brain kinetics in baboons. (18)F-AZAN was synthesized using a modified (18)F-FDG synthesis module. The regional distribution of (18)F-AZAN in the brain was evaluated in baseline and cytisine-blocking studies of 4 male Papio anubis baboons. PET modeling procedures were used for calculation of regional distribution volume (V(T)), nondisplaceable binding potential (BP(ND)), and receptor occupancy. (18)F-AZAN rapidly entered the baboon brain, reached a steady state within 90 min after injection, and specifically labeled cerebral nAChRs. The peak radioactivity in the thalamus was 540 (percentage standardized uptake value) at 18 ± 7 min (n = 4) after bolus injection. Mathematical data analysis demonstrated that scanning for only 90 min is sufficient for determination of PET outcome variables (BP(ND), 3.2 [unitless] and V(T), 32-35 mL/mL in thalamus). The dose-dependent blocking experiments with cytisine demonstrated that (18)F-AZAN binds specifically with β2-containing (predominantly α4β2) nAChRs. (18)F-AZAN specifically labels nAChRs in baboon brains with a high value of BP(ND) and it requires only 90 min of PET scanning to produce estimates of V(T) and BP(ND) in the various brain regions. The blocking of nAChRs with cytisine is dose-dependent and it showed that (18)F-AZAN is suitable for application in nicotinic drug evaluation. In summary, (18)F-AZAN is superior to 2-(18)F-FA and 6-(18)F-FA for imaging cerebral β2-containing nAChRs in baboons. Further evaluations of (18)F-AZAN in the human brain are under way.
    Journal of Nuclear Medicine 12/2011; 53(1):121-9. · 5.77 Impact Factor
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    ABSTRACT: (18)F-fluorobenzyl triphenyl phosphonium (FBnTP) has recently been introduced as a myocardial perfusion PET agent. We used a rat model of transient coronary occlusion to determine the stability of the perfusion defect size over time and the magnitude of redistribution. Wistar rats (n = 15) underwent thoracotomy and 2-min occlusion of the left coronary artery (LCA), followed by reperfusion. During occlusion, (18)F-FBnTP (92.5 MBq) and (201)Tl-thallium chloride (0.74 MBq) were injected intravenously. One minute before the animals were sacrificed at 5, 45, and 120 min after reperfusion, the LCA was occluded again and 2% Evans blue was injected intravenously to determine the ischemic territory. The hearts were excised, frozen, and sliced for serial dual-tracer autoradiography and histology. Dynamic in vivo (18)F-FBnTP PET was performed on a subgroup of animals (n = 4). (18)F-FBnTP showed stable ischemic defects at all time points after tracer injection and reperfusion. The defects matched the blue dye defect (y = 0.97x+1.5, R(2) = 0.94, y = blue-dye defect, x = (18)F-FBnTP defect). Count density analysis showed no defect fill-in at 45 min but slightly increased activity at 120 min (LCA/remote uptake ratio = 0.19 ± 0.02, 0.19 ± 0.05, and 0.34 ± 0.06 at 5, 45, and 120 min, respectively, P < 0.05). For comparison, (201)Tl showed complete redistribution at 120 min (LCA/remote = 0.42 ± 0.04, 0.72 ± 0.03, and 0.97 ± 0.05 at 5, 45, and 120 min, respectively, P < 0.001). Persistence of the (18)F-FBnTP defect over time was confirmed by in vivo dynamic small-animal PET. In a transient coronary occlusion model, perfusion defect size using the new PET agent (18)F-FBnTP remained stable for at least 45 min and matched the histologically defined ischemic area. This lack of significant redistribution suggests a sufficient time window for future clinical protocols with tracer injection remote from the scanner, such as in a stress testing laboratory or chest pain unit.
    Journal of Nuclear Medicine 06/2011; 52(6):965-9. · 5.77 Impact Factor
  • Journal of Labelled Compounds 04/2011; 26(1‐12):205 - 206.
