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Abstract

Trace amines (TAs) are endogenous neuromodulators that play a functional role in the synaptic transmission within central nervous system (CNS), targeting trace amine-associated receptors (TAARs). Starting from our previous computational studies on TAAR1 and TAAR5 interactions with the unselective ligand 3-iodothyronamine (T1AM), we investigated the functional activity at murine and human TAAR1 and murine TAAR5 receptors of twenty-seven biguanide-based derivatives, including six newly synthesized compounds. Phenyl (BIG2, BIG4, BIG8 and BIG22) or benzyl (BIG10-BIG16) biguanides were found to be selective murine and human TAAR1 agonists with potencies in nanomolar or low micromolar range, respectively. In particular, compounds BIG2 and BIG12-BIG14 were the most promising and they could be considered valuable lead compounds worthy of further investigations.

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... In this scenario, we started the study of new TAAR1 ligands, exploring phenyl or benzyl biguanides (SET1, Figure 2) as novel chemotypes [29] that share a selective murine and human TAAR1 agonism behavior with respect to murine TAAR5. In particular, the SET1 derivatives were endowed with higher specificity towards the mouse receptor (nanomolar range) with respect to the human orthologue (low micromolar range). ...
... In particular, the SET1 derivatives were endowed with higher specificity towards the mouse receptor (nanomolar range) with respect to the human orthologue (low micromolar range). Molecular docking studies at the m/hTAAR1 receptors enlightened the relevance of the ligand's basic core in forming a key salt bridge with a conserved m/hTAAR1 D3.32 aspartic acid, and of the aromatic moiety in engaging π-π stacking and van der Waals contacts with a number of recurrent aromatic residues characterizing the receptor cavity [1, 29,30]. In this context, we recently reported the development of two quantitative structure-activity relationship (QSAR) models exploring the agonism ability offered by different chemotypes towards murine and human TAAR1, including the aforementioned SET1 derivatives and the most potent agonists disclosed by Roche [31] (Supplementary data S1). ...
... As the last step in this work, we performed molecular docking studies of the newly developed amidine-containing derivatives exploiting our hTAAR1 model [29,31]. Specifically, we focused on the most promising derivatives, 1, 2, 6 and 15, and on β-PEA as the reference compound. ...
Article
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Targeting trace amine-associated receptor 1 (TAAR1) receptor continues to offer an intriguing opportunity to develop innovative therapies in different pharmacological settings. Pursuing our endeavors in the search for effective and safe human TAAR1 (hTAAR1) ligands, we synthesized a new series of 1-amidino-4-phenylpiperazine derivatives (1-16) based on the application of a combined pharmacophore model/scaffold simplification strategy for an in-house series of biguanide-based TAAR1 agonists. Most of the novel compounds proved to be more effective than their prototypes, showing nanomolar EC50 values in functional activity at hTAAR1 and low general cytotoxicity (CC50 > 80 µM) when tested on the Vero-76 cell line. In this new series, the main determinant for TAAR1 agonism ability appears to result from the appropriate combination between the steric size and position of the substituents on the phenyl ring rather than from their different electronic nature, since both electron-withdrawing and electron donor groups are permitted. In particular, the ortho-substitution seems to impose a more appropriate spatial geometry to the molecule that entails an enhanced TAAR1 potency profile, as experienced, in the following order, by compounds 15 (2,3-diCl, EC50 = 20 nM), 2 (2-CH3, EC50 = 30 nM), 6 (2-OCH3, EC50 = 93 nM) and 3 (2-Cl, EC50 = 160 nM). Apart from the interest in them as valuable leads for the development of promising hTAAR1 agonists, these simple small molecules have further allowed us to identify the minimal structural requirements for producing an efficient hTAAR1 targeting ability.
... More recently, virtual screening strategies were deployed to discover new TAAR1-targeting chemotypes, diversifying the typical 3-iodothyronamine structure [35,36]. As a result, Lam and coworkers outlined Guanabenz (23) and closely related benzylidene aminoguanidine (22)(23)(24) derivatives as mTAAR1 agonists (Figure 1). ...
... As already mentioned, the quest to develop novel TAAR1 ligands was mainly obstructed by selectivity and species-specificity caveats [39][40][41][42]. In particular, the different responsiveness of compounds between mTAAR1 and hTAAR1, highlights shortcomings in using murine models in the development of new hTAAR1 agents, as verified even in case of our in-house biguanide series [36]. ...
... In this context, preliminary differences in the TAAR1 binding modes of the endogenous ligand T1AM as well as of biguanide agonists towards the two species were observed exploiting the inhouse homology models of both h/mTAAR1 [36,41,42]. Concerning biguanides, compound 33 (mTAAR1 pEC50 = 7.44, hTAAR1 pEC50 = 5.92) assumed a much more extended and folded conformation at the mTAAR1 and hTAAR1 cavities, respectively. ...
Article
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The design of novel chemical classes acting towards several G-protein-coupled receptors (GPCRs) represents a leading strategy in drug discovery, aimed at deriving effective and safe candidates for further assessment. During the last years, TAAR1 arose as a promising druggable target in medicinal chemistry, being of interest in the treatment of several pathologies, such as neuropsychiatric disorders, type 2 diabetes and obesity. Nevertheless, the limited number of known potent and selective ligands and the species-specificity responsiveness exhibited by those derivatives nowadays available make the discovery of novel compounds a challenging task. Herein, we discuss the development of two quantitative-structure activity relationship (QSAR) models around the agonism ability experienced by different chemo-types toward murine and human TAAR1 (m/hTAAR1) with the aim at deciphering some clues involved in their species-specificity responsiveness. Qualitatively, these information were evaluated guiding for the synthesis of novel ligands, which proved to feature selective agonism ability with respect to the mTAAR1 and hTAAR1 orthologues.
... The prediction of the absorption, distribution, metabolism, excretion and toxicity properties (ADMET) properties was performed using the Advanced Chemistry Development Percepta platform (www.acdlabs.com). Any ADMET descriptor was evaluated by Percepta based on training libraries implemented in the software, which include a consistent pool of molecules whose pharmacokinetic and toxicity profiles are experimentally known [32,33]. ...
... Compounds 37-51 were synthesized by a convergent approach based on the coupling between the 2-heteroarylphenoxyethylamines (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) and the tosylate 36 [25], as depicted in Figure 3. ...
... With the sole exception of 35, the 2-heteroaryl-phenoxyethylamines (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) were obtained via Suzuki crosscoupling, as previously described [26]. Briefly, the furan or thiophene derivatives 4-7 were synthesized with good/excellent yields starting from the commercially available boronic acids and the nitrile intermediate 1 (Path A). ...
Article
Future Med Chem. 2018 Jul 25. doi: 10.4155/fmc-2018-0107. [Epub ahead of print] Synthesis and biological evaluation of 1,3-dioxolane-based 5-HT1A receptor agonists for CNS disorders and neuropathic pain. Franchini S(1), Bencheva LI(1), Battisti UM(1), Tait A(1), Sorbi C(1), Fossa P(2), Cichero E(2), Ronsisvalle S(3), Aricò G(3), Denora N(4), Iacobazzi RM(5), Cilia A(6), Pirona L(6), Brasili L(1). Author information: (1)Dipartimento di Scienze della Vita, Università degli Studi di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy. (2)Dipartimento di Farmacia, Università degli Studi di Genova, Viale Benedetto XV 3, 16132 Genova, Italy. (3)Dipartimento di Scienze del Farmaco Sezione di Chimica Farmaceutica e Sezione di Farmacologia e Tossicologia, Università degli Studi di Catania, Viale Andrea Doria 6, 95125, Catania, Italy. (4)Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari "Aldo Moro", Via E. Orabona 4, I-70125 Bari, Italy. (5)Istituto tumori IRCCS "Giovanni Paolo II", Via O. Flacco, 65, 70124 Bari, Italy. (6)Divisione Ricerca e Sviluppo, Recordati S.p.A., Via Civitali 1, 20148 Milano, Italy. AIM: Targeting 5-HT1A receptor (5-HT1AR) as a strategy for CNS disorders and pain control. METHODOLOGY: A series of 1,3-dioxolane-based 2-heteroaryl-phenoxyethylamines was synthesized by a convergent approach and evaluated at α1-adrenoceptors and 5-HT1AR by binding and functional experiments. Absorption, distribution, metabolism, excretion and toxicity prediction studies were performed to explore the drug-likeness of the compounds. RESULTS & CONCLUSION: The most promising compound, the pyridin-4-yl derivative, emerged as a potent and selective 5-HT1AR agonist (pKi = 9.2; pD2 = 8.83; 5-HT1A/α1 = 135). In vitro it was able to permeate by passive diffusion MDCKII-MDR1 monolayer mimicking the blood-brain barrier and showed promising neuroprotective activity. DOI: 10.4155/fmc-2018-0107 PMID: 30043643
... For instance, selectivity for the β-phenyl moiety is enhanced by its accommodation near residue 7.39 in the human and rat receptors, but not the mouse orthologue, wherein the phenolic portion of Y7.39 occludes this space (Tan et al., 2009). High-throughput virtual docking simulations with such homology modelling of TAAR1 gave way to new avenues beyond the scaffolds of the endogenous ligands Francesconi et al., 2020;Lam et al., 2015;Tonelli et al., 2017). The new chemotypes evaluated (e.g., multi-cyclic biguanide derivatives) confirm that the pharmacophoric requirements are a cationic moiety (typically an amine group) and an aromatic/heteroaromatic ring separated by a variable spacer (Guariento et al., 2018;Tonelli et al., 2017). ...
... High-throughput virtual docking simulations with such homology modelling of TAAR1 gave way to new avenues beyond the scaffolds of the endogenous ligands Francesconi et al., 2020;Lam et al., 2015;Tonelli et al., 2017). The new chemotypes evaluated (e.g., multi-cyclic biguanide derivatives) confirm that the pharmacophoric requirements are a cationic moiety (typically an amine group) and an aromatic/heteroaromatic ring separated by a variable spacer (Guariento et al., 2018;Tonelli et al., 2017). The importance of the positive charge is in forming a salt-bridge with the conserved D3.32 residue . ...
... and 4) What are the necessary conditions for TAAR1 heteromerization, and are these conditions met by receptors other than D2R? With the advent of fluorescence/bioluminescence resonance energy transfer (FRET/BRET)-based biosensors (Olsen et al., 2020;Xin et al., 2019), the power of high-throughput ligand-docking simulations (Guariento et al., 2018;Lam et al., 2015;Tonelli et al., 2017), and the increasingly feasible study of conformational dynamics (Nyon et al., 2015), the answers to these questions will revolutionize the future of TAAR1 drug discovery and the treatment of psychiatric disorders at large. Finally, future research will need to determine whether the efficacy offered by TAAR agonists is superior to existing treatment options on either multi-dimensionally assessed clinician-rated outcomes and/or patient-reported outcomes. ...
Article
There is a need for innovation with respect to therapeutics in psychiatry. Available evidence indicates that the trace amine-associated receptor 1 (TAAR1) agonist SEP-363856 is promising, as it improves measures of cognitive and reward function in schizophrenia. Hedonic and cognitive impairments are transdiagnostic and constitute major burdens in mood disorders. Herein, we systematically review the behavioural and genetic literature documenting the role of TAAR1 in reward and cognitive function; and propose a mechanistic model of TAAR1's functions in the brain. Notably, TAAR1 activity confers antidepressant-like effects, enhances attention and response inhibition, and reduces compulsive reward seeking without impairing normal function. Further characterization of the mechanisms responsible suggests ion-homeostatic, metabolic, neurotrophic, and anti-inflammatory enhancements in the limbic system. Multiple lines of evidence establish the viability of TAAR1 as a biological target for the treatment of mood disorders.
