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Johnström P, Bergman L, Varnäs K, Malmquist J, Halldin C, Farde L. Development of rapid multistep carbon-11 radiosynthesis of the myeloperoxidase inhibitor AZD3241 to assess brain exposure by PET microdosing. Nucl Med Biol 2015; 42:555-60. [PMID: 25726760 DOI: 10.1016/j.nucmedbio.2015.02.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 01/16/2015] [Accepted: 02/03/2015] [Indexed: 01/10/2023]
Abstract
INTRODUCTION The myeloperoxidase inhibitor AZD3241 has been selected as a candidate drug currently being developed to delay progression in patients with neurodegenerative brain disorders. Part of the decision tree for translation of AZD3241 into clinical studies included the need for assessment of brain exposure in non-human primates by PET microdosing. For that purpose a rapid multistep method for (11)C-labeling of AZD3241 was developed. METHODS AZD3241 was labeled in the thio-carbonyl position starting from [(11)C]potassium cyanide in a 4-step procedure using microwave assisted heating. In the first step [(11)C]potassium cyanide was converted to [(11)C]potassium thiocyanate followed by reaction with benzoyl chloride to yield benzoyl [(11)C]isothiocyanate. The benzoyl [(11)C]isothiocyanate was subsequently reacted with the precursor ethyl 3-(2-isopropoxyethylamino)-1H-pyrrole-2-carboxylate and the formed intermediate underwent a base catalyzed cyclization to obtain [(11)C]AZD3241 in the final step. To assess [(11)C]AZD3241 brain exposure PET measurements were performed in three cynomolgus monkeys. RESULTS [(11)C]AZD3241 was produced in good and reproducible radiochemical yield 710 ± 294 MBq (mean ± SD, n = 7). Total time of synthesis was 60 min from end of bombardment. The specific radioactivity was 9 ± 4GBq/μmol and the radiochemical purity was >98%. Following iv administration of [(11)C]AZD3241 there was a rapid presence of radioactivity in brain in each of the three monkeys. The distribution of [(11)C]AZD3241 to brain was fast and a Cmax of 1.9 to 2.6% of the injected radioactivity was observed within 1.5 min. [(11)C]AZD3241 was homogeneously distributed in brain. CONCLUSION The MPO inhibitor AZD3241 was successfully labeled with carbon-11 in a challenging 4-step procedure in good radiochemical yield allowing PET microdosing studies in cynomolgus monkey. [(11)C]AZD3241 rapidly entered brain and confirmed adequate brain exposure to support translation of AZD3241 to phase 2a studies in patients.
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Finnema SJ, Hughes ZA, Haaparanta-Solin M, Stepanov V, Nakao R, Varnäs K, Varrone A, Arponen E, Marjamäki P, Pohjanoksa K, Vuorilehto L, Babalola PA, Solin O, Grimwood S, Sallinen J, Farde L, Scheinin M, Halldin C. Amphetamine decreases α2C-adrenoceptor binding of [11C]ORM-13070: a PET study in the primate brain. Int J Neuropsychopharmacol 2015; 18:pyu081. [PMID: 25522417 PMCID: PMC4360244 DOI: 10.1093/ijnp/pyu081] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The neurotransmitter norepinephrine has been implicated in psychiatric and neurodegenerative disorders. Examination of synaptic norepinephrine concentrations in the living brain may be possible with positron emission tomography (PET), but has been hampered by the lack of suitable radioligands. METHODS We explored the use of the novel α2C-adrenoceptor antagonist PET tracer [(11)C]ORM-13070 for measurement of amphetamine-induced changes in synaptic norepinephrine. The effect of amphetamine on [(11)C]ORM-13070 binding was evaluated ex vivo in rat brain sections and in vivo with PET imaging in monkeys. RESULTS Microdialysis experiments confirmed amphetamine-induced elevations in rat striatal norepinephrine and dopamine concentrations. Regional [(11)C]ORM-13070 receptor binding was high in the striatum and low in the cerebellum. After injection of [(11)C]ORM-13070 in rats, mean striatal specific binding ratios, determined using cerebellum as a reference region, were 1.4±0.3 after vehicle pretreatment and 1.2±0.2 after amphetamine administration (0.3mg/kg, subcutaneous). Injection of [(11)C]ORM-13070 in non-human primates resulted in mean striatal binding potential (BP ND) estimates of 0.65±0.12 at baseline. Intravenous administration of amphetamine (0.5 and 1.0mg/kg, i.v.) reduced BP ND values by 31-50%. Amphetamine (0.3mg/kg, subcutaneous) increased extracellular norepinephrine (by 400%) and dopamine (by 270%) in rat striata. CONCLUSIONS Together, these results indicate that [(11)C]ORM-13070 may be a useful tool for evaluation of synaptic norepinephrine concentrations in vivo. Future studies are required to further understand a potential contribution of dopamine to the amphetamine-induced effect.