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    ABSTRACT: The peptide hormone ghrelin mediates through action on its receptor, the growth hormone secretagogue receptor (GHSR), and is known to play an important role in a variety of metabolic functions including appetite stimulation, weight gain, and suppression of insulin secretion. In light of the fact that obesity is one of the major health problems plaguing the modern society, the ghrelin signaling system continues to remain an important and attractive pharmacological target for the treatment of obesity. In vivo imaging of the GHSR could shed light on the mechanism by which ghrelin affects feeding behavior and thus offers a new therapeutic perspective for the development of effective treatments. Recently, a series of piperidine-substituted quinazolinone derivatives was reported to be selective and potent GHSR antagonists with high binding affinities. Described herein is the synthesis, in vitro, and in vivo evaluation of (S)-6-(4-fluorophenoxy)-3-((1-[(11)C]methylpiperidin-3-yl)methyl)-2-o-tolylquinazolin-4(3H)-one ([(11)C]1), a potential PET radioligand for imaging GHSR.
    Bioorganic & medicinal chemistry 02/2011; 19(7):2368-72. · 2.82 Impact Factor
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    ABSTRACT: Prior studies, all using SPECT techniques, failed to find any differences for dopamine transporter (DAT) in restless legs syndrome (RLS) subjects. The distinct pharmacokinetic properties associated with SPECT-determined DAT along with rapid biodynamic changes in DAT may, however, have missed membrane-bound DAT differences. The current studies assessed real-time DAT binding potentials (BP) in striatum of RLS patients using (11)C-methylphenidate and PET techniques. RLS medications were stopped at least 11 days prior to the PET study. Clinical severity of RLS was also assessed. PET scans were performed at 2 different times of day (starting at 08:30 and 19:30) in separate groups of subjects. The primary outcome measure was total striatal DAT BP. Thirty-six patients with primary RLS and 34 age- and gender-matched controls. RLS subjects had significantly lower DAT binding in the striatum compared to controls on both the Day and the Night scans. DAT was decreased in putamen and caudate but not the ventral striatum of RLS subjects. There were no diurnal differences in DAT for the total group or for control and RLS separately. DAT BP did not correlate with any clinical measures of RLS. The current study found a significant decrease in DAT BP in two independent studies. These results when viewed along with prior RLS SPECT and autopsy studies of DAT, and cell culture studies with iron deficiency and DAT, suggest that membrane-bound striatal DAT, but not total cellular DAT, may be decreased in RLS.
    Sleep 01/2011; 34(3):341-7. · 5.10 Impact Factor
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    ABSTRACT: Several studies have examined the link between the cannabinoid CB1 receptor and several neuropsychiatric illnesses, including schizophrenia. As such, there is a need for in vivo imaging tracers so that the relationship between CB1 and schizophrenia (SZ) can be further studied. In this paper, we present our first human studies in both healthy control patients and patients with schizophrenia using the novel PET tracer, [(11)C]OMAR (JHU75528), we have shown its utility as a tracer for imaging human CB1 receptors and to investigate normal aging and the differences in the cannabinoid system of healthy controls versus patients with schizophrenia. A total of ten healthy controls and nine patients with schizophrenia were included and studied with high specific activity [(11)C]OMAR. The CB1 binding (expressed as the distribution volume; V(T)) was highest in the globus pallidus and the cortex in both controls and patients with schizophrenia. Controls showed a correlation with the known distribution of CB1 and decline of [(11)C]OMAR binding with age, most significantly in the globus pallidus. Overall, we observed elevated mean binding in patients with schizophrenia across all regions studied, and this increase was statistically significant in the pons (p<0.05), by the Students t-test. When we ran a regression of the control subjects V(T) values with age and then compared the patient data to 95% prediction limits of the linear regression, three patients fell completely outside for the globus pallidus, and in all other regions there were at least 1-3 patients outside of the prediction intervals. There was no statistically significant correlations between PET measures and the individual Brief Psychiatry Rating Score (BPRS) subscores (r=0.49), but there was a significant correlation between V(T) and the ratio of the BPRS psychosis to withdrawal score in the frontal lobe (r=0.60), and middle and posterior cingulate regions (r=0.71 and r=0.79 respectively). In conclusion, we found that [(11)C] OMAR can image human CB1 receptors in normal aging and schizophrenia. In addition, our initial data in subjects with schizophrenia seem to suggest an association of elevated binding specific brain regions and symptoms of the disease.
