Synthesis of [¹¹C]PBR170, a novel imidazopyridine, for imaging the translocator protein with PET.

The translocator protein (TSPO) ligand 2-(6,8-dichloro-2-(4-ethoxyphenyl)imidazo[1,2-a]pyridin-3-yl)-N-(2-fluoropyridin-3-yl)-N-methylacetamide (PBR170), is a novel imidazopyridineacetamide with high affinity (2.6 nm) and selectivity for the TSPO. The synthesis of [(11)C]PBR170 was accomplished by N-methylation of the corresponding desmethyl precursor with [(11)C]methyl iodide in the presence of sodium hydroxide in dimethylformamide.

Synthesis and biological characterisation of 18F-SIG343 and 18F-SIG353, novel and high selectivity σ2 radiotracers, for tumour imaging properties.

Background: Sigma2 (σ2) receptors are highly expressed in cancer cell lines and in tumours. Two novel selective 18F-phthalimido σ2 ligands, 18F-SIG343 and 18F-SIG353, were prepared and characterised for their potential tumour imaging properties.

Methods: Preparation of 18F-SIG343 and 18F-SIG353 was achieved via nucleophilic substitution of their respective nitro precursors.

Central nervous system expression and PET imaging of the translocator protein in relapsing-remitting experimental autoimmune encephalomyelitis.

Unlabelled: Glial neuroinflammation is associated with the development and progression of multiple sclerosis. PET imaging offers a unique opportunity to evaluate neuroinflammatory processes longitudinally in a noninvasive and clinically translational manner. (18)F-PBR111 is a newly developed PET radiopharmaceutical with high affinity and selectivity for the translocator protein (TSPO), expressed on activated glia.

PET imaging of brain inflammation during early epileptogenesis in a rat model of temporal lobe epilepsy.

Background: Recently, inflammatory cascades have been suggested as a target for epilepsy therapy. Positron emission tomography (PET) imaging offers the unique possibility to evaluate brain inflammation longitudinally in a non-invasive translational manner. This study investigated brain inflammation during early epileptogenesis in the post-kainic acid-induced status epilepticus (KASE) model with post-mortem histology and in vivo with [18F]-PBR111 PET.

Radiation dosimetry of the translocator protein ligands [18F]PBR111 and [18F]PBR102.

Introduction: The translocator protein (TSPO) ligands [18F]PBR111 and [18F]PBR102 show promise for imaging neuroinflammation. Our aim was to estimate the radiation dose to humans from primate positron emission tomography (PET) studies using these ligands and compare the results with those obtained from studies in rodents.

Methods: [18F]PBR111 and [18F]PBR102 PET-computed tomography studies were carried out in baboons.

Evaluation of [¹²³I]-CLINDE as a potent SPECT radiotracer to assess the degree of astroglia activation in cuprizone-induced neuroinflammation.

Purpose: The purpose of this study was to assess the feasibility and sensitivity of the high-affinity translocator protein (TSPO) ligand [(123)I]-CLINDE in imaging TSPO changes in vivo and characterise and compare astroglial and TSPO changes in the cuprizone model of demyelination and remyelination in C57BL/6 mice.

Methods: C57BL/6 mice were fed with cuprizone for 4 weeks to induce demyelination followed by 2-4 weeks of standard diet (remyelination). Groups of mice were followed by in vivo single photon emission computed tomography (SPECT)/CT imaging using [(123)I]-CLINDE and uptake correlated with biodistribution, autoradiography, immunohistochemistry, immunofluorescence and real-time polymerase chain reaction (RT-PCR).

A rapid solid-phase extraction method for measurement of non-metabolised peripheral benzodiazepine receptor ligands, [(18)F]PBR102 and [(18)F]PBR111, in rat and primate plasma.

Objectives: To develop a rapid and reliable method for estimating non-metabolised PBR ligands fluoroethoxy ([(18)F]PBR102)- and fluoropropoxy ([(18)F]PBR111)-substituted 2-(6-chloro-2-phenyl)imidazo[1,2-a]pyridine-3-yl)-N,N-diethylacetamides in plasma.

Methods: Rats and baboons were imaged with PET up to 2 h postinjection of [(18)F]PBR102 and [(18)F]PBR111 under baseline conditions, after pre-blocking or displacement with PK11195. Arterial plasma samples were directly analysed by reverse-phase solid-phase extraction (RP-SPE) and RP-HPLC and by normal-phase TLC.

Discovery of [18F]N-(2-(diethylamino)ethyl)-6-fluoronicotinamide: a melanoma positron emission tomography imaging radiotracer with high tumor to body contrast ratio and rapid renal clearance.

