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A novel amide synthesis methodology is described using amines, CO2 and Grignard reagents and Mitsunobu reagents. The method was applied to carbon-11 radiochemistry to label amides using cyclotron-produced [11C]CO2. The synthetic utility of the one-pot labelling methodology was demonstrated by producing [11C]melatonin. The incorporation of [11C]CO2 into [11C]melatonin was 36% – determined by radioHPLC 2 min post [11C]CO2 delivery. [ABSTRACT FROM AUTHOR]

The excitatory amino acid transporter 2 (EAAT2) plays a key role in the clearance and recycling of glutamate - the major excitatory neurotransmitter in the mammalian brain. EAAT2 loss/dysfunction triggers a cascade of neurodegenerative events, comprising glutamatergic excitotoxicity and neuronal death. Nevertheless, our current knowledge regarding EAAT2 in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD), is restricted to post-mortem analysis of brain tissue and experimental models. Thus, detecting EAAT2 in the living human brain might be crucial to improve diagnosis/therapy for ALS and AD. This perspective article describes the role of EAAT2 in physio/pathological processes and provides a structure-activity relationship of EAAT2-binders, bringing two perspectives: therapy (activators) and diagnosis (molecular imaging tools).

The presence of positron emission tomography (PET) centers at most major hospitals worldwide, along with the improvement of PET scanner sensitivity and the introduction of total body PET systems, has increased the interest in the PET tracer development using the short-lived radionuclides carbon-11. In the last few decades, methodological improvements and fully automated modules have allowed the development of carbon-11 tracers for clinical use. Radiolabeling natural compounds with carbon-11 by substituting one of the backbone carbons with the radionuclide has provided important information on the biochemistry of the authentic compounds and increased the understanding of their in vivo behavior in healthy and diseased states. The number of endogenous and natural compounds essential for human life is staggering, ranging from simple alcohols to vitamins and peptides. This review collates all the carbon-11 radiolabeled endogenous and natural exogenous compounds synthesised to date, including essential information on their radiochemistry methodologies and preclinical and clinical studies in healthy subjects.

This guideline on molar activity (A m ) and specific activity (A s ) focusses on small molecules, peptides and macromolecules radiolabelled for diagnostic and therapeutic applications. In this guideline we describe the definition of A m and A s , and how these measurements must be standardised and harmonised. Selected examples highlighting the importance of A m and A s in imaging studies of saturable binding sites will be given, and the necessity of using appropriate materials and equipment will be discussed. Furthermore, common A m pitfalls and remedies are described. Finally, some aspects of A m in relation the emergence of a new generation of highly sensitive PET scanners will be discussed., (© 2021. The Author(s).)

Positron emission tomography (PET) is a powerful functional imaging technique that requires the use of positron emitting nuclides. Carbon-11 ( 11 C) radionuclide has several advantages related to the ubiquity of carbon atoms in biomolecules and the conservation of pharmacological properties of the molecule upon isotopic exchange of carbon-12 with carbon-11. However, due to the short half-life of 11 C (20.4 minutes) and the low scale with which it is produced by the cyclotron (sub-nanomolar concentrations), quick, robust and chemospecific radiolabelling strategies are required to minimise activity loss during incorporation of the 11 C nuclide into the final product. To address some of the constraints of working with 11 C, the use of silicon-based chemistry for 11 C-labelling was proposed as a rapid and effective route for radiopharmaceutical production due to the broad applicability and high efficiency showed in organic chemistry. In the past years several organic chemistry methodologies have been successfully applied to 11 C-chemistry. In this short review, we examine silicon-based 11 C-chemistry, with a particular emphasis on the radiotracers that have been successfully produced and potential improvements to further expand the applicability of silicon in radiochemistry.

A copper-catalysed radiosynthesis of carbon-11 radiolabelled carboxylic acids was developed by reacting terminal alkynes and cyclotron-produced carbon-11 carbon dioxide ([ 11 C]CO 2 ) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). A small library of 11 C-labelled propiolic acid derivatives were obtained with a total synthesis time of 15 min from end of bombardment (EOB) with a (non-isolated) radiochemical yield ranging from 7% to 28%., (© 2021 The Authors. Journal of Labelled Compounds and Radiopharmaceuticals published by John Wiley & Sons Ltd.)

