Large-scale High-throughput Screening Revealed 5'-(carbonylamino)-2,3'- bithiophene-4'-carboxylate as Novel Template for Antibacterial Agents.

BACKGROUND: The key issue in the development of novel antimicrobials is a rapid expansion of new bacterial strains resistant to current antibiotics. Indeed, World Health Organization has reported that bacteria commonly causing infections in hospitals and in the community, e.g. E. Coli, K. pneumoniae and S. aureus, have high resistance vs the last generations of cephalosporins, carbapenems and fluoroquinolones. During the past decades, only few successful efforts to develop and launch new antibacterial medications have been performed. This study aims to identify new class of antibacterial agents using novel high-throughput screening technique. METHODS: We have designed library containing 125K compounds not similar in structure (Tanimoto coeff.< 0.7) to that published previously as antibiotics. The HTS platform based on double reporter system pDualrep2 was used to distinguish between molecules able to block translational machinery or induce SOS-response in a model E. coli system. MICs for most active chemicals in LB and M9 medium were determined using broth microdilution assay. RESULTS: In an attempt to discover novel classes of antibacterials, we performed HTS of a large-scale small molecule library using our unique screening platform. This approach permitted us to quickly and robustly evaluate a lot of compounds as well as to determine the mechanism of action in the case of compounds being either translational machinery inhibitors or DNA-damaging agents/replication blockers. HTS has resulted in several new structural classes of molecules exhibiting an attractive antibacterial activity. Herein, we report as promising antibacterials. Two most active compounds from this series showed MIC value of 1.2 (5) and 1.8 µg/mL (6) and good selectivity index. Compound 6 caused RFP induction and low SOS response. In vitro luciferase assay has revealed that it is able to slightly inhibit protein biosynthesis. Compound 5 was tested on several archival strains and exhibited slight activity against gram-negative bacteria and outstanding activity against S. aureus. The key structural requirements for antibacterial potency were also explored. We found, that the unsubstituted carboxylic group is crucial for antibacterial activity as well as the presence of bulky hydrophobic substituents at phenyl fragment. CONCLUSION: The obtained results provide a solid background for further characterization of the 5'- (carbonylamino)-2,3'-bithiophene-4'-carboxylate derivatives discussed herein as new class of antibacterials and their optimization campaign.

Identification of pyrrolo-pyridine derivatives as novel class of antibacterials.

A series of 5-oxo-4H-pyrrolo[3,2-b]pyridine derivatives was identified as novel class of highly potent antibacterial agents during an extensive large-scale high-throughput screening (HTS) program utilizing a unique double-reporter system-pDualrep2. The construction of the reporter system allows us to perform visual inspection of the underlying mechanism of action due to two genes-Katushka2S and RFP-which encode the proteins with different imaging signatures. Antibacterial activity of the compounds was evaluated during the initial HTS round and subsequent rescreen procedure. The most active molecule demonstrated a MIC value of 3.35 µg/mL against E. coli with some signs of translation blockage (low Katushka2S signal) and no SOS response. The compound did not demonstrate cytotoxicity in standard cell viability assay. Subsequent structural morphing and follow-up synthesis may result in novel compounds with a meaningful antibacterial potency which can be reasonably regarded as an attractive starting point for further in vivo investigation and optimization.

Substituted Furanocoumarins as Novel Class of Antibacterial Translation Inhibitors.

INTRODUCTION: A variety of organic compounds has been reported to have antibacterial activity. However, antimicrobial resistance is one of the main problems of current anti-infective therapy, and the development of novel antibacterials is one of the main challenges of current drug discovery. METHODS: Using our previously developed dual-reporter High-Throughput Screening (HTS) platform, we identified a series of furanocoumarins as having high antibacterial activity. The construction of the reporter system allows us to differentiate three mechanisms of action for the active compounds: inhibition of protein synthesis (induction of Katushka2S), DNA damaging (induction of RFP) or other (inhibition of bacterial growth without reporter induction). RESULTS: Two primary hit-molecules of furanocoumarin series demonstrated relatively low MIC values comparable to that observed for Erythromycin (Ery) against E. coli and weakly induced both reporters. Dose-dependent translation inhibition was shown using in vitro luciferase assay, however it was not confirmed using C14-test. A series of close structure analogs of the identified hits was obtained and investigated using the same screening platform. Compound 19 was found to have slightly lower MIC value (15.18 µM) and higher induction of Katushka2S reporter in contrast to the parent structures. Moreover, translation blockage was clearly identified using both in vitro luciferase assay and C14 test. The standard cytotoxicity test revealed a relatively low cytotoxicity of the most active molecules. CONCLUSION: High antibacterial activity in combination with low cytotoxicity was demonstrated for a series of furanocoumarins. Further optimization of the described structures may result in novel and attractive lead compounds with promising antibacterial efficiency.

