Synthesis, characterization, and monkey positron emission tomography (PET) studies of [18F]Y1-973, a PET tracer for the neuropeptide Y Y1 receptor

Neuropeptide Y receptor subtype 1 (NPY Y1) has been implicated in appetite regulation, and antagonists of NPY Y1 are being explored as potential therapeutics for obesity. An NPY Y1 PET tracer is useful for determining the level of target engagement by NPY Y1 antagonists in preclinical and clinical studies. Here we report the synthesis and evaluation of [(18)F]Y1-973, a novel PET tracer for NPY Y1. [(18)F]Y1-973 was radiolabeled by reaction of a primary chloride with [(18)F]KF/K2.2.2 followed by deprotection with HCl. [(18)F]Y1-973 was produced with high radiochemical purity (>98%) and high specific activity (>1000 Ci/mmol). PET studies in rhesus monkey brain showed that the distribution of [(18)F]Y1-973 was consistent with the known NPY Y1 distribution; uptake was highest in the striatum and cortical regions and lowest in the pons, cerebellum nuclei, and brain stem. Blockade of [(18)F]Y1-973 uptake with NPY Y1 antagonist Y1-718 revealed a specific signal that was dose-dependently reduced in all regions of grey matter to a similarly low level of tracer uptake, indicative of an NPY Y1 specific signal. In vitro autoradiographic studies with [(18)F]Y1-973 in rhesus monkey and human brain tissue slices revealed an uptake distribution consistent with the in vivo PET studies. Highest binding density was observed in the dentate gyrus, caudate-putamen, and cortical regions; moderate binding density in the hypothalamus and thalamus; and lowest binding density in the globus pallidus and cerebellum. In vitro saturation binding studies in rhesus monkey and human caudate-putamen homogenates confirmed a similarly high B(max)/K(d) ratio for [(18)F]Y1-973, suggesting the tracer may provide a specific signal in human brain of similar magnitude to that observed in rhesus monkey. [(18)F]Y1-973 is a suitable PET tracer for imaging NPY Y1 in rhesus monkey with potential for translation to human PET studies.     

与人体肥胖相关的神经肽Y受体Y1基因的克隆及序列分析

目的 克隆与肥胖相关的人神经肽Y受体Y1(NPYlR)基因,并鉴定该克隆基因序列的正确性.方法 从人的脂肪组织中提取总RNA并进行反转录,以此为模板用PCR扩增NPY1R基因的cDNA,然后与pET 28a+载体重组,筛选阳性克隆和DNA序列分析鉴定,测序后与GeneBank中NPY1R基因进行同源性比较和序列分析.结果 PER扩增出一个1100 bp左右的DNA片段,与载体重组后DNA序列分析鉴定,DNA序列分析显示克隆的DNA片段是人NPY1R基因,且所克隆的基因共编码384个氨基酸,分子量为44 KD,与GeneBank中NPY1R基因序列同源性达100%.结论 克隆的人NPY1R基因与GeneBank中NPY1R序列完全一致,为进一步应用分子生物学技术深入研究NPY1R与人体肥胖发生、发展及转化等相关作用机制及应用该基因进行其基因蛋白表达奠定了基础.     

PET Imaging Studies in Rhesus Monkey with the Cannabinoid-1 (CB1) Receptor Ligand [11C]CB-119

