Discovery of new erbB4 inhibitors: Repositioning an orphan chemical library by inverse virtual screening

Repositioning of Small Molecules through the Inverse Virtual Screening in silico Tool: Case of Benzothiazole-Based Inhibitors of Soluble Epoxide Hydrolase (sEH)

Computational techniques accelerate drug discovery by identifying bioactive compounds for specific targets, optimizing molecules with moderate activity, or facilitating the repositioning of inactive items onto new targets. Among them, the Inverse Virtual Screening (IVS) approach is aimed at the evaluation of one or a small set of molecules against a panel of targets for addressing target identification. In this work, a focused library of benzothiazole-based compounds was re-investigated by IVS. Four items, originally synthesized and tested on bromodomain-containing protein 9 (BRD9) but yielding poor binding, were critically re-analyzed, disclosing only a partial fit with 3D structure-based pharmacophore models, which, in the meanwhile, were developed for this target. Afterwards, these compounds were re-evaluated through IVS on a panel of proteins involved in inflammation and cancer, identifying soluble epoxide hydrolase (sEH) as a putative interacting target. Three items were subsequently confirmed as able to interfere with sEH activity, leading to inhibition percentages spanning from 70 % up to 30 % when tested at 10 μM. Finally, one benzothiazole-based compound emerged as the most promising inhibitor featuring an IC50 in the low micromolar range (IC50=6.62±0.13 μM). Our data confirm IVS as a predictive tool for accelerating the target identification and repositioning processes.

Target identification by structure-based computational approaches: Recent advances and perspectives

The use of computational techniques in the early stages of drug discovery has recently experienced a boost, especially in the target identification step. Finding the biological partner(s) for new or existing synthetic and/or natural compounds by "wet" approaches may be challenging; therefore, preliminary in silico screening is even more recommended. After a brief overview of some of the most known target identification techniques, recent advances in structure-based computational approaches for target identification are reported in this digest, focusing on Inverse Virtual Screening and its recent applications. Moreover, future perspectives concerning the use of such methodologies, coupled or not with other approaches, are analyzed.

Rational design of the zonulin inhibitor AT1001 derivatives as potential anti SARS-CoV-2

Although vaccines are greatly mitigating the worldwide pandemic diffusion of SARS-Cov-2, therapeutics should provide many distinct advantages as complementary approach to control the viral spreading. Here, we report the development of new tripeptide derivatives of AT1001 against SARS-CoV-2 M^pro. By molecular modeling, a small compound library was rationally designed and filtered for enzymatic inhibition through FRET assay, leading to the identification of compound 4. X-ray crystallography studies provide insights into its binding mode and confirm the formation of a covalent bond with M^pro C145. In vitro antiviral tests indicate the improvement of biological activity of 4 respect to AT1001. In silico and X-ray crystallography analysis led to 58, showing a promising activity against three SARS-CoV-2 variants and a valuable safety in Vero cells and human embryonic lung fibroblasts. The drug tolerance was also confirmed by in vivo studies, along with pharmacokinetics evaluation. In summary, 58 could pave the way to develop a clinical candidate for intranasal administration.

Identification of 2,4-Dinitro-Biphenyl-Based Compounds as MAPEG Inhibitors

We identified 2,4-dinitro-biphenyl-based compounds as new inhibitors of leukotriene C₄ synthase (LTC₄ S) and 5-lipoxygenase-activating protein (FLAP), both members of the "Membrane Associated Proteins in Eicosanoid and Glutathione metabolism" (MAPEG) family involved in the biosynthesis of pro-inflammatory eicosanoids. By molecular docking we evaluated the putative binding against the targets of interest, and by applying cell-free and cell-based assays we assessed the inhibition of LTC₄ S and FLAP by the small molecules at low micromolar concentrations. The present results integrate the previously observed inhibitory profile of the tested compounds against another MAPEG member, i. e., microsomal prostaglandin E₂ synthase (mPGES)-1, suggesting that the 2,4-dinitro-biphenyl scaffold is a suitable molecular platform for a multitargeting approach to modulate pro-inflammatory mediators in inflammation and cancer treatment.

Drug Discovery of Plausible Lead Natural Compounds That Target the Insulin Signaling Pathway: Bioinformatics Approaches

The growing smooth talk in the field of natural compounds is due to the ancient and current interest in herbal medicine and their potentially positive effects on health. Dozens of antidiabetic natural compounds were reported and tested in vivo, in silico, and in vitro. The role of these natural compounds, their actions on the insulin signaling pathway, and the stimulation of the glucose transporter-4 (GLUT4) insulin-responsive translocation to the plasma membrane (PM) are all crucial in the treatment of diabetes and insulin resistance. In this review, we collected and summarized a group of available in vivo and in vitro studies which targeted isolated phytochemicals with possible antidiabetic activity. Moreover, the in silico docking of natural compounds with some of the insulin signaling cascade key proteins is also summarized based on the current literature. In this review, hundreds of recent studies on pure natural compounds that alleviate type II diabetes mellitus (type II DM) were revised. We focused on natural compounds that could potentially regulate blood glucose and stimulate GLUT4 translocation through the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. On attempt to point out potential new natural antidiabetic compounds, this review also focuses on natural ingredients that were shown to interact with proteins in the insulin signaling pathway in silico, regardless of their in vitro/in vivo antidiabetic activity. We invite interested researchers to test these compounds as potential novel type II DM drugs and explore their therapeutic mechanisms.