... For instance, selectivity for the β-phenyl moiety is enhanced by its accommodation near residue 7.39 in the human and rat receptors, but not the mouse orthologue, wherein the phenolic portion of Y7.39 occludes this space (Tan et al., 2009). High-throughput virtual docking simulations with such homology modeling of TAAR1 gave way to new avenues beyond the scaffolds of the endogenous ligands Cichero et al., 2014;Lam et al., 2015;Tonelli et al., 2017). The new chemotypes evaluated (e.g., multi-cyclic biguanide derivatives) confirm that the pharmacophoric requirements are a cationic moiety (typically an amine) and an aromatic/heteroaromatic ring separated by a variable spacer (Guariento et al., 2018;Tonelli et al., 2017). ...
... High-throughput virtual docking simulations with such homology modeling of TAAR1 gave way to new avenues beyond the scaffolds of the endogenous ligands Cichero et al., 2014;Lam et al., 2015;Tonelli et al., 2017). The new chemotypes evaluated (e.g., multi-cyclic biguanide derivatives) confirm that the pharmacophoric requirements are a cationic moiety (typically an amine) and an aromatic/heteroaromatic ring separated by a variable spacer (Guariento et al., 2018;Tonelli et al., 2017). The importance of the positive charge is in forming a saltbridge with the conserved D3.32 residue, and the lengths of either rigid or rotating spacers must allow for the cyclic moiety to stabilize near 7.39 and 7.43 (Tan et al., 2009;Tonelli and Cichero, 2020). ...
... Some of the key remaining questions are 1) How does TAAR1 affect CREB-mediated transcription in the different populations/cell-types of the brain?, 2) Which signal transduction cascades are most relevant to which symptoms?, 3) Where in the brain is TAAR1 expressed as a monomer and where is it expressed as a heteromer?, and 4) What are the necessary conditions for TAAR1 heteromerization, and are these conditions met by receptors other than D2R? With the advent of fluorescence resonance energy transfer (FRET)-based biosensors (Olsen et al., 2020;Xin et al., 2019), the power of high-throughput liganddocking simulations (Guariento et al., 2018;Lam et al., 2015;Tonelli et al., 2017), and the increasingly feasible study of conformational dynamics (Nyon et al., 2015), the answers to these questions will revolutionize the future of TAAR1 drug discovery and the treatment of psychiatric disorders at large. ...
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ABSTRACT: There is a need for innovation with respect to therapeutics in psychiatry. Available evidence indicates that the trace amine-associated receptor 1 (TAAR1) agonist SEP-363856 is promising, as it improves measures of cognitive and reward function in schizophrenia. Hedonic and cognitive impairments are transdiagnostic and constitute major burdens in mood disorders. Herein, we systematically review the behavioural and genetic literature documenting the role of TAAR1 in reward and cognitive function; and propose a mechanistic model of TAAR1's functions in the brain. Notably, TAAR1 activity confers antidepressant-like effects, enhances attention and response inhibition, and reduces compulsive reward seeking without impairing normal function. Further characterization of the mechanisms responsible suggests ion-homeostatic, metabolic, neurotrophic, and anti-inflammatory enhancements in the limbic system. Multiple lines of evidence establish the viability of TAAR1 as a biological target for the treatment of mood disorders. Free access to published full text: https://authors.elsevier.com/c/1dovsY3M3Wc3u
... Recently, higher reaction temperatures and shorter reaction times were reported by Tonelli et al. who described the preparation of different cycloalkyl-and benzylbiguanides with relatively good yields (69-84%) after only 1 h of fusion at 180-200 °C (Scheme 3B) [18]. ...
... As a representative example, Böttcher et al. recently described the addition of 1,3-diaminobenzene to two equivalents of cyanoguanidine at low pH in aqueous hydrochloric acid to produce the corresponding bisbiguanide with moderate yield (Scheme 6A) [20]. A similar approach was reported by van Kuijk et al. who performed the addition of an ali-Scheme 3: Synthesis of biguanides by the direct fusion of cyanoguanidine and amine hydrochlorides [17,18]. ...
Article
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Biguanide is a unique chemical function, which has attracted much attention a century ago and is showing resurgent interest in recent years after a long period of dormancy. This class of compounds has found broad applications such as reaction catalysts, organic strong bases, ligands for metal complexation, or versatile starting materials in organic synthesis for the preparation of nitrogen-containing heterocycles. Moreover, biguanides demonstrate a wide range of biological activities and some representatives are worldwide known such as metformin, the first-line treatment against type II diabetes, or chlorhexidine, the gold standard disinfectant and antiseptic. Although scarcely represented, the number of "success stories" with biguanide-containing compounds highlights their value and their unexploited potential as future drugs in various therapeutic fields or as efficient metal ligands. This review provides an extensive and critical overview of the synthetic accesses to biguanide compounds, as well as their comparative advantages and limitations. It also underlines the need of developing new synthetic methodologies to reach a wider variety of biguanides and to overcome the underrepresentation of these compounds.
... Recently, a number of highly selective TAAR1 agonists and partial agonists with different chemical scaffolds have been developed and synthesized [10][11][12][13][14][15][16][17]. Cichero et al. proposed some activated hTAAR1's key residues responsible for its agonist recognition and identified several Abbreviations: mTAAR1, mouse trace amine-associated receptor; hTAAR1, human trace amine-associated receptor; EPPTB, N-(3-ethoxy-phenyl)-4-pyrrolidin-1-yl-3-trifluoromethyl-benzamide; TM, transmembrane; ICL, intracellular loop; ECL, extracellular loop; SID, simulation interaction diagram; RMSD, root mean square deviation; PRCG, Polak-Ribier conjugate gradient. ...
Article
Trace amine-associated receptor 1 (TAAR1) plays a critical role in regulating monoaminergic activity. EPPTB is the only known selective potent antagonist of the mouse (m) TAAR1 presently, while it was shown to be weak at antagonizing human (h) TAAR1. The lack of high-resolution structure of TAAR1 hinders the understanding of the differences in the interaction modes between EPPTB and m/hTARR1. The purpose of this study is to probe these interaction modes using homology modeling, molecular docking, molecular dynamics (MD) simulations, and molecular mechanics-generalized Born surface area (MM-GBSA) binding energy calculations. Eight populated conformers of hTAAR1-EPPTB complex were observed during the MD simulations and could be used in structure-based virtual screening in future. The MM-GBSA binding energy of hTAAR1-EPPTB complex (−96.5 kcal/mol) is larger than that of mTAAR1-EPPTB complex (−106.7 kcal/mol), which is consistent with the experimental finding that EPPTB has weaker binding affinity to hTAAR1. The several residues in binding site of hTAAR1 (F1544.56, T1945.42 and I2907.39) are different from these of mTAAR1 (Y1534.56, A1935.42 and Y2877.39), which might contribute to the binding affinity difference. Our docking analysis on another hTAAR1 antagonist Compound 3 has found that 1). this compound binds in different pockets of our mTAAR1 and hTAAR1 homology models with a slightly stronger binding affinity to hTAAR1; 2). both antagonists bind to a very similar pocket of hTAAR1.
... In addition, other groups have described ligands based on 3iodothyronamine (Chiellini et al., 2015) and a diphenylmethane scaffold (Chiellini et al., 2016) that possess nanomolar EC 50 values for mouse TAAR1 in functional assays. Homology modelling of human TAAR1 has also recently been developed (Cichero, Espinoza, Gainetdinov, Brasili, & Fossa, 2013), and this has identified a variety of chemical scaffolds showing both agonist and antagonist activity (Cichero et al., 2014), including a series of biguanide derivatives with nanomolar agonist potency at human TAAR1 (Tonelli, Espinoza, Gainetdinov, & Cichero, 2017). The development of such in silico models has also begun to shed light on the atomic basis of both the broad ligand tuning (Kleinau et al., 2011) and species differences in ligand binding to TAAR1 (Reese et al., 2014;Tan et al., 2009). ...
Article
Full-text available
The discovery in 2001 of a G protein-coupled receptor family, subsequently termed trace amine-associated receptors (TAAR), triggered a resurgence of interest in so-called trace amines. Initial optimism quickly faded, however, as the TAAR family presented a series of challenges preventing the use of standard medicinal chemistry and pharmacology technologies. Consequently the development of basic tools for probing TAAR and translating findings from model systems to humans has been problematic. Despite these challenges the last 5 years have seen considerable advances, in particular with respect to TAAR1, which appears to function as an endogenous rheostat, maintaining central neurotransmission within defined physiological limits, in part through receptor heterodimerization yielding biased signaling outputs. Regulation of the dopaminergic system is particularly well understood and clinical testing of TAAR1 directed ligands for schizophrenia and psychiatric disorders have begun. In addition, pre-clinical animal models have identified TAAR1 as a novel target for drug addiction and metabolic disorders. Growing evidence also suggests a role for TAARs in regulating immune function. This review critically discusses the current state of TAAR research, highlighting recent developments and focussing on human TAARs, their functions, and clinical implications. Current gaps in knowledge are identified, along with the research reagents and translational tools still required for continued advancement of the field. Through this, a picture emerges of an exciting field on the cusp of significant developments, with the potential to identify new therapeutic leads for some of the major unmet medical needs in the areas of neuropsychiatry and metabolic disorders.
... Recent synthetic efforts were aimed to discover new TAAR1-targeting chemotypes, relying on computationally driven virtual screenings [95]. In this context, we reported our work developed on the basis of homology modeling and molecular docking calculations of the endogenous ligand T 1 AM. ...
Article
G-protein-coupled receptors represent main targets of several clinically relevant drugs, playing nowadays a leading part for further drug discovery process. Trace amine-associated receptor's family (TAARs) assumed an intriguing role as druggable target in medicinal chemistry, being TAAR1 the most investigated. Indeed, related ligands proved to be intertwined in several circuits involved in pathological pathways or therapeutic routes. Herein, we highlight relevant efforts in the search of novel agonists, focusing on responsiveness featured by different chemotypes toward rodent and human TAAR1, in order to explore species-specificity preferences. We also discuss the main strategies guiding so far the design of new TAAR1 agonists, giving a perspective of the structure-based methodologies aimed at deriving new insights for more potent and selective derivatives.
... Finally, the reliability of the selected docking poses was assessed using a short ~1 ps run of molecular dynamics (MD) at constant temperature, followed by an all-atom energy minimization (LowModeMD implemented in MOE software). This kind of module allowed to perform an exhaustive conformational analysis of the ligand-receptor binding site complex, as we previously discussed about other case studies [21,40,41]. analyzed and discussed all the results; M.T., L.N., E.C. and F.G. wrote the paper. ...
Article
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Recently we identified cycloguanil-like dihydrotriazine derivatives, which provided host-factor directed antiviral activity against influenza viruses and respiratory syncytial virus (RSV), by targeting the human dihydrofolate reductase (hDHFR) enzyme. In this context we deemed interesting to further investigate the structure activity relationship (SAR) of our first series of cycloguanil-like dihydrotriazines, designing two novel azaspiro dihydrotriazine scaffolds. The present study allowed the exploration of the potential chemical space, around these new scaffolds, that are well tolerated for maintaining the antiviral effect by means of interaction with the hDHFR enzyme. The new derivatives confirmed their inhibitory profile against influenza viruses, especially type B. In particular, the two best compounds shared potent antiviral activity (4: EC50 = 0.29 μM; 6: EC50 = 0.19 μM), which was comparable to that of zanamivir (EC50 = 0.14 μM), and better than that of ribavirin (EC50 = 3.2 μM). In addition, these two compounds proved to be also effective against RSV (4: EC50 = 0.40 μM, SI ≥ 250; 6: EC50 = 1.8 μM, SI ≥ 56), surpassing the potency and selectivity index (SI) of ribavirin (EC50 = 5.8 μM, SI > 43). By a perspective of these results, the above adequately substituted azaspiro dihydrotriazines may represent valuable hit compounds worthy of further structural optimization to develop improved host DHFR-directed antiviral agents.
