ChemMedChem

Thiazole-based sigma-1 receptor ligands: Diversity by late-stage C-H arylation of thiazoles, structure affinity and selectivity relationships and molecular interactions ()
Spirocyclic thiophene derivatives represent promising sigma-1 ligands with high sigma-1 affinity and selectivity over the sigma-2 subtype. In order to increase ligand efficiency, the thiophene ring was replaced bioisosterically by a thiazole ring and the pyran ring was opened. Late-stage diversification by regioselective C-H arylation of thiazoles 9a-c resulted in a set of 53 compounds with high diversity. This set of compounds was analyzed with respect to sigma-1 affinity, sigma-1/sigma-2 selectivity, lipophilicity (logD7.4), lipophilicity-corrected ligand efficiency (LELP) and molecular target interactions. The most promising candidates are the pyridyl substituted thiazole derivatives 33c and 34c possessing low nanomolar 1 affinity (Ki = 1.3 nM and 1.9 nM), high 1/2 selectivity (>1500-fold), low lipophilicity (logD7.4 = 1.8) and very good ligand efficiency (LELP = 5.5) indicating promising pharmacodynamics and pharmacokinetics. Molecular simulation studies including docking and deconvolution of the free binding energy into its major components led to reduced hydrophobic stabilization of the pyridyl derivatives 33c and 34c, which is compensated by lower desolvation energy.
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Chemoproteomics-aided medicinal chemistry for the discovery of EPHA2 inhibitors ()
The receptor tyrosine kinase EPHA2 has gained interest as therapeutic drug target in cancer and infectious diseases. However, EPHA2 research and EPHA2-based therapies have been hampered by the lack of selective small molecule inhibitors. Here, we report on the synthesis and evaluation of dedicated EPHA2 inhibitors based on the clinical BCR-ABL/SRC inhibitor Dasatinib as a lead structure. We designed hybrid structures of Dasatinib and the previously known EPHA2 binders CHEMBL249097, PD-173955 and a known EPHB4 inhibitor in order to exploit both the ATP pocket entrance as well as the ribose pocket as binding epitopes in the kinase EPHA2. Medicinal chemistry and inhibitor design was guided by a chemical proteomic approach allowing for early selectivity profiling of the newly synthesized inhibitor candidates. Concomitant protein crystallography of 17 inhibitor co-crystals delivered detailed insight into the atomic interactions that underlie the structure-affinity-relationship. Finally, the anti-proliferative effect of the inhibitor candidates was confirmed in the glioblastoma cell line SF-268. In this work, we thus discovered a novel EPHA2 inhibitor candidate 4a featuring an improved selectivity profile while maintaining potency against EPHA2 and anti-cancer activity in SF-268 cells.
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Synthesis, ADMET properties, and biological evaluation of benzothiazole compounds targeting CXCR2 ()
Herein, we describe the synthesis and biological evaluation of a series of novel benzothiazoles based on a diaryl urea scaffold previously reported in some allosteric CXCR2 inhibitors. From a library of 41 new compounds, 17 showed significant inhibition of CXCR2 with IC50 less than 10 M and selectivity over CXCR4. Our ADMET simulations suggest favorable drug-like properties for the active compounds. Importantly, we developed a predictive model that can distinguish active from inactive compounds and will serve as a valuable tool to guide the design of optimized compounds to be evaluated in preclinical models.
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Kinome-Wide Profiling Prediction of Small Molecules ()
Extensive kinase profiling data, covering more than half of the human kinome, are nowadays available and allow construction of activity prediction models of high practical use. Proteochemometric (PCM) approaches utilize compound and protein descriptors, which enables the extrapolation of bioactivity values also to so far unexplored kinases. In this study, the potential of PCM to make large-scale predictions on the entire kinome is explored, considering the applicability on novel compounds and kinases, including clinically relevant mutants. A rigorous validation indicates high prediction power on left-out kinases and superiority over individual kinase QSAR models for new compounds. Furthermore, external validation on clinically relevant mutant kinases reveals an excellent prediction power for mutations spread across the ATP binding site.
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Synthesis and Antineoplastic Evaluation of Mitochondrial Complex II (Succinate Dehydrogenase) Inhibitors Derived from Atpenin A5 ()
Mitochondrial complex II (CII) is an emerging target for numerous human diseases. Sixteen analogues of the CII inhibitor natural product atpenin A5 were prepared to evaluate the structure-activity relationship of the C-5 pyridine side chain. The side chain ketone moiety was determined to be pharmacophoric, engendering a bioactive conformation. Analogue 16c displayed CII IC50 = 64 nM, retained selectivity for CII over mitochondrial complex I (>156-fold) and possessed a ligand-lipophilicity efficiency of 5.62, desirable metrics for a lead compound. This derivative and other highly potent complex II inhibitors possess potent and selective anti-proliferative activity in multiple human prostate cancer cell lines under both normoxia and hypoxia, acting to inhibit mitochondrial electron transport.
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Towards the Identification of Novel Breast Cancer Inhibitors Specific for GPER-Expressing Cells ()
Together with ERα/β, GPER (G protein-coupled estrogen receptor) mediates important pathophysiological signaling pathways induced by estrogens and is currently regarded as a promising target for ER-negative and triple-negative breast cancer. Only a few selective GPER modulators have been reported to date and their use in cancer cell lines has often led to contradictory results. Here we report the application of virtual screening and cell-based studies for the identification of new chemical scaffolds with a specific anti-proliferative effect against GPER-expressing breast cancer cell lines.
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Comparison of the Human A2A Adenosine Receptor Recognition by Adenosine and Inosine: New Insights from Supervised Molecular Dynamics Simulations. ()
Adenosine deaminase converts adenosine to inosine. Differently by adenosine, modest attention has been dedicated to the physiological roles of inosine. Nevertheless, recent studies demonstrate that inosine has neuroprotective, cardioprotective immunomodulatory, and antidepressive effects. It has been recently reported by Welihinda and collaborators that inosine is a less potent agonist than adenosine at the A2A AR. To better depict the differences in receptor recognition mechanism of both adenosine and inosine, in this work supervised molecular dynamics (SuMD) simulations have been performed and analyzed.