Identification of Novel Antibacterials Using Machine Learning Techniques.

Many pharmaceutical companies are avoiding the development of novel antibacterials due to a range of rational reasons and the high risk of failure. However, there is an urgent need for novel antibiotics especially against resistant bacterial strains. Available in silico models suffer from many drawbacks and, therefore, are not applicable for scoring novel molecules with high structural diversity by their antibacterial potency. Considering this, the overall aim of this study was to develop an efficient in silico model able to find compounds that have plenty of chances to exhibit antibacterial activity. Based on a proprietary screening campaign, we have accumulated a representative dataset of more than 140,000 molecules with antibacterial activity against Escherichia coli assessed in the same assay and under the same conditions. This intriguing set has no analogue in the scientific literature. We applied six in silico techniques to mine these data. For external validation, we used 5,000 compounds with low similarity towards training samples. The antibacterial activity of the selected molecules against E. coli was assessed using a comprehensive biological study. Kohonen-based nonlinear mapping was used for the first time and provided the best predictive power (av. 75.5%). Several compounds showed an outstanding antibacterial potency and were identified as translation machinery inhibitors in vitro and in vivo. For the best compounds, MIC and CC50 values were determined to allow us to estimate a selectivity index (SI). Many active compounds have a robust IP position.

Deep learning enables rapid identification of potent DDR1 kinase inhibitors.

We have developed a deep generative model, generative tensorial reinforcement learning (GENTRL), for de novo small-molecule design. GENTRL optimizes synthetic feasibility, novelty, and biological activity. We used GENTRL to discover potent inhibitors of discoidin domain receptor 1 (DDR1), a kinase target implicated in fibrosis and other diseases, in 21 days. Four compounds were active in biochemical assays, and two were validated in cell-based assays. One lead candidate was tested and demonstrated favorable pharmacokinetics in mice.

2-Pyrazol-1-yl-thiazole derivatives as novel highly potent antibacterials.

The present report describes our efforts to identify new structural classes of compounds having promising antibacterial activity using previously published double-reporter system pDualrep2. This semi-automated high-throughput screening (HTS) platform has been applied to perform a large-scale screen of a diverse small-molecule compound library. We have selected a set of more than 125,000 molecules and evaluated them for their antibacterial activity. On the basis of HTS results, eight compounds containing 2-pyrazol-1-yl-thiazole scaffold exhibited moderate-to-high activity against ΔTolC Escherichia coli. Minimum inhibitory concentration (MIC) values for these molecules were in the range of 0.037-8 µg ml-1. The most active compound 8 demonstrated high antibacterial potency (MIC = 0.037 µg ml-1), that significantly exceed that measured for erythromycin (MIC = 2.5 µg ml-1) and was comparable with the activity of levofloxacin (MIC = 0.016 µg ml-1). Unfortunately, this compound showed only moderate selectivity toward HEK293 eukaryotic cell line. On the contrary, compound 7 was less potent (MIC = 0.8 µg ml-1) but displayed only slight cytotoxicity. Thus, 2-pyrazol-1-yl-thiazoles can be considered as a valuable starting point for subsequent optimization and morphing.

Identification of N-Substituted Triazolo-azetidines as Novel Antibacterials using pDualrep2 HTS Platform.

AIM AND OBJECTIVE: Antibiotic resistance is a serious constraint to the development of new effective antibacterials. Therefore, the discovery of the new antibacterials remains one of the main challenges in modern medicinal chemistry. This study was undertaken to identify novel molecules with antibacterial activity. MATERIALS AND METHODS: Using our unique double-reporter system, in-house large-scale HTS campaign was conducted for the identification of antibacterial potency of small-molecule compounds. The construction allows us to visually assess the underlying mechanism of action. After the initial HTS and rescreen procedure, luciferase assay, C14-test, determination of MIC value and PrestoBlue test were carried out. RESULTS: HTS rounds and rescreen campaign have revealed the antibacterial activity of a series of Nsubstituted triazolo-azetidines and their isosteric derivatives that has not been reported previously. Primary hit-molecule demonstrated a MIC value of 12.5 µg/mL against E. coli Δ tolC with signs of translation blockage and no SOS-response. Translation inhibition (26%, luciferase assay) was achieved at high concentrations up to 160 µg/mL, while no activity was found using C14-test. The compound did not demonstrate cytotoxicity in the PrestoBlue assay against a panel of eukaryotic cells. Within a series of direct structural analogues bearing the same or bioisosteric scaffold, compound 2 was found to have an improved antibacterial potency (MIC=6.25 µg/mL) close to Erythromycin (MIC=2.5-5 µg/mL) against the same strain. In contrast to the parent hit, this compound was more active and selective, and provided a robust IP position. CONCLUSION: N-substituted triazolo-azetidine scaffold may be used as a versatile starting point for the development of novel active and selective antibacterial compounds.