... Regarding the design of a specific synthetic ligand with high selectivity and potency on TAAR1, biguanidederivatives are attractive ligands. Quantitative structureactivity relationship (QSAR) studies allowed the rational design of novel biguanides, and the synthesis of new piperazine-derivatives was in line with the QSAR results [25,26]. ...
Article
Albeit cholinergic depletion remains the key event in Alzheimer’s Disease (AD), recent information describes stronger links between monoamines (trace amines, catecholamines, histamine, serotonin, and melatonin) and AD than those known in the past century. Therefore, new drug design strategies focus efforts to translate the scope on these topics and to offer new drugs which can be applied as therapeutic tools in AD. In the present work, we reviewed the state-of-art regarding genetic, neuropathology and neurochemistry of AD involving monoamine systems. Then, we compiled the effects of monoamines found in the brain of mammals as well as the reported effects of their derivatives and some structure-activity relationships. Recent derivatives have triggered exciting effects and pharmacokinetic properties in both murine models and humans. In some cases, the mechanism of action is clear, essentially through the interaction on G-protein-coupled receptors as revised in this manuscript. Additional mechanisms are inhibition of enzymes for their biotransformation, regulation of free-radicals in the central nervous system and others for the found effects on Tau phosphorylation or amyloid-beta accumulation. All these data make the monoamines and their derivatives attractive potential elements for AD therapy.
... Mor has appeared over half a century and preliminarily verified the effectiveness in the treatment of numerous viral infection, including hepatitis C, influenza symptoms, mumps disease, varicella zoster, and tobacco mosaic virus (Gasparini, Amicizia, Lai, Bragazzi, & Panatto, 2014;Magri et al., 2015;Sheppard, 1993), but the pharmacological mechanism of antiviral effects is rarely reported. In contrast, most studies about Mor only were focused on the content determination, physical properties and derivatives synthesis (Skrzypek, 2011;Tonelli, Espinoza, Gainetdinov, & Cichero, 2017;Zhan, Zhang, Li, & Du, 2011). The another chemical, ribavirin (Rib), is effective in the treatment of a large amounts of viruses in aquaculture, such as nervous necrosis virus, infectious pancreatic necrosis virus, viral haemorrhagic septicaemia virus, chum salmon reovirus, GCRV and infectious hematopoietic necrosis virus (Marroquí, Estepa, & Perez, 2007;Morick & Saragovi, 2017;Zhu, Liu, Ling, & Wang, 2015). ...
Article
Our previous studies have verified that moroxydine hydrochloride (Mor) could inhibit replication of grass carp reovirus (GCRV) and suppress apoptosis of Ctenopharyngodon idella kidney cells, but be lack of information whether exists on antiviral activity in vivo. The paper was undertaken to explore the antiviral response of Mor against GCRV in grass carp and investigate the safety of drug for aquatic organisms. The results showed that injection treatment of Mor could more effectively inhibit GCRV replication than immersion administration. All the RNA systheses of vp3 and vp6 on day 7 in head kidney, gill, hepatopancreas and dorsal muscle in the Mor injection group were lesser than 0.07‐fold than that of in control group. And the GCRV‐inducing grass carp mortality was effectively controlled within 7 days post Mor injection therapy. Additionally, the reduction of superoxide dismutase activity, total antioxidant capacity and catalase activity in serum was effectively controlled by Mor. Moreover, drug safety assessment results showed that 500 mg/L of Mor was safe to C. idella, Bacillus subtilis, Chlorella vulgaris and Tetrahymena thermophila, which was far higher than the therapeutic concentration. The present study proved Mor as harmless formulations or products had potential value in the control of GCRV in aquaculture, with the advantage of super in vivo antiviral activity and environmental safety.
... This represents a conformational search method that uses implicit vibrational analysis to focus a MD trajectory along the low-mode vibrations [41][42][43]. This has the effect of searching for minima along the valleys and troughs on the potential energy surface, thereby performing an exhaustive conformational analysis of the ligand-receptor binding site complex, as we previously discussed about other case studies [44][45][46]. ...
Article
Full-text available
Respiratory RNA viruses are responsible for recurrent acute respiratory illnesses that still represent a major medical need. Previously we developed a large variety of benzimidazole derivatives able to inhibit these viruses. Herein, two series of (thio)semicarbazone- and hydrazone-based benzimidazoles have been explored, by derivatizing 5-acetyl benzimidazoles previously reported by us, thereby evaluating the influence of the modification on the antiviral activity. Compounds 6, 8, 16 and 17, bearing the 5-(thio)semicarbazone and 5-hydrazone functionalities in combination with the 2-benzyl ring on the benzimidazole core structure, acted as dual inhibitors of influenza A virus and human coronavirus. For respiratory syncytial virus (RSV), activity is limited to the 5-thiosemicarbazone (25) and 5-hydrazone (22) compounds carrying the 2-[(benzotriazol-1/2-yl)methyl]benzimidazole scaffold. These molecules proved to be the most effective antiviral agents, able to reach the potency profile of the licensed drug ribavirin. The molecular docking analysis explained the SAR of these compounds around their binding mode to the target RSV F protein, revealing the key contacts for further assessment. The herein-investigated benzimidazole-based derivatives may represent valuable hit compounds, deserving subsequent structural improvements towards more efficient antiviral agents for the treatment of pathologies caused by these human respiratory viruses.
... Up to now, exploiting computational methods for the in silico prediction of descriptors related to the pharmacokinetic (PK) and toxicity profile of small molecules has offered a useful tool to identify drug-like compounds [36], as we previously performed for other case studies [37][38][39]. ...
Article
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Cystic fibrosis (CF) is the autosomal recessive disorder most recurrent in Caucasian populations. To combat this disease, many life-prolonging therapies are required and deeply investigated, including the development of the so-called cystic fibrosis transmembrane conductance regulator (CFTR) modulators, such as correctors and potentiators. Combination therapy with the two series of drugs led to the approval of several multi-drug effective treatments, such as Orkambi, and to the recent promising evaluation of the triple-combination Elexacaftor-Tezacaftor-Ivacaftor. This scenario enlightened the effectiveness of the multi-drug approach to pave the way for the discovery of novel therapeutic agents to contrast CF. The recent X-crystallographic data about the human CFTR in complex with the well-known potentiator Ivacaftor (VX-770) opened the possibility to apply a computational study aimed to explore the key features involved in the potentiator binding. Herein, we discussed molecular docking studies performed onto the chemotypes so far discussed in the literature as CFTR potentiator, reporting the most relevant interactions responsible for their mechanism of action, involving Van der Waals interactions and π–π stacking with F236, Y304, F305 and F312, as well as H-bonding F931, Y304, S308 and R933. This kind of positioning will stabilize the effective potentiator at the CFTR channel. These data have been accompanied by pharmacophore analyses, which promoted the design of novel derivatives endowed with a main (hetero)aromatic core connected to proper substituents, featuring H-bonding moieties. A highly predictive quantitative-structure activity relationship (QSAR) model has been developed, giving a cross-validated r2 (r2cv) = 0.74, a non-cross validated r2 (r2ncv) = 0.90, root mean square error (RMSE) = 0.347, and a test set r2 (r2pred) = 0.86. On the whole, the results are expected to gain useful information to guide the further development and optimization of new CFTR potentiators.
... During the last years, the drug discovery process relied on the in silico prediction of absorption, distribution, metabolism, excretion properties (ADME). Applying computational approaches to gain information on the pharmacokinetics (PK) and toxicity profile of ligands accelerated the lead optimization process [30,31]. Herein, we performed a computational prediction of PK properties shown by the newly screened compounds 1 and 2 compared to the previously developed mTAAR5 antagonists 1a and 2a. ...
Article
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Trace amine-associated receptor 5 (TAAR5) is a G protein-coupled receptor that belongs to the TAARs family (TAAR1-TAAR9). TAAR5 is expressed in the olfactory epithelium and is responsible for sensing 3-methylamine (TMA). However, recent studies showed that TAAR5 is also expressed in the limbic brain regions and is involved in the regulation of emotional behaviour and adult neurogenesis, suggesting that TAAR5 antagonism may represent a novel therapeutic strategy for anxiety and depression. We used the AtomNet® model, the first deep learning neural network for structure-based drug discovery, to identify putative TAAR5 ligands and tested them in an in vitro BRET assay. We found two mTAAR5 antagonists with low to submicromolar activity that are able to inhibit the cAMP production induced by TMA. Moreover, these two compounds also inhibited the mTAAR5 downstream signalling, such as the phosphorylation of CREB and ERK. These two hits exhibit drug-like properties and could be used to further develop more potent TAAR5 ligands with putative anxiolytic and antidepressant activity.
... Ligand-based molecular docking is a computational technique that can be used, among other methods, as a starting point for understanding the targeted mechanism of action of a given molecular structure. In the form of free-binding energy values, the obtained results may indicate an increased/decreased affinity of the analyzed molecule towards the selected target compared to the native ligand (a known inhibitor), given that the binding energy decreases when the compounds' affinity increases [64][65][66]. For our current study, we used a molecular docking-based protocol to identify possible protein targets for the 37 RGEO components, whose inhibition could be correlated with their in vitro antimicrobial activity. ...
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The research aimed to investigate the chemical composition and antioxidant and antibac-terial potential of the essential oil (EO) isolated from the aerial parts (flowers, leaves, and stems) of Ruta graveolens L., growing in western Romania. Ruta graveolens L. essential oil (RGEO) was isolated by steam distillation (0.29% v/w), and the content was assessed by gas chromatography-mass spec-trometry (GC-MS). Findings revealed that 2-Undecanone (76.19%) and 2-Nonanone (7.83%) followed by 2-Undecanol (1.85%) and 2-Tridecanone (1.42%) are the main detected compounds of the oil. The RGEO exerted broad-spectrum antibacterial and antifungal effects, S. pyogenes, S. aureus, and S. mutans being the most susceptible tested strains. The antioxidant activity of RGEO was assessed by peroxide and thiobarbituric acid value, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), and β-carotene/linoleic acid bleaching testing. The results indicated moderate radical scavenging and relative antioxidative activity in DPPH and β-carotene bleaching tests. However, between the 8th and 16th days of the incubation period, the inhibition of primary oxidation compounds induced by the RGEO was significantly stronger (p < 0.001) than butylated hydroxyanisole (BHA). Molecular docking analysis highlighted that a potential antimicrobial mechanism of the RGEO could be exerted through the inhibition of D-Alanine-d-alanine ligase (DDl) by several RGEO components. Docking analysis also revealed that a high number RGEO components could exert a potential in vitro protein-targeted antioxidant effect through xanthine oxidase and lipoxygenase inhibition. Consequently, RGEO could be a new natural source of antiseptics and antioxidants, representing an option for the use of synthetic additives in the food and pharmaceutical industry. Citation: Jianu, C.; Goleț, I.; Stoin, D.; Cocan, I.; Bujancă, G.; Mișcă, C.; Mioc, M.; Mioc, A.; Șoica, C.; Lukinich-Gruia, A.T.; et al.
... Recently, the drug discovery process relied on the predictive ability of in-silico evaluation of absorption, distribution, metabolism, and excretion parameters (ADME). Evaluation by computational methods of the putative pharmacokinetic (PK) properties of ligands, deeply accelerated the hit-to-lead and lead optimization process [56][57][58]. In the search of effective and drug-like HSP70 modulators, it should be noticed that MKT-077 was found to be susceptible to rapid metabolism, due to oxidation of the benzothiazole ring and of the pyridinium group [55]. ...