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1,2,4-Triazole-3-thione compounds as inhibitors of di-zinc metallo-β-lactamases ()
Metallo-β-lactamases (MBL) cause resistance of Gram-negative bacteria to β-lactam antibiotics and are of serious concern because they can inactivate the last-resort carbapenems and because MBL inhibitors of clinical value are still lacking. We have previously identified the original binding mode of a 4-amino-1,2,4-triazole-3-thione compound, IIIA, within the di-zinc active site of the L1 MBL. Here, we present the crystallographic structure of a complex of L1 with the corresponding non-amino compound IIIB. Unexpectedly, IIIB showed a similar but reverse binding mode compared to IIIA. These 3D structures suggested that the triazole-thione scaffold was suitable to bind to the catalytic site of di-zinc metallo-enzymes. Based on these results, we synthesized 54 analogues of IIIA or IIIB. Nineteen showed IC50 values in the μM range towards at least one of five representative MBLs (L1, VIM-4, VIM-2, NDM-1, IMP-1). Five of these exhibited a significant inhibition of at least four enzymes, including NDM-1, VIM-2 and IMP-1. Active compounds mainly featured either halogen or bulky bicyclic aryl substituents. Finally, some compounds were also tested on several microbial di-nuclear Zn-dependent hydrolases belonging to the MBL fold superfamily (i.e. endonucleases and glyoxalase II) to explore their activity toward structurally similar but functionally distinct enzymes. While the bacterial tRNases were not inhibited, the best IC50's towards plasmodial glyoxalase II were in the 10 μM range.
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Design, synthesis and structure-activity relationship analysis of novel thiazolo[3,2-a]pyrimidin derivatives with anti-inflammatory activity in acute lung injury ()
Acute lung injury (ALI) results in high lethality rate, and interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) contribute most to tissue deterioration in ALI. In this study, we designed and synthesized a new series of thiazolo[3,2-a]pyrimidine derivatives based on lead compound 6, and evaluated their anti-inflammatory activities. The structure-activity relationship studies led to the discovery of two highly potent inhibitors. The promising compounds 11e and 11l inhibited lipopolysaccharide (LPS)-induced IL-6 and TNF-α release in a dose-dependent manner in mouse primary peritoneal macrophages (MPMs). Furthermore, administration of 11e and 11l resulted in lung histopathological improvements and attenuated LPS-caused ALI in vivo. Taken together, these data indicate that the novel thiazolo[3, 2-a]pyrimidine derivatives, 11e and 11l, could be developed as candidates for the treatment of ALI.
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Recent advances on synthetic α-glucosidase inhibitors ()
For the past few years, there are more and more people with type 2 diabetes due to unhealthy diet, less exercise and overweight. To find novel and efficient anti-diabetes agents becomes an urgent task for scientists. Among those anti-diabetes drugs, α-glucosidase inhibitor drugs are proved to have many advantages which are inaccessible for other drugs, therefore, large amounts of new compounds as α-glucosidase inhibitors have been reported lately. In this review, we summarized those newly found α-glucosidase inhibitors and their structure-activity relationship in anti-diabetic studies, wishing to provide better structures as α-glucosidase inhibitors or even pre-clinical candidates. Beyond that, some enlightening synthetic strategies of relevant compounds are highlighted.
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Rational design and synthesis of 1-(arylideneamino)-4-aryl-1H-imidazole-2-amine derivatives as antiplatelet agents ()
Based on the previous studies indicating the pharmacophoric role of hydrazone group and azole rings for antiplatelet aggregation activity, a few series of compounds with both hydrazone and azole (imidazole) ring in their structures were synthesized and their platelet aggregation inhibitory effect was evaluated. Two compounds among the 1-(arylideneamino)-4-aryl-1H-imidazole-2-amine derivatives compound 4a and 4p showed IC50 values comparable to that of aspirin against collagen as platelet aggregation inducer. Structural comparison of the synthesized compounds revealed that those compounds with para-substituted phenyl ring on imidazole ring are among the most active compounds against the platelet aggregation induced by arachidonic acid (AA) and the presence of thiophene ring in these compounds (6b, 6c and 6d) will maximize their antiplatelet activity.
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Identification of α7 Nicotinic Acetylcholine Receptor Silent Agonists based on the Spirocyclic Quinuclidine-Δ2-Isoxazoline Scaffold: Synthesis and Electrophysiological Evaluation ()
Compound 11 (3-(benzyloxy)-1'-methyl-1'-azonia-4H-1'-azaspiro[isoxazole-5,3'-bicyclo[2.2.2]octane] iodide) was selected from a previous set of nicotinic ligands as a suitable model ligand for the design of new silent agonists of α7 nAChRs. Silent agonists evoke little or no channel activation but can induce the α7 desensitized Ds state, sensitive to a type II positive allosteric modulator (PAM) such as PNU-120596. Introduction of meta-substituents into the benzyloxy moiety of 11 led to the two sets of tertiary amines and quaternary ammonium salts based on the spirocyclic quinuclidinyl-Δ2-isoxazoline scaffold. Electrophysiological assays performed on Xenopus laevis oocytes expressing human α7 nAChRs highlighted four compounds which are endowed with a significant silent agonism profile. The structure-activity relationships on this group of analogs put in evidence the crucial role of the positive charge at the quaternary quinuclidine nitrogen. Moreover, the present study indicates that meta-substituents, in particular halogens, on the benzyloxy substructure direct specific interactions able to stabilize a desensitized conformational state of the receptor and induce silent activity.
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Nucleic Acid Templated Reactions for Chemical Biology ()
Nucleic acid directed bioorthogonal reactions offer the fascinating opportunity to potentially unveil and redirect a plethora of intracellular mechanisms. Nano- to picomolar amounts of specific RNA molecules serve as templates and catalyze the selective formation of molecules that i) exert biological effects or ii) provide measurable signals for RNA detection. Turnover of reactants on the template is a valuable asset when concentrations of RNA templates are low. The idea is to use RNA templated reactions to fully control biodistribution of drugs as well as pushing the detection limits of DNA or RNA analytes to extraordinary sensitivities. In this paper, we review recent and instructive examples of conditional synthesis or release of compounds for in cellulo protein interference and intracellular nucleic acid imaging.
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Lanthanide complexes in molecular magnetic resonance imaging and theranostics ()
Lanthanide complexes have attracted continuous attention in the biomedical field and today various imaging applications make use of their versatile magnetic and luminescence properties. In this minireview, we give insights into the mechanistic aspects that allow modulating the relaxation or chemical exchange saturation transfer (CEST) features, thus the MRI efficiency of paramagnetic lanthanide chelates in order to create agents that are capable of providing an MRI response as a function of a specific biomarker. We focus on the detection of neurotransmitters, enzymatic activities and amyloid peptides. We also describe two selected theranostic strategies: (i) a novel approach directed at monitoring drug release from liponanoparticles and (ii) molecular or nanoparticle probes for the MRI visualization of photosensitizer delivery in photodynamic therapy.
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Residence Time (RT), a new parameter to predict neurosteroidogenic efficacy of Translocator Protein (TSPO) ligands: N,N-dialkyl-2-arylindol-3-ylglyoxylamides, a case study ()
Targeting neuroactive steroid biosynthetic pathway by specific 18 kDa Translocator Protein (TSPO) ligands may represent a therapeutic approach in a variety of neurodegenerative and neuropsychiatric diseases. However, the lack of correlation between the binding affinity and the in vitro steroidogenic efficacy has limited the identification of lead compounds by a traditional affinity-based drug discovery strategy. Our recent researches indicate that the key factor for robust steroidogenic TSPO ligand efficacy is not the binding affinity per se, but rather the time the compound spends into the target, namely its Residence Time (RT). The assessment of this kinetic parameter during the in vitro characterization of compounds appears mandatory in order to obtain structure-efficacy relationships suitable for the future development of novel molecules with promising pharmacological properties.