Purpose  The in vitro and in vivo evaluation of the selective, high affinity (human CB1 IC₅₀ 0.49 nM) inverse agonist CB1R tracer [¹¹C]CB-119, a close analog of the previously disclosed [¹⁸F]MK-9470, was undertaken. Procedures  [¹¹C]CB-119 was synthesized with high specific activity by alkylation of a phenolic precursor with [¹¹C]methyl iodide. In vitro autoradiographic studies using rhesus brain slices were carried out using [³H]CB-119, and in vivo imaging studies were carried out using [¹¹C]CB-119 in rhesus monkeys under baseline and blocked conditions. Results  Autoradiographic studies in rhesus brain showed the expected distribution pattern for CB1R with highest binding in the cerebral cortex, cerebellum, caudate/putamen, globus pallidus, substantia nigra, and hippocampus. Lower binding was seen in the posterior hypothalamus, ventral tegmental area, and periventricular gray area, and the lowest binding was in the thalamic nuclei. The binding of [³H]CB-119 was fully blocked by the addition of 10 μM CB-119. Rhesus positron emission tomography imaging studies showed very good brain uptake and a distribution pattern consistent with that seen in the autoradiographic studies. The kinetics of tracer uptake was slow. The brain uptake was blocked by pretreatment with taranabant, a CB1R inverse agonist. The specific signal (total/nonspecific) in rhesus putamen at 90 min was ~6:1. Conclusions  [¹¹C]CB-119 is a suitable tracer for imaging central CB1 receptors.     

In vivo imaging of adenosine A1 receptors in the human brain with [18F]CPFPX and positron emission tomography

The important roles played by the A(1) adenosine receptor (A(1)AR) in brain physiology and pathology make this receptor a target for in vivo imaging. Here we describe the distribution of A(1)ARs in the living human brain with PET, made possible for the first time by the highly potent and selective A(1)AR antagonist 8-cyclopentyl-3-(3-[(18)F]fluoropropyl)-1-propylxanthine ([(18)F]CPFPX). In vivo data demonstrate a rapid cerebral uptake, peaking at 2.9 +/- 0.6% injected dose/liter at 3.3 +/- 1.3 min, followed by a gradual washout. Consistent with the results of autoradiography, high receptor densities occurred in the putamen and the mediodorsal thalamus. Neocortical regions showed regional differences in [(18)F]CPFPX binding, with high accumulation in temporal > occipital > parietal > frontal lobes and a lower level of binding in the sensorimotor cortex. Ligand accumulation was low in cerebellum, midbrain, and brain stem. Metabolism of [(18)F]CPFPX is rapid outside the central nervous system, but the metabolites do not penetrate the blood-brain barrier. In conclusion, in vivo application of [(18)F]CPFPX, a highly potent and selective PET ligand, for the first time allows the imaging of A(1)ARs in the living human brain.     

与人体肥胖相关的神经肽Y受体Y2基因的克隆及序列分析

目的 克隆与肥胖相关的人神经肽Y受体Y2(NPY2R)基因,并鉴定该克隆基因序列的正确性.方法 从人的脂肪组织中提取总RNA并进行反转录,以此为模板用PCR扩增NPY2R基因的eDNA,然后与pET 28a+载体重组,筛选阳性克隆和DNA序列分析鉴定,测序后与GeneBank中NPY2R基因进行同源性比较和序列分析.结果 PCR扩增出一个1100 bp左右的DNA片段,与载体重组和DNA序列分析鉴定,DNA序列分析显示克隆的DNA片段是人NPY2R基因,且所克隆的基因共编码381个氨基酸,分子量为4.2 kD,与GeneBank中NPY2R基因序列同源性达100%.结论 克隆的人NPY2R基因与GeneBank中NPY2R序列完全一致,为进一步应用分子生物学技术深入研究NPY2R与人体肥胖发生、发展及转化等相关作用机制及应用该基因进行其基因蛋白表达奠定了基础.     

Assessment of serotonin release capacity in the human brain using dexfenfluramine challenge and [18F]altanserin positron emission tomography