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Finnema SJ, Scheinin M, Shahid M, Lehto J, Borroni E, Bang-Andersen B, Sallinen J, Wong E, Farde L, Halldin C, Grimwood S. Application of cross-species PET imaging to assess neurotransmitter release in brain. Psychopharmacology (Berl) 2015; 232:4129-57. [PMID: 25921033 PMCID: PMC4600473 DOI: 10.1007/s00213-015-3938-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 04/09/2015] [Indexed: 01/03/2023]
Abstract
RATIONALE This review attempts to summarize the current status in relation to the use of positron emission tomography (PET) imaging in the assessment of synaptic concentrations of endogenous mediators in the living brain. OBJECTIVES Although PET radioligands are now available for more than 40 CNS targets, at the initiation of the Innovative Medicines Initiative (IMI) "Novel Methods leading to New Medications in Depression and Schizophrenia" (NEWMEDS) in 2009, PET radioligands sensitive to an endogenous neurotransmitter were only validated for dopamine. NEWMEDS work-package 5, "Cross-species and neurochemical imaging (PET) methods for drug discovery", commenced with a focus on developing methods enabling assessment of changes in extracellular concentrations of serotonin and noradrenaline in the brain. RESULTS Sharing the workload across institutions, we utilized in vitro techniques with cells and tissues, in vivo receptor binding and microdialysis techniques in rodents, and in vivo PET imaging in non-human primates and humans. Here, we discuss these efforts and review other recently published reports on the use of radioligands to assess changes in endogenous levels of dopamine, serotonin, noradrenaline, γ-aminobutyric acid, glutamate, acetylcholine, and opioid peptides. The emphasis is on assessment of the availability of appropriate translational tools (PET radioligands, pharmacological challenge agents) and on studies in non-human primates and human subjects, as well as current challenges and future directions. CONCLUSIONS PET imaging directed at investigating changes in endogenous neurochemicals, including the work done in NEWMEDS, have highlighted an opportunity to further extend the capability and application of this technology in drug development.
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Dahl K, Schou M, Ulin J, Sjöberg CO, Farde L, Halldin C. 11C-carbonylation reactions using gas–liquid segmented microfluidics. RSC Adv 2015. [DOI: 10.1039/c5ra20646d] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A novel gas–liquid segmented microfluidic platform has been developed, allowing for the direct access to11C-labelled drug-like molecules.
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Schou M, Varnäs K, Sandell J, Johnström P, Cselenyi Z, Svensson S, Nakao R, Amini N, Bergman L, Sumic A, Gulyas B, Lindström-Böö E, Halldin C, Farde L. Synthesis, radiolabeling, and in vivo pharmacokinetic evaluation of the amyloid beta radioligand [11C]AZD4694 in nonhuman primates. Mol Imaging Biol 2014; 16:173-9. [PMID: 24002613 DOI: 10.1007/s11307-013-0666-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE [(18)F]AZD4694 (2-(2-(18)F-fluoro-6-(methylamino)-3-pyridyl)benzofuran-5-ol) is a radioligand suitable for imaging of amyloid beta deposits in the living human brain using positron emission tomography (PET). Here, we report the preparation and pharmacokinetic profile of its carbon-11 (t1/2 = 20.4 min) labeled isotopolog [(11)C]AZD4694 and compare [(11)C]AZD4694 with the hitherto most widely applied amyloid PET radioligand [(11)C]Pittsburgh Compound B (PiB). PROCEDURES The immediate unlabeled precursor to [(11)C]AZD4694 was prepared in a four-step convergent synthesis. Subsequent N-(11)C-methylation of this precursor with [(11)C]methyl iodide yielded [(11)C]AZD4694, which after isolation and formulation was injected into cynomolgus monkeys. The radioactivity in nonhuman primate brain following injection of [(11)C]AZD4694 and [(11)C]PiB was measured using PET. RESULTS [(11)C]AZD4694 was prepared in a 60 % incorporation yield. In a head to head comparison with [(11)C]PiB, it appeared that [(11)C]AZD4694 displayed slightly lower nonspecific binding in white matter than [(11)C]PiB as well as more rapid pharmacokinetics in the brain. CONCLUSIONS The advantageous pharmacokinetic profile and low nonspecific binding render [(11)C]AZD4694 a promising PET radioligand for imaging of amyloid beta in the human brain with PET.