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The Drug Discovery and Development Industry in India - Two Decades of Proprietary Small-Molecule R&D ()
This review provides a comprehensive survey of proprietary drug discovery and development efforts performed by Indian companies between 1994 and mid-2016. It is based on the identification and detailed analysis of pharmaceutical, biotechnology and contract research companies active in proprietary New Chemical Entity R&D in India. Information on preclinical and clinical development compounds has been collected by company, therapeutic indication, mode of action, target class, and development status. The analysis focuses on the overall pipeline and its evolution over two decades, contributions by type of company, therapeutic focus, attrition rates, and contribution to Western pharmaceutical pipelines through licensing agreements. This comprehensive analysis is the first of its kind, and represents in our view a significant contribution to the understanding of the current state of the drug discovery and development industry in India.
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Targeting DNA-PK for Cancer Therapy ()
The catalytic activity of DNA-dependent protein kinase (DNA-PK) is critical to its ability to repair lethal DNA-double strand breaks (DSBs). This includes repair of DSB lesions resulting from oxidative stress, oncogene-induced transcription, or following therapeutic treatment of cancer cells. Armed with this knowledge, many attempts have been made to identify small molecule inhibitors of DNA-PK activity as an approach to induce tumour chemo- and radio-sensitisation. This review examines the structures of known reversible and irreversible inhibitors, including those based upon chromen-4-one, arylmorpholine, and benzaldehyde scaffolds. DNA-PK catalytic inhibitors, such as VX-984 and M3814, have now progressed into clinical development, which should help to further advance our understanding of whether this approach represents a promising therapeutic strategy for the treatment of cancer.
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Synthesis and SAR Study of Anticancer Protoflavone Derivatives: Investigation of Cytotoxicity and Interaction with ABCB1 and ABCG2 Multidrug Efflux Transporters ()
There is a constant need for new therapies against multidrug-resistant (MDR) cancer. Natural compounds are a promising source of novel anticancer agents. We recently showed that protoflavones display activity in MDR cancer cell lines that overexpress the P-glycoprotein (P-gp) drug efflux pump. In this study, 52 protoflavones, including 22 new derivatives, were synthesized and tested against a panel of drug-sensitive parental cells and their MDR derivatives obtained by transfection with the human ABCB1 or ABCG2 genes, or by adaptation to chemotherapeutics. With the exception of protoapigenone, identified as a weak ABCG2 substrate, all protoflavones bypass resistance conferred by these two transporters. The majority of the compounds were found to exhibit mild to strong (up to 13-fold) selectivity against the MCF-7Dox and KB-V1 cell lines, but not to transfected MDR cells engineered to overexpress the MDR transporters. Our results suggest that protoflavones can overcome MDR cancer by evading P-gp-mediated efflux. Protoflavones vs. MDR cancer: Two drug efflux pumps, ABCB1 and ABCG2, confer multidrug resistance (MDR) on numerous cancer cell types. New protoflavones were synthesized and tested against a panel of drug-sensitive cancer cells and their MDR counterparts. In vitro studies with various A-ring and 1′-substituted protoflavones revealed derivatives that evade efflux or selectively kill adapted MDR cells. 6-methoxyprotoflavone 1′-O-allyl ether acted with mild MDR selectivity in a murine lymphoma cell line transfected with the human ABCB1 gene.
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Discovery of 1-Hydroxypyridine-2(1H)-thione-6-carboxylic Acid as a First-in-Class Low-Cytotoxic Nanomolar Metallo β-Lactamase Inhibitor ()
VIM-2 is one of the most common carbapenem-hydrolyzing metallo β-lactamases (MBL) found in many drug-resistant Gram-negative bacterial strains. Currently, there is a lack of effective lead compounds with optimal therapeutic potential within our drug development pipeline. Here we report the discovery of 1-hydroxypyridine-2(1H)-thione-6-carboxylic acid (3) as a first-in-class metallo β-lactamase inhibitor (MBLi) with a potent inhibition Ki of 13 nm against VIM-2 that corresponds to a remarkable 0.99 ligand efficiency. We further established that 3 can restore the antibiotic activity of amoxicillin against VIM-2-producing E. coli in a whole cell assay with an EC50 of 110 nm. The potential mode of binding of 3 from molecular modeling provided structural insights that could corroborate the observed changes in the biochemical activities. Finally, 3 possesses a low cytotoxicity (CC50) of 97 μm with a corresponding therapeutic index of 880, making it a promising lead candidate for further optimization in combination antibacterial therapy. An old dog with new tricks! Pyrithione is a well-established pharmacophore for zinc-specific chelation. The discovery of 1-hydroxypyridine-2(1H)-thione-6-carboxylic acid as a first-in-class metallo β-lactamase inhibitor that can rescue β-lactam antibiotic activity represents a promising lead for further development.
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Steroid–AuI–NHC Complexes: Synthesis and Antibacterial Activity ()
A series of gold(I) pioneer complexes bearing N-heterocyclic carbenes and steroid derivatives (ethynylestradiol and ethisterone) with the generic formula [Au(R2-imidazol-2-ylidene)(steroid)] (where R=CH3 or CH2CH2OCH3) were synthesized, and the X-ray structure of a rare of gold(I)–estradiol derivative is discussed. Toxicity studies reveal notable antibacterial activity of the gold-based compounds, which is significantly increased in vivo by the presence of the estradiol unit. Toxicity profiling was estimated in vitro versus Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, and in vivo on Galleria mellonella larvae against E. coli. The strategic combination of N-heterocyclic carbene AuI complexes and estrogen derivatives exhibits an improved in vivo antibacterial activity on larvae of G. mellonella against E. coli. The presence of the steroids is determinant for the increased in vivo activity. This finding presents a pioneering perspective on the search for effective antimicrobial agents, as the results are comparable to those obtained using a mammalian model.
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Structure–Activity Relationship Studies of the Cyclic Depsipeptide Natural Product YM-254890, Targeting the Gq Protein ()
Extracellular signals perceived by G protein-coupled receptors are transmitted via G proteins, and subsequent intracellular signaling cascades result in a plethora of physiological responses. The natural product cyclic depsipeptides YM-254890 and FR900359 are the only known compounds that specifically inhibit signaling mediated by the Gq subfamily. In this study we exploit a newly developed synthetic strategy for this compound class in the design, synthesis, and pharmacological evaluation of eight new analogues of YM-254890. These structure–activity relationship studies led to the discovery of three new analogues, YM-13, YM-14, and YM-18, which displayed potent and selective Gq inhibitory activity. This provides pertinent information for the understanding of the Gq inhibitory mechanism by this class of compounds and importantly provides a pathway for the development of labeled YM-254890 analogues. Behind the signal: Three new selective Gq signaling inhibitors (YM-13, YM-14, and YM-18) were discovered that show potencies equivalent with that of the natural compound YM-254890. These results provide pertinent information for understanding the Gq inhibitory mechanism. Importantly, they also provide a pathway for the development of labeled YM-254890 analogues.