Although alterations of serotonin (5-HT) system functioning have been proposed for a variety of psychiatric disorders, a direct method quantitatively assessing 5-HT release capacity in the living human brain is still lacking. Therefore, we evaluated a novel method to assess 5-HT release capacity in vivo using dexfenfluramine challenge and [¹⁸F]altanserin positron emission tomography (PET).Thirteen healthy male subjects received placebo and single oral doses of 40 mg (n = 6) or 60 mg (n = 7) of the potent 5-HT releaser dexfenfluramine separated by an interval of 14 days. Three further subjects received placebo on both days. Two hours after placebo/drug administration, 250 MBq of the 5-HT_2A receptor selective PET-radiotracer [¹⁸F]altanserin was administered intravenously as a 30 s bolus. Dynamic PET data were subsequently acquired over 90 min. Moreover, arterial blood samples were drawn for measurement of total activity and metabolite correction of the input function. Dexfenfluramine as well as cortisol and prolactin plasma concentration-time profiles was quantitatively determined. Tracer distribution volumes for five volumes-of-interest (prefrontal and occipital cortex, insula, thalamus, caudatum) were calculated by the Logan plot and a 2-tissue compartment model. Dexfenfluramine dose-dependently decreased the total distribution volume of [¹⁸F]altanserin in cortical regions independent of the PET modeling approach. Cortisol and prolactin plasma concentrations were dose-dependently increased by dexfenfluramine. The decrease in cortical [¹⁸F]altanserin receptor binding under dexfenfluramine was correlated with the increase of plasma prolactin. These data suggest that the combination of a dexfenfluramine-induced 5-HT release and subsequent assessment of 5-HT_2A receptor availability with [¹⁸F]altanserin PET is suitable to measure cortical 5-HT release capacity in the human brain.     

Gender-dependent increases with healthy aging of the human cerebral cannabinoid-type 1 receptor binding using [(18)F]MK-9470 PET

The endocannabinoid system (ECS) is implicated as a regulator of homeostasis of several cerebral functions and is a novel target for drug treatment of neuropyschiatric disorders. So far, the cerebral cannabinoid-type 1 receptor (CB1R) has only been studied using in vitro, animal model, electrophysiological and post-mortem data. We have used positron emission tomography (PET) using a high-affinity, subtype-selective radioligand, [(18)F]MK-9470, to assess the in vivo cerebral CB1R distribution and its variation with healthy aging and gender. Fifty healthy volunteers (25 M/25 F, 18-69 years) underwent [(18)F]MK-9470 PET. Parametric [(18)F]MK-9470 binding maps were constructed, corrected for partial volume effects and analyzed using statistical parametric mapping in a combined categorical (gender) and covariate (age) design. We found that [(18)F]MK-9470 binding to CB1R increased with aging but only in women (p(FWE)<0.05, corrected for multiple comparisons); this was most pronounced in the basal ganglia, lateral temporal cortex and limbic system, especially in the hippocampus. Men showed higher [(18)F]MK-9470 binding then women (p<0.001, uncorrected), in clusters of the limbic system and cortico-striato-thalamic-cortical circuit. Region-dependent and gender-related upregulation of [(18)F]MK-9470 binding with aging is in line with ex vivo findings in rodent studies and may be associated with a changing homeostatic capacity or compensation mechanisms in the ECS that is modulated by sex hormones. In vivo PET of the CB1R will likely improve our understanding of the ECS in several neurological and psychiatric disorders.     

[18F]‐FBEM,a tracer targeting cell‐surface protein thiols for cell trafficking imaging

We used [¹⁸F]‐4‐fluorobenzamido‐N‐ethylamino‐maleimide ([¹⁸F]‐FBEM) to radiolabel cells ex vivo for in vivo positron emission tomography (PET) in order to assess cell trafficking in mice. In contrast to commonly used imaging agents, [¹⁸F]‐FBEM forms a covalent bond with thiol groups present on the cells surface. The stability of the probe in aqueous medium was tested at different pH values and cross‐experiment showed that thiol‐labeling efficiency was retained (at least) up to pH 9. The labeling procedure did not affect significantly the cell viability. To illustrate the procedure, PET images of living mice injected intravenously with labeled T lymphocytes were obtained. They showed the expected cell homing in the spleen that was absent in mice injected with free label. Copyright © 2013 John Wiley & Sons, Ltd.     

