Exploring the chemical space of functionalized [1,2,4]triazolo[4,3-a]quinoxaline-based compounds targeting the bromodomain of BRD9.

Here we report a detailed structure-activity relationship (SAR) study related to [1,2,4]triazolo[4,3-a]quinoxaline-based compounds targeting the reader module of bromodomain containing-protein 9 (BRD9). 3D structure-based pharmacophore models, previously introduced by us, were here employed to evaluate a second generation of compounds, exploring different substitution patterns on the heterocyclic core. Starting from the promising data obtained from our previously identified [1,2,4]triazolo[4,3-a]quinoxaline-based compounds 1-4, the combination of in silico studies, chemical synthesis, biophysical and in vitro assays led to the identification of a new set of derivatives, selected for thoroughly exploring the chemical space of the bromodomain binding site. In more details, the investigation of different linkers at C-4 position highlighted the amine spacer as mandatory for the binding with the protein counterpart and the crucial role of the alkyl substituents at C-1 for increasing the selectivity toward BRD9. Additionally, the importance of a hydrogen bond donor group, critical to anchor the ZA region and required for the interaction with Ile53 residue, was inferred from the analysis of our collected results. Herein we also propose an optimization and an update of our previously reported "pharm-druglike2" 3D structure-based pharmacophore model, introducing it as "pharm-druglike2.1". Compounds 24-26, 32, 34 and 36 were identified as new valuable BRD9 binders featuring IC50 values in the low micromolar range. Among them, 24 and 36 displayed an excellent selectivity towards BRD9 and a good antiproliferative effect on a panel of leukemia models, especially toward CCRF-CEM cell line, with no cytotoxicity on healthy cells. Notably, the interaction of 24 and 36 with the bromodomain and PHD finger-containing protein 1 (BRPF1) also emerged, disclosing them as new and unexplored dual inhibitors for these two proteins highly involved in leukemia. These findings highlight the potential for the identification of new attractive dual epidrugs as well as a promising starting point for the development of chemical degraders endowed with anticancer activities.

A multidisciplinary functional proteomics-aided strategy as a tool for the profiling of a novel cytotoxic thiadiazolopyrimidone.

In recent years, thiadiazolopyrimidine derivatives have been acknowledged for their striking poly-pharmacological framework, thus representing an interesting scaffold for the development of new therapeutic candidates. This paper examines the synthesis and the interactome characterization of a novel bioactive thiadiazolopyrimidone (compound 1), endowed with cytotoxic activity on HeLa cancer cells. In detail, starting from a small set of synthesized thiadiazolopyrimidones, a multi-disciplinary strategy has been carried out on the most bioactive one to disclose its potential biological targets by functional proteomics, using a label-free mass spectrometry based platform coupling Drug Affinity Responsive Target Stability and targeted Limited Proteolysis-Multiple Reaction Monitoring. The identification of Annexin A6 (ANXA6) as compound 1 most reliable cellular partner paved the way to deepen the protein-ligand interaction through bio-orthogonal approaches and to prove compound 1 action on migration and invasion processes governed by ANXA6 modulation. The identification of compund 1 as the first ANXA6 protein modulator represents a relevant tool to further explore the biological role of ANXA6 in cancer, as well as to develop novel anticancer candidates.

Identification of 2,4,5-trisubstituted-2,4-dihydro-3H-1,2,4-triazol-3-one-based small molecules as selective BRD9 binders.