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Plavén-Sigray P, Gustavsson P, Farde L, Borg J, Stenkrona P, Nyberg L, Bäckman L, Cervenka S. Dopamine D1 receptor availability is related to social behavior: A positron emission tomography study. Neuroimage 2014; 102 Pt 2:590-5. [DOI: 10.1016/j.neuroimage.2014.08.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 08/06/2014] [Accepted: 08/09/2014] [Indexed: 10/24/2022] Open
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Nord M, Cselenyi Z, Forsberg A, Rosenqvist G, Tiger M, Lundberg J, Varrone A, Farde L. Distinct regional age effects on [11C]AZ10419369 binding to 5-HT1B receptors in the human brain. Neuroimage 2014; 103:303-308. [PMID: 25255943 DOI: 10.1016/j.neuroimage.2014.09.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 08/21/2014] [Accepted: 09/15/2014] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Age-related changes in the serotonin system have been described, and proposed to be associated with behavioral changes observed particularly in the elderly population. The 5-HT1B receptor is thought to have a regulatory role in a number of physiological functions, and has been implicated in several age-related diseases. The purpose of the present study was to examine if the availability of 5-HT1B receptors is decreasing with age in healthy subjects. METHODS Data from five previous studies were reanalyzed and pooled, generating data from fifty-one healthy subjects, age 20 to 70, that had been examined with positron emission tomography (PET) and the 5-HT1B specific radioligand [11C]AZ10419369 at baseline conditions. The binding potential (BPND) in cortical and subcortical areas was calculated using the simplified reference tissue model (SRTM). After correction for partial volume effects (PVEc), the correlation between age and regional BPND was examined. RESULTS A statistically significant negative correlation between age and BPND was obtained for neocortical regions and the ventral striatum (VST). The average reduction in BPND per decade was 8% in cortex and 4% in VST. The BPND in the caudate nucleus and the putamen was mainly unaffected by age. CONCLUSION The 5-HT1B receptor availability decreases by age in cortical regions, whereas it remains stable in the caudate nucleus and putamen. By consequence, age-matching of control subjects will be necessary in future clinical studies.
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Fridén M, Wennerberg M, Antonsson M, Sandberg-Ställ M, Farde L, Schou M. Identification of positron emission tomography (PET) tracer candidates by prediction of the target-bound fraction in the brain. EJNMMI Res 2014; 4:50. [PMID: 26116114 PMCID: PMC4452637 DOI: 10.1186/s13550-014-0050-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 09/07/2014] [Indexed: 11/13/2022] Open
Abstract
Background Development of tracers for imaging with positron emission tomography (PET) is often a time-consuming process associated with considerable attrition. In an effort to simplify this process, we herein propose a mechanistically integrated approach for the selection of tracer candidates based on in vitro measurements of ligand affinity (Kd), non-specific binding in brain tissue (Vu,brain), and target protein expression (Bmax). Methods A dataset of 35 functional and 12 non-functional central nervous system (CNS) PET tracers was compiled. Data was identified in literature for Kd and Bmax, whereas a brain slice methodology was used to determine values for Vu,brain. A mathematical prediction model for the target-bound fraction of tracer in the brain (ftb) was derived and evaluated with respect to how well it predicts tracer functionality compared to traditional PET tracer candidate selection criteria. Results The methodology correctly classified 31/35 functioning and 12/12 non-functioning tracers. This predictivity was superior to traditional classification criteria or combinations thereof. Conclusions The presented CNS PET tracer identification approach is rapid and accurate and is expected to facilitate the development of novel PET tracers for the molecular imaging community. Electronic supplementary material The online version of this article (doi:10.1186/s13550-014-0050-6) contains supplementary material, which is available to authorized users.
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Fatouros-Bergman H, Cervenka S, Flyckt L, Edman G, Farde L. Meta-analysis of cognitive performance in drug-naïve patients with schizophrenia. Schizophr Res 2014; 158:156-62. [PMID: 25086658 DOI: 10.1016/j.schres.2014.06.034] [Citation(s) in RCA: 173] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 06/18/2014] [Accepted: 06/18/2014] [Indexed: 12/27/2022]
Abstract
Cognitive deficits represent a significant characteristic of schizophrenia. However, a majority of the clinical studies have been conducted in antipsychotic drug treated patients. Thus, it remains unclear if significant cognitive impairments exist in the absence of medication. This is the first meta-analysis of cognitive findings in drug-naïve patients with schizophrenia. Cognitive data from 23 studies encompassing 1106 patients and 1385 controls published from 1992 to 2013 were included. Tests were to a large extent ordered in cognitive domains according to the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) battery. Analysis was performed with STATA using the random-effects model and heterogeneity as well as Egger's publication bias was assessed. Overall the results show that patients performed worse than healthy controls in all cognitive domains with medium to large effect sizes. Verbal memory, speed of processing and working memory were three of the domains with the greatest impairments. The pattern of results is in line with previous meta-analytic findings in antipsychotic treated patients. The present meta-analysis confirms the existence of significant cognitive impairments at the early stage of the illness in the absence of antipsychotic medication.