The high melanoma uptake and rapid body clearance displayed by our series of [(123)I]iodonicotinamides prompted the development of [(18)F]N-(2-(diethylamino)ethyl)-6-fluoronicotinamide ([(18)F]2), a novel radiotracer for PET melanoma imaging. Significantly, unlike fluorobenzoates, [(18)F]fluorine incorporation on the nicotinamide ring is one step, facile, and high yielding. [(18)F]2 displayed high tumor uptake, rapid body clearance via predominantly renal excretion, and is currently being evaluated in preclinical studies for progression into clinical trials to assess the responsiveness of therapeutic agents.

Synthesis and evaluation of novel radioiodinated nicotinamides for malignant melanoma.

Introduction: A series of iodonicotinamides based on the melanin-binding iodobenzamide compound N-2-diethylaminoethyl-4-iodobenzamide was prepared and evaluated for the potential imaging and staging of disseminated metastatic melanoma.

Methods: [(123)I]Iodonicotinamides were prepared by iododestannylation reactions using no-carrier-added iodine-123 and evaluated in vivo by biodistribution and competition studies and by single photon emission computed tomography (SPECT) imaging in black and albino nude mice bearing B16F0 murine melanotic and A375 human amelanotic melanoma tumours, respectively.

Results: The iodonicotinamides displayed low-affinity binding for sigma(1)-sigma(2) receptors (K(i)>300 nM).

Synthesis and biological evaluation of substituted [18F]imidazo[1,2-a]pyridines and [18F]pyrazolo[1,5-a]pyrimidines for the study of the peripheral benzodiazepine receptor using positron emission tomography.

The fluoroethoxy and fluoropropoxy substituted 2-(6-chloro-2-phenyl)imidazo[1,2- a]pyridin-3-yl)- N, N-diethylacetamides 8 (PBR102) and 12 (PBR111) and 2-phenyl-5,7-dimethylpyrazolo[1,5- a]pyrimidin-3-yl)- N, N-diethylacetamides 15 (PBR099) and 18 (PBR146) were synthesized and found to have high in vitro affinity and selectivity for the peripheral benzodiazepine receptors (PBRs) when compared with the central benzodiazepine receptors (CBRs). The corresponding radiolabeled compounds [ (18)F] 8 [ (18)F] 12, [ (18)F] 15, and [ (18)F] 18 were prepared from their p-toluenesulfonyl precursors in 50-85% radiochemical yield. In biodistribution studies in rats, the distribution of radioactivity of the [ (18)F]PBR compounds paralleled the known localization of PBRs.

Evaluation of CLINDE as potent translocator protein (18 kDa) SPECT radiotracer reflecting the degree of neuroinflammation in a rat model of microglial activation.

Background: The translocator protein (TSPO; 18 kDa), the new name of the peripheral-type benzodiazepine receptor, is localised in mitochondria of glial cells and expressed in very low concentrations in normal brain. Their expression rises after microglial activation following brain injury. Accordingly, TSPO are potential targets to evaluate neuroinflammatory changes in a variety of CNS disorders.

Pharmacological evaluation of [123I]-CLINDE: a radioiodinated imidazopyridine-3-acetamide for the study of peripheral benzodiazepine binding sites (PBBS).

Purpose: The study aims to evaluate the iodinated imidazopyridine, N',N'-diethyl-6-Chloro-(4'-[(123)I]iodophenyl)imidazo[1,2-a]pyridine-3-acetamide ([(123)I]-CLINDE) as a tracer for the study of peripheral benzodiazepine binding sites (PBBS).

Materials And Methods: In vitro studies were performed using membrane homogenates and sections from kidney, adrenals, and brain cortex of Sprague-Dawley (SD) rats and incubated with [(123)I]-CLINDE. For in vivo studies, the rats were injected with [(123)I]-CLINDE.

In vivo imaging of brain lesions with [(11)C]CLINME, a new PET radioligand of peripheral benzodiazepine receptors.

The peripheral benzodiazepine receptor (PBR) is expressed by microglial cells in many neuropathologies involving neuroinflammation. PK11195, the reference compound for PBR, is used for positron emission tomography (PET) imaging but has a limited capacity to quantify PBR expression. Here we describe the new PBR ligand CLINME as an alternative to PK11195.

Preparation and biologic evaluation of a novel radioiodinated benzylpiperazine, 123I-MEL037, for malignant melanoma.

Unlabelled: Radiopharmaceuticals that can target the random metastatic dissemination of melanoma tumors may present opportunities for imaging and staging the disease as well as potential radiotherapeutic applications. A novel molecule, 2-(2-(4-(4-(123)I-iodobenzyl)piperazin-1-yl)-2-oxoethyl)isoindoline-1,3-dione (MEL037), was synthesized, labeled with 123I, and evaluated for application in melanoma tumor scintigraphy and radiotherapy.