    NeuroImage 10/2010; 52(4):1505-13. · 6.25 Impact Factor
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    ABSTRACT: Recently, A-836339 [2,2,3,3-tetramethylcyclopropanecarboxylic acid [3-(2-methoxyethyl)-4,5-dimethyl-3H-thiazol-(2Z)-ylidene]amide] (1) was reported to be a selective CB2 agonist with high binding affinity. Here we describe the radiosynthesis of [11C]A-836339 ([11C]1) via its desmethyl precursor as a candidate radioligand for imaging CB2 receptors with positron-emission tomography (PET). Whole body and the regional brain distribution of [11C]1 in control CD1 mice demonstrated that this radioligand exhibits specific uptake in the CB2-rich spleen and little specific in vivo binding in the control mouse brain. However, [11C]1 shows specific cerebral uptake in the lipopolysaccharide (LPS)-induced mouse model of neuroinflammation and in the brain areas with Abeta amyloid plaque deposition in a mouse model of Alzheimer's disease (APPswe/PS1dE9 mice). These data establish a proof of principle that CB2 receptors binding in the neuroinflammation and related disorders can be measured in vivo.
    Bioorganic & medicinal chemistry 07/2010; 18(14):5202-7. · 2.82 Impact Factor
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    ABSTRACT: An (18)F-labeled PET amyloid-beta (Abeta) imaging agent could facilitate the clinical evaluation of late-life cognitive impairment by providing an objective measure for Alzheimer disease (AD) pathology. Here we present the results of a clinical trial with (E)-4-(2-(6-(2-(2-(2-(18)F-fluoroethoxy)ethoxy)ethoxy)pyridin-3-yl)vinyl)-N-methyl benzenamine ((18)F-AV-45 or florbetapir [corrected] F 18). An open-label, multicenter brain imaging, metabolism, and safety study of (18)F-AV-45 was performed on 16 patients with AD (Mini-Mental State Examination score, 19.3 +/- 3.1; mean age +/- SD, 75.8 +/- 9.2 y) and 16 cognitively healthy controls (HCs) (Mini-Mental State Examination score, 29.8 +/- 0.45; mean age +/- SD, 72.5 +/- 11.6 y). Dynamic PET was performed over a period of approximately 90 min after injection of the tracer (370 MBq [10 mCi]). Standardized uptake values and cortical-to-cerebellum standardized uptake value ratios (SUVRs) were calculated. A simplified reference tissue method was used to generate distribution volume ratio (DVR) parametric maps for a subset of subjects. Valid PET data were available for 11 AD patients and 15 HCs. (18)F-AV-45 accumulated in cortical regions expected to be high in Abeta deposition (e.g., precuneus and frontal and temporal cortices) in AD patients; minimal accumulation of the tracer was seen in cortical regions of HCs. The cortical-to-cerebellar SUVRs in AD patients showed continual substantial increases through 30 min after administration, reaching a plateau within 50 min. The 10-min period from 50 to 60 min after administration was taken as a representative sample for further analysis. The cortical average SUVR for this period was 1.67 +/- 0.175 for patients with AD versus 1.25 +/- 0.177 for HCs. Spatially normalized DVRs generated from PET dynamic scans were highly correlated with SUVR (r = 0.58-0.88, P < 0.005) and were significantly greater for AD patients than for HCs in cortical regions but not in subcortical white matter or cerebellar regions. No clinically significant changes in vital signs, electrocardiogram, or laboratory values were observed. (18)F-AV-45 was well tolerated, and PET showed significant discrimination between AD patients and HCs, using either a parametric reference region method (DVR) or a simplified SUVR calculated from 10 min of scanning 50-60 min after (18)F-AV-45 administration.
    Journal of Nuclear Medicine 06/2010; 51(6):913-20. · 5.77 Impact Factor
  • Current Radiopharmaceuticals 01/2010; 2(3):195-198.
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    ABSTRACT: The most abundant subtype of cerebral nicotinic acetylcholine receptors (nAChR), alpha4beta2, plays a critical role in various brain functions and pathological states. Imaging agents suitable for visualization and quantification of alpha4beta2 nAChRs by positron emission tomography (PET) would present unique opportunities to define the function and pharmacology of the nAChRs in the living human brain. In this study, we report the synthesis, nAChR binding affinity, and pharmacological properties of several novel 3-pyridyl ether compounds. Most of these derivatives displayed a high affinity to the nAChR and a high subtype selectivity for alpha4beta2-nAChR. Three of these novel nAChR ligands were radiolabeled with the positron-emitting isotope (11)C and evaluated in animal studies as potential PET radiotracers for imaging of cerebral nAChRs with improved brain kinetics.