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Cystic fibrosis (CF) is caused by different mutations related to the cystic fibrosis transmembrane regulator protein (CFTR), with F508del being the most common. Pioneering the development of CFTR modulators, thanks to the development of effective correctors or potentiators, more recent studies deeply encouraged the administration of triple combination therapeutics. However, combinations of molecules interacting with other proteins involved in functionality of the CFTR channel recently arose as a promising approach to address a large rescue of F508del-CFTR. In this context, the design of compounds properly targeting the molecular chaperone Hsp70, such as the allosteric inhibitor MKT-077, proved to be effective for the development of indirect CFTR modulators, endowed with ability to amplify the accumulation of the rescued protein. Herein we performed structure-based studies of a number of allosteric HSP70 inhibitors, considering the recent X-ray crystallographic structure of the human enzyme. This allowed us to point out the main interaction supporting the binding mode of MKT-077, as well as of the related analogues. In particular, cation-π and π–π stacking with the conserve residue Tyr175 deeply stabilized inhibitor binding at the HSP70 cavity. Molecular docking studies had been followed by QSAR analysis and then by virtual screening of aminoaryl thiazoles (I–IIIa) as putative HSP70 inhibitors. Their effectiveness as CFTR modulators has been verified by biological assays, in combination with VX-809, whose positive results confirmed the reliability of the whole applied computational method. Along with this, the “in-silico” prediction of absorption, distribution, metabolism, and excretion (ADME) properties highlighted, once more, that AATs may represent a chemical class to be further investigated for the rational design of novel combination of compounds for CF treatment.
... During the last years, efforts in the drug discovery process relied on the effectiveness of in-silico evaluation of absorption, distribution, metabolism, and excretion properties (ADME). Indeed, applying computational methods aimed at gaining information on the pharmacokinetic (PK) and toxicity behavior of compounds deeply accelerated the lead optimization process [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. On this basis, we performed a computational evaluation of the main PK properties related to the drug-like profile of the most promising in-house series of benzimidazoles, in comparison with the prediction obtained for the (pre)clinical TMC353121, BMS-433771, JNJ-2408068, and Phase II clinical candidates JNJ-53718678, GS-5806, and RV521, taken as reference compounds. ...
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Targeting the fusion (F) protein has been recognized as a fruitful strategy for the development of anti-RSV agents. Despite the considerable efforts so far put into the development of RSV F protein inhibitors, the discovery of adequate therapeutics for the treatment of RSV infections is still awaiting a positive breakthrough. Several benzimidazole-containing derivatives have been discovered and evaluated in clinical trials, with only some of them being endowed with a promising pharmacokinetic profile. In this context, we applied a computational study based on a careful analysis of a number of X-ray crystallographic data of the RSV F protein, in the presence of different clinical candidates. A deepen comparison of the related electrostatic features and H-bonding motifs allowed us to pave the way for the following molecular dynamic simulation of JNJ-53718678 and then to perform docking studies of the in-house library of potent benzimidazole-containing anti-RSV agents. The results revealed not only the deep flexibility of the biological target but also the most relevant and recurring key contacts supporting the benzimidazole F protein inhibitor ability. Among them, several hydrophobic interactions and π-π stacking involving F140 and F488 proved to be mandatory, as well as H-bonding to D486. Specific requirements turning in RSV F protein binding ability were also explored thanks to structure-based pharmacophore analysis. Along with this, in silico prediction of absorption, distribution, metabolism, excretion (ADME) properties, and also of possible off-target events was performed. The results highlighted once more that the benzimidazole ring represents a privileged scaffold whose properties deserve to be further investigated for the rational design of novel and orally bioavailable anti-RSV agents.
... Since both linear and cyclic biguanides inhibit CLIC1 activity [38], we analyzed biguanide-based compounds derived from either metformin (linear structure) or cycloguanil (cyclic structure). Linear aryl-biguanides (Q46, Q42, Q48, and Q49), previously studied as trace amine-associated receptor 1 agonists [73], included, as best substitution pattern, lipophilic groups on the aromatic ring, such as 4-Cl (Q42) and 4-CH 3 (Q49) granting potencies in the μM range, while the polar 4-OCH 3 group (Q48) produced a negative effect, abolishing the activity. In silico analysis of the pharmacokinetic profile of both linear aryl-biguanides (Q42, Q46, Q48-50) and cycloguanil-like derivatives (Q51-Q54) predicted a slightly better ability to cross the BBB than metformin, but not enough to avoid a carrier-mediated organic cation transport. ...
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Background Chloride intracellular channel-1 (CLIC1) activity controls glioblastoma proliferation. Metformin exerts antitumor effects in glioblastoma stem cells (GSCs) inhibiting CLIC1 activity, but its low potency hampers its translation in clinical settings. Methods We synthesized a small library of novel biguanide-based compounds that were tested as antiproliferative agents for GSCs derived from human glioblastomas, in vitro using 2D and 3D cultures and in vivo in the zebrafish model. Compounds were compared to metformin for both potency and efficacy in the inhibition of GSC proliferation in vitro (MTT, Trypan blue exclusion assays, and EdU labeling) and in vivo (zebrafish model), migration (Boyden chamber assay), invasiveness (Matrigel invasion assay), self-renewal (spherogenesis assay), and CLIC1 activity (electrophysiology recordings), as well as for the absence of off-target toxicity (effects on normal stem cells and toxicity for zebrafish and chick embryos). Results We identified Q48 and Q54 as two novel CLIC1 blockers, characterized by higher antiproliferative potency than metformin in vitro, in both GSC 2D cultures and 3D spheroids. Q48 and Q54 also impaired GSC self-renewal, migration and invasion, and displayed low systemic in vivo toxicity. Q54 reduced in vivo proliferation of GSCs xenotransplanted in zebrafish hindbrain. Target specificity was confirmed by recombinant CLIC1 binding experiments using microscale thermophoresis approach. Finally, we characterized GSCs from GBMs spontaneously expressing low CLIC1 protein, demonstrating their ability to grow in vivo and to retain stem-like phenotype and functional features in vitro. In these GSCs, Q48 and Q54 displayed reduced potency and efficacy as antiproliferative agents as compared to high CLIC1-expressing tumors. However, in 3D cultures, metformin and Q48 (but not Q54) inhibited proliferation, which was dependent on the inhibition dihydrofolate reductase activity. Conclusions These data highlight that, while CLIC1 is dispensable for the development of a subset of glioblastomas , it acts as a booster of proliferation in the majority of these tumors and its functional expression is required for biguanide antitumor class-effects. In particular, the biguanide-based derivatives Q48 and Q54, represent the leads to develop novel compounds endowed with better pharmacological profiles than metformin, to act as CLIC1-blockers for the treatment of CLIC1-expressing glioblastomas, in a precision medicine approach.
... This represents a conformational search method that uses implicit vibrational analysis to focus a MD trajectory along the low-mode vibrations [41][42][43]. This has the effect of searching for minima along the valleys and troughs on the potential energy surface, thereby performing an exhaustive conformational analysis of the ligand-receptor binding site complex, as we previously discussed about other case studies [44][45][46]. ...
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Biguanides are compounds in which two guanidine moieties are fused to form a highly conjugated system. Biguanides are highly basic and hence they are available as salts mostly hydrochloride salts, these cationic species have been found to exhibit many therapeutic properties. This review covers the research and development carried out on biguanides and accounts the various therapeutic applications of drugs containing biguanide group—such as antimalarial, antidiabetic, antiviral, anticancer, antibacterial, antifungal, anti-tubercular, antifilarial, anti-HIV, as well as other biological activities. The aim of this review is to compile all the medicinal chemistry applications of this class of compounds so as to pave way for the accelerated efforts in finding the drug action mechanisms associated with this class of compounds. Importance has been given to the organic chemistry of these biguanide derivatives also.
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20(R)-25-methoxyl-dammarane-3β,12β,20-triol (CN Patent: 201010107476.7, AD-1) is a promising antitumor compound, was isolated from total hydrolyzed saponins extracted from Panax notoginseng leaves. A sensitive and rapid method for the simultaneous detection of AD-1 and its 8 major metabolites in rat feces was developed in this study. AD-1 (20 mg/kg) was orally administered to male rats by gastric intubation. Then, the feces samples were collected. After addition of internal standard (Mifepristone), feces samples were pretreated by protein precipitation followed by liquid-liquid extraction. Chromatographic separation was performed on an Angela C18 column with gradient elution using a mobile phase composed of acetonitrile and water (containing 5 mM ammonium acetate) at a flow rate of 0.3 mL/min. The analytes were detected without any interference from the multiple reaction monitoring (MRM) mode using positive electrospray ionization. Calibration curves offered satisfactory linearity (r > 0.995) within the determined ranges. Both intra-day and inter-day variances were lower than 15%, and the accuracy was within 85-115%. The fecal excretion recoveries of AD-1 (M0), metabolite 1 (M1), M2, M3, M4, M5, M6, M7 and M8 were 41.36%, 0.62%, 6.20%, 0.50%, 6.99%, 2.07%, 1.86%, 0.41% and 0.29%, respectively. The observed excretion profiles for AD-1 and its metabolites after oral administration are helpful to understand the poor oral bioavailability of AD-1, and will aid further investigations of AD-1 as a pharmacologically active component. Moreover, the in silico ADME (Absorption, Distribution, Metabolism, Excretion) predictions indicated that the metabolites were non-toxic and present passive gastrointestinal absorption. In previous studies, we found that M5, a metabolite of AD-1, has strong cytotoxicity against ovarian cancer cells. Further molecular docking studies showed that the most potent metabolite, M5, effectively binds to poly ADP-ribose polymerase-1 (PARP-1), which may provide novel solutions for treating ovarian cancer.
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This study focuses on the development of new synthetic pathways to monosubstituted biguanides from amines. An exhaustive comparison of the conditions and reagents used for biamidine transfer was performed. New reagents were synthesized and optimized conditions for the synthesis of substituted biguanides under mild conditions were developed. Eventually, two high-yielding and straightforward protocols for the transfer of a biamidine group to various amines are proposed and their scope and limitations have been explored. These conditions include: i) a direct chromatography-free procedure and ii) an eco-friendly procedure in water compatible with bio-inspired molecules. They are particularly efficient for the demanding conversion of aliphatic amines.
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Introduction: The greater interest in TAAR1-mediated potential for the treatment of different pathologies, especially those related to CNS disorders, has given a considerable boost to the search for developing TAAR1-selective small molecules. Areas covered: During the last decade the medicinal chemistry efforts have allowed the yield of various chemotypes to be properly dressed towards TAAR1 receptor. The more relevant chemical features and structure-activity relationship studies on the TAAR1 ligands will be discussed in order to guide future drug discovery investigations. Expert opinion: The discovery of TAAR receptors have allowed better investigation of the role played by TAs, not only as secondary neuromodulators, but also as neurotransmitters, even if it should still be completely clarified. This has drawn new ways for further insights around the TAAR1 involvement in numerous diseases. Despite this, the limited number of promising ligands targeting hTAAR1 orthologue makes the discovery of novel compounds still a challenging task. Relevant efforts have to be focused on safe ligands, devoid of any side-efficacy towards other highly related GPCR (monoaminergic systems). Moreover, species-specificity preferences experienced by numerous compounds so far investigated, based on rodent models and translated to the human environment, turn in a critical bottleneck in drug discovery.