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Tiger M, Rück C, Forsberg A, Varrone A, Lindefors N, Halldin C, Farde L, Lundberg J. Reduced 5-HT(1B) receptor binding in the dorsal brain stem after cognitive behavioural therapy of major depressive disorder. Psychiatry Res 2014; 223:164-70. [PMID: 24916155 DOI: 10.1016/j.pscychresns.2014.05.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 05/08/2014] [Accepted: 05/19/2014] [Indexed: 12/15/2022]
Abstract
Major depression is a significant contributor to the global burden of disease, and its pathophysiology is largely unknown. The serotonin hypothesis is, however, the model with most supporting data, although the details are only worked out to some extent. Recent clinical imaging measurements indeed imply a role in major depressive disorder (MDD) for the inhibitory serotonin autoreceptor 5-hydroxytryptamine1B (5-HT1B). The aim of the current study was to examine 5-HT1B receptor binding in the brain of MDD patients before and after psychotherapy. Ten patients with an ongoing untreated moderate depressive episode were examined with positron emission tomography (PET) and the 5-HT1B receptor selective radioligand [(11)C]AZ10419369, before and after treatment with internet-based cognitive behavioural therapy. All of the patients examined responded to treatment, and 70% were in remission by the time of the second PET measurement. A statistically significant 33% reduction of binding potential (BPND) was found in the dorsal brain stem (DBS) after treatment. No other significant changes in BPND were found. The DBS contains the raphe nuclei, which regulate the serotonin system. This study gives support for the importance of serotonin and the 5-HT1B receptor in the biological response to psychological treatment of MDD.
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Finnema SJ, Stepanov V, Nakao R, Sromek AW, Zhang T, Neumeyer JL, George SR, Seeman P, Stabin MG, Jonsson C, Farde L, Halldin C. (18)F-MCL-524, an (18)F-Labeled Dopamine D2 and D3 Receptor Agonist Sensitive to Dopamine: A Preliminary PET Study. J Nucl Med 2014; 55:1164-70. [PMID: 24790219 DOI: 10.2967/jnumed.113.133876] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 03/17/2014] [Indexed: 02/02/2023] Open
Abstract
UNLABELLED PET has been used to examine changes in neurotransmitter concentrations in the living brain. Pioneering PET studies on the dopamine system have used D2 and D3 receptor (D2/D3) antagonists such as (11)C-raclopride. However, more recently developed agonist radioligands have shown enhanced sensitivity to endogenous dopamine. A limitation of available agonist radioligands is that they incorporate the short-lived radioisotope (11)C. In the current study, we developed the (18)F-labeled D2/D3 receptor agonist (R)-(-)-2-(18)F-fluoroethoxy-N-n-propylnorapomorphine ((18)F-MCL-524). METHODS In total, 10 PET measurements were conducted on 5 cynomolgus monkeys. Initially, the binding of (18)F-MCL-524 was compared with that of (11)C-MNPA in 3 monkeys. Second, the specificity of (18)F-MCL-524 binding was examined in pretreatment studies using raclopride (1.0 mg/kg) and d-amphetamine (1.0 mg/kg). Third, a preliminary kinetic analysis was performed using the radiometabolite-corrected arterial input function of the baseline studies. Finally, 2 whole-body PET measurements were conducted to evaluate biodistribution and radiation dosimetry after intravenous injection of (18)F-MCL-524. RESULTS (18)F-MCL-524 entered the brain and provided striatum-to-cerebellum ratios suitable for reliable quantification of receptor binding using the multilinear reference tissue model. Mean striatal nondisplaceable binding potential (BPND) values were 2.0 after injection of (18)F-MCL-524 and 1.4 after (11)C-MNPA. The ratio of the BPND values of (18)F-MCL-524 and (11)C-MNPA was 1.5 across striatal subregions. After administration of raclopride and d-amphetamine, the (18)F-MCL-524 BPND values were reduced by 89% and 56%, respectively. Preliminary kinetic analysis demonstrated that BPND values obtained with the 1-tissue- and 2-tissue-compartment models were similar to values obtained with the multilinear reference tissue model. Estimated radiation doses were highest for gallbladder (0.27 mSv/MBq), upper large intestine (0.19 mSv/MBq), and small intestine (0.17 mSv/MBq). The estimated effective dose was 0.035 mSv/MBq. CONCLUSION The (18)F-labeled agonist (18)F-MCL-524 appears suitable for quantification of D2/D3 receptor binding in vivo, and the results encourage extension to human studies. The longer half-life of (18)F makes (18)F-MCL-524 attractive for studies on modulation of the dopamine concentration-for example, in combination with simultaneous measurement of changes in blood-oxygen-level-dependent signal using bimodal PET/functional MRI.