Syntheses and preliminary evaluation of [18F]AlF‐NOTA‐G‐TMTP1 for PET imaging of high aggressive hepatocellular carcinoma

The goal of this study is to evaluate a new ¹⁸F‐labeled imaging agent for diagnosing high metastatic (aggressive) hepatocellular carcinoma using positron emission tomography (PET). The new ¹⁸F‐labeled imaging agent [¹⁸F]AlF‐NOTA‐G‐TMTP1 was synthesized and radiolabeled with ¹⁸F using NOTA‐AlF chelation method. The tumor‐targeting characteristics of [¹⁸F]AlF‐NOTA‐G‐TMTP1 was assessed in HepG2, SMCC‐7721, HCC97L and HCCLM3 xenografts. The total synthesis time was about 20 min with radiochemical yield of 25 ± 6%. The specific activity was about 11.1–14.8 GBq/µmol at the end of synthesis based on the amount of peptide used and the amount of radioactivity trapped on the C₁₈ column. The log P value of [¹⁸F]AlF‐NOTA‐G‐TMTP1 was ‐3.166 ± 0.022. [¹⁸F]AlF‐NOTA‐G‐TMTP1 accumulated in SMCC‐7721 and HCCLM3 tumors (high metastatic potential) in vivo and result in tumor/muscle (T/M) ratios of 4.5 ± 0.3 and 4.7 ± 0.2 (n = 4) as measured by PET at 40 min post‐injection (p.i.). Meanwhile, the tumor/muscle (T/M) ratios of HepG2 and HCC97L tumors (low metastatic potential) were1.6 ± 0.3 and 1.8 ± 0.4. The tumor uptake of [¹⁸F]AlF‐NOTA‐G‐TMTP1 could be inhibited 61.9% and 57.6% by unlabeled G‐TMTP1 in SMCC‐7721 and HCCLM3 xenografts at 40 min p.i., respectively. Furthermore, [¹⁸F]AlF‐NOTA‐G‐TMTP1 showed pretty low activity in the liver and intestines in all tumor bearing mice, such in vivo distribution pattern would be advantageous for the detection of hepatic carcinoma. Overall, [¹⁸F]AlF‐NOTA‐G‐TMTP1 may specifically target high metastatic or/and aggressive hepatocellular carcinoma with low background activity and, therefore, holds the potential to be used as an imaging agent for detecting tumor lesions within the liver area. Copyright © 2016 John Wiley & Sons, Ltd.     

18F]Ciprofloxacin, a new positron emission tomography tracer for noninvasive assessment of the tissue distribution and pharmacokinetics of ciprofloxacin in humans

The biodistribution and pharmacokinetics of the fluorine-18-labeled fluoroquinolone antibiotic [(18)F]ciprofloxacin in tissue were studied noninvasively in humans by means of positron emission tomography (PET). Special attention was paid to characterizing the distribution of [(18)F]ciprofloxacin to select target tissues. Healthy volunteers (n = 12) were orally pretreated for 5 days with therapeutic doses of unlabeled ciprofloxacin. On day 6, subjects received a tracer dose (mean injected amount, 700 +/- 55 MBq, which contained about 0.6 mg of unlabeled ciprofloxacin) of [(18)F]ciprofloxacin as an intravenous bolus. Thereafter, PET imaging and venous blood sampling were initiated. Time-radioactivity curves were measured for liver, kidney, lung, heart, spleen, skeletal muscle, and brain tissues for up to 6 h after radiotracer administration. The first application of [(18)F]ciprofloxacin in humans has demonstrated the safety and utility of the newly developed radiotracer for pharmacokinetic PET imaging of the tissue ciprofloxacin distribution. Two different tissue compartments of radiotracer distribution could be identified. The first compartment including the kidney, heart, and spleen, from which the radiotracer was washed out relatively quickly (half-lives [t(1/2)s], 68, 57, and 106 min, respectively). The second compartment comprised liver, muscle, and lung tissue, which displayed prolonged radiotracer retention (t(1/2), >130 min). The highest concentrations of radioactivity were measured in the liver and kidney, the main organs of excretion (standardized uptake values [SUVs], 4.9 +/- 1.0 and 9.9 +/- 4.4, respectively). The brain radioactivity concentrations were very low (<1 kBq. g(-1)) and could therefore not be quantified. Transformation of SUVs into absolute concentrations (in micrograms per milliliter) allowed us to relate the concentrations at the target site to the susceptibilities of bacterial pathogens. In this way, the frequent use of ciprofloxacin for the treatment of a variety of infections could be corroborated.     