AVN-322 is a Safe Orally Bio-Available Potent and Highly Selective Antagonist of 5-HT6R with Demonstrated Ability to Improve Impaired Memory in Animal Models.

BACKGROUND: In recent years, 5-hydroxytryptamine subtype 6 receptor (5-HT6 receptor, 5- HT6R) has emerged as a promising therapeutic target for the treatment of neuropathological disorders, including Alzheimer's disease (AD) and schizophrenia. 5-HT6 receptors were hypothesized to be implicated in the processes of learning, memory, and cognition with 5-HT6R antagonists being effective in animal models of cognition and memory impairment. Several selective 5-HT6R ligands are currently undergoing clinical trials for treatment of AD. METHODS: We describe results of preclinical development of a novel and highly selective and potent 5- HT6R antagonist, AVN-322, as a clinical candidate for the treatment of AD to improve concurrent debilitation of memory and cognition in the AD patients, and schizophrenia as a substance with antipsychotic effect. In the manuscript, we present its in vitro and vivo efficacy, ADME, pharmacokinetics in animals and in humans, and toxicity. RESULTS: While having high binding affinity in medium picomolar range, the lead compound demonstrates substantially better selectivity index then the reference drug candidates currently being tested in clinical studies. AVN-322 showed high oral bioavailability and favorable blood-brain barrier (BBB) penetration. In vivo testing revealed its clear cognition enhancing effect. AVN-322 significantly restored both scopolamine- and MK-801-induced cognitive dysfunction and demonstrated antipsychotic potential. CONCLUSION: Taking into account its good safety profile and favorable pharmacokinetics, AVN-322 can be reasonably considered as a novel drug candidate for the treatment of neurological disorders such as AD and/or schizophrenia.

Identification of Novel Small-Molecule ASGP-R Ligands.

During the past decade asialoglycoprotein receptor (ASGP-R) expressed predominantly by hepatocytes has attracted a considerable attention as a convenient biomolecular trap for targeted drug delivery. Currently, several selective galactose-containing ligands equipped by drug molecules, e.g. known anticancer therapeutics, as well as diagnostic tools are under active preclinical development. In this paper, we have carried out a rational in silico screening among the molecules available in ChemDiv collection and compounds provided by our colleagues to reveal potential ASGP-R binders. Thus, 3D molecular docking approach provided a set of 100 `high score` molecules that was subsequently evaluated in vitro using an advanced Surface Plasmon Resonance (SPR) technique. As a result, dozens of novel small-molecule ASGP-R ligands with high diversity in structure were identified. Several hits showed the binding affinity much more better than that determined for galactose and Nacetylgalactosamine which were used as reference compounds. The disclosed molecules can be reasonably regarded as promising molecular devices for targeted drug delivery to hepatocytes.

Small-molecule PSMA ligands. Current state, SAR and perspectives.

Prostate cancer (PC) is the prevalent malignancy widespread among men in the Western World. Prostate specific membrane antigen (PSMA) is an established PC marker and has been considered as a promising biological target for anti-PC drug delivery and diagnostics. The protein was found to be overexpressed in PC cells, including metastatic, and the neovasculature of solid tumors. These properties make PSMA-based approach quite appropriate for effective PC imaging and specific drug therapy. Through the past decade, a variety of PSMA-targeted agents has been systematically evaluated. Small-molecule compounds have several advantages over other classes, such as improved pharmacokinetics and rapid blood clearance. These low-weight ligands have similar structure and can be divided into three basic categories in accordance with the type of their zinc-binding core-head. Several PSMA binders are currently undergoing clinical trials generally for PC imaging. The main goal of the present review is to describe the recent progress achieved within the title field and structure activity relationships (SAR) disclosed for different PSMA ligands. Recent in vitro and in vivo studies for each type of the compounds described have also been briefly summarized.

Synthesis, isomerization and biological activity of novel 2-selenohydantoin derivatives.