A substantial fraction of coronavirus disease 2019 (COVID-19) patients experience neurological manifestations. Nevertheless, brain changes caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain largely unknown. Here, we provide a brief overview of positron emission tomography (PET) applications that could advance current understanding of CNS pathophysiological alterations associated with SARS-CoV-2 infection., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Introduction: A sufficient dietary intake of the vitamin niacin is essential for normal cellular function. Niacin is transported into the cells by the monocarboxylate transporters: sodium-dependent monocarboxylate transporter (SMCT1 and SMCT2) and monocarboxylate transporter (MCT1). Despite the importance of niacin in biological systems, surprisingly, its in vivo biodistribution and trafficking in living organisms has not been reported. The availability of niacin radiolabelled with the short-lived positron emitting radionuclide carbon-11 ([ 11 C]niacin) would enable the quantitative in vivo study of this endogenous micronutrient trafficking using in vivo PET molecular imaging., Methods: [ 11 C]Niacin was synthesised via a simple one-step, one-pot reaction in a fully automated system using cyclotron-produced carbon dioxide ([ 11 C]CO 2 ) and 3-pyridineboronic acid ester via a copper-mediated reaction. [ 11 C]Niacin was administered intravenously in healthy anaesthetised mice placed in a high-resolution nanoScan PET/CT scanner. To further characterize in vivo [ 11 C]niacin distribution in vivo, mice were challenged with either niacin or AZD3965, a potent and selective MCT1 inhibitor. To examine niacin gastrointestinal absorption and body distribution in vivo, no-carrier-added (NCA) and carrier-added (CA) [ 11 C]niacin formulations were administered orally., Results: Total synthesis time including HPLC purification was 25 ± 1 min from end of [ 11 C]CO 2 delivery. [ 11 C]Niacin was obtained with a decay corrected radiochemical yield of 17 ± 2%. We report a rapid radioactivity accumulation in the kidney, heart, eyes and liver of intravenously administered [ 11 C]niacin which is consistent with the known in vivo SMCTs and MCT1 transporter tissue expression. Pre-administration of non-radioactive niacin decreased kidney-, heart-, ocular- and liver-uptake and increased urinary excretion of [ 11 C]niacin. Pre-administration of AZD3965 selectively decreased [ 11 C]niacin uptake in MCT1-expressing organs such as heart and retina. Following oral administration of NCA [ 11 C]niacin, a high level of radioactivity accumulated in the intestines. CA abolished the intestinal accumulation of [ 11 C]niacin resulting in a preferential distribution to all tissues expressing niacin transporters and the excretory organs., Conclusions: Here, we describe the efficient preparation of [ 11 C]niacin as PET imaging agent for probing the trafficking of nutrient demand in healthy rodents by intravenous and oral administration, providing a translatable technique to enable the future exploration of niacin trafficking in humans and to assess its application as a research tool for metabolic disorders (dyslipidaemia) and cancer., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Formamides are common motifs of biologically-active compounds (e.g. formylated peptides) and are frequently employed as intermediates to yield a number of other functional groups. A rapid, simple and reliable route to [carbonyl- 11 C]formamides would enable access to this important class of compounds as in vivo PET imaging agents., Results: A novel radiolabelling strategy for the synthesis of carbon-11 radiolabelled formamides ([ 11 C]formamides) is presented. The reaction proceeded with the conversion of a primary amine to the corresponding [ 11 C]isocyanate using cyclotron-produced [ 11 C]CO 2 , a phosphazene base (2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine, BEMP) and phosphoryl chloride (POCl 3 ). The [ 11 C]isocyanate was subsequently reduced to [ 11 C]formamide using sodium borohydride (NaBH 4 ). [ 11 C]Benzyl formamide was obtained with a radiochemical yield (RCY) of 80% in 15 min from end of cyclotron target bombardment and with an activity yield of 12%. This novel method was applied to the radiolabeling of aromatic and aliphatic formamides and the chemotactic amino acid [ 11 C]formyl methionine (RCY = 48%)., Conclusions: This study demonstrates the feasibility of 11 C-formylation of primary amines with the primary synthon [ 11 C]CO 2 . The reactivity is proportional to the nucleophilicity of the precursor amine. This novel method can be used for the production of biomolecules containing a radiolabelled formyl group.