The use of 2-deoxy-2-[18F]fluoro-D-glucose (FDG-PET) positron emission tomography in the routine diagnosis of epilepsy.

PURPOSE: Positron emission tomography with 2-deoxy fluoroglucose positron emission tomography (18-FDG-PET) is widely used in the pre-surgical evaluation of subjects with epilepsy, but little is known of its usefulness in a non-surgical population. PROCEDURES: We analyzed the sensitivity of PET as a diagnostic tool in a large unselected population of epilepsy subjects. Pre-surgical and non-surgical portions of this population were individually assessed as well. The relationship of PET abnormalities to other neurodiagnostic tests was examined. Statistical assessment relied primarily on contingency tables (chi-square tests), with ANOVA or non-parametric assessment used as necessary. RESULTS: While PET was more likely to identify areas of decreased metabolism in the surgical population than in the non-surgical populations, it nevertheless found a significant number of abnormalities in the total population and in the non-surgical group alone. Even in groups in which the clinical diagnosis was unknown, abnormalities were found 40% of the time. PET was useful as an exclusionary diagnostic tool for non-epileptic seizures (NES) and primary generalized epilepsies (PGE) with sensitivity, specificity, and accuracy > 90%. The PET was somewhat more sensitive than magnetic resonance imaging (MRI) in finding abnormalities in the total population, but was less sensitive than electroencephalography (EEG). CONCLUSION: PET may be a useful diagnostic tool in the general epilepsy population even when a definitive clinical diagnosis is not suggested by other modalities.     

11C]AZ10419369: a selective 5-HT1B receptor radioligand suitable for positron emission tomography (PET). Characterization in the primate brain

The 5-HT1B receptor has been implicated in several psychiatric disorders and is a potential pharmacological target in the treatment of depression. Here we report the synthesis of a novel PET radioligand, [11C]AZ10419369 (5-methyl-8-(4-methyl-piperazin-1-yl)-4-oxo-4H-chromene-2-carboxylic acid (4-morpholin-4-yl-phenyl)-amide), for in vivo visualization of 5-HT1B receptors in the brains of macaques and humans subjects. [11C]AZ10419369 was prepared by N-methylation of (8-(1-piperazinyl)-5-methylchrom-2-en-4-one-2-(4-morpholinophenyl) carboxamide, using carbon-11 methyl triflate. Regional brain uptake patterns of [11C]AZ10419369 were characterized by PET measurements in two macaques and a preliminary study in two human subjects. In addition, AZ10419369 was prepared in tritium labeled form for in vitro autoradiography studies in macaque brain tissue sections. The radiochemical purity of [11C]AZ10419369 was >99% and specific radioactivity was >3600 Ci/mmol. After iv injection of [11C]AZ10419369, 3-4% was in brain after 7.5 min. The regional brain distribution of radioactivity was similar in humans and macaques showing the highest uptake of radioactivity in the occipital cortex and the basal ganglia, in accord with autoradiographic studies performed using [3H]AZ10419369. Uptake was moderate in the temporal and frontal cortical regions, lower in the thalamus and lowest in the cerebellum. In macaques pre-treated with the selective 5-HT1B receptor antagonist, AR-A000002, binding was reduced in a dose-dependent manner, consistent with specific binding to 5-HT1B receptors. These data support [11C]AZ10419369 as a suitable radioligand for labeling 5-HT1B receptors in the primate brain. This radioligand may be useful in future studies evaluating drug-induced receptor occupancy and measurement of brain 5-HT1B receptor levels in patients with psychiatric disorders.     