A set of novel selenohydantoins were synthesized via a convenient and versatile approach involving the reaction of isoselenocyanates with various amines. We also revealed an unexpected Z→E isomerization of pyridin-2-yl-substituted selenohydantoins in the presence of Cu(2+) cations. The detailed mechanism of this transformation was suggested on the basis of quantum-chemical calculations, and the key role of Cu(2+) was elucidated. The obtained compounds were subsequently evaluated against a panel of different cancer cell lines. As a result, several molecules were identified as promising micromolar hits with good selectivity index. Instead of analogous thiohydantoins, which have been synthesized previously, selenohydantoins demonstrated a relatively high antioxidant activity comparable (or greater) to the reference molecule, Ebselen, a clinically approved drug candidate. The most active compounds have been selected for further biological trials.

Computational insight into the chemical space of plant growth regulators.

An enormous technological progress has resulted in an explosive growth in the amount of biological and chemical data that is typically multivariate and tangled in structure. Therefore, several computational approaches have mainly focused on dimensionality reduction and convenient representation of high-dimensional datasets to elucidate the relationships between the observed activity (or effect) and calculated parameters commonly expressed in terms of molecular descriptors. We have collected the experimental data available in patent and scientific publications as well as specific databases for various agrochemicals. The resulting dataset was then thoroughly analyzed using Kohonen-based self-organizing technique. The overall aim of the presented study is to investigate whether the developed in silico model can be applied to predict the agrochemical activity of small molecule compounds and, at the same time, to offer further insights into the distinctive features of different agrochemical categories. The preliminary external validation with several plant growth regulators demonstrated a relatively high prediction power (67%) of the constructed model. This study is, actually, the first example of a large-scale modeling in the field of agrochemistry.

A Comprehensive Insight into the Chemical Space and ADME Features of Small Molecule NS5A Inhibitors.

Non-structural 5A (NS5A) protein plays a crucial role in the replication of hepatitis C virus (HCV) and during the past decade has attracted increasing attention as a promising biological target for the treatment of viral infections and related disorders. Small-molecule NS5A inhibitors have shown significant antiviral activity in vitro and in vivo. Several lead molecules are reasonably regarded as novel highly potent drug candidates with favorable ADME features and tolerable side effects. The first-in-class daclatasvir has recently been launched into the market and 14 novel molecules are currently under evaluation in clinical trials. From this perspective, we provide an overview of the available chemical space of small-molecule NS5A inhibitors and their PK properties, mainly focusing on the diversity in structure and scaffold representation.

Non-dopamine receptor ligands for the treatment of Parkinson's disease. Insight into the related chemical/property space.

Extensive biochemical and clinical studies have increasingly recognized Parkinson's disease as a highly complex and multi-faceted neurological disorder having branched non-motor symptoms including sleep disorders, pain, constipation, psychosis, depression, and fatigue. A wide range of biological targets in the brain deeply implicated in this pathology resulted in a plethora of novel small-molecule compounds with promising activity. This review thoroughly describes the chemical space of non-dopamine receptor ligands in terms of diversity, isosteric/bioisosteric morphing, and molecular descriptors.

In Silico Approaches to the Design of NS5A Inhibitors.

In recent years, nonstructural protein 5A (NS5A) has rapidly emerged as a promising therapeutic target for Hepatitis C (HCV) virus therapy. It is involved in both viral RNA replication and virus assembly and NS5A plays a critical role in the regulation of HCV life cycle. NS5A replication complex inhibitors (NS5A RCIs) have demonstrated strong antiviral activity in vitro and in vivo. However, wild-type resistance mutations and a wide range of genotypes significantly reduce their clinical efficacy. The exact mechanism of NS5A action still remains elusive, therefore several in silico models have been constructed to gain insight into the drug binding and subsequent structural optimization to overcome resistance. This paper provides a comprehensive overview of the computational studies towards NS5A mechanism of action and the design of novel small-molecule inhibitors.

Design, synthesis and biological evaluation of novel 5-oxo-2-thioxoimidazolidine derivatives as potent androgen receptor antagonists.

A series of novel highly active androgen receptor (AR) antagonists containing spiro-4-(5-oxo-3-phenyl-2-thioxoimidazolidin-1-yl)-2-(trifluoromethyl)benzonitrile core was designed based on the SAR studies available from the reported AR antagonists and in silico modeling. Within the series, compound (R)-6 (ONC1-13B) and its related analogues, including its active N-dealkylated metabolite, were found to be the most potent molecules with the target activity (IC50, androgen-sensitive human PCa LNCaP cells) in the range of 59-80 nM (inhibition of PSA production). The disclosed hits were at least two times more active than bicalutamide, nilutamide and enzalutamide within the performed assay. Several compounds were classified as partial agonists. Hit-compounds demonstrated benefit pharmacokinetic profiles in rats. Comparative SAR and 3D molecular docking studies were performed for the hit compounds elucidating the observed differences in the binding potency.