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Synthesis of Imidazolium Oligomers with Planar and Stereo Cores and Their Antimicrobial Applications ()
A series of imidazolium oligomers with novel planar and stereo core structures were designed and synthesized. These compounds have symmetric structures with different cores, tails, and linkers. These new imidazolium oligomers demonstrated a desirable set of bioactivities against four types of clinically relevant microbes including E. coli, S. aureus, P. aeruginosa, and C. albicans. The planar oligomers with three di-imidazolium arms and n-octyl tails showed good antimicrobial activity and biocompatibility. Oligomers with ortho-xylylene linkers exhibited higher antimicrobial activity and higher hemolytic ability than those oligomers with para-xylylene linkers. These results shed light on the structure–property relationships of synthetic polymeric antimicrobial agents. Flat vs. chiral: A series of imidazolium oligomers with planar or chiral center cores were designed and synthesized. They showed good antimicrobial and antifungal activity and biocompatibility. Results of structure–property relationship studies shed light on the function-oriented design of synthetic polymeric antimicrobial agents.
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Identification of Transthyretin Fibril Formation Inhibitors Using Structure-Based Virtual Screening ()
Transthyretin (TTR) is the primary carrier for thyroxine (T4) in cerebrospinal fluid and a secondary carrier in blood. TTR is a stable homotetramer, but certain factors, genetic or environmental, could promote its degradation to form amyloid fibrils. A docking study using crystal structures of wild-type TTR was planned; our aim was to design new ligands that are able to inhibit TTR fibril formation. The computational protocol was thought to overcome the multiple binding modes of the ligands induced by the peculiarity of the TTR binding site and by the pseudosymmetry of the site pockets, which generally weaken such structure-based studies. Two docking steps, one that is very fast and a subsequent step that is more accurate, were used to screen the Aldrich Market Select database. Five compounds were selected, and their activity toward inhibiting TTR fibril formation was assessed. Three compounds were observed to be actives, two of which have the same potency as the positive control, and the other was found to be a promising lead compound. These results validate a computational protocol that is able to archive information on the key interactions between database compounds and TTR, which is valuable for supporting further studies. Rapid and accurate! Inhibitors of transthyretin (TTR) fibril deposition were identified thanks to a structure-based virtual screening of the entire Aldrich Market Select database. The first results of this protocol, despite the unique peculiarity of the TTR site with its symmetry and multi-binding mode, allowed the detection of two very active inhibitors and one scaffold for optimization. Much information, however, is still stored in the outputs.
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Novel, Selective, and Developable Dopamine D3 Antagonists with a Modified “Amino” Region ()
This Minireview describes a presentation made at the XXIV National Meeting in Medicinal Chemistry (NMMC) held in Perugia (Italy), September 11–14, 2016. It relates to the discovery of novel templates of the so-called “amino” region of dopamine D3 receptor antagonists. Moving from the early scaffolds, which were modified in the amine portion, this review discusses the variations that led to the discovery of new systems published in 2016, which allowed the identification of compounds endowed with great selectivity over the dopamine D2 receptor and the human ether-à-go-go-related gene (hERG) ion channel. The main efforts in characterizing these compounds were devoted not only to determining their potency and selectivity relative to closely associated targets (e.g., the dopamine D2 receptor), but to ensure a large therapeutic window versus liability points such as hERG. In particular, we present examples of derivatives with selectivities greater than 2000-fold. Furthermore, much focus is devoted to the overall developability of the scaffolds, ensuring that appropriate physicochemical and pharmacokinetic parameters are present in all compounds progressing through the screening cascade. New scaffolds! This Minireview describes the discovery of novel templates of the so-called “amino” region of dopamine D3 receptor antagonists. Moving from the early scaffolds, which were modified in the amine portion, this review discusses the variations that led to the discovery of new systems published in 2016, which allowed the identification of compounds endowed with great selectivity over the dopamine D2 receptor and hERG channels.
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Cannabinoid Type 1 Receptor (CB1) Ligands with Therapeutic Potential for Withdrawal Syndrome in Chemical Dependents of Cannabis sativa ()
Cannabis sativa withdrawal syndrome is characterized mainly by psychological symptoms. By using computational tools, the aim of this study was to propose drug candidates for treating withdrawal syndrome based on the natural ligands of the cannabinoid type 1 receptor (CB1). One compound in particular, 2-n-butyl-5-n-pentylbenzene-1,3-diol (ZINC1730183, also known as stemphol), showed positive predictions as a human CB1 ligand and for facile synthetic accessibility. Therefore, ZINC1730183 is a favorable candidate scaffold for further research into pharmacotherapeutic alternatives to treat C. sativa withdrawal syndrome. Off the hook: Most drugs used to treat chemical dependence treat the symptoms but not the underlying biological target. This study was designed to identify potential CB1 agonists to treat C. sativa withdrawal syndrome. Pharmacophore-based ligand screening and classification by structural similarity revealed a group of seven compounds for which predictions of pharmacokinetics, toxicology, biological activity, and synthetic accessibility were carried out. One compound stood out as particularly well suited for further development, with the ultimate goal of decreasing the damage caused by drug dependency.
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Target Deconvolution Efforts on Wnt Pathway Screen Reveal Dual Modulation of Oxidative Phosphorylation and SERCA2 ()
Wnt signaling is critical for development, cell proliferation and differentiation, and mutations in this pathway resulting in constitutive signaling have been implicated in various cancers. A pathway screen using a Wnt-dependent reporter identified a chemical series based on a 1,2,3-thiadiazole-5-carboxamide (TDZ) core with sub-micromolar potency. Herein we report a comprehensive mechanism-of-action deconvolution study toward identifying the efficacy target(s) and biological implication of this chemical series involving bottom-up quantitative chemoproteomics, cell biology, and biochemical methods. Through observing the effects of our probes on metabolism and performing confirmatory cellular and biochemical assays, we found that this chemical series inhibits ATP synthesis by uncoupling the mitochondrial potential. Affinity chemoproteomics experiments identified sarco(endo)plasmic reticulum Ca2+-dependent ATPase (SERCA2) as a binding partner of the TDZ series, and subsequent validation studies suggest that the TDZ series can act as ionophores through SERCA2 toward Wnt pathway inhibition. Waste not, Wnt not: We identified a 1,2,3-thiadiazole-5-carboxamide chemical series in a Wnt pathway inhibition screen. We generated chemical probes to identify the targets of this series based on our efforts to optimize potency and physical properties. Using a combination of biochemical, cell biology, and chemoproteomics methods, we found two previously unreported mechanisms for this pharmacophore: uncouplers of the mitochondrial potential and Ca2+ ionophores through interaction with SERCA2.