Preclinical Acute Toxicity Studies and Dosimetry Estimates of the Novel Sigma-1 Receptor Radiotracer, [18F]SFE

[¹⁸F]1-(2-Fluoroethyl)-4-[(4-cyanophenoxy)methyl]piperidine ([¹⁸F]SFE) is a novel, selective, high-affinity sigma-1 receptor radioligand that has been preclinically well characterized in rodents. To support an investigational new drug (IND) application for the first evaluation of [¹⁸F]SFE in humans, single-organ and whole-body radiation adsorbed doses associated with [¹⁸F]SFE injection were estimated from rat distribution data. In addition, single- and multiple-dose toxicity studies were conducted in rabbits and in dogs. Multiple-dose toxicity studies in rabbits and single-dose toxicity studies in beagles suggest at least a 100-fold safety margin for humans studies at a mass dose limit of 4.0 μg per intravenous injection, based on the combined no observable adverse effect levels (NOAEL, mg/m²) measured in these species. Radiation dosimetry estimates obtained from rat biodistribution analyses of [¹⁸F]SFE suggest that most tissues would receive about 0.010–0.020 mGy/MBq, while the adrenal glands, brain, bone, liver, lungs, and spleen would receive slightly higher doses (0.024–0.044 mGy/MBq). The adrenal glands were identified as the critical organ, because they received the highest adsorbed radiation dose. The total exposure resulting from a 5 mCi administration of [¹⁸F]SFE is well below the FDA-defined limits for yearly cumulative and per-study exposures to research participants. These combined results support the expectation that [¹⁸F]SFE will be safe for use in human positron emission tomography (PET) imaging studies with the administration of 5 mCi and a mass dose equal to or less than 4.0 μg SFE per injection.     

In vitro and in vivo evaluation of [18F]-FDEGPECO as a PET tracer for imaging the metabotropic glutamate receptor subtype 5 (mGluR5)

(E)-3-(pyridin-2-ylethynyl)cyclohex-2-enone O-2-(2-(18)F-fluoroethoxy)ethyl oxime, ([(18)F]-FDEGPECO), a novel high affinity radioligand for the metabotropic glutamate receptor subtype 5 (mGluR5) was assessed for its potential as a PET imaging agent. In vitro autoradiography on rat brain slices resulted in a heterogeneous and displaceable binding to mGluR5-rich brain regions. [(18)F]-FDEGPECO showed high stability in rat plasma and brain homogenate as well as in human plasma and microsomes. Good blood-brain barrier passage was predicted from an in vitro transport assay with P-glycoprotein-transfected hMDR1-MDCK cells. In vivo PET imaging on rats revealed specific uptake of radioactivity in the mGluR5-rich brain regions such as hippocampus, striatum and cortex while the cerebellum, a region with low mGluR5-expression, showed negligible uptake. Blockade experiments by co-injection of [(18)F]-FDEGPECO and M-MPEP (6mg/kg), an antagonist for mGluR5, reduced the level of radioactivity in mGluR5-regions to that of the cerebellum, pointing to an effective blockade of specifically bound [(18)F]-FDEGPECO. Postmortem biodistribution studies at 15min p.i. confirmed the distribution pattern observed in PET. HPLC analysis of rat brain extracts indicated that 98.5% and 91% of the total radioactivity were parent compound at 5min and 17min p.i., respectively. Taken together, the high affinity and the high in vivo specificity of [(18)F]-FDEGPECO for mGluR5 in the rat brain as well as the lack of in vivo defluorination make this new [(18)F]-labeled ABP688 derivative a suitable ligand for the preclinical PET imaging of mGluR5. These favorable characteristics warrant further evaluation in humans.     

Correlation between serotonin synthesis and 5-HT1A receptor binding in the living human brain: a combined alpha-[11C]MT and [18F]MPPF positron emission tomography study