Design, synthesis and biological evaluation of novel potent MDM2/p53 small-molecule inhibitors.

Regioselective synthesis, biological evaluation and 3D-molecular modeling for a series of novel diastereomeric 2-thioxo-5H-dispiro[imidazolidine-4,3-pyrrolidine-2,3-indole]-2,5(1H)-diones are described. The studied compounds have been tentatively identified as potent small molecule MDM2/p53 PPI inhibitors and can therefore be reasonably regarded as promising anticancer therapeutics.

Discovery of novel highly potent hepatitis C virus NS5A inhibitor (AV4025).

A series of next in class small-molecule hepatitis C virus (HCV) NS5A inhibitors with picomolar potency containing 2-pyrrolidin-2-yl-5-{4-[4-(2-pyrrolidin-2-yl-1H-imidazol-5-yl)buta-1,3-diynyl]phenyl}-1H-imidazole cores was designed based on the SAR studies available for the reported NS5A inhibitors. Compound 13a (AV4025), with (S,S,S,S)-stereochemistry (EC50 = 3.4 ± 0.2 pM, HCV replicon genotype 1b), was dramatically more active than were the compounds with two (S)- and two (R)-chiral centers. Human serum did not significantly reduce the antiviral activity (<4-fold). Relatively favorable pharmacokinetic features and good oral bioavailability were observed during animal studies. Compound 13a was well tolerated in rodents (in mice, LD50 = 2326 mg/kg or higher), providing a relatively high therapeutic index. During safety, pharmacology and subchronic toxicity studies in rats and dogs, it was not associated with any significant pathological or clinical findings. This compound is currently being evaluated in phase I/II clinical trials for the treatment of HCV infection.

Computational approaches to the design of novel 5-HT6 R ligands.

5-Hydroxytryptamine (5-HT, serotonin) subtype 6 receptor (5-HT6 receptor, 5-HT6 R) belongs to a 5-HT subclass of a relatively wide G protein-coupled receptor (GPCR) family. Accumulated biological data indicate that 5-HT6 R antagonists and agonists have a great potential for the treatment of neuropathological disorders, such as Parkinson's disease, Alzheimer's disease, and schizophrenia. A number of painstaking efforts have been made toward the design of novel 5-HT6 R ligands; however, there are still no drugs that successfully passed all the clinical trials and entered the market, except for several multimodal ligands. Novel active molecules are strongly needed to progress this development forward. The in silico drug design has some benefits compared with the other rough approaches in terms of thoroughness and predictive accuracy; therefore, it can be effectively used as a solid foundation for the design of novel 5-HT6 R ligands with high potency and selectivity. Here, we provide an overview of the reported computational approaches to the design of novel 5-HT6 R ligands.

Novel oral anti-influenza drug candidate AV5080.

OBJECTIVES: Development of a novel drug candidate with improved potency against influenza virus neuraminidase compared with currently available therapeutics, and high activity against oseltamivir-resistant viruses. METHODS: A number of synthetic compounds were evaluated for antiviral properties in vitro and in vivo. Three-dimensional molecular docking, assisted by a pharmacophore model, was applied to classify compounds within the series by their inhibitory potency. Compound stability in blood and in animal models was determined. Pharmacokinetic studies in dogs and rats after oral or intravenous administration were performed. RESULTS: A novel highly potent drug candidate [(3R,4R,5S)-5-[(diaminomethylene)amino]-3-(1-ethylpropoxy)-4-[(fluoroacetyl)amino]cyclohex-1-ene-1-carboxylic acid; AV5080] was synthesized and tested. AV5080 exhibited high activity against influenza virus neuraminidase in vitro, with IC(50) values of 0.03 nM and 0.07 nM against the neuraminidase of A/Duck/Minnesota/1525/1981/H5N1 and A/Perth/265/2009/H1N1 (wild-type), respectively. Notably, AV5080 was highly active against oseltamivir-resistant influenza viruses. CONCLUSIONS: Based on the results presented in this study, AV5080 is a promising novel oral drug candidate for the treatment of influenza, including oseltamivir-resistant types. Further pre-clinical development of AV5080 is warranted.