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A Time-Resolved FRET Cell-Based Binding Assay for the Apelin Receptor ()
Analogues of apelin-13 carrying diverse spacers and an ad hoc DY647-derived fluorophore were designed and synthesized by chemoselective acylation of α-hydrazinopeptides. The resulting probes retain very high affinity and efficacy for both the wild-type and SNAP-tagged apelin receptor (ApelinR). They give a time-resolved FRET (TR-FRET) signal with rare-earth lanthanides used as donor fluorophores grafted onto the SNAP-tagged receptor. This specific signal allowed the validation of a binding assay with a high signal-to-noise ratio. In such an assay, the most potent sub-nanomolar fluorescent probe was found to be competitively displaced by the endogenous apelin peptides with binding constants similar to those obtained in a classical radioligand assay. We have thus validated the first TR-FRET cell-based binding assay for ApelinR with potential high-throughput screening applications. The search is on! There is still a need for the rapid discovery of apelin receptor ligands for use as pharmacological probes and precursors of drug candidates. As an alternative to radioligand binding assays, we report herein an unprecedented, efficient, robust, and safe time-resolved binding assay to investigate ligand–apelin receptor interactions at the cell surface with potential application for high-throughput screening.
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Molecular Features of the YAP Inhibitor Verteporfin: Synthesis of Hexasubstituted Dipyrrins as Potential Inhibitors of YAP/TAZ, the Downstream Effectors of the Hippo Pathway ()
Porphyrin derivatives, in particular verteporfin (VP), a photosensitizer initially designed for cancer therapy, have been identified as inhibitors of the YAP–TEAD interaction and transcriptional activity. Herein we report the efficient convergent synthesis of the dipyrrin half of protoporphyrin IX dimethyl ester (PPIX-DME), in which the sensitive vinyl group was created at the final stage by a dehydroiodination reaction. Two other dipyrrin derivatives were synthesized, including dipyrrin 19 [(Z)-2-((3,5-dimethyl-4-vinyl-2H-pyrrol-2-ylidene)methyl)-3,5-dimethyl-4-vinyl-1H-pyrrole], containing two vinyl groups. We found that VP and dipyrrin 19 showed significant inhibitory effects on TEAD transcriptional activity in MDA-MB-231 human breast cancer cells, whereas other compounds did not show significant changes. In addition, we observed a marked decrease in both YAP and TAZ levels following VP treatment, whereas dipyrrin 19 treatment primarily decreased the levels of YAP and receptor kinase AXL, a downstream target of YAP. Together, our data suggest that, due to their chemical structures, porphyrin- and dipyrrin-related derivatives can directly target YAP and/or TAZ proteins and inhibit TEAD transcriptional activity. Directed dipyrrins: An efficient convergent synthesis yielded hexasubstituted dipyrrins structurally related to verteporfin (VP), with a sensitive vinyl group created at the final stage by a dehydroiodination reaction. While VP showed a direct effect on YAP and TAZ levels, one dipyrrin affected only YAP levels, suggesting that dipyrrin-related compounds may directly affect the expression of YAP and/or TAZ.
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Structure–Activity Relationships on Cinnamoyl Derivatives as Inhibitors of p300 Histone Acetyltransferase ()
Human p300 is a polyhedric transcriptional coactivator that plays a crucial role in acetylating histones on specific lysine residues. A great deal of evidence shows that p300 is involved in several diseases, including leukemia, tumors, and viral infection. Its involvement in pleiotropic biological roles and connections to diseases provide the rationale to determine how its modulation could represent an amenable drug target. Several p300 inhibitors (i.e., histone acetyltransferase inhibitors, HATis) have been described so far, but they all suffer from low potency, lack of specificity, or low cell permeability, which thus highlights the need to find more effective inhibitors. Our cinnamoyl derivative, 2,6-bis(3-bromo-4-hydroxybenzylidene)cyclohexanone (RC56), was identified as an active and selective p300 inhibitor and was proven to be a good hit candidate to investigate the structure–activity relationship toward p300. Herein, we describe the design, synthesis, and biological evaluation of new HATis structurally related to our hit; moreover, we investigate the interactions between p300 and the best-emerged hits by means of induced-fit docking and molecular-dynamics simulations, which provided insight into the peculiar chemical features that influence their activity toward the targeted enzyme. HAT trick: Histone acetyltransferase (HAT) is an attractive anticancer target. Several HAT inhibitors have been identified, but they all exhibit low potency or pharmacodynamics limits. Herein we report the design and synthesis along with biological evaluations and theoretical investigations of potent and selective cinnamoyl compounds, highlighting the peculiar features required to develop an effective HAT inhibitor.
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Identifying Protein Allosteric Transitions for Drug Discovery with 1D NMR ()
Allosteric drugs present many advantages over orthosteric drugs and are therefore an attractive approach in drug discovery, despite being highly challenging. First, the binding of ligands in protein allosteric pockets do not ensure an allosteric effect, and second, allosteric ligands can possess diverse modes of pharmacology even within a compound family. Herein we report a new method to: 1) detect allosteric communication between protein binding sites, and 2) compare the effect of allosteric ligands on the allosteric transitions of the protein target. The method, illustrated with glycogen phosphorylase, consists of comparing 1D saturation transfer difference (STD) NMR spectra of a molecular spy (here fragments) in the absence and presence of allosteric ligands. The modification of the STD NMR spectrum of the fragment indicates whether the protein dynamics/conformations have been changed in the presence of the allosteric modulator, thereby highlighting allosteric coupling between the binding pocket of the reference compound (in this case the fragment) and the allosteric pocket. The other site: Allosteric drug discovery is an attractive approach for the generation of drugs with improved safety, while being highly challenging. Fundamental issues are the identification of allosterically coupled protein pockets and the observation of the allosteric effect resulting from ligand binding. Herein we report a method for the detection and comparison of ligand-induced allosteric transitions based on 1D NMR spectroscopy.
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Benzylphenylpyrrolizinones with Anti-amyloid and Radical Scavenging Effects, Potentially Useful in Alzheimer's Disease Treatment ()
Herein we describe the drug design steps developed to increase the radical scavenging and β-amyloid aggregation inhibitory activities of a previously described series of benzylidenephenylpyrrolizinones. Among the newly synthesized derivatives, some benzylphenylpyrrolizinones exhibited interesting results in regard to those activities. Initial druggability parameters were measured, and suggest these compounds as a suitable starting point for potential alternatives in treating Alzheimer's disease. Pick up & break up: This study aimed at increasing the radical scavenging and anti-Aβ-aggregation activities of a series of benzylidenephenylpyrrolizinones. Some of the new derivatives showed promising results in this regard. These compounds could serve as a good starting point for new drugs to treat Alzheimer's disease.