Serotonin (5-HT) is one of the major neurotransmitters and has been implicated in a wide variety of cerebral functions. Several lines of evidence indicate that 5HT(1A) receptors exert a negative feedback in the synthesis and release of serotonin. While most of what is known about serotonin comes from studies in animals, much less empirical evidence exists about the serotonergic system in the living human brain. This study aims to assess the correlation between serotonin synthesis and 5-HT(1A) receptor binding using positron emission tomography (PET) in humans. Six healthy male volunteers underwent 2 PET scans in the same day: one measuring alpha-[(11)C]MT K [ml/g/min] trapping constant (a measure of serotonin synthesis) and one measuring 5-HT(1A) receptor binding potential BP(ND) with [(18)F]MPPF. Volumes of interest (VOIs) selected a priori included: anterior cingulate cortex (ACC), anterior insula, hippocampus, amygdala, thalamus, hypothalamus and midbrain raphe nuclei. Correlation analyses were conducted voxel-by-voxel and with manually traced VOIs. A significant negative correlation between serotonin synthesis and 5-HT(1A) binding potential was found bilaterally in hippocampus and anterior insula and in the left ACC. The combination of [(18)F]MPPF and alpha-[(11)C]MT PET offers a means to investigate key determinants of 5-HT neurotransmission under physiological and psychopathological conditions in the human brain in vivo.     

Using positron emission tomography 2-deoxy-2-[18F]fluoro-D-glucose, 11CO, and 15O-water for monitoring androgen independent prostate cancer.

PURPOSE: Monitoring of androgen independent prostate cancer (AIPC) therapy involves monitoring prostate specific antigen (PSA) blood serum concentrations; however, the reliability of small changes in PSA values has been questioned. We performed a small pilot study to determine whether PET might be a useful monitor of changes during anti-angiogenic therapy in AIPC. PROCEDURES: Changes in tumor blood flow ([15O] water), blood volume ([11C]CO), 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake and metabolic volume were measured before and during thalidomide treatment and compared with changes in PSA in six patients with AIPC. RESULTS: The percent change in PSA correlated with the FDG Delta%SUV(mean) (r=0.94, P<0.01) and Delta%metabolic tumor volume (r=0.91, P<0.01) but less well with Delta%blood volume (r=0.65, P=0.14). Percent change blood flow values showed an inverse correlation with percent changes in PSA (r=-0.83, P=0.032). CONCLUSIONS: PET measures of tumor blood flow and metabolism may have use in monitoring the physiologic changes occurring during anti-angiogenic therapy in AIPC.     

Pharmacological characterization and feeding-suppressive property of FMS586 [3-(5,6,7,8-tetrahydro-9-isopropyl-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride], a novel, selective, and orally active antagonist for neuropeptide Y Y5 receptor

We evaluated the pharmacological profiles of FMS586 [3-(5,6,7,8-tetrahydro-9-isopropyl-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride], a novel tetrahydrocarbazole derivative as a neuropeptide Y (NPY) Y5 receptor antagonist. This compound showed a highly selective in vitro affinity for Y5 (IC(50) = 4.3 +/- 0.4 nM) relative to other NPY receptor subtypes like Y1 or Y2. Its binding to Y5 was found to be fully antagonistic from cyclic AMP accumulation assays in human embryonic kidney 293 cells. Pharmacokinetic analysis revealed sufficient oral availability and brain permeability of this compound accompanied with clear dose relation. We attempted to assess the selectivity of FMS586 and, thereby, to infer the physiological role of Y5 in the following feeding experiments in normal rats. An intracerebroventricular injection of NPY and Y5-selective agonist peptide induced acute and robust feeding responses in satiated rats, and prior administration of FMS586 at the doses from 25 to 100 mg/kg clearly inhibited these responses by approximately 55 and 90%, respectively. This compound also showed dose-dependent but transient suppression in natural feeding models of both overnight fasting-induced hyperphagia and spontaneous daily intake. FMS586 did not modulate food intake induced by the topical injection of norepinephrine, galanin, or gamma-aminobutyric acid receptor agonist muscimol to the paraventricular nucleus. In addition, we confirmed the Y5-specific activity profile of FMS586 by immunohistochemical analysis. Taken together, we propose not only that our compound potentially expresses specific blockade of central Y5 signals but also that Y5 receptor would certainly contribute to physiological regulation of food intake in normal rats, as suggested from its origin.     