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The discovery of novel potent neuraminidase (NA) inhibitors remains an attractive approach for treating infectious diseases caused by influenza. In this study, we describe the design and synthesis of novel N-substituted oseltamivir derivatives for probing the 150-cavity which is nascent to the activity site of NA. NA inhibitory studies showed that new derivatives demonstrated the inhibitory activity with IC50 values at nM level against NA of a clinical influenza virus strain. Moreover, the in silico ADME predictions showed that the selected compounds had comparable properties with oseltamivir carboxylate, which demonstrated the druggablity of these derivatives. Furthermore, molecular docking studies showed that the most potent compound 6f and 10i could adopt different modes of binding interaction with NA, which may provide novel solutions for treating oseltamivir-resistant influenza. Based on the research results, we consider that compounds 6f and 10i have the potential for further studies as novel antiviral agents.
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The origin of cancer is related to the dysregulation of multiple signal pathways and of physiological processes. Bromodomain-containing protein 4 (BRD4) has become an attractive target for the development of anticancer and anti-inflammatory agents since it can epigenetically regulate the transcription of growth-promoting genes. The synthesized BRD4 inhibitors with new chemical structures can reduce the drug resistance, but their binding modes and the inhibitory mechanism remain unclear. Here, we initially constructed robust QSAR models based on 68 reported tetrahydropteridin analogues using topomer CoMFA and HQSAR. On the basis of QSAR results, we designed 16 novel tetrahydropteridin analogues with modified structures and carried out docking studies. Instead of significant hydrogen bondings with amino acid residue Ans140 as reported in previous research, the molecular docking modelling suggested a novel docking pose that involves the amino acid residues (Trp81, Pro82, Val87, Leu92, Leu94, Cys136, Asp144, and Ile146) at the active site of BRD4. The MD simulations, free energy calculations, and residual energy contributions all indicate that hydrophobic interactions are decisive factors affecting bindings between inhibitors and BRD4. The current study provides new insights that can aid the discovery of BRD4 inhibitors with enhanced anti-cancer ability.
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Herein we continued our previous work on the developmente of CB2 ligands reporting the design and synthesis of a series of benzimidazole-containing derivatives that were explored as selective CB2 ligands in binding affinity towards both CB1 and CB2 receptors. Seven out of eighteen compounds featured preferential binding ability to CB2 over CB1 receptor with potencies in sub-micromolar or low micromolar range. In particular, we identified two promising hit compounds, the agonist 1-[2-(N,N-diethylamino)ethyl]-2-(4-ethoxybenzyl)-5-trifluoromethylbenzimidazole 3 (CB2: Ki= 0.42 µM) and the inverse agonist/antagonist 1-butyl-2-(3,4-dichlorobenzyl)-5-trifluoromethylbenzimidazole (11) (CB2: Ki= 0.37 µM). Docking studies also performed on other benzimidazoles reported in the literature supported the structure-activity relationship observed within this series of compounds and allow to reveal the key contacts involved in the agonist and/or inverse agonist behaviour displayed by these derivatives. The in silico evaluation of ADMET properties suggested a favorable pharmacokinetic and safety profile, promoting the drug-likeness of these compounds towards a further optimization process.
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Ulotaront (SEP-363856) is a trace-amine associated receptor 1 (TAAR1) agonist with 5-HT1A receptor agonist activity in Phase 3 clinical development, with FDA Breakthrough Therapy Designation, for the treatment of schizophrenia. TAAR1 is a G-protein-coupled receptor (GPCR) that is expressed in cortical, limbic, and midbrain monoaminergic regions. It is activated by endogenous trace amines, and is believed to play an important role in modulating dopaminergic, serotonergic, and glutamatergic circuitry. TAAR1 agonism data are reported herein for ulotaront and its analogues in comparison to endogenous TAAR1 agonists. In addition, a human TAAR1 homology model was built around ulotaront to identify key interactions and attempt to better understand the scaffold-specific TAAR1 agonism structure–activity relationships.
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Biguanides are a very interesting class of molecules which have been extensively studied for their medicinal applications. The structural and electronic structural aspects of biguanides have been explored in detail; however, even today, scientific literature continues to represent biguanides incorrectly as 1a. The X-ray crystal structure analysis and various spectroscopic studies such as UV, ¹H and ¹⁵N NMR have confirmed that biguanide exists as tautomer 1b. Electronic structure analysis also supports the existence of 1b. This review focuses on the structure and electronic structure of biguanides and aims to emphasize the importance of the correct representation of a structure. There is a need to commence the use of 1b for the general representation of biguanides in textbooks and research articles which will ensure a correct perspective for further studies on these molecules.
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Biogenic amines are a collection of endogenous molecules that play pivotal roles as neurotransmitters and hormones. In addition to the “classical” biogenic amines resulting from decarboxylation of aromatic acids, including dopamine (DA), norepinephrine, epinephrine, serotonin (5-HT) and histamine, other biogenic amines, present at much lower concentrations in the central nervous system (CNS), and hence referred to as “trace” amines (TAs), are now recognized to play significant neurophysiological and behavioural functions. At the turn of the century, the discovery of the trace amine-associated receptor 1 (TAAR1), a phylogenetically conserved G protein-coupled receptor that is responsive to both TAs, such as β-phenylethylamine, octopamine and tyramine, and structurally-related amphetamines, unveiled mechanisms of action for TAs other than interference with aminergic pathways, laying the foundations for deciphering the functional significance of TAs and its mammalian CNS receptor, TAAR1. Although its molecular interactions and downstream targets have not been fully elucidated, TAAR1 activation triggers accumulation of intracellular cAMP, modulates PKA and PKC signalling and interferes with the β-arrestin2-dependent pathway via G protein-independent mechanisms. TAAR1 is uniquely positioned to exert direct control over DA and 5-HT neuronal firing and release, which has profound implications for understanding the pathophysiology of, and therefore designing more efficacious therapeutic interventions for, a range of neuropsychiatric disorders that involve aminergic dysregulation, including Parkinson’s disease, schizophrenia, mood disorders and addiction. Indeed, the recent development of novel pharmacological tools targeting TAAR1 has uncovered the remarkable potential of TAAR1-based medications as new generation pharmacotherapies in neuropsychiatry. This review summarizes recent developments in the study of TAs and TAAR1, their intricate neurochemistry and pharmacology, and their relevance for neurodegenerative and neuropsychiatric disease.
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2-Aminooxazolines were discovered as a novel structural class of TAAR1 ligands. Starting from a known adrenergic compound 1, structural modifications were made to obtain highly potent and selective TAAR1 ligands such as 12 (RO5166017), 18 (RO5256390), 36 (RO5203648), and 48 (RO5263397). These compounds exhibit drug-like physicochemical properties, have good oral bioavailability, and display in vivo activity in a variety of animal models relevant for psychiatric diseases and addiction.
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Several recent studies have focused on a detailed analysis of the trace amine-associated receptor type 5 (TAAR5) pharmacology, up to now revealing only a limited number of species-specific ligands, which are also active towards other TAAR receptors. In this context, we developed our work on TAAR5 applying a structure-based computational protocol, revolving around homology modeling and virtual screening calculations. In detail, mTAAR5 and hTAAR5 homology models were built, in order to explore any pattern of structural requirements which could be involved in species-specific differences. Successively, the mTAAR5 model was employed to perform a virtual screening of an in-house library of compounds, including different five-membered ring derivatives, linked to a phenyl ring through a flexible or a rigid basic moiety. The computational protocol applied allowed to select a number of chemical scaffolds that were tested in a biological assay leading to the discovery of the first two mTAAR5 antagonists.
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Objective: Type 2 diabetes and obesity are emerging pandemics in the 21st century creating worldwide urgency for the development of novel and safe therapies. We investigated trace amine-associated receptor 1 (TAAR1) as a novel target contributing to the control of glucose homeostasis and body weight. Methods: We investigated the peripheral human tissue distribution of TAAR1 by immunohistochemistry and tested the effect of a small molecule TAAR1 agonist on insulin secretion in vitro using INS1E cells and human islets and on glucose tolerance in C57Bl6, and db/db mice. Body weight effects were investigated in obese DIO mice. Results: TAAR1 activation by a selective small molecule agonist increased glucose-dependent insulin secretion in INS1E cells and human islets and elevated plasma PYY and GLP-1 levels in mice. In diabetic db/db mice, the TAAR1 agonist normalized glucose excursion during an oral glucose tolerance test. Sub-chronic treatment of diet-induced obese (DIO) mice with the TAAR1 agonist resulted in reduced food intake and body weight. Furthermore insulin sensitivity was improved and plasma triglyceride levels and liver triglyceride content were lower than in controls. Conclusions: We have identified TAAR1 as a novel integrator of metabolic control, which acts on gastrointestinal and pancreatic islet hormone secretion. Thus TAAR1 qualifies as a novel and promising target for the treatment of type 2 diabetes and obesity.
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Objectives: The trace amine-associated receptor 1 (Taar1) is a Gs protein-coupled receptor activated by trace amines, such as β-phenylethylamine (β-PEA) and 3-iodothyronamine (T1AM). T1AM is an endogenous biogenic amine and thyroid hormone derivative that exerts several biological functions. However, the physiological relevance of T1AM acting via Taar1 is still under discussion. Therefore, we studied the structural and functional evolution of Taar1 in vertebrates to provide evidence for a conserved Taar1-mediated T1AM function. Study design: We searched public sequence databases to retrieve Taar1 sequence information from vertebrates. We cloned and functionally characterized Taar1 from selected vertebrate species using cAMP assays to determine the evolutionary conservation of T1AM action at Taar1. Results: We found intact open reading frames of Taar1 in more than 100 vertebrate species, including mammals, sauropsids and amphibians. Evolutionary conservation analyses of Taar1 protein sequences revealed a high variation in amino acid residues proposed to be involved in agonist binding, especially in rodent Taar1 orthologs. Functional characterization showed that T1AM, β-PEA and p-tyramine (p-Tyr) act as agonists at all tested orthologs, but EC50 values of T1AM at rat Taar1 differed significantly when compared to all other tested vertebrate Taar1. Conclusions: The high structural conservation of Taar1 throughout vertebrate evolution highlights the physiological relevance of Taar1, but species-specific differences in T1AM potency at Taar1 orthologs suggest a specialization of rat Taar1 for T1AM recognition. In contrast, β-PEA and p-Tyr potencies were rather conserved throughout all tested Taar1 orthologs. We provide evidence that the observed differences in potency are related to differences in constraint during Taar1 evolution.
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Trace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor expressed in the mammalian brain and known to influence subcortical monoaminergic transmission. Monoamines, such as dopamine, play also an important role within the prefrontal cortex (PFC) circuitry, which is critically involved in high order cognitive processes. TAAR1 selective ligands have shown potential antipsychotic, antidepressant and pro-cognitive effects in experimental animal models; however, it remains unclear if TAAR1 can affect PFC-related processes and functions. In this study, we document distinct pattern of expression of TAAR1 in the PFC, as well as altered subunit composition and deficient functionality of the glutamate N-methyl-D-aspartate (NMDA) receptors in the pyramidal neurons of layer V of PFC in mice lacking TAAR1. The dysregulated cortical glutamate transmission in TAAR1-KO mice was associated with aberrant behaviors in several tests, indicating a perseverative and impulsive phenotype of mutants. Conversely, pharmacological activation of TAAR1 with selective agonists reduced premature impulsive responses observed in the fixed-interval conditioning schedule in normal mice. Our study indicates that TAAR1 plays an important role in the modulation of NMDA receptor-mediated glutamate transmission in the PFC and related functions. Furthermore, these data suggest that development of TAAR1-based drugs could provide a novel therapeutic approach for the treatment of disorders related to aberrant cortical functions.Neuropsychopharmacology accepted article preview online, 09 March 2015. doi:10.1038/npp.2015.65.