The water-soluble vitamin biotin is essential for cellular growth, development, and well-being, but its absorption, distribution, metabolism, and excretion are poorly understood. This paper describes the radiolabeling of biotin with the positron emission tomography (PET) radionuclide carbon-11 ([ 11 C]biotin) to enable the quantitative study of biotin trafficking in vivo. We show that intravenously administered [ 11 C]biotin is quickly distributed to the liver, kidneys, retina, heart, and brain in rodents-consistent with the known expression of the biotin transporter-and there is a surprising accumulation in the brown adipose tissue (BAT). Orally administered [ 11 C]biotin was rapidly absorbed in the small intestine and swiftly distributed to the same organs. Preadministration of nonradioactive biotin inhibited organ uptake and increased excretion. [ 11 C]Biotin PET imaging therefore provides a dynamic in vivo map of transporter-mediated biotin trafficking in healthy rodents. This technique will enable the exploration of biotin trafficking in humans and its use as a research tool for diagnostic imaging of obesity/diabetes, bacterial infection, and cancer.

A novel carboxylation radiosynthesis methodology is described starting from cyclotron-produced [ 11 C]CO 2 and fluoride-activated silane derivatives. Six carbon-11 labelled carboxylic acids were obtained from their corresponding trimethylsilyl and trialkoxysilyl precursors in a one-pot labelling methodology. The radiochemical yields ranged from 19% to 93% within 12 minutes post [ 11 C]CO 2 delivery with a trapping efficiency of 21-89%.

Aim: The receptor for advanced glycation end products (RAGE) is a viable target for early Alzheimer's disease (AD) diagnosis using positron emission tomography (PET) as RAGE overexpression precedes Aβ plaque formation. The development of a carbon-11 analog of FPS-ZM1 (N-benzyl-4-chloro-N-cyclohexylbenzamide, [ 11 C]FPS-ZM1), possessing nanomolar affinity for RAGE, may enable the imaging of RAGE for early AD detection. Methodology & results: Herein we report an optimized [ 11 C]CO 2 -to-[ 11 C]CO chemical conversion for the synthesis of [ 11 C]FPS-ZM1 and in vitro brain autoradiography. The [ 11 C]CO 2 -to-[ 11 C]CO conversion via 11 C-silanecarboxylate derivatives was achieved with a 57% yield within 30 s from end of [ 11 C]CO 2 delivery. [ 11 C]FPS-ZM1 was obtained with a decay-corrected isolated radiochemical yield of 9.5%. Conclusion: [ 11 C]FPS-ZM1 distribution in brain tissues of wild-type versus transgenic AD model mice showed no statistically significant difference and high nondisplaceable binding.

Background: Glioblastoma multiform (GBM), a malignant brain tumour, has a very often poor prognosis. The therapeutic approach is represented by surgery followed by radiotherapy and chemotherapy. Hypoxia is a factor that causes a reduction of both radiotherapy and chemotherapy effectiveness in GBM and other cancers. Through the use of [ 64 Cu][Cu(ATSM)], a hypoxia-targeting positron emission tomography (PET) radiotracer, is possible to identify the presence of hypoxic areas within a lesion and therefore modulate the therapeutic approach according to the findings., Case Presentation: In this case report, we observed an increase of radiotracer uptake from early acquisition to late acquisition in hypoxia sites and high correlation between [ 64 Cu][Cu(ATSM) PET/CT results and expression of the hypoxia marker HIF-1α., Conclusions: [ 64 Cu][Cu(ATSM) PET/CT represents a valid opportunity to reveal in vivo hypoxic areas in GBM lesion which can guide clinicians on selecting GMB patient's therapeutic scheme.