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Ito H, Shimada H, Shinotoh H, Takano H, Sasaki T, Nogami T, Suzuki M, Nagashima T, Takahata K, Seki C, Kodaka F, Eguchi Y, Fujiwara H, Kimura Y, Hirano S, Ikoma Y, Higuchi M, Kawamura K, Fukumura T, Böö ÉL, Farde L, Suhara T. Quantitative Analysis of Amyloid Deposition in Alzheimer Disease Using PET and the Radiotracer ¹¹C-AZD2184. J Nucl Med 2014; 55:932-8. [PMID: 24732152 DOI: 10.2967/jnumed.113.133793] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 01/27/2013] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Characteristic neuropathologic changes in Alzheimer disease (AD) are amyloid-β deposits and neurofibrillary tangles. Recently, a new radioligand for amyloid senile plaques, (11)C-labeled 5-(6-{[tert-butyl(dimethyl)silyl]oxy}-1,3-benzothiazol-2-yl)pyridin-2-amine ((11)C-AZD2184), was developed, and it was reported to show rapid brain uptake followed by rapid washout. In this study, (11)C-AZD2184 binding in control subjects and AD patients was examined in more detail by compartment model analysis using a metabolite-corrected arterial input function. The accuracy of simplified quantitative methods using a reference brain region was also evaluated. METHODS After intravenous bolus injection of (11)C-AZD2184, a dynamic PET scan was obtained for 90 min in 6 control subjects and 8 AD patients. To obtain the arterial input function, arterial blood sampling and high-performance liquid chromatography analysis were performed. RESULTS Time-activity curves in all brain regions could be described using the standard 2-tissue-compartment model. The total distribution volume ratios to reference region (DVR) in cerebral cortical regions were significantly higher in AD patients than in control subjects. Although there was no conspicuous accumulation of radioactivity in white matter as compared with other amyloid radioligands, DVR values in the centrum semiovale were more than 1 for both control subjects and AD patients, suggesting binding to myelin. The standardized uptake value ratio calculated from integrated time-activity curves in brain regions and the reference region was statistically in good agreement with DVR. CONCLUSION Although the white matter binding of (11)C-AZD2184 may have some effect on cortical measurement, it can be concluded that the kinetic behavior of (11)C-AZD2184 is suitable for quantitative analysis. The standardized uptake value ratio can be used as a validated measure of (11)C-AZD2184 binding in clinical examinations without arterial input function.
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Nagy K, Tóth M, Major P, Patay G, Egri G, Häggkvist J, Varrone A, Farde L, Halldin C, Gulyás B. Performance evaluation of the small-animal nanoScan PET/MRI system. J Nucl Med 2013; 54:1825-32. [PMID: 23990683 DOI: 10.2967/jnumed.112.119065] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
UNLABELLED nanoScan is a high-resolution integrated system for consecutive PET and MR imaging of small laboratory animals. We evaluated the performance of the system, using the NEMA NU 4-2008 protocol for the PET component and the NEMA MS 1-2007, MS 2-2008, and MS 3-2007 standards for the MR imaging component. METHODS The imaging system uses magnetically shielded position-sensitive photomultiplier tubes and a compact 1-T permanent-magnet MR imaging platform. Spatial resolution, sensitivity, counting rate capabilities, and image quality parameters were evaluated in accordance with the aforementioned NEMA standards. Further in vivo evaluation experiments complement the physical validation results. RESULTS The spatial resolution of the PET system enabled the 0.8-mm rods of a Derenzo phantom to be resolved. With point source and 2-dimensional filtered backprojection reconstruction, the resolution varied from 1.50 to 2.01 mm in full width at half maximum in the radial direction and from 1.32 to 1.65 mm in the tangential direction within the radius of 25 mm. Peak absolute sensitivity was 8.41%. Scatter fraction was 17.3% and 34.0%, and maximum noise-equivalent counting rate was 406 and 119 kcps in the mouselike and ratlike phantom, respectively. The image quality test found a nonuniformity of 3.52% and a spillover ratio of 6.2% and 5.8% in water and air, respectively. In testing of the MR imaging component, artifact-free images with high signal-to-noise ratio were recorded. Geometric distortion was below 5%, and image uniformity was at least 94.5% and 96.6% for the 60- and 35-mm radiofrequency coils, respectively. CONCLUSION The nanoScan integrated small-animal PET/MR imaging system has excellent spatial resolution and sensitivity. The performance characteristics of the PET and the MR imaging components are not compromised as a result of their integration onto a single platform. Because of its combination of features and performance parameters, the system provides crucial advantages for preclinical imaging studies over existing PET/CT systems, especially in neurologic and oncologic research.