Quantification of the glycine transporter 1 in rhesus monkey brain using [18F]MK-6577 and a model-based input function

Background

Glycine transporter 1 (GlyT1) inhibitors have emerged as potential treatments for schizophrenia due to their potentiation of NMDA receptor activity by modulating the local concentrations of the NMDA co-agonist glycine. [¹⁸F]MK-6577 is a potent and selective GlyT1 inhibitor PET tracer. Although differences in ligand kinetics can be expected between non-human primates and humans, the tracer pre-clinical evaluation can provide valuable information supporting protocol design and quantification in the clinical space. The main objective of this work was to evaluate the in vivo kinetics of [¹⁸F]MK-6577 in rhesus monkey brain. Additionally, a method for estimating the tracer input function from the tracer brain tissue kinetics and venous sampling was validated. This technique was applied for determination of the dose-occupancy relationship of a GlyT1 inhibitor in monkey brain.

Methods

Compartmental and Logan graphical analysis were utilized for quantification of the [¹⁸F]MK-6577 binding using the measured tracer arterial input function. The stability of the tracer volume of distribution relative to scan length was assessed. The proposed model-based input function method takes advantage of the agreement between the tracer concentration in arterial and venous plasma from ~ 5 min. The approach estimates the initial peak of the input curve by adding a gamma like function term to the measured venous curve. The parameters of the model function were estimated by simultaneously fitting several brain time activity curves to a compartmental model.

Results

Good agreement was found between the model-based and the measured arterial plasma curve and the corresponding distribution volumes. The Logan analysis was the preferred method of analysis providing reliable and stable volume of distribution and occupancy results using a 90 and possibly 60 min scan length.

Conclusion

The model-based input function method and Logan analysis are well suited for quantification of [¹⁸F]MK-6577 binding and GlyT1 occupancy in monkey brain.     

Characterization of N-(1-Acetyl-2,3-dihydro-1H-indol-6-yl)-3-(3-cyano-phenyl)-N-[1-(2-cyclopentyl-ethyl)-piperidin-4yl]acrylamide (JNJ-5207787), a small molecule antagonist of the neuropeptide Y Y2 receptor

The in vitro pharmacological properties of N-(1-Acetyl-2,3-dihydro-1H-indol-6-yl)-3-(3-cyano-phenyl)-N-[1-(2-cyclopentyl-ethyl)-piperidin-4yl]-acrylamide (JNJ-5207787), a novel neuropeptide Y Y(2) receptor (Y(2)) antagonist, were evaluated. JNJ-5207787 inhibited the binding of peptide YY (PYY) to human Y(2) receptor in KAN-Ts cells (pIC(50) = 7.00 +/- 0.10) and to rat Y(2) receptors in rat hippocampus (pIC(50) = 7.10 +/- 0.20). The compound was >100-fold selective versus human Y(1),Y(4), and Y(5) receptors as evaluated by radioligand binding. In vitro receptor autoradiography data in rat brain tissue sections confirmed the selectivity of JNJ-5207787. [(125)I]PYY binding sites sensitive to JNJ-5207787 were found in rat brain regions known to express Y(2) receptor (septum, hypothalamus, hippocampus, substantia nigra, and cerebellum), whereas insensitive binding sites were observed in regions known to express Y(1) receptor (cortex and thalamus). JNJ-5207787 was demonstrated to be an antagonist via inhibition of PYY-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate binding ([(35)S]GTPgammaS) in KAN-Ts cells (pIC(50) corrected = 7.20 +/- 0.12). This was confirmed auto-radiographically in rat brain sections where PYY-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate binding was inhibited by JNJ-5207787 (10 microM) in hypothalamus, hippocampus, and substantia nigra. After intraperitoneal administration in rats (30 mg/kg), JNJ-5207787 penetrated into the brain (C(max) = 1351 +/- 153 ng/ml at 30 min) and occupied Y(2) receptor binding sites as revealed by ex vivo receptor autoradiography. Hence, JNJ-5207787 is a potent and selective pharmacological tool available to establish the potential role of central and peripheral Y(2) receptors in vivo.