Introduction: Primary aldosteronism accounts for 6-15% of hypertension cases, the single biggest contributor to global morbidity and mortality. Whilst ~50% of these patients have unilateral aldosterone-producing adenomas, only a minority of these have curative surgery as the current diagnosis of unilateral disease is poor. Carbon-11 radiolabelled metomidate ([ 11 C]MTO) is a positron emission tomography (PET) radiotracer able to selectively identify CYP11B1/2 expressing adrenocortical lesions of the adrenal gland. However, the use of [ 11 C]MTO is limited to PET centres equipped with on-site cyclotrons due to its short half-life of 20.4 min. Radiolabelling a fluorometomidate derivative with fluorine-18 (radioactive half life 109.8 min) in the para-aromatic position ([ 18 F]FAMTO) has the potential to overcome this disadvantage and allow it to be transported to non-cyclotron-based imaging centres., Methods: Two strategies for the one-step radio-synthesis of [ 18 F]FAMTO were developed. [ 18 F]FAMTO was obtained via radiofluorination via use of sulfonium salt (1) and boronic ester (2) precursors. [ 18 F]FAMTO was evaluated in vitro by autoradiography of pig adrenal tissues and in vivo by determining its biodistribution in rodents. Rat plasma and urine were analysed to determine [ 18 F]FAMTO metabolites., Results: [ 18 F]FAMTO is obtained from sulfonium salt (1) and boronic ester (2) precursors in 7% and 32% non-isolated radiochemical yield (RCY), respectively. Formulated [ 18 F]FAMTO was obtained with >99% radiochemical and enantiomeric purity with a synthesis time of 140 min from the trapping of [ 18 F]fluoride ion on an anion-exchange resin (QMA cartridge). In vitro autoradiography of [ 18 F]FAMTO demonstrated exquisite specific binding in CYP11B-rich pig adrenal glands. In vivo [ 18 F]FAMTO rapidly accumulates in adrenal glands. Liver uptake was about 34% of that in the adrenals and all other organs were <12% of the adrenal uptake at 60 min post-injection. Metabolite analysis showed 13% unchanged [ 18 F]FAMTO in blood at 10 min post-administration and rapid urinary excretion. In vitro assays in human blood showed a free fraction of 37.5%., Conclusions: [ 18 F]FAMTO, a new 18 F-labelled analogue of metomidate, was successfully synthesised. In vitro and in vivo characterization demonstrated high selectivity towards aldosterone-producing enzymes (CYP11B1 and CYP11B2), supporting the potential of this radiotracer for human investigation., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

A novel carbon-11 radiolabelling methodology for the synthesis of the dialkylcarbonate functional group has been developed. The method uses cyclotron-produced short-lived [ 11 C]CO 2 (half-life 20.4 min) directly from the cyclotron target in a one-pot synthesis. Alcohol in the presence of base trapped [ 11 C]CO 2 efficiently forming an [ 11 C]alkylcarbonate intermediate that subsequently reacted with an alkylchloride producing the di-substituted [ 11 C]carbonate (34% radiochemical yield, determined by radio-HPLC) in 5 minutes from the end of [ 11 C]CO 2 cyclotron delivery., Competing Interests: Conflicts of Interest The authors declare that there are no conflicts of interest regarding the publication of this paper.