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Objective: Application of 3-iodothyronamine (3-T1AM) results in decreased body temperature and body weight in rodents. The trace amine-associated receptor (TAAR) 1, a family A G protein-coupled receptor, is a target of 3-T1AM. However, 3-T1AM effects still persist in mTaar1 knockout mice, which suggest so far unknown further receptor targets that are of physiological relevance. TAAR5 is a highly conserved TAAR subtype among mammals and we here tested TAAR5 as a potential 3-T1AM target. First, we investigated mouse Taar5 (mTaar5) expression in several brain regions of the mouse in comparison to mTaar1. Secondly, to unravel the full spectrum of signaling capacities, we examined the distinct Gs-, Gi/o-, G12/13-, Gq/11- and MAP kinase-mediated signaling pathways of mouse and human TAAR5 under ligand-independent conditions and after application of 3-T1AM. We found overlapping localization of mTaar1 and mTaar5 in the amygdala and ventromedial hypothalamus of the mouse brain. Second, the murine and human TAAR5 (hTAAR5) display significant basal activity in the Gq/11 pathway but show differences in the basal activity in Gs and MAP kinase signaling. In contrast to mTaar5, 3-T1AM application at hTAAR5 resulted in significant reduction in basal IP3 formation and MAP kinase signaling. In conclusion, our data suggest that the human TAAR5 is a target for 3-T1AM, exhibiting inhibitory effects on IP3 formation and MAP kinase signaling pathways, but does not mediate Gs signaling effects as observed for TAAR1. This study also indicates differences between TAAR5 orthologs with respect to their signaling profile. In consequence, 3-T1AM-mediated effects may differ between rodents and humans.
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The trace amine-associated receptor 1 (TAAR1) has emerged as a promising target for medication development in addiction due to its ability to regulate dopamine (DA) transmission. We tested in rats the efficacy of RO5203648 and RO5256390, partial and full TAAR1 agonists, respectively, in models of cocaine relapse. Using a model of context-induced relapse, both RO5203648 and RO5256390 dose-dependently suppressed cocaine seeking after a 2-week period of withdrawal from chronic cocaine self-administration. In a model of extinction-reinstatement, RO5203648 completely inhibited cocaine-primed reinstatement of cocaine seeking. At doses that effectively suppressed cocaine seeking neither RO5203648 nor RO5256390 altered responding maintained by a natural reward. Moreover, fast-scan cyclic voltammetry data showed that RO5203648 prevented cocaine-induced DA overflow in the nucleus accumbens without altering DA half-life, suggesting that the partial TAAR1 agonist attenuated cocaine-stimulated DA overflow by mechanisms other than direct interference with DA uptake. Collectively, these data provide strong evidence in support of TAAR1 as a neuropharmacological target for the treatment of cocaine addiction.Neuropsychopharmacology accepted article peview online, 11 April 2014. doi:10.1038/npp.2014.88.
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Metformin is widely prescribed for the treatment of type II diabetes. Recently, it has been proposed that this compound or related biguanides may have antineoplastic activity. Biguanides may exploit specific metabolic vulnerabilities of transformed cells by acting on them directly, or may act by indirect mechanisms that involve alterations of the host environment. Preclinical data suggest that drug exposure levels are a key determinant of proposed direct actions. With respect to indirect mechanisms, it will be important to determine whether recently demonstrated metformin-induced changes in levels of candidate systemic mediators such as insulin or inflammatory cytokines are of sufficient magnitude to achieve therapeutic benefit. Results of the first generation of clinical trials now in progress are eagerly anticipated. Ongoing investigations may justify a second generation of trials that explore pharmacokinetic optimization, rational drug combinations, synthetic lethality strategies, novel biguanides, and the use of predictive biomarkers.
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Monohydrochloride salts of diverse 1-arylbiguanides and 1,5-diarylbiguanides were synthesized by the reaction of anilinium chlorides with dicyandiamide or sodium dicyanamide, and the biguanidinium chlorides were converted into the corresponding biguanides by deprotonation with methanolic NaOCH3. The resulting biguanides and their salts were fully characterized by spectroscopic methods, and the structures of representative compounds were determined by X-ray crystallography.Key words: biguanide, biguanidinium, synthesis, structure, hydrogen bonds, noncovalent interactions, supramolecular chemistry.
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In addition to the canonical olfactory receptors, TAARs were currently suggested to be a second class of chemosensory receptors in the olfactory epithelium of vertebrates. In contrast to several deorphanized murine TAARs, agonists for the intact human TAAR genes 2, 5, 6, 8 and 9 that are potentially expressed in the human olfactory epithelium have not been determined so far. Moreover, the physiological relevance of TAARs still remains elusive. We present the first successful functional expression of a human TAAR and agonists of human TAAR5. We performed a ligand screening using recombinantly expressed human TAAR5 in HANA3A cells and Xenopus laevis oocytes. In order to measure receptor activity, we used a cAMP-dependent reporter gene assay and two-electrode voltage clamp technique. As a result, human TAAR5 can be activated in a concentration-dependent manner by trimethylamine and with less efficacy by dimethylethylamine. It could neither be activated by any other of the tested single amines with a related chemical structure (42 in total), nor by any of the tested odorant mixtures. The hypothesis that Single Nucleotide Polymorphisms (SNP) within the reading frame of an olfactory receptor gene can cause a specific anosmia, formed the basis for clarifying the question, if anosmia for trimethylamine is caused by a SNP in a TAAR coding sequence. All functional human TAAR gene reading frames of subjects with specific anosmia for trimethylamine were amplified and products analyzed regarding SNP distribution. We demonstrated that the observed specific anosmia for trimethylamine is not correlated with a SNP in the coding sequence of one of the putatively functional human TAAR genes.
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Certain biogenic amines, such as 2-PEA, TYR, or T1AM, modulate blood pressure, cardiac function, brain monoaminergic systems, and olfaction-guided behavior by specifically interacting with members of a group of rhodopsin-like receptors, TAAR. A receptor that is absent from olfactory epithelia but had long been identified in the brain and a variety of peripheral tissues, TAAR1 has been found recently in blood B cells, suggesting a functional role of TAAR1 in these cells. With the present study, we have set out to clarify the expression and functional roles of TAAR in different isolated human blood leukocyte types. Here, we report the functional expression of TAAR1 and its closest relative TAAR2 in blood PMN and T and B cells. Both receptors are coexpressed in a subpopulation of PMN, where they are necessary for the chemosensory migration toward the TAAR1 ligands 2-PEA, TYR, and T1AM, with EC(50) values of 0.43 ± 0.05 nM, 0.52 ± 0.05 nM, and 0.25 ± 0.04 nM, respectively. The same amines, with similar potencies, triggered cytokine or Ig secretion, in purified blood T or B cells, respectively. Notably, 2-PEA regulated mRNA expression of 28 T cell function-related genes, above all of the CCL5. In siRNA-guided experiments, TAAR1 and TAAR2 proved to be necessary for amine-induced blood leukocyte functions. In summary, our results demonstrate that biogenic amines potently regulate blood cell functions via TAAR1 and TAAR2 and open the perspective of their specific pharmacological modulation.
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Schizophrenia is a chronic, severe and highly complex mental illness. Current treatments manage the positive symptoms, yet have minimal effects on the negative and cognitive symptoms, two prominent features of the disease with critical impact on the long-term morbidity. In addition, antipsychotic treatments trigger serious side effects that precipitate treatment discontinuation. Here, we show that activation of the trace amine-associated receptor 1 (TAAR1), a modulator of monoaminergic neurotransmission, represents a novel therapeutic option. In rodents, activation of TAAR1 by two novel and pharmacologically distinct compounds, the full agonist RO5256390 and the partial agonist RO5263397, blocks psychostimulant-induced hyperactivity and produces a brain activation pattern reminiscent of the antipsychotic drug olanzapine, suggesting antipsychotic-like properties. TAAR1 agonists do not induce catalepsy or weight gain; RO5263397 even reduced haloperidol-induced catalepsy and prevented olanzapine from increasing body weight and fat accumulation. Finally, TAAR1 activation promotes vigilance in rats and shows pro-cognitive and antidepressant-like properties in rodent and primate models. These data suggest that TAAR1 agonists may provide a novel and differentiated treatment of schizophrenia as compared with current medication standards: TAAR1 agonists may improve not only the positive symptoms but also the negative symptoms and cognitive deficits, without causing adverse effects such as motor impairments or weight gain.Molecular Psychiatry advance online publication, 29 May 2012; doi:10.1038/mp.2012.57.
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The ability of dopamine receptors to interact with other receptor subtypes may provide mechanisms for modulating dopamine-related functions and behaviors. In particular, there is evidence suggesting that the trace amine-associated receptor 1 (TAAR1) affects the dopaminergic system by regulating the firing rate of dopaminergic neurons or by altering dopamine D2 receptor (D2R) responsiveness to ligands. TAAR1 is a Gα(s) protein-coupled receptor that is activated by biogenic amines, "trace amines," such as β-phenylethylamine (β-PEA) and tyramine that are normally found at low concentrations in the mammalian brain. In the present study, we investigated the biochemical mechanism of interaction between TAAR1 and D2R and the role this interaction plays in D2R-related signaling and behaviors. Using a bioluminescence resonance energy transfer biosensor for cAMP, we demonstrated that the D2R antagonists haloperidol, raclopride, and amisulpride were able to enhance selectively a TAAR1-mediated β-PEA increase of cAMP. Moreover, TAAR1 and D2R were able to form heterodimers when coexpressed in human embryonic kidney 293 cells, and this direct interaction was disrupted in the presence of haloperidol. In addition, in mice lacking TAAR1, haloperidol-induced striatal c-Fos expression and catalepsy were significantly reduced. Taken together, these data suggest that TAAR1 and D2R have functional and physical interactions that could be critical for the modulation of the dopaminergic system by TAAR1 in vivo.
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Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor (GPCR) that is nonselectively activated by endogenous metabolites of amino acids. TAAR1 is considered a promising drug target for the treatment of psychiatric and neurodegenerative disorders. However, no selective ligand to identify TAAR1-specific signaling mechanisms is available yet. Here we report a selective TAAR1 antagonist, EPPTB, and characterize its physiological effects at dopamine (DA) neurons of the ventral tegmental area (VTA). We show that EPPTB prevents the reduction of the firing frequency of DA neurons induced by p-tyramine (p-tyr), a nonselective TAAR1 agonist. When applied alone, EPPTB increases the firing frequency of DA neurons, suggesting that TAAR1 either exhibits constitutive activity or is tonically activated by ambient levels of endogenous agonist(s). We further show that EPPTB blocks the TAAR1-mediated activation of an inwardly rectifying K(+) current. When applied alone, EPPTB induces an apparent inward current, suggesting the closure of tonically activated K(+) channels. Importantly, these EPPTB effects were absent in Taar1 knockout mice, ruling out off-target effects. We additionally found that both the acute application of EPPTB and the constitutive genetic lack of TAAR1 increase the potency of DA at D2 receptors in DA neurons. In summary, our data support that TAAR1 tonically activates inwardly rectifying K(+) channels, which reduces the basal firing frequency of DA neurons in the VTA. We hypothesize that the EPPTB-induced increase in the potency of DA at D2 receptors is part of a homeostatic feedback mechanism compensating for the lack of inhibitory TAAR1 tone.
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Tyramine, beta-phenylethylamine, tryptamine, and octopamine are biogenic amines present in trace levels in mammalian nervous systems. Although some "trace amines" have clearly defined roles as neurotransmitters in invertebrates, the extent to which they function as true neurotransmitters in vertebrates has remained speculative. Using a degenerate PCR approach, we have identified 15 G protein-coupled receptors (GPCR) from human and rodent tissues. Together with the orphan receptor PNR, these receptors form a subfamily of rhodopsin GPCRs distinct from, but related to the classical biogenic amine receptors. We have demonstrated that two of these receptors bind and/or are activated by trace amines. The cloning of mammalian GPCRs for trace amines supports a role for trace amines as neurotransmitters in vertebrates. Three of the four human receptors from this family are present in the amygdala, possibly linking trace amine receptors to affective disorders. The identification of this family of receptors should rekindle the investigation of the roles of trace amines in mammalian nervous systems and may potentially lead to the development of novel therapeutics for a variety of indications.