Targeting bromodomain-containing protein 9 (BRD9) represents a promising strategy for the development of new agents endowed with anticancer properties. With this aim, a set of 2,4,5-trisubstituted-2,4-dihydro-3H-1,2,4-triazol-3-one-based compounds was investigated following a combined approach that relied on in silico studies, chemical synthesis, biophysical and biological evaluation of the most promising items. The protocol was initially based on molecular docking experiments, accounting a library of 1896 potentially synthesizable items tested in silico against the bromodomain of BRD9. A first set of 21 compounds (1-21) was selected and the binding on BDR9 was assessed through AlphaScreen assays. The obtained results disclosed compounds 17 and 20 able to bind BRD9 in the submicromolar range (IC50 = 0.35 ± 0.18 µM and IC50 = 0.14 ± 0.03 µM, respectively) showing a promising selectivity profile when tested against further nine bromodomains. Taking advantage of 3D structure-based pharmacophore models, additional 10 derivatives were selected in silico for the synthetic step and binding assessment, highlighting seven compounds (22, 23, 25, 26, 28, 29, 31) able to selectively bind BRD9 among different bromodomains. The ability of the identified BRD9 binders to cross artificial membranes in vitro was also assessed, revealing a very good passive permeability profile. Preliminary studies were carried out on a panel of healthy and cancer human cell lines to explore the biological behavior of the selected compounds, disclosing a moderate activity and significant selectivity profile towards leukaemia cells. These results highlighted the applicability of the reported multidisciplinary approach for accelerating the selection of promising items and for driving the chemical synthesis of novel selective BRD9 binders. Moreover, the low molecular weight of the reported 2,4,5-trisubstituted-2,4-dihydro-3H-1,2,4-triazol-3-one-based BRD9 binders suggests the possibility for further exploring the chemical space in order to obtain new analogues with improved potency.

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.

Structural Refinement of 2,4-Thiazolidinedione Derivatives as New Anticancer Agents Able to Modulate the BAG3 Protein.

The multidomain BAG3 protein is a member of the BAG (Bcl-2-associated athanogene) family of co-chaperones, involved in a wide range of protein-protein interactions crucial for many key cellular pathways, including autophagy, cytoskeletal dynamics, and apoptosis. Basal expression of BAG3 is elevated in several tumor cell lines, where it promotes cell survival signaling and apoptosis resistance through the interaction with many protein partners. In addition, its role as a key player of several hallmarks of cancer, such as metastasis, angiogenesis, autophagy activation, and apoptosis inhibition, has been established. Due to its involvement in malignant transformation, BAG3 has emerged as a potential and effective biological target to control multiple cancer-related signaling pathways. Recently, by using a multidisciplinary approach we reported the first synthetic BAG3 modulator interfering with its BAG domain (BD), based on a 2,4-thiazolidinedione scaffold and endowed with significant anti-proliferative activity. Here, a further in silico-driven selection of a 2,4-thiazolidinedione-based compound was performed. Thanks to a straightforward synthesis, relevant binding affinity for the BAG3BD domain, and attractive biological activities, this novel generation of compounds is of great interest for the development of further BAG3 binders, as well as for the elucidation of the biological roles of this protein in tumors. Specifically, we found compound 6 as a new BAG3 modulator with a relevant antiproliferative effect on two different cancer cell lines (IC50: A375 = 19.36 µM; HeLa = 18.67 µM).

Introducing structure-based three-dimensional pharmacophore models for accelerating the discovery of selective BRD9 binders.

A well-structured in silico workflow is here reported for disclosing structure-based pharmacophore models against bromodomain-containing protein 9 (BRD9), accelerating virtual screening campaigns and facilitating the identification of novel binders. Specifically, starting from 23 known ligands co-crystallized with BRD9, three-dimensional pharmacophore models, namely placed in a reference protein structure, were developed. Specifically, we here introduce a fragment-related pharmacophore model, useful for the identification of new promising small chemical probes targeting the protein region responsible of the acetyllysine recognition, and two further pharmacophore models useful for the selection of compounds featuring drug-like properties. A pharmacophore-driven virtual screening campaign was then performed to facilitate the selection of new selective BRD9 ligands, starting from a large library of commercially available molecules. The identification of a promising BRD9 binder (7) prompted us to re-iterate this computational workflow on a second focused in-house built library of synthesizable compounds and, eventually, three further novel BRD9 binders were disclosed (8-10). Moreover, all these compounds were tested among a panel comprising other nine bromodomains, showing a high selectivity for BRD9. Preclinical bioscreens for potential anticancer activity highlighted compound 7 as that showing the most promising biological effects, proving the reliability of this in silico pipeline and confirming the applicability of the here introduced structure-based three-dimensional (3D) pharmacophore models as straightforward tools for the selection of new BRD9 ligands.