Introduction: The development of clinically useful tracers for PET imaging is enormously challenging and expensive. The intranasal (IN) route of administration is purported to be a viable route for delivering drugs to the brain but has, as yet, not been investigated for the delivery of PET tracers. If the intranasal (IN) pathway presents a viable option, it extends the PET imaging field by increasing the number of tracers available for human use. Here we report the results of a rodent study testing the feasibility of the IN route to administer radiotracers for brain PET imaging., Methods: We used two different, well characterised, brain penetrant radiotracers, [ 18 F]fluorodeoxyglucose ([ 18 F]FDG) and [ 18 F]fallypride, and aimed to evaluate the pharmacokinetics after administration of the tracers via the intranasal route, and contrast this to intravenous administration. Image acquisition was carried out after tracer administration and arterial blood samples were collected at different time intervals, centrifuged to extract plasma and gamma counted. We hypothesised that [brain region]:[plasma] ratios would be higher via the intranasal route as there are two inputs, one directly from the nose to the brain, and another from the peripheral circulation. To assess the feasibility of using this approach clinically, we used these data to estimate radiation dosimetry in humans., Results: Contrary to our hypothesis, in case of both radiotracers, we did not see a higher ratio in the expected brain regions, except in the olfactory bulb, that is closest to the nose. It appears that the radiotracers move into the olfactory bulb region, but then do not progress further into other brain regions. Moreover, as the nasal cavity has a small surface area, the extrapolated dosimetry estimations for intranasal human imaging showed an unacceptably high level (15 mSv/MBq) of cumulative skin radiation exposure., Conclusions: Therefore, although an attractive route for brain permeation, we conclude that the intranasal route would present difficulties due to non-specific signal and radiation dosimetry considerations for brain PET imaging., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Human cytomegalovirus (HCMV) is an opportunistic pathogen causing a variety of severe viral infections, including irreversible congenital disabilities. Nowadays, HCMV infection is treated by inhibiting the viral DNA polymerase. However, DNA polymerase inhibitors have several drawbacks. An alternative strategy is to use compounds against the packaging machinery or terminase complex, which is essential for viral replication. Our discovery that raltegravir ( 1 ), a human immunodeficiency virus drug, inhibits the nuclease function of UL89, one of the protein subunits of the complex, prompted us to further develop terminase inhibitors. On the basis of the structure of 1 , a library of diketoacid (α,γ-DKA and β,δ-DKA) derivatives were synthesized and tested for UL89-C nuclease activity. The mode of action of α,γ-DKA derivatives on the UL89 active site was elucidated by using X-ray crystallography, molecular docking, and in vitro experiments. Our studies identified α,γ-DKA derivative 14 able to inhibit UL89 in vitro in the low micromolar range, making 14 an optimal candidate for further development and virus-infected cell assay., Competing Interests: The authors declare no competing financial interest.

No in vivo imaging biomarker currently exists for BACE, a drug target for Alzheimer's disease (AD). A strategy aiming to find a novel brain-penetrant positron emission tomography (PET) radiotracer for BACE1 led to the discovery of a highly potent and selective aminothiazine inhibitor, PF-06684511. This scaffold has been now evaluated as BACE1 PET radiotracer ([ 18 F]PF-06684511) after labeling with fluorine-18 ( 18 F), allowing its evaluation in non-human primates (NHP) as the first a brain-penetrant PET radiotracer for imaging BACE1 in vivo.

Cyclotron-produced carbon-11 is a highly valuable radionuclide for the production of positron emission tomography (PET) radiotracers. It is typically produced as relatively unreactive carbon-11 carbon dioxide ([ 11 C]CO 2 ), which is most commonly converted into a more reactive precursor for synthesis of PET radiotracers. The development of [ 11 C]CO 2 fixation methods has more recently enabled the direct radiolabelling of a diverse array of structures directly from [ 11 C]CO 2 , and the advantages afforded by the use of a loop-based system used in 11 C-methylation and 11 C-carboxylation reactions inspired us to apply the [ 11 C]CO 2 fixation "in-loop." In this work, we developed and investigated a new ethylene tetrafluoroethylene (ETFE) loop-based [ 11 C]CO 2 fixation method, enabling the fast and efficient, direct-from-cyclotron, in-loop trapping of [ 11 C]CO 2 using mixed DBU/amine solutions. An optimised protocol was integrated into a proof-of-concept in-loop flow radiosynthesis of N,N'-[ 11 C]dibenzylurea. This reaction exhibited an average 78% trapping efficiency and a crude radiochemical purity of 83% (determined by radio-HPLC), giving an overall nonisolated radiochemical yield of 72% (decay-corrected) within just 3 minutes from end of bombardment. This proof-of-concept reaction has demonstrated that efficient [ 11 C]CO 2 fixation can be achieved in a low-volume (150 μL) ETFE loop and that this can be easily integrated into a rapid in-loop flow radiosynthesis of carbon-11-labelled products. This new in-loop methodology will allow fast radiolabelling reactions to be performed using cheap/disposable ETFE tubing setup (ideal for good manufacturing practice production) thereby contributing to the widespread usage of [ 11 C]CO 2 trapping/fixation reactions for the production of PET radiotracers., (© 2017 The Authors. Journal of Labelled Compounds and Radiopharmaceuticals Published by John Wiley & Sons, Ltd.)