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1,3,5-Trisubstituted Pyrazoles as Potent Negative Allosteric Modulators of the mGlu2/3 Receptors ()
The metabotropic glutamate subtype 2 (mGlu2) receptor is a presynaptic membrane receptor distributed widely in brain that provides feedback inhibitory control of glutamate release. Inhibition of the mGlu2 receptor function with a negative allosteric modulator (NAM) enhances activity-dependent glutamate release, which may be of therapeutic benefit for the treatment of neurological and psychiatric disorders. An attractive pyrazole hit was identified after a high-throughput screening (HTS) campaign. The evolution of this hit is described by structure–activity relationship (SAR) studies on specific parts of the molecule. From near micromolar potency we could obtain compounds with single-digit nanomolar activity in the mGlu2 NAM GTPγS assay. In addition to SAR on in vitro potency, a more detailed overview is given with a specific set of compounds on the excellent agreement between in vitro potency, free brain concentration, and ex vivo mGlu2 receptor occupancy. Finally, to obtain improved drug-like compounds, plans for future research are suggested toward increasing free brain concentration while maintaining high in vitro potency. Much positive in the negative: A medicinal chemistry exploration of the high-throughput screening hit 1 resulted in compounds 17 and 19, both of which have single-digit nanomolar potency against the metabotropic glutamate 2 receptor (mGluR2) and excellent correlation with unbound brain fraction at ED50 from ex vivo occupancy assays. These findings support the development of mGluR2 negative allosteric modulators (NAMs) to treat neurological and psychiatric disorders.
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Physiochemical Tuning of Potent Escherichia coli Anti-Adhesives by Microencapsulation and Methylene Homologation ()
Thiazolylaminomannosides (TazMan) are FimH antagonists with anti-adhesive potential against adherent-invasive Escherichia coli (AIEC) promoting gut inflammation in patients with Crohn's disease. The lead TazMan is highly potent in vitro, but shows limited in vivo efficiency, probably due to low pH stability and water solubility. We recently developed a second generation of stable TazMan, but the anti-adhesive effect was lower than the first. Herein we report a co-crystal structure of the lead TazMan in FimH, revealing that the anomeric NH group and the second thiazole moiety provide a positive hydrogen bonding interaction with a trapped water molecule, and π-stacking with Tyr48 of FimH, respectively. Consequently, we developed NeoTazMan homologated with a methylene group for low-pH and mannosidase stability with a conserved NH group and bearing various heterocyclic aglycones. Microencapsulation of the lead NeoTazMan in γ-cyclodextrin dramatically improved water solubility without disrupting the affinity for FimH or the anti-adhesive effect against AIEC isolated from patients with Crohn's disease. TazMania! We developed a new generation of potent anti-adhesives that target pathogenic Escherichia coli strains which promote gut inflammation in Crohn's disease. The neo-thiazolylmannosides were homologated by a methyl group and included in a γ-cyclodextrin carrier to form a water-soluble NeoTazMan@γCD complex with anti-adhesive effects against E. coli.
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Structure-Based Design and Synthesis of Harmine Derivatives with Different Selectivity Profiles in Kinase versus Monoamine Oxidase Inhibition ()
Dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) is an emerging biological target with implications in diverse therapeutic areas such as neurological disorders (Down syndrome, in particular), metabolism, and oncology. Harmine, a natural product that selectively inhibits DYRK1A amongst kinases, could serve as a tool compound to better understand the biological processes that arise from DYRK1A inhibition. On the other hand, harmine is also a potent inhibitor of monoamine oxidase A (MAO-A). Using structure-based design, we synthesized a collection of harmine analogues with tunable selectivity toward these two enzymes. Modifications at the 7-position typically decreased affinity for DYRK1A, whereas substitution at the 9-position had a similar effect on MAO-A inhibition but DYRK1A inhibition was maintained. The resulting collection of compounds can help to understand the biological role of DYRK1A and also to assess the interference in the biological effect originating in MAO-A inhibition. Choosing sides: The different orientations of harmine in the X-ray structures of this natural product bound to DYRK1A and monoamine oxidase A (MAO-A) suggest chemical ways to fine-tune the selectivity profile of this compound class. These structure-guided transformations led to the abolition of DYRK1A and/or MAO-A inhibition in harmine derivatives as well as to the synthesis of dual inhibitors of mixed inhibition ratio.
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Synthesis and Antiproliferative Effect of Ethyl 4-[4-(4-Substituted Piperidin-1-yl)]benzylpyrrolo[1,2-a]quinoxalinecarboxylate Derivatives on Human Leukemia Cells ()
Acute leukemia is a hematological malignancy with high incidence and recurrence rates and is characterized by an accumulation of blasts in bone marrow due to proliferation of immature lymphoid or myeloid cells associated with a blockade of differentiation. The heterogeneity of leukemia led us to look for new specific molecules for leukemia subtypes or for therapy-resistant cases. Among heterocyclic derivatives that attracted attention due to their wide range of biological activities, we focused our interest on the pyrrolo[1,2-a]quinoxaline heterocyclic framework that has been previously identified as an interesting scaffold for antiproliferative activities against various human cancer cell lines. In this work, new ethyl 4-[4-(4-substituted piperidin-1-yl)]benzylpyrrolo[1,2-a]quinoxalinecarboxylate derivatives (1 a–o) were designed, synthesized, and evaluated against five different leukemia cell lines, including Jurkat and U266 (lymphoid cell lines) and K562, U937, and HL60 (myeloid cell lines), as well as on normal human peripheral blood mononuclear cells (PBMCs). This new pyrrolo[1,2-a]quinoxaline series showed interesting cytotoxic potential against all tested leukemia cell lines. In particular, pyrroloquinoxalines 1 a and 1 m,n seem to be interesting due to their high activity against leukemia and their low activity against normal hematopoietic cells, leading to a high index of selectivity. An antileukemia army: New ethyl 4-[4-(4-substituted piperidin-1-yl)]benzylpyrrolo[1,2-a]quinoxalinecarboxylate derivatives were designed, synthesized, and evaluated against five leukemia cell lines, as well as normal human peripheral blood mononuclear cells. These new pyrrolo[1,2-a]quinoxalines showed interesting cytotoxic potential against all leukemia cell lines tested, with three pyrroloquinoxalines having particularly high activity against leukemia and low activity against normal hematopoietic cells.