    Bioorganic & medicinal chemistry 08/2009; 17(13):4367-77. · 2.82 Impact Factor
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    ABSTRACT: Apoptosis is a key mechanism in numerous pathologies. However, there are no effective noninvasive means available for an early detection and quantitative assessment of evolution dynamics of the apoptotic process. Here, we have characterized the ability of the novel PET voltage sensor (18)F-fluorobenzyl triphenyl phosphonium ((18)F-FBnTP) to quantify the time-dependent apoptotic action of the taxanes paclitaxel and docetaxel in vitro and in vivo. The duration-dependent treatment effect of paclitaxel on (18)F-FBnTP uptake was assayed in human MDA-MB-231 breast carcinoma cells. The expression of the proapoptotic Bax and antiapoptotic Bcl-2 mitochondrial proteins, release of the apoptogen cytochrome c, and activation of executioner caspase-3 were determined by Western blotting. The fraction of viable cells was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The effect of docetaxel on (18)F-FBnTP and (18)F-FDG uptake in orthotopic prostate tumors in mice was compared. (18)F-FBnTP cellular uptake in viable cells declined linearly with the increasing duration of paclitaxel treatment, from 3 to 24 h, and plateaued at 48 h. The extent of decrease of (18)F-FBnTP correlated strongly with the Bax-to-Bcl-2 ratio (R(2) = 0.83) and release of cytochrome c (R(2) = 0.92), but preceded in time the caspase-3 cleavage. The P-glycoprotein blocker verapamil did not interfere with (18)F-FBnTP cellular uptake. (18)F-FBnTP prostate tumor contrast was greater than (18)F-FDG prostate tumor contrast. Docetaxel caused a marked decrease (52.4%) of (18)F-FBnTP tumor uptake, within 48 h, whereas (18)F-FDG was much less affected (12%). The voltage sensor (18)F-FBnTP is a viable means for quantification of paclitaxel pharmacodynamics. (18)F-FBnTP permits the detection of paclitaxel apoptotic action in vivo earlier than does (18)F-FDG. (18)F-FBnTP may afford a novel approach for early detection and quantitative assessment of the cumulative-effect kinetics of proapoptotic drugs and conditions using PET.
    Journal of Nuclear Medicine 05/2009; 50(5):774-80. · 5.77 Impact Factor
  • ChemInform 01/2009; 40(14).
  • [show abstract] [hide abstract]
    ABSTRACT: The most abundant subtype of cerebral nicotinic acetylcholine receptors (nAChR), α4β2, plays a critical role in various brain functions and pathological states. Imaging agents suitable for visualization and quantification of α4β2 nAChRs by positron emission tomography (PET) would present unique opportunities to define the function and pharmacology of the nAChRs in the living human brain. In this study, we report the synthesis, nAChR binding affinity, and pharmacological properties of several novel 3-pyridyl ether compounds. Most of these derivatives displayed a high affinity to the nAChR and a high subtype selectivity for α4β2-nAChR. Three of these novel nAChR ligands were radiolabeled with the positron-emitting isotope 11C and evaluated in animal studies as potential PET radiotracers for imaging of cerebral nAChRs with improved brain kinetics.
    Bioorganic & Medicinal Chemistry - BIOORGAN MED CHEM. 01/2009; 17(13):4367-4377.

Publication Stats

5k Citations
749.46 Total Impact Points


  • 1985–2013
    • Johns Hopkins Medicine
      • Division of Nuclear Medicine
      Baltimore, MD, United States
  • 1990–2012
    • Johns Hopkins University
      • • Department of Radiology
      • • Department of Environmental Health Sciences
      Baltimore, MD, United States
  • 1999
    • Sungkyunkwan University
      • Department of Nuclear Medicine
      Sŏul, Seoul, South Korea
  • 1998
    • National Institute on Drug Abuse
      • Division of Intramural Research (IRP)
      Bethesda, MD, United States
  • 1997–1998
    • University of Maryland, Baltimore
      • • Department of Pharmacology
      • • Department of Psychiatry
      Baltimore, MD, United States
    • National Institute on Drug Abuse
      Maryland, United States
  • 1996
    • Chang Gung Memorial Hospital
      • Department of Nuclear Medicine
      Taipei, Taipei, Taiwan
  • 1995
    • Australian Nuclear Science and Technology Organisation
      Kirrawee, New South Wales, Australia