The receptor for advanced glycation endproducts (RAGE) is an ubiquitous, transmembrane, immunoglobulin-like receptor that exists in multiple isoforms and binds to a diverse range of endogenous extracellular ligands and intracellular effectors. Ligand binding at the extracellular domain of RAGE initiates a complex intracellular signaling cascade, resulting in the production of reactive oxygen species (ROS), immunoinflammatory effects, cellular proliferation, or apoptosis with concomitant upregulation of RAGE itself. To date, research has mainly focused on the correlation between RAGE activity and pathological conditions, such as cancer, diabetes, cardiovascular diseases, and neurodegeneration. Because RAGE plays a role in many pathological disorders, it has become an attractive target for the development of inhibitors at the extracellular and intracellular domains. This review describes the role of endogenous RAGE ligands/effectors in normo- and pathophysiological processes, summarizes the current status of exogenous small-molecule inhibitors of RAGE and concludes by identifying key strategies for future therapeutic intervention.

The development of a fast and novel methodology to generate carbon-11 carbon monoxide ([ 11 C]CO) from cyclotron-produced carbon-11 carbon dioxide ([ 11 C]CO 2 ) mediated by a fluoride-activated disilane species is described. This methodology allows up to 74 % conversion of [ 11 C]CO 2 to [ 11 C]CO using commercially available reagents, readily available laboratory equipment and mild reaction conditions (room temperature). As proof of utility, radiochemically pure [carbonyl- 11 C]N-benzylbenzamide was successfully synthesized from produced [ 11 C]CO in up to 74 % radiochemical yield (RCY) and >99 % radiochemical purity (RCP) in ≤10 min from end of [ 11 C]CO 2 delivery., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The development of a novel electrochemical methodology to generate carbon-11 carbon monoxide ([ 11 C]CO) from cyclotron-produced carbon-11 carbon dioxide ([ 11 C]CO 2 ) using Ni(cyclam) and Zn(cyclen) complexes is described. This methodology allows up to 10% yields of [ 11 C]CO from [ 11 C]CO 2 . Produced [ 11 C]CO was subsequently converted to [ 11 C]N-benzylbenzamide under mild conditions with a radiochemical purity (RCP) of >98%.

An accurate in vivo measure of myelin content is essential to deepen our insight into the mechanisms underlying demyelinating and dysmyelinating neurological disorders, and to evaluate the effects of emerging remyelinating treatments. Recently [(11)C]PIB, a positron emission tomography (PET) tracer originally conceived as a beta-amyloid marker, has been shown to be sensitive to myelin changes in preclinical models and humans. In this work, we propose a reference-region methodology for the voxelwise quantification of brain white-matter (WM) binding for [(11)C]PIB. This methodology consists of a supervised procedure for the automatic extraction of a reference region and the application of the Logan graphical method to generate distribution volume ratio (DVR) maps. This approach was assessed on a test-retest group of 10 healthy volunteers using a high-resolution PET tomograph. The [(11)C]PIB PET tracer binding was shown to be up to 23% higher in WM compared with gray matter, depending on the image reconstruction. The DVR estimates were characterized by high reliability (outliers <1%) and reproducibility (intraclass correlation coefficient (ICC) >0.95). [(11)C]PIB parametric maps were also found to be significantly correlated (R(2)>0.50) to mRNA expressions of the most represented proteins in the myelin sheath. On the contrary, no correlation was found between [(11)C]PIB imaging and nonmyelin-associated proteins.