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A Molecular Dynamics–Shared Pharmacophore Approach to Boost Early-Enrichment Virtual Screening: A Case Study on Peroxisome Proliferator-Activated Receptor α ()
Molecular dynamics (MD) simulations can be used, prior to virtual screening, to add flexibility to proteins and study them in a dynamic way. Furthermore, the use of multiple crystal structures of the same protein containing different co-crystallized ligands can help elucidate the role of the ligand on a protein′s active conformation, and then explore the most common interactions between small molecules and the receptor. In this work, we evaluated the contribution of the combined use of MD on crystal structures containing the same protein but different ligands to examine the crucial ligand–protein interactions within the complexes. The study was carried out on peroxisome proliferator-activated receptor α (PPARα). Findings derived from the dynamic analysis of interactions were then used as features for pharmacophore generation and constraints for generating the docking grid for use in virtual screening. We found that information derived from short multiple MD simulations using different molecules within the binding pocket of the target can improve the early enrichment of active ligands in the virtual screening process for this receptor. In the end we adopted a consensus scoring based on docking score and pharmacophore alignment to rank our dataset. Our results showed an improvement in virtual screening performance in early recognition when screening was performed with the Molecular dYnamics SHAred PharmacophorE (MYSHAPE) approach. The MYSHAPE approach is a new way of studying ligand–receptor interactions. In this method, a pharmacophore model is created that exploits information derived from multiple short MD simulations, using different molecules within the binding pocket of the target. Conformational information is retrieved from the full trajectory and not only from clustered frames. This approach can help improve virtual screening performance, especially for the early enrichment of active ligands in the virtual screening process.
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Cover Picture: Probing Mercaptobenzamides as HIV Inactivators via Nucleocapsid Protein 7 (ChemMedChem 10/2017) ()
The front cover picture shows the C-terminal domain of Nucleocapsid Protein 7 (NCp7) of the human immunodeficiency virus (HIV) and the likely mode by which an S-acetylmercaptobenzamide molecule reacts with the protein. Acetyl transfer from the mercaptobenzamide to the sulfur of a cysteine in NCp7 destabilizes the zinc coordination, which leads to protein unfolding and loss of function. These types of molecules are being developed as potential new treatments for HIV infection. More information can be found in the Communication by Daniel H. Appella et al. on page 714 in Issue 10, 2017 (DOI: 10.1002/cmdc.201700141).
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Probing Mercaptobenzamides as HIV Inactivators via Nucleocapsid Protein 7 ()
Human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein 7 (NCp7), a zinc finger protein, plays critical roles in viral replication and maturation and is an attractive target for drug development. However, the development of drug-like molecules that inhibit NCp7 has been a significant challenge. In this study, a series of novel 2-mercaptobenzamide prodrugs were investigated for anti-HIV activity in the context of NCp7 inactivation. The molecules were synthesized from the corresponding thiosalicylic acids, and they are all crystalline solids and stable at room temperature. Derivatives with a range of amide side chains and aromatic substituents were synthesized and screened for anti-HIV activity. Wide ranges of antiviral activity were observed, with IC50 values ranging from 1 to 100 μm depending on subtle changes to the substituents on the aromatic ring and side chain. Results from these structure–activity relationships were fit to a probable mode of intracellular activation and interaction with NCp7 to explain variations in antiviral activity. Our strategy to make a series of mercaptobenzamide prodrugs represents a general new direction to make libraries that can be screened for anti-HIV activity. The bare-knuckle round in the fight against HIV: Mercapotobenzamide derivatives could become the next generation of drugs to treat HIV infection by targeting and inactivating nucleocapsid protein 7 (NCp7). This protein contains two zinc-coordinated knuckles that bind to HIV RNA and are essential for viral replication. Certain mercaptobenzamide derivatives promote the acetylation of NCp7, loss of zinc coordination, and eliminate the ability of NCp7 to bind HIV RNA. Herein we describe how to quickly make mercaptobenzamide analogues to screen for antiviral activity.
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Immunogenicity of a Fully Synthetic MUC1 Glycopeptide Antitumor Vaccine Enhanced by Poly(I:C) as a TLR3-Activating Adjuvant ()
Fully synthetic MUC1 glycopeptide antitumor vaccines have a precisely specified structure and induce a targeted immune response without suppression of the immune response when using an immunogenic carrier protein. However, tumor-associated aberrantly glycosylated MUC1 glycopeptides are endogenous structures, “self-antigens”, that exhibit only low immunogenicity. To overcome this obstacle, a fully synthetic MUC1 glycopeptide antitumor vaccine was combined with poly(inosinic acid:cytidylic acid), poly(I:C), as a structurally defined Toll-like receptor 3 (TLR3)-activating adjuvant. This vaccine preparation elicited extraordinary titers of IgG antibodies which strongly bound human breast cancer cells expressing tumor-associated MUC1. Beside the humoral response, the poly(I:C) glycopeptide vaccine induced a pro-inflammatory environment, very important to overcome the immune-suppressive mechanisms, and elicited a strong cellular immune response crucial for tumor elimination. Do you see what I:C? A synthetic vaccine consisting of a tumor-associated MUC1 glycopeptide (red) and a polio virus T-cell epitope (green) supported by poly(I:C) as a synthetic adjuvant was found to induce a dramatically strong, tumor-cell-recognizing immune response including complement-activating IgG subtypes. Antitumor-effective cytokines and cytotoxic T-cells were also induced by this fully synthetic vaccine formulation.
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Neladenoson Bialanate Hydrochloride: A Prodrug of a Partial Adenosine A1 Receptor Agonist for the Chronic Treatment of Heart Diseases ()
Adenosine is known to be released under a variety of physiological and pathophysiological conditions to facilitate the protection and regeneration of injured ischemic tissues. The activation of myocardial adenosine A1 receptors (A1Rs) has been shown to inhibit myocardial pathologies associated with ischemia and reperfusion injury, suggesting several options for new cardiovascular therapies. When full A1R agonists are used, the desired protective and regenerative cardiovascular effects are usually overshadowed by unintended pharmacological effects such as induction of bradycardia, atrioventricular (AV) blocks, and sedation. These unwanted effects can be overcome by using partial A1R agonists. Starting from previously reported capadenoson we evaluated options to tailor A1R agonists to a specific partiality range, thereby optimizing the therapeutic window. This led to the identification of the potent and selective agonist neladenoson, which shows the desired partial response on the A1R, resulting in cardioprotection without sedative effects or cardiac AV blocks. To circumvent solubility and formulation issues for neladenoson, a prodrug approach was pursued. The dipeptide ester neladenoson bialanate hydrochloride showed significantly improved solubility and exposure after oral administration. Neladenoson bialanate hydrochloride is currently being evaluated in clinical trials for the treatment of heart failure. Good gets even better: Partial adenosine A1 receptor (A1R) activation is associated with a positive impact on heart failure without the detriments of full A1R agonism. Starting from capadenoson, we describe the identification of neladenoson bialanate hydrochloride, which has a good pharmacokinetic and safety profile. Neladenoson bialanate hydrochloride is currently being assessed in clinical studies for the treatment of heart failure.