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Following studies in the late 1990s that indicated that poor pharmacokinetics and toxicity were important causes of costly late-stage failures in drug development, it has become widely appreciated that these areas should be considered as early as possible in the drug discovery process. However, in recent years, combinatorial chemistry and high-throughput screening have significantly increased the number of compounds for which early data on absorption, distribution, metabolism, excretion (ADME) and toxicity (T) are needed, which has in turn driven the development of a variety of medium and high-throughput in vitro ADMET screens. Here, we describe how in silico approaches will further increase our ability to predict and model the most relevant pharmacokinetic, metabolic and toxicity endpoints, thereby accelerating the drug discovery process.
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The trace amine-associated receptor 1 (TAAR1) is a G-protein-coupled receptors (GPCR) potently activated by a variety of molecules besides trace amines (TAs), including thyroid hormone-derivatives like 3-iodothyronamine (T1AM), catechol-O-methyltransferase products like 3-methoxytyramine, and amphetamine-related compounds. Accordingly, TAAR1 is considered a promising target for medicinal development. To gain more insights into TAAR1 physiological functions and validation of its therapeutic potential we recently developed a new class of thyronamine-like derivatives. Among them compound SG2 showed high affinity and potent agonist activity at mouse TAAR1. In the present work we describe design, the synthesis and SAR study of a new series of compounds (1-16) obtained by introducing specific structural changes at key points of our lead-compound SG2 skeleton. Five of the newly synthesized compounds displayed mTAAR1 agonist activity higher than both SG2 and T1AM. Selected diphenylmethane analogs, namely 1 and 2, showed potent functional activity in in vitro and in vivo models.
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Moroxydine hydrochloride (Mor) is known to have multi-antiviral activities against DNA and RNA viruses but very little information exists on its pharmacology. The paper was undertaken to explore the antiviral response and antiapoptotic mechanism of Mor against grass carp reovirus (GCRV) in Ctenopharyngodon idella kidney (CIK) cells. The results showed that exposing GCRV-infected cell to 6.3 μg mL−1 of Mor for 96 h avoid ca. 50% apoptosis. Meanwhile, Mor had lower cytotoxicity than ribavirin (Rib) as the value of safe concentration was threefold higher than effective concentration and the compound could ensure sufficient into and out of cells within 4 h when tested at the maximal safe concentration. Mor blocked the GCRV-induced cytopathic effects and eliminated nucleocapsids in CIK cells to keep the normal morphological structure. Moreover, the expressions of viral protein genes were significantly inhibited especially the guanylyl transferase and RNA-dependent RNA polymerase related expression. Furthermore, GCRV caused Bcl-2 down-regulation and Bax mitochondrial translocation was prevented by treatment of CIK cells with Mor. The downstream effector, caspase activity was also significantly inhibited in Mor treated cells. The potential mechanism might be that mitochondrial apoptotic signals were not activated by the intervention of Mor for targeting viral gene expression. Taken together, Mor showed high anti-GCRV activity and had been proved as a secure and promising agent in viral controlling in aquaculture industry.
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Herein we report the synthesis and biological activity of new sigma receptor (σR) ligands obtained by combining different substituted five-membered heterocyclic rings with appropriate σR pharmacophoric amines. Radioligand binding assay, performed on guinea pig brain membranes, identified 25b (1-(1,4-dioxaspiro[4.5]decan-2-ylmethyl)-4-benzylpiperazine) as the most interesting compound of the series, displaying high affinity and selectivity for σ1R (pKiσ1 = 9.13; σ1/σ2 = 47). The ability of 25b to modulate the analgesic effect of the κ agonist (−)-U-50,488H and μ agonist morphine was evaluated in vivo by radiant heat tail-flick test. It exhibited anti-opioid effects on both κ and μ receptor-mediated analgesia, suggesting an agonistic behavior at σ1R. Docking studies were performed on the theoretical σ1R homology model. The present work represents a new starting point for the design of more potent and selective σ1R ligands.
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Trace Amines (TA) are side-products of the synthesis of classical neurotransmitters within the brain. TAs exert their effect by binding to a family of G protein-coupled receptors termed Trace Amine-Associated Receptors (TAARs). TAAR1 is the best characterised member of this family and studies on TAAR1 have shown that this receptor is a negative regulator of dopamine transmission. Considering the limited number of pharmacological probes available for TAAR1, we aimed to identify novel ligands of this receptor using structure-based virtual screening. A homology model of TAAR1 was generated and over three million commercially available compounds were screened against the orthosteric site using molecular docking. Among the 42 top-ranked compounds that were tested in functional assays, three partial agonists with EC50 values ranging from 1 to 52 μM were discovered. In addition, four potentially weak antagonists were identified. Ten analogs of the two most potent agonists from the screen were also evaluated and three of these displayed equal or greater activity compared to the parent compound. Several of the discovered ligands represent novel scaffolds and are thus promising starting points for development of new pharmacological tools for studying TAAR1 biology.
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Trace amine associated receptor 1 (TAAR1) is a GPCR expressed in brain and periphery activated by a wide spectrum of agonists that include, but are not limited to, trace amines (TAs), amphetamine-like psychostimulants and endogenous thyronamines, such as thyronamine (T0AM) and 3-iodothyronamine (T1AM). Such polypharmacology has made it challenging to understand the role and the biology of TAAR1. In an effort to understand the molecular basis of TAAR1 activation, we rationally designed and synthesized a small family of thyronamine derivatives. Among them, compounds 2 and 3 appeared to be a good mimic of the parent endogenous thyronamine, T0AM and T1AM respectively, both in vitro and in vivo. Thus, these compounds offer suitable tools for studying the physiological roles of mouse TAAR1, and could represent the starting point for the development of more potent and selective TAAR1 ligands.
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Small heat-shock proteins, possessing chaperone-like activity, represented crucial proteins actively involved in maintain protein homeostasis, which act to prevent improper polypeptide aggregation and deposition of misfolded proteins. In this context, a number of mutations concerning the HspB1 protein proved to be associated with the development of several neuropathologies. Unfortunately, molecular mechanisms underlying the onset of these diseases and in particular the changes induced by the mutations in HspB1 structure, remain poorly characterized. On the other hand, more recent studies demonstrated that HspB1 overexpression leads to an overactive chaperone activity, which in turn contributes to the anticancer agent resistance. On these basis, Hsp27 could represent a good innovative target for development of novel cancer therapy. Therefore, in this work a computational study, based on the homology model of the complete Hsp27 protein and of several pathological mutant forms, was developed. Finally, the derived model was employed to perform, for the first time, docking simulations on a recently identified Hsp27 inhibitor, disclosing a new useful panorama to be exploited for the further development of new compounds. Copyright © 2015 Elsevier Ltd. All rights reserved.
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The Protein Data Bank (PDB; http://www.rcsb.org/pdb/ ) is the single worldwide archive of structural data of biological macromolecules. This paper describes the goals of the PDB, the systems in place for data deposition and access, how to obtain further information, and near-term plans for the future development of the resource.
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Trace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor that is expressed in brain and periphery and responds to a class of compounds called trace amines, such as β-phenylethylamine (β-PEA), tyramine, tryptamine, octopamine. The receptor is known to have a very rich pharmacology and could be also activated by different classes of compounds, including dopaminergic, adrenergic and serotonergic ligands. It is expected that targeting hTAAR1 could provide a novel pharmacological approach for several human disorders, such as schizophrenia, depression, attention deficit hyperactivity disorder, Parkinson's disease and metabolic diseases. Only recently, a small number of selective hTAAR1 agonists (among which RO5166017 and T1 AM) and antagonist (EPPTB), have been reported in literature. With the aim to identify new molecular entities able to act as ligands for this target, we used an homology model for the hTAAR1 and performed a virtual screening procedure on an in-house database of compounds. A number of interesting molecules were selected and by testing them in an in vitro assay we found several agonists and one antagonist, with activities in the low micromolar range. These compounds could represent the starting point for the development of more potent and selective TAAR1 ligands. This article is protected by copyright. All rights reserved.
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Amphetamines are widely abused drugs that interfere with dopamine transport and storage. Recently however, another mechanism of action was identified: stereoselective activation of the Gαs protein-coupled trace amine-associated receptor 1. To identify structural determinants of this stereoselectivity we functionally evaluated six mutant receptors in vitro then used homology modeling and dynamic simulation to predict drug affinities. Converting Asp102 to Ala rendered mouse and rat TAAR1 insensitive to β-phenylethylamine, AMPH and METH. Mutating Met268 in rTAAR1 to Thr shifted the concentration-response profiles for AMPH and METH isomers rightward an order of magnitude whereas replacing Thr268 with Met in mTAAR1 resulted in profiles leftward shifted 10-30 fold. Replacing Asn287 with Tyr in rTAAR1 produced a mouse-like receptor while the reciprocal mTAAR1 mutant was rTAAR1-like. These results confirm TAAR1 is an AMPH/METH receptor in vitro and establish residues 102 and 268 as major contributors to AMPH/METH binding with 287 determining species stereoselectivity.
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The Protein Data Bank (PDB; http://www.rcsb.org/pdb/ ) is the single worldwide archive of structural data of biological macromolecules. This paper describes the goals of the PDB, the systems in place for data deposition and access, how to obtain further information, and near-term plans for the future development of the resource.
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An alternate synthesis of biologically active 4,6-diamino-1-aryl-1,2-dihydro-s-triazines by the condensation of arylbiguanides and ketones or aldehydes under acid conditions is described.
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The synthesis of a new class of 1,2-dihydro-s-triazines, with experimental anti-vitamin, anti-malarial, anti-tumor, and anti-coccidial activity, is described. The scope and limitations of this previously unreported synthesis, which involves the condensation in one step of an arylamine hydrochloride, dicyandiamide or N1-methyldicyandiamide, and a ketone or an aldehyde, are outlined. Under the influence of alkali and heat, these compounds, to which the structure 4,6-diamino-1-aryl-1,2-dihydro-s-triazine has been assigned, undergo an irreversible, intramolecular rearrangement to a series of isomeric 4-amino-6-arylamino-1,2-dihydro-s-triazines with reduced biological activity. The mechanism of the rearrangement and evidence for the structure of these dihydrotriazines are discussed.
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A series of N1-alkyl- and aralkylbiguanides has been synthesized and examined for hypoglycemic activity in guinea pigs. The relationship between structure and hypoglycemic activity is discussed.
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Trace Amine-Associated Receptor 1 (TAAR1) is a G protein-coupled receptor that belongs to the family of TAAR receptors and responds to a class of compounds called trace amines, such as β-phenylethylamine (β-PEA) and 3-iodothyronamine (T(1) AM). The receptor is known to have a very rich pharmacology and could be also activated by other classes of compounds, including adrenergic and serotonergic ligands. It is expected, that targeting TAAR1 could provide a novel pharmacological approach to correct monoaminergic dysfunctions found in several brain disorders, such as schizophrenia, depression, attention deficit hyperactivity disorder and Parkinson's disease. Only recently, the first selective TAAR1 agonist RO5166017 has been identified. To explore the molecular mechanisms of protein-agonist interaction and speed up the identification of new chemical entities acting on this biomolecular target, we derived a homology model for the hTAAR1. The putative protein binding site has been explored by comparing the hTAAR1 model with the β2-adrenoreceptor binding site, available by X-ray crystallization studies, and with the homology modeled 5HT(1A) receptor. The obtained results, in tandem with docking studies performed with RO5166017, β-PEA and T(1) AM, provided an opportunity to reasonably identify the hTAAR1 key residues involved in ligand recognition and thus define important starting points to design new agonists. © 2012 John Wiley & Sons A/S.