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Airaksinen AJ, Finnema SJ, Balle T, Varnäs K, Bang-Andersen B, Gulyás B, Farde L, Halldin C. Radiosynthesis and evaluation of new α1-adrenoceptor antagonists as PET radioligands for brain imaging. Nucl Med Biol 2013; 40:747-54. [PMID: 23810488 DOI: 10.1016/j.nucmedbio.2013.05.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 05/06/2013] [Accepted: 05/18/2013] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Evaluation of the α1-adrenoceptors in relation to brain pathophysiology and drug treatment has been hindered by lack of α1-adrenoceptor specific radioligands with sufficient brain exposure. Our aim was to develop an α1-adrenoceptor specific PET radioligand for brain imaging. METHODS Two sertindole analogues 1-(4-fluorophenyl)-5-(1-methyl-1H-1,2,4-triazol-3-yl)-3-(1-[(11)C]methylpiperidin-4-yl)-1H-indole [(11)C]3 and 1-(4-fluorophenyl)-3-(1-[(11)C]methylpiperidin-4-yl)-5-(pyrimidin-5-yl)-1H-indole ([(11)C]Lu AA27122) [(11)C]4 were synthesized and evaluated as α1-adrenoceptor PET radioligands in cynomolgus monkey. Compounds 3 and 4 were selected due to their promising in vitro preclinical profile; high affinity and selectivity for the α1-adrenoceptor, favourable blood brain barrier permeability rates in Caco-2 monolayers and promising brain tissue/plasma ratio, assessed by equilibrium dialysis of free fraction in plasma and brain homogenate. RESULTS Compounds [(11)C]3 and [(11)C]4 were synthesized from their desmethyl piperidine precursors with high specific radioactivity (>370 GBq/μmol) using [(11)C]methyl iodide. The 1,2,4-triazole analogue [(11)C]3 exhibited poor brain uptake, but the corresponding pyrimidyl analogue [(11)C]4 exhibited high brain exposure and binding in α1-adrenoceptor rich brain regions. However, the binding could not be inhibited by pretreatment with prazosin (0.1 mg/kg and 0.3 mg/kg). The results were extended by autoradiography of [(11)C]4 binding in human brain sections and competition with antagonists from different structural families, revealing that only a minor portion of the observed binding of [(11)C]4 in brain was α1-adrenoceptor specific. CONCLUSION Though [(11)C]3 and [(11)C]4 proved not suitable as PET radioligands, the study provided further understanding of structural features influencing brain exposure of the chemical class of compounds related to the antipsychotic drug sertindole. It provided valuable insight in the delicacy of blood brain barrier penetration for structurally related compounds and underlines the importance for improved protocols for evaluation of brain penetration of future PET ligands.
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Finnema S, Bang-Andersen B, Jørgensen M, Christoffersen C, Gulyás B, Wikström H, Farde L, Halldin C. The dopamine D1receptor agonist (S)-[11C]N-methyl-NNC 01-0259 is not sensitive to changes in dopamine concentration-a positron emission tomography examination in the monkey brain. Synapse 2013; 67:586-95. [DOI: 10.1002/syn.21664] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 02/28/2013] [Accepted: 03/09/2013] [Indexed: 11/07/2022]
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Varnäs K, Jučaitė A, McCarthy DJ, Stenkrona P, Nord M, Halldin C, Farde L, Kanes S. A PET study with [11C]AZ10419369 to determine brain 5-HT1B receptor occupancy of zolmitriptan in healthy male volunteers. Cephalalgia 2013; 33:853-60. [DOI: 10.1177/0333102413476372] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aim To investigate the occupancy at brain 5-hydroxytryptamine (5-HT) 1B receptors in human subjects after administration of the antimigraine drug zolmitriptan. Methods Positron emission tomography (PET) studies were undertaken using the radioligand [11C]AZ10419369 in eight control subjects at baseline and after administration of zolmitriptan orodispersible tablets. The subjects were examined after two consecutive administrations of 10 mg zolmitriptan, approximately 1 week apart. Two of the subjects were subsequently examined after administration of 5 mg zolmitriptan. One week after the last administration of zolmitriptan five of the subjects underwent additional PET measurements without drug pretreatment. Results After administration of 10 mg zolmitriptan, mean receptor occupancy was 4–5%. No consistent changes in 5-HT1B receptor binding were observed for subjects who received 5 mg zolmitriptan. There was a statistically significant negative relationship between binding potential ( BPND) and plasma concentration of zolmitriptan and the active metabolite 183C91, respectively. All of the five subjects who were examined 1 week after dosing with zolmitriptan showed higher BPND post drug administration compared with baseline. Conclusion This is the first demonstration of CNS 5-HT1B receptor occupancy of a triptan. The findings are consistent with the low receptor occupancy previously reported in PET studies with agonists at other G protein coupled receptors.