Hidradenitis Suppurativa and Comorbid Disorder Biomarkers, Druggable Genes, New Drugs and Drug Repurposing-A Molecular Meta-Analysis

Chronic inflammation and dysregulated epithelial differentiation, especially of hair follicle keratinocytes, have been suggested as the major pathogenetic pathways of hidradenitis suppurativa/acne inversa (HS). On the other hand, obesity and metabolic syndrome have additionally been considered as an important risk factor. With adalimumab, a drug has already been approved and numerous other compounds are in advanced-stage clinical studies. A systematic review was conducted to detect and corroborate HS pathogenetic mechanisms at the molecular level and identify HS molecular markers. The obtained data were used to confirm studied and off-label administered drugs and to identify additional compounds for drug repurposing. A robust, strongly associated group of HS biomarkers was detected. The triad of HS pathogenesis, namely upregulated inflammation, altered epithelial differentiation and dysregulated metabolism/hormone signaling was confirmed, the molecular association of HS with certain comorbid disorders, such as inflammatory bowel disease, arthritis, type I diabetes mellitus and lipids/atherosclerosis/adipogenesis was verified and common biomarkers were identified. The molecular suitability of compounds in clinical studies was confirmed and 31 potential HS repurposing drugs, among them 10 drugs already launched for other disorders, were detected. This systematic review provides evidence for the importance of molecular studies to advance the knowledge regarding pathogenesis, future treatment and biomarker-supported clinical course follow-up in HS.

Peptide Derivatives of the Zonulin Inhibitor Larazotide (AT1001) as Potential Anti SARS-CoV-2: Molecular Modelling, Synthesis and Bioactivity Evaluation

A novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been identified as the pathogen responsible for the outbreak of a severe, rapidly developing pneumonia (Coronavirus disease 2019, COVID-19). The virus enzyme, called 3CLpro or main protease (M^pro), is essential for viral replication, making it a most promising target for antiviral drug development. Recently, we adopted the drug repurposing as appropriate strategy to give fast response to global COVID-19 epidemic, by demonstrating that the zonulin octapeptide inhibitor AT1001 (Larazotide acetate) binds M^pro catalytic domain. Thus, in the present study we tried to investigate the antiviral activity of AT1001, along with five derivatives, by cell-based assays. Our results provide with the identification of AT1001 peptide molecular framework for lead optimization step to develop new generations of antiviral agents of SARS-CoV-2 with an improved biological activity, expanding the chance for success in clinical trials.

Identification of 2-(thiophen-2-yl)acetic Acid-Based Lead Compound for mPGES-1 Inhibition

We report the implementation of our in silico/synthesis pipeline by targeting the glutathione-dependent enzyme mPGES-1, a valuable macromolecular target in both cancer therapy and inflammation therapy. Specifically, by using a virtual fragment screening approach of aromatic bromides, straightforwardly modifiable by the Suzuki-Miyaura reaction, we identified 3-phenylpropanoic acid and 2-(thiophen-2-yl)acetic acid to be suitable chemical platforms to develop tighter mPGES-1 inhibitors. Among these, compounds 1c and 2c showed selective inhibitory activity against mPGES-1 in the low micromolar range in accordance with molecular modeling calculations. Moreover, 1c and 2c exhibited interesting IC₅₀ values on A549 cell lines compared to CAY10526, selected as reference compound. The most promising compound 2c induced the cycle arrest in the G₀/G₁ phase at 24 h of exposure, whereas at 48 and 72 h, it caused an increase of subG₀/G₁ fraction, suggesting an apoptosis/necrosis effect.

Deep Learning-Based Ligand Design Using Shared Latent Implicit Fingerprints from Collaborative Filtering

In their previous work, Srinivas et al. [ J. Cheminf. 2018, 10, 56] have shown that implicit fingerprints capture ligands and proteins in a shared latent space, typically for the purposes of virtual screening with collaborative filtering models applied on known bioactivity data. In this work, we extend these implicit fingerprints/descriptors using deep learning techniques to translate latent descriptors into discrete representations of molecules (SMILES), without explicitly optimizing for chemical properties. This allows the design of new compounds based upon the latent representation of nearby proteins, thereby encoding druglike properties including binding affinities to known proteins. The implicit descriptor method does not require any fingerprint similarity search, which makes the method free of any bias arising from the empirical nature of the fingerprint models [Srinivas, R.; J. Cheminf. 2018, 10, 56]. We evaluate the properties of the potentially novel drugs generated by our approach using physical properties of druglike molecules and chemical complexity. Additionally, we analyze the reliability of the biological activity of the new compounds generated using this method by employing models of protein-ligand interaction, which assists in assessing the potential binding affinity of the designed compounds. We find that the generated compounds exhibit properties of chemically feasible compounds and are predicted to be excellent binders to known proteins. Furthermore, we also analyze the diversity of compounds created using the Tanimoto distance and conclude that there is a wide diversity in the generated compounds.