A novel chemical methodology is described for the conversion of [(11)C]CO2 to [(11)C]CO. Diphenylmethyl silanes trap [(11)C]CO2 and release [(11)C]CO rapidly when triggered by TBAF. Released [(11)C]CO was used to produce [(11)C]N-benzylbenzamide and AMPA receptor ligand, [(11)C], in radiochemical yields >90% within 6 min from [(11)C]CO2 production.

Background: The main pathogenic event of prion disorders has been identified in the deposition of the disease-associated prion protein (PrP(Sc)), which is accompanied by metal dyshomeostasis., Results: The multitarget-directed ligand 1, designed by combining a heteroaromatic prion recognition motif to an 8-hydroxyquinoline metal chelator, has been developed as a potential antiprion disease-modifying agent. Importantly, 1 was found to effectively clear PrP(Sc) from scrapie-infected cells, and, at the same time, inhibit metal-induced prion aggregation and reactive oxygen species generation. 1 was also characterized in terms of pharmacokinetic properties in a preliminary in vitro investigation., Conclusion: Compound 1 has emerged as a suitable lead candidate against prion diseases and as a good starting point for a further optimization process.

Prion diseases (PrDs) are fatal neurodegenerative disorders, for which no effective therapeutic and diagnostic tools exist. The main pathogenic event has been identified as the misfolding of a disease-associated prion protein. Nevertheless, pathogenesis seems to involve an intricate array of concomitant processes. Thus, it may be unlikely that drugs acting on single targets can effectively control PrDs. In addition, diagnosis occurs late in the disease process, by which point it is difficult to determine a successful therapeutic intervention. In this context, multitarget ligands (MTLs) and theranostic ligands (TLs) emerge for their potential to effectively cure and diagnose PrDs. In this review, we discuss the medicinal chemistry challenges of identifying novel MTLs and TLs against PrDs, and envision their impact on prion drug discovery.

Prion diseases are rare neurodegenerative diseases characterized by the conversion of the prion protein from its native state (PrP(C)) towards the so-called 'scrapie form', rich in β-strands. Computational approaches, here briefly reviewed, are instrumental to understand the intrinsic instability of PrP(C) fold and how the latter is affected by mutations, binding of metals as well as by different environmental conditions, such as pH and temperature. These studies also provide a structural basis for the binding of anti-prion compounds, which may block the conversion to the scrapie form and, consequently, may inhibit fibril formation.

Mutations in the prion protein (PrP) can cause spontaneous prion diseases in humans (Hu) and animals. In transgenic mice, mutations can determine the susceptibility to the infection of different prion strains. Some of these mutations also show a dominant-negative effect, thus halting the replication process by which wild type mouse (Mo) PrP is converted into Mo scrapie. Using all-atom molecular dynamics (MD) simulations, here we studied the structure of HuPrP, MoPrP, 10 Hu/MoPrP chimeras, and 1 Mo/sheepPrP chimera in explicit solvent. Overall, ∼2 μs of MD were collected. Our findings suggest that the interactions between α1 helix and N-terminal of α3 helix are critical in prion propagation, whereas the β2-α2 loop conformation plays a role in the dominant-negative effect. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:4 .

Metadynamics is emerging as a useful free energy method in physics, chemistry and biology. Recently, it has been applied also to investigate ligand binding to biomolecules of pharmacological interest. Here, after introducing the basic idea of the method, we review applications to challenging targets for pharmaceutical intervention. We show that this methodology, especially when combined with a variety of other computational approaches such as molecular docking and/or molecular dynamics simulation, may be useful to predict structure and energetics of ligand/target complexes even when the targets lack a deep binding cavity, such as DNA and proteins undergoing fibrillation in neurodegenerative diseases. Furthermore, the method allows investigating the routes of molecular recognition and the associated binding energy profiles, providing a molecular interpretation to experimental data.