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de Manzano Ö, Cervenka S, Jucaite A, Hellenäs O, Farde L, Ullén F. Individual differences in the proneness to have flow experiences are linked to dopamine D2-receptor availability in the dorsal striatum. Neuroimage 2013; 67:1-6. [PMID: 23128075 DOI: 10.1016/j.neuroimage.2012.10.072] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 10/15/2012] [Accepted: 10/26/2012] [Indexed: 10/27/2022] Open
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Schou M, Varnäs K, Jucaite A, Gulyás B, Halldin C, Farde L. Radiolabeling of the cannabinoid receptor agonist AZD1940 with carbon-11 and PET microdosing in non-human primate. Nucl Med Biol 2013; 40:410-4. [PMID: 23352602 DOI: 10.1016/j.nucmedbio.2012.10.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2012] [Revised: 08/28/2012] [Accepted: 10/30/2012] [Indexed: 10/27/2022]
Abstract
INTRODUCTION N-(2-tert-butyl-1-((4,4-difluorocyclohexyl)methyl)-1H-benzo[d]imidazol-5-yl)ethanesulfonamide (AZD1940) is a candidate drug for treatment of neuropathic pain. As part of the preclinical evaluation of AZD1940, a microdosing study with positron emission tomography (PET) was conducted to assess brain exposure. METHODS AZD1940 was radiolabeled with carbon-11 in the benzimidazole moiety. The radioactive precursor, lithium [(11)C]pivalate was obtained via (11)C-carboxylation of tert-butyl lithium. The target compound, [(11)C]AZD1940, was in turn obtained by the microwave assisted reaction between lithium [(11)C]pivalate and the o-phenylene diamine analog of AZD1940 (N-(3-amino-4-((4,4-difluorocyclohexyl)methylamino)phenyl)ethanesulfonamide) in neat phosphorous oxychloride. A brain PET measurement was performed in cynomolgus monkey. RESULTS The overall radiochemical yield of final formulated radiochemically pure (>99%) [(11)C]AZD1940 was 0.4% (uncorrected for decay) and the specific radioactivity was 13GBq/μmol at time of administration (58min after end of bombardment). After intravenous injection to cynomolgus monkey, the maximum concentration of radioactivity detected in the brain region of interest was 0.7% of the total injected radioactivity. The regional distribution of radioactivity within brain was homogenous. CONCLUSIONS AZD1940 was radiolabelled with carbon-11 and its brain exposure, assessed using PET, was relatively low in comparison to peripheral organ exposure.
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Kodaka F, Ito H, Kimura Y, Fujie S, Takano H, Fujiwara H, Sasaki T, Nakayama K, Halldin C, Farde L, Suhara T. Test-retest reproducibility of dopamine D2/3 receptor binding in human brain measured by PET with [11C]MNPA and [11C]raclopride. Eur J Nucl Med Mol Imaging 2012; 40:574-9. [PMID: 23238524 DOI: 10.1007/s00259-012-2312-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 11/21/2012] [Indexed: 01/28/2023]
Abstract
PURPOSE Dopamine D receptors (DRs) have two affinity states for endogenous dopamine, referred to as high-affinity state (D ), which has a high affinity for endogenous dopamine, and low-affinity state (D ). The density of D can be measured with (R)-2-CHO-N-n-propylnorapomorphine ([C]MNPA), while total density of D and D (DRs) can be measured with [C]raclopride using positron emission tomography (PET). Thus, the ratio of the binding potential (BP) of [C]MNPA to that of [C]raclopride ([C]MNPA/[C]raclopride) may reflect the proportion of the density of D to that of DRs. In the caudate and putamen, [C]MNPA/[C]raclopride reflects the proportion of the density of D to that of DRs. To evaluate the reliability of the PET paradigm with [C]MNPA and [C]raclopride, we investigated the test-retest reproducibility of non-displaceable BP (BP ) measured with [C]MNPA and of [C]MNPA/[C]raclopride in healthy humans. METHODS Eleven healthy male volunteers underwent two sets of PET studies on separate days that each included [C]MNPA and [C]raclopride scans. BP values in the caudate and putamen were calculated. Test-retest reproducibility of BP of [C]MNPA and [C]MNPA/[C]raclopride was assessed by intra-subject variability (absolute variability) and test-retest reliability (intraclass correlation coefficient: ICC). RESULTS The absolute variability of [C]MNPA BP was 5.30 ± 3.96 % and 12.3 ± 7.95 % and the ICC values of [C]MNPA BP were 0.72 and 0.82 in the caudate and putamen, respectively. The absolute variability of [C]MNPA/[C]raclopride was 6.11 ± 3.68 % and 11.60 ± 5.70 % and the ICC values of [C]MNPA/[C]raclopride were 0.79 and 0.80 in the caudate and putamen, respectively. CONCLUSION In the present preliminary study, the test-retest reproducibility of BP of [C]MNPA and of [C]MNPA/[C]raclopride was reliable in the caudate and putamen.