In silico Analysis Revealed Potential Anti-SARS-CoV-2 Main Protease Activity by the Zonulin Inhibitor Larazotide Acetate

The most severe outcome of COVID-19 infection is the development of interstitial pneumonia causing acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS), both responsible for the infected patients' mortality. ALI and ARDS are characterized by a leakage of plasma components into the lungs, compromising their ability to expand and optimally engage in gas exchange with blood, resulting in respiratory failure. We have previously reported that zonulin, a protein dictating epithelial and endothelial permeability in several districts, including the airways, is involved in ALI pathogenesis in mouse models, and that its peptide inhibitor Larazotide acetate (also called AT1001) ameliorated ALI and subsequent mortality by decreasing mucosal permeability to fluid and extravasation of neutrophils into the lungs. With the recent crystallographic resolution of the SARS-CoV-2 main protease (M^pro), an enzyme fundamental in the viral lifecycle, bound to peptidomimetic inhibitors N3 and 13b, we were able to perform molecular modeling investigation showing that AT1001 presents structural motifs similar to co-crystallized ligands. Specifically, molecular docking, MM-GBSA-based predictions and molecular dynamics showed that AT1001 docks extremely well in the M^pro catalytic domain through a global turn conformational arrangement without any unfavorable steric hindrance. Finally, we have observed that AT1001 can be superimposed onto the crystallized structures of N3 and 13b, establishing a higher number of interactions and accordingly a tighter binding. In vitro studies confirmed AT1001 anti-M^pro and preliminary investigation indicted an anti-viral activity. Combined, these studies suggest that AT1001, besides its well-demonstrated effect in ameliorating mucosal permeability in ALI/ARDS, may also exert a direct anti-SARS-CoV-2 effect by blocking the M^pro. AT1001 has been used extensively in a variety of animal models of ALI demonstrating robust safety and efficacy; it is currently in phase 3 trials in celiac subjects showing strong safety and efficacy profiles. We therefore propose its use as a specific anti-SARS-CoV-2 multitargeting treatment for the current pandemic.

Garcinol and Related Polyisoprenylated Benzophenones as Topoisomerase II Inhibitors: Biochemical and Molecular Modeling Studies

Garcinol, a polyisoprenylated benzophenone isolated from Garcinia genus, has been reported to inhibit eukaryotic topoisomerase I and topoisomerase II at concentrations comparable to that of etoposide (∼25-100 μM). With the aim to clarify the underlying molecular mechanisms by which garcinol inhibits human topoisomerase IIα and topoisomerase IIβ, biochemical assays along with molecular docking and molecular dynamics studies were carried out on garcinol and six congeners. The biochemical results revealed that garcinol derivatives appear to act as catalytic inhibitors of topoisomerase II and to inhibit ATP hydrolysis by topoisomerase II via some form of mixed inhibition. The computational investigation identified the structural elements responsible for binding to the biological target and also provided information for the eventual design of more selective and potent analogues. Collectively, our data suggest that garcinol-type agents may bind to the DNA binding surface and/or ATP domain of type II topoisomerases to antagonize function.

Identification of the 2-Benzoxazol-2-yl-phenol Scaffold as New Hit for JMJD3 Inhibition

JMJD3 is a member of the KDM6 subfamily and catalyzes the demethylation of lysine 27 on histone H3 (H3K27). This protein was identified as a useful tool in understanding the role of epigenetics in inflammatory conditions and in cancer as well. Guided by a virtual fragment screening approach, we identified the benzoxazole scaffold as a new hit suitable for the development of tighter JMJD3 inhibitors. Compounds were synthesized by a microwave-assisted one-pot reaction under catalyst and solvent-free conditions. Among these, compound 8 presented the highest inhibitory activity (IC₅₀ = 1.22 ± 0.22 μM) in accordance with molecular modeling calculations. Moreover, 8 induced the cycle arrest in S-phase on A375 melanoma cells.

Glucopyranosylbianthrones from the Algerian Asphodelus tenuifolius: Structural Insights and Biological Evaluation on Melanoma Cancer Cells

Two new glucopyranosylbianthrones (1 and 2) were isolated from the aerial part of the plant Asphodelus tenuifolius, collected in Southwest Algeria. The 2D structures of 1 and 2 were defined by NMR analysis, HRESIMS data, and comparison with literature data. The comparison of experimental and calculated electronic circular dichroism and NMR data led to characterization of the ( M) and ( P) atropisomeric forms of the glucopyranosylbianthrones, asphodelins (1) and (2), respectively. The in vitro activities of these two metabolites were evaluated in human melanoma A375 cells, and both the compounds inhibited cell proliferation in a concentration-dependent manner, with IC₅₀ values of 20.6 ± 0.8 and 23.2 ± 1.1 μM, respectively. Considering their biological profile, an inverse virtual screening approach was employed to identify and suggest putative anticancer interacting targets.