Methods: The tumor imaging potential of 123I-MEL037 was studied in vivo in C57BL/6J female mice bearing the B16F0 murine melanoma tumor and in BALB/c nude mice bearing the A375 human amelanotic melanoma tumor by biodistribution, competition studies, and SPECT.

Synthesis and evaluation of novel radioiodinated benzamides for malignant melanoma.

The imaging potential of a series of [123I]benzamides was studied in mice bearing B16F0 melanoma tumors. Compound [123I]25 exhibited tumor uptake >8 %ID/g at 1 h, while that of [123I]14d and [123I]25 reached a maximum of 9-12 %ID/g at 6 h. Standardized uptake values of [123I]14d were higher than 100 between 24 and 72 h after injection.

Influence of trishomocubanes on sigma receptor binding of N-(1-benzyl-piperidin-4-yl)-4-[123I]iodobenzamide in vivo in the rat brain.

Three new trishomocubane analogues based on the 4-azahexacyclo[5.4.1.

Synthesis and in vitro binding of N,N-dialkyl-2-phenylindol-3-yl-glyoxylamides for the peripheral benzodiazepine binding sites.

A series of N,N-dialkyl-2-phenylindol-3-ylglyoxylamides bearing the halogens iodine and bromine were synthesised and their binding affinity for the peripheral benzodiazepine binding sites (PBBS) in rat kidney mitochondrial membranes was evaluated using [(3)H]PK11195. Central benzodiazepine receptor (CBR) affinities were also evaluated in rat cortices using [(3)H]flumazenil to determine their selectivity for PBBS over CBR. The tested compounds had PBBS binding affinities (IC(50)) ranging from 7.

Pharmacological evaluation of an [(123)I] labelled imidazopyridine-3-acetamide for the study of benzodiazepine receptors.

In vitro binding of the iodinated imidazopyridine, N',N'-dimethyl-6-methyl-(4'-[(123)I]iodophenyl)imidazo[1,2-a]pyridine-3-acetamide [(123)I]IZOL to benzodiazepine binding sites on brain cortex, adrenal and kidney membranes is reported. Saturation experiments showed that [(123)I]IZOL, bound to a single class of binding site (n(H)=0.99) on adrenal and kidney mitochondrial membranes with a moderate affinity (K(d)=30 nM).

Synthesis and biological evaluation of a series of flavone derivatives as potential radioligands for imaging the multidrug resistance-associated protein 1 (ABCC1/MRP1).

Multidrug resistance (MDR) is one of the major problems affecting the treatment of cancer. In vivo visualization and quantification of MDR proteins would be of great value to better select the therapeutic strategy. Six flavone-based compounds were synthesized and evaluated for their cytotoxic activity and MDR-reversing capacity using hMRP1 or hMDR1 overexpressing cell lines for in vitro assays.

Investigation of m1/m4 muscarinic receptors in the anterior cingulate cortex in schizophrenia, bipolar disorder, and major depression disorder.

Abnormal cholinergic neurotransmission has been suggested to occur in psychiatric illness. Therefore, this study investigated cholinergic muscarinic receptors in the anterior cingulate cortex (ACC) of schizophrenia, bipolar disorder and major depression disorder (n=15 per group). We used quantitative autoradiography to measure [(3)H]pirenzepine binding to M1 and M4 receptors.

Synthesis and evaluation of iodine-123 labelled tricyclic tropanes as radioligands for the serotonin transporter.

The tricyclic tropane analogues (1S,3S,6R,10S)-(Z)-10-(benzoyloxymethyl)-9-(3-chloro-4-iodobenzylidene)-7-azatricyclo[4.3.1.

Synthesis and in vivo evaluation of [11C]zolpidem, an imidazopyridine with agonist properties at central benzodiazepine receptors.

The synthesis and evaluation of [(11)C]zolpidem, an imidazopyridine with agonist properties at central benzodiazepine receptors, is reported herein. The reaction of desmethylzolpidem with [(11)C] methyl iodide afforded the title compound [(11)C]zolpidem in a yield of 19.19 +/- 3.

Pharmacological evaluation of (S)-8-[123I]iodobretazenil: a radioligand for in vivo studies of central benzodiazepine receptors.

In vitro studies on cortical membranes indicated (S)-8-[(123)I]iodobretazenil bound saturably to a single population of binding sites (B(max) = 2.33 pmol/mg protein) with a dissociation constant K(d) = 1.9 nM.