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Chen K, Langbaum J, Fleisher A, Roontiva A, Liu X, Thiyyagura P, Bandy D, Richter N, Jakimovich L, Prouty A, Cselenyi Z, Farde L, Budd S, Reiman E. P1‐155: Amyloid PET imaging using AZD4694 and unusually brief radiotracer uptake and scanning periods. Alzheimers Dement 2012. [DOI: 10.1016/j.jalz.2012.05.433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Chen K, Langbaum JB, Fleisher AS, Roontiva A, Liu X, Thiyyagura P, Bandy D, Richter N, Jakimovich L, Prouty A, Cselenyi Z, Farde L, Budd S, Reiman EM. IC‐O3‐04: Amyloid PET imaging using AZD4694 and unusually brief radiotracer uptake and scanning periods. Alzheimers Dement 2012. [DOI: 10.1016/j.jalz.2012.05.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Tarkiainen J, Vercouillie J, Guilloteau D, Gulyás B, Sóvágó J, Cselényi Z, Emond P, Chalon S, Sandell J, Hiltunen J, Farde L, Halldin C. Carbon-11 labelling of madam in two different positions: A highly selective pet radioligand for the serotonin transporter. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.2580440167] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Sandell J, Mccarron JA, Halldin C, Pike VW, Gulyas B, Cselenyi Z, Sovago J, Marchais S, Wikström HV, Farde L. [18F]6FPWAY - a prospective 5-HT1A receptor radioligand - radiolabeling and pet examination in monkey - comparison with [11C]6FPWAY. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.2580440158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Jučaite A, Cselényi Z, Arvidsson A, Ahlberg G, Julin P, Varnäs K, Stenkrona P, Andersson J, Halldin C, Farde L. Kinetic analysis and test-retest variability of the radioligand [11C](R)-PK11195 binding to TSPO in the human brain - a PET study in control subjects. EJNMMI Res 2012; 2:15. [PMID: 22524272 PMCID: PMC3350394 DOI: 10.1186/2191-219x-2-15] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 04/23/2012] [Indexed: 12/02/2022] Open
Abstract
Background Positron-emission tomography and the radioligand [11C](R)-PK11195 have been used for the imaging of the translocator protein (TSPO) and applied to map microglia cells in the brain in neuropsychiatric disorders. [11C](R)-PK11195 binding has been quantified using reference region approaches, with the reference defined anatomically or using unsupervised or supervised clustering algorithms. Kinetic compartment modelling so far has not been presented. In the present test-retest study, we examine the characteristics of [11C](R)-PK11195 binding in detail, using the classical compartment analysis with a metabolite-corrected arterial input function. Methods [11C](R)-PK11195 binding was examined in six control subjects at two separate occasions, 6 weeks apart. Results of one-tissue and two-tissue compartment models (1TCM, 2TCM) were compared using the Akaike criteria and F-statistics. The reproducibility of binding potential (BPND) estimates was evaluated by difference in measurements (error in percent) and intraclass correlation coefficients (ICCs). Results [11C](R)-PK11195 binding could be described by 2TCM which was the preferred model. Measurement error (in percent) indicated good reproducibility in large brain regions (mean error: whole brain 4%, grey matter 5%), but not in smaller subcortical regions (putamen 25%, caudate 55%). The ICC values were moderate to low, highest for the white matter (0.73), whole brain and thalamus (0.57), and cortical grey matter (0.47). Sizeable [11C](R)-PK11195 BPND could be identified throughout the human brain (range 1.11 to 2.21). Conclusions High intra-subject variability of [11C](R)-PK11195 binding limits longitudinal monitoring of TSPO changes. The interpretation of [11C](R)-PK11195 binding by 2TCM suggests that the presence of specific binding to TSPO cannot be excluded at physiological conditions.
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Någren K, Halldin C, Pike VW, Allonen T, Hietala J, Swahn CG, Andrée B, Farde L, Osman S, Grasby P. Radioactive metabolites of the 5-HT1A receptor pet radioligand, [carbonyl-11C]way-100635, measured in human plasma samples. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.25804401167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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