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An Integrin-Targeting RGDK-Tagged Nanocarrier: Anticancer Efficacy of Loaded Curcumin ()
Herein we report the design and development of α5β1 integrin-specific noncovalent RGDK–lipopeptide-functionalized single-walled carbon nanotubes (SWNTs) that selectively deliver the anticancer drug curcumin to tumor cells. RGDK tetrapeptide-tagged amphiphiles were synthesized that efficiently disperse SWNTs with a suspension stability index of >80 % in cell culture media. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)- and lactate dehydrogenase (LDH)-based cell viability assays in tumor (B16F10 melanoma) and noncancerous (NIH3T3 mouse fibroblast) cells revealed the non-cytotoxic nature of these RGDK–lipopeptide–SWNT conjugates. Cellular uptake experiments with monoclonal antibodies against αvβ3, αvβ5, and α5β1 integrins showed that these SWNT nanovectors deliver their cargo (Cy3-labeled oligonucleotides, Cy3-oligo) to B16F10 cells selectively via α5β1 integrin. Notably, the nanovectors failed to deliver the Cy3-oligo to NIH3T3 cells. The RGDK–SWNT is capable of delivering the anticancer drug curcumin to B16F10 cells more efficiently than NIH3T3 cells, leading to selective killing of B16F10 cells. Results of Annexin V binding based flow cytometry experiments are consistent with selective killing of tumor cells through the late apoptotic pathway. Biodistribution studies in melanoma (B16F10)-bearing C57BL/6J mice showed tumor-selective accumulation of curcumin intravenously administered via RGDK–lipopeptide–SWNT nanovectors. Right on target: An RGDK-tagged single-walled nanotube (SWNT) vector was shown to selectively transport Cy3-labeled oligonucleotides into B16F10 melanoma cells while avoiding noncancerous NIH3T3 cells. α5β1 Integrins overexpressed at the B16F10 cell surface facilitate this internalization process. SWNTs loaded with the anticancer drug curcumin were found to selectively kill B16F10 cells more efficiently than NIH3T3 cells. Moreover, tumor-selective accumulation of curcumin in C57BL/6J mice with B16F10 melanoma via the RGDK–lipopeptide–SWNT vector underscores its potential as an anticancer agent.
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Structure–Activity Relationship Studies, SPR Affinity Characterization, and Conformational Analysis of Peptides That Mimic the HNK-1 Carbohydrate Epitope ()
The design of molecules that mimic biologically relevant glycans is a significant goal for understanding important biological processes and may lead to new therapeutic and diagnostic agents. In this study we focused our attention on the trisaccharide human natural killer cell-1 (HNK-1), considered the antigenic determinant of myelin-associated glycoprotein and the target of clinically relevant auto-antibodies in autoimmune neurological disorders such as IgM monoclonal gammopathy and demyelinating polyneuropathy. We describe a structure–activity relationship study based on surface plasmon resonance binding affinities aimed at the optimization of a peptide that mimics the HNK-1 minimal epitope. We developed a cyclic heptapeptide that shows an affinity of 1.09×10−7 m for a commercial anti-HNK1 mouse monoclonal antibody. Detailed conformational analysis gave possible explanations for the good affinity displayed by this novel analogue, which was subsequently used as an immunological probe. However, preliminary screening indicates that patients′ sera do not specifically recognize this peptide, showing that murine monoclonal antibodies cannot be used as a guide to select immunological probes for the detection of clinically relevant human auto-antibodies. Cyclopeptides as sugar substitutes: Peptides can be instrumental to the development of immunological probes recognized by specific antibodies with improved affinity and specificity. We describe a structure–activity relationship study based on surface plasmon resonance binding affinities, aimed at the optimization of a peptide that mimics the HNK-1 trisaccharide minimal epitope. We developed a cyclic heptapeptide that shows an affinity of 1.09×10−7 m for a commercial anti-HNK1 mouse monoclonal antibody.
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A Multitarget Approach toward the Development of 8-Substituted Purines for Photoprotection and Prevention of UV-Related Damage ()
Ultraviolet (UV) light is the most abundant and significant modifiable risk factor for skin cancer and many other skin diseases such as early photo-aging. Across the solar radiation spectrum, UV light is the main cause behind skin problems. In the search for novel photoprotective compounds, a new series of 8-substituted purines were synthesized from commercially available 6-hydroxy-4,5-diaminopyrimidine hemisulfate or 4,5-diaminopyrimidine. All title compounds were investigated for their UV filtering, antioxidant, antifungal, and antiproliferative activities. For the photoprotection assays we used a diffuse transmittance technique to determine the sun protection factor (SPF) in vitro, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP) tests for evaluating the antioxidant activity of the more potent compounds. Among them, 8-(2,5-dihydroxyphenyl)-7H-purin-6-ol (compound 26) proved to be a good radical scavenger and is also endowed with broad-spectrum UVA filtering capabilities, suitable for further development as a protective molecule. Multitasking purines! A series of 8-substituted purines was synthesized and evaluated for antioxidant, UV-filtering, antifungal, and antiproliferative activities. We discovered compounds with high antioxidant activity, capacity as potential broad-spectrum UVA filters, and good inhibitory activity toward human endothelial HMEC-1 cells. The best multifunctional compound has hydroxy groups at positions 2 and 5 of the phenyl ring and at position 6 of the purine ring.
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Synthesis and Pharmacological Evaluation of Identified and Putative Metabolites of the A1 Adenosine Receptor Antagonist 8-Cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine (CPFPX) ()
The A1 adenosine receptor (A1AR) antagonist [18F]8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine ([18F]CPFPX), used in imaging human brain A1ARs by positron emission tomography (PET), is stable in the brain, but rapidly undergoes transformation into one major (3-(3-fluoropropyl)-8-(3-oxocyclopenten-1-yl)-1-propylxanthine, M1) and several minor metabolites in blood. This report describes the synthesis of putative metabolites of CPFPX as standards for the identification of those metabolites. Analysis by (radio)HPLC revealed that extracts of human liver microsomes incubated with no-carrier-added (n.c.a.)[18F]CPFPX contain the major metabolite, M1, as well as radioactive metabolites corresponding to derivatives functionalized at the cyclopentyl moiety, but no N1-despropyl species or metabolites resulting from functionalization of the N3-fluoropropyl chain. The putative metabolites were found to displace the binding of [3H]CPFPX to the A1AR in pig brain cortex at Ki values between 1.9 and 380 nm and the binding of [3H]ZM241385 to the A2AAR in pig striatum at Ki values >180 nm. One metabolite, a derivative functionalized at the ω-position of the N1-propyl chain, showed high affinity (Ki 2 nm) to and very good selectivity (>9000) for the A1AR. Finding the soft spots: This report describes the in vitro metabolic functionalization of the A1AR antagonist [18F]CPFPX in human liver microsome preparations. Ten putative metabolites were synthesized and evaluated as A1AR and A2AAR ligands. Metabolic profiling revealed the formation of one metabolite resulting from ω-hydroxylation of the N1-propyl chain and two metabolites arising from oxygenation of the cyclopentyl substituent. The highly active and subtype-selective hydroxylated metabolite 15 a is a convenient starting point for further development, and its altered lipophilicity may offer advantages in terms of unspecific binding and its use as a radioligand.
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