Article
A series of 1-(ω-phenylalkyl)-4,6-diamino-1, 2-dihydro-s-triazines was synthesized by acid catalyzed condensation of 1-(ω-phenylalkyl)biguanides with acetone, aromatic aldehydes and ω-phenylalkyl aldehydes; the intermediate biguanides were prepared by fusion of ω-phenylalkylamines with cyanoguanidine at 150°. 4, 6-Diamino-1, 2-dihydro-2,2-dimethyl-1-(4-phenylbutyl)- and 1-(3-phenylpropyl)-s-triazines (Xe and Xd) were potent inhibitors of dihydrofolic reductase, being complexed with the enzyme about two hundred times better than the substrate, dihydrofolic acid; further Xd and Xe were about 15-fold better inhibitors of dihydrofolic reductase than the earlier investigated 1-(p-chlorophenyl)-4, 6-diamino-1,2-dihydro-2,2-dimethyl-s-triazine, the antimalarial drug.When the 2,2-dimethyl group was replaced by p-acetamidophenyl (IX) or phenyl (VIII), in inhibitors such as Xd and Xe, activity was reduced only 5-30 fold; the corresponding change in 1-(m-chlorophenyl)-4, 6-diamino-1,2-dihydro-2, 2-dimethyl-s-triazine (V) gave a 19,000-fold reduction in activity with the 2-(p-acetamidophenyl) analog (VII) and a 550-fold decrease in activity with the 2-phenyl analog. These decreases in activity are attributed to a combination of intramolecular steric effects, intermolecular (enzymeinhibitor) steric inhibition of binding, and inductive effects. By evaluation of suitable candidate compounds, these effects were partially separated for individual study.
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TAARs (trace amine-associated receptors) are G-protein-coupled receptors that respond to low abundance, endogenous amines such as tyramine and tryptamine, and represent potential targets for neuropsychiatric diseases. However, some members of this receptor subfamily either have no ligand identified or remain difficult to express and characterize using recombinant systems. In the present paper we report the successful expression of human and mouse TAAR1, and the characterization of their responses to various natural and synthetic agonists. In HEK (human embryonic kidney)-293/CRE-bla cells, mouse TAAR1 showed a robust response to trace amines as measured using either a cAMP assay or a beta-lactamase reporter assay, whereas human TAAR1 showed a weaker, but still measurable, response. When certain fragments of human TAAR1 were replaced with the corresponding regions of mouse TAAR1, the chimaeric receptor showed a much stronger response in cAMP production. Examination of a series of agonists on these receptors revealed that the human and the chimaeric receptor are almost identical in pharmacology, but distinct from the mouse receptor. We also screened small libraries of pharmacologically active agents on TAAR1 and identified a series of synthetic agonists, some of which are also ligands of the enigmatic imidazoline receptor. The findings of the present study not only shed light on the pharmacological species difference of TAAR1, but also raise new possibilities about the mechanism of some of the imidazoline-related agents.
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Endogenous trace amines (TAs) of unknown biological function are structurally related to classic monoaminergic neurotransmitters and found at low concentrations in the mammalian brain. Their recently discovered group of G protein-coupled receptors, trace amine-associated receptors (TAARs), may represent putative targets not only for trace and other amines but also for a variety of monoaminergic compounds, including amphetamines and monoamine metabolites. The trace amine-associated receptor 1 (TAAR1), which is in part associated with the monoaminergic neuronal circuitry controlling various functions, including movement, is the best characterized of the class, although little is known about its regulation and function. Here we review the pharmacology and biochemical properties of the TAAR1 and its physiological functions as revealed in studies involving knockout mice lacking this receptor. Potential therapeutic applications of future selective TAAR1 agonists and antagonists are also discussed. Although understanding of biology and functions mediated by other TAARs is still in its infancy, it is expected that further characterization of the functional roles and biochemical properties of TAARs and identification of endogenous and exogenous ligands will eventually promote these receptors as an attractive class of targets to correct monoaminergic processes that could be dysfunctional in a host of disorders of brain and periphery.
Article
In addition to the major monoamines (dopamine, noradrenaline, serotonin) there exists in the nervous tissue of all species examined a group of monoamines described as exotic amines, trace amines or microamines. Among the endogeneous microamines found in the mammalian brain are β phenylethylamine, phenylethanolamine, m and p tyramine, octopamine and tryptamine. Despite their very low concentrations, microamines are interesting for several reasons: they are heterogeneously distributed within the brain; they are present in the same subcellular fraction as catecholamines and 5 HT; they have a high turnover rate; they release and/or replace catecholamines from storage sites and block reuptake; they may be excreted abnormally in the urine of patients with migraine, Parkinson's disease, schizophrenia and depression; some of them are behaviorally active. Analytical procedures for micramines are described and their biosynthesis and catabolism discussed. Out of them octopamine proved to be the most prospective candidate as a transmitter in the invertebrate nervous system as it fulfilled six of the seven criteria for identification of chemical transmitters (it has been shown to be present in neurons; presence of synthetic enzymes as well as precursors and intermediates has been demonstrated; it was released during nerve stimulation; exogeneous octopamine mimics the effect of the released transmitter; pharmacological agents interact with both the synaptically released transmitter and octopamine in an identical manner. The physiological means of inactivation and/or removal from the synapse, however, remain unknown). Among the other microamines, there is little evidence for a role in invertebrates.
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The aim of this report was to indicate the correlation between chemical structure and antiviral activity of some biguanide derivatives obtained according to Monsanto Chemicals Ltd. Neth. Appl. 289. 283. The studies were carried out on the culture of monkey kidney cells infected with parainfluenza Sendai virus and on the mice infected with influenza virus. The increase of antiviral activities of N-Phenylbiguanide and N-p-Ethoxyphenylbiguanide was estimated.
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In this study 2-guanidinebenzimidazole (GBI) and 1-phenylbiguanide (PBG) appear to be capable of decreasing gastric acid secretion, while the compounds dimethylbiguanide and cyanoguanidine do not. Thus, the antisecretory effect is present when the biguanide groups are associated with lipophilic molecules. GBI and PBG depress gastric acid secretion, even when it has been stimulated by carbamoylcholine (carbachol) or betazole. The antihistamine effects of GBI and PBG on betazole-stimulated gastric acid secretion were confirmed by the inhibitory activity of these compounds on the isolated guinea pig auricle stimulated by histamine. The antimuscarine activity of GBI and PBG on carbachol-stimulated gastric acid secretion in rats is also supported by the way in which these same drugs depress the motility of the duodenum and colon of the anaesthetized cat stimulated by prostigmine. The above mentioned effects of these compounds are also associated with myolytic activity, since they decrease the spontaneous and histamine-stimulated motility of the duodenum and colon. GBI and PBG probably depress gastric acid secretion by interfering with both histamine and acetylcholine receptors and with other sites involved in the secretory process.
Article
In this study 2-guanidine-4-methylquinazoline (2-GMQ) appeared to decrease basal and stimulated gastric acid secretion, while structurally related compounds as dimethyl-biguanide, cyanoguanidine and 2-cyanoamino-4-methylpyrymidine did not. Thus, there is an antisecretory effect when the biguanide group is associated with a lipophilic structure. The antisecretive effects exerted by 2-GMQ are associated with anti H2-histamine activity. The anti H2-histamine nature of the effects of 2-GMQ was confirmed by the capacity of this compound of depressing the chronotropic activity of the isolated guinea pig auricle increased by histamine, as well as relaxant activity in rat uterus contracted by histamine, since both preparations are rich in H2-histamine receptors.
A review is presented which began as a literature survey listing verbatim over fifty abstracts and references to the use of moroxydine in the treatment of a number of viral disorders throughout Europe and Scandinavia between 1960 and 1985. The list was first circulated in 1990 and was revised six times as new information became available. The sources are unusual in their diversity and originally appeared in several other languages besides English. Moroxydine may be effective against a number of DNA and RNA viruses, influenza being the original application of the substance when it emerged in the late 1950's. The drug received some attention around 1960, and the introduction of thalidomide at around the same time (1961) is one likely explanation for its current obscurity. Side-effects are reported to be mild and infrequent, and evidence exists that the substance possesses other characteristics which plead for further investigation.
Article
Octopamine (OA), a biogenic monoamine structurally related to noradrenaline, acts as a neurohormone, a neuromodulator and a neurotransmitter in invertebrates. It is present in relatively high concentrations in neuronal as well as in non-neuronal tissues of most invertebrate species studied. It functions as a model for the study of modulation in general. OA modulates almost every physiological process in invertebrates studied so far. Among the targets are peripheral organs, sense organs, and processes within the central nervous system. The known actions of OA in the central nervous system include desensitization of sensory inputs, influence on learning and memory, or regulation of the 'mood' of the animal. Together with tyramine, OA it is the only neuroactive non-peptide transmitter whose physiological role is restricted to invertebrates. This focussed the interest on the corresponding OA receptors. They are believed to be good targets for highly specific insecticides as they are not found in vertebrates. All octopamine receptors belong to the family of G-protein coupled receptors. Four of them could be distinguished using pharmacological tools. They show different coupling to second messenger systems including activation and inhibition of adenylyl cyclase, activation of phospholipase C and coupling to a chloride channel. Recently, octopamine receptors from molluscs and insects have been cloned. Further studies of all aspects of octopaminergic neurotransmission should give deeper insights into modulation of peripheral and sense organs and within the central nervous system in general.
Article
The syntheses, structural elucidation based on NMR spectroscopy and X-ray analysis of 8 as well as antitumor activities of novel 2,4-diamino-1,3,5-triazine derivatives 5 and 7-22 are described. Screenings performed at NCI showed that most derivatives possessed a moderate to strong growth inhibition activity on various tumor panel cell lines between 0.148 and 56.2 microM concentrations. 2-Amino-6-bromomethyl-4-(3,5,5-trimethyl-2-pyrazoline)-1,3,5-triazine 11 showed the most potent antitumor activity with the mean midpoint values of log(10) GI50, log(10) TGI50 and log(10) LC50 of all tests equal to -5.26, -4.81 and -4.37, respectively and therefore, it can be considered as a lead structure for further development of anticancer agents.
Article
The trace amine para-tyramine is structurally and functionally related to the amphetamines and the biogenic amine neurotransmitters. It is currently thought that the biological activities elicited by trace amines such as p-tyramine and the psychostimulant amphetamines are manifestations of their ability to inhibit the clearance of extracellular transmitter and/or stimulate the efflux of transmitter from intracellular stores. Here we report the discovery and pharmacological characterization of a rat G protein-coupled receptor that stimulates the production of cAMP when exposed to the trace amines p-tyramine, beta-phenethylamine, tryptamine, and octopamine. An extensive pharmacological survey revealed that psychostimulant and hallucinogenic amphetamines, numerous ergoline derivatives, adrenergic ligands, and 3-methylated metabolites of the catecholamine neurotransmitters are also good agonists at the rat trace amine receptor 1 (rTAR1). These results suggest that the trace amines and catecholamine metabolites may serve as the endogenous ligands of a novel intercellular signaling system found widely throughout the vertebrate brain and periphery. Furthermore, the discovery that amphetamines, including 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy"), are potent rTAR1 agonists suggests that the effects of these widely used drugs may be mediated in part by this receptor as well as their previously characterized targets, the neurotransmitter transporter proteins.