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.

Discovery of noscapine derivatives as potential ß-tubulin inhibitors.

Twenty novel 1,2,3-triazole noscapine derivatives were synthesized starting from noscapine by consecutive N-demethylation, reduction of lactone ring, N-propargylation and Huisgen 1,3-dipolar cycloaddition reaction. In order to select the most promising molecules to subject to further biophysical and biological evaluation, a molecular docking analysis round was performed using noscapine as reference compound. The molecules featuring docking predicted binding affinity better than that of noscapine were then subjected to MTT assay against MCF7 cell line. The obtained results disclosed that all the selected triazole derivatives exhibited a remarkably lower cell viability compared to noscapine in the range of 20 µM in 48 h. In an attempt to correlate the biological activity with the ability to bind tubulin, the surface plasmon resonance (SPR) assay was employed. Compounds 8a, 8h, 9c, 9f and 9j were able to bind tubulin with affinity constant values in the nanomolar range and higher if compared to noscapine. Integrating computational predictions and experimental evaluation, two promising compounds (8h and 9c) were identified, whose relevant cytotoxicity was supposed to be correlated with tubulin binding affinity. These findings shed lights onto structural modifications of noscapine toward the identification of more potent cytotoxic agents targeting tubulin.

Targeting mPGES-1 by a Combinatorial Approach: Identification of the Aminobenzothiazole Scaffold to Suppress PGE2 Levels.

Microsomal prostaglandin E2 synthase-1 (mPGES-1), the terminal enzyme responsible for the production of inducible prostaglandin E2, has become an attractive target for the treatment of inflammation and cancer pathologies. Starting from an aminobenzothiazole scaffold, used as an unprecedented chemical core for mPGES-1 inhibition, a Combinatorial Virtual Screening campaign was conducted, using the X-ray crystal structure of human mPGES-1. Two combinatorial libraries (6 × 104) were obtained by decorating the aminobenzothiazole scaffold with all acyl chlorides and boronates available at the Merck database. The scientific multidisciplinary approach included virtual screening workflow, synthesis, and biological evaluation and led to the identification of three novel aminobenzothiazoles 1, 3, and 13 acting as mPGES-1 inhibitors. The three disclosed hits are able to inhibit mPGES-1 in a cell-free system (IC50 = 1.4 ± 0.2, 0.7 ± 0.1, and 1.7 ± 0.2 µM, respectively), and all are endowed with antitumoral properties against A549 human cancer cell lines at micromolar concentrations (28.5 ± 1.1, 18.1 ± 0.8, and 19.2 ± 1.3 µM, respectively).

A Combinatorial Virtual Screening Approach Driving the Synthesis of 2,4-Thiazolidinedione-Based Molecules as New Dual mPGES-1/5-LO Inhibitors.

Dual inhibition of microsomal prostaglandin E2 synthase-1 (mPGES-1) and 5-lipoxygenase (5-LO), two key enzymes involved in pro-inflammatory eicosanoid biosynthesis, represents a new strategy for treating inflammatory disorders. Herein we report the discovery of 2,4-thiazolidinedione-based mPGES-1/5-LO dual inhibitors following a multidisciplinary protocol, involving virtual combinatorial screening, chemical synthesis, and validation of the biological activities for the selected compounds. Following the multicomponent-based chemical route for the decoration of the 2,4-thiazolidinedione core, a large library of virtual compounds was built (∼2.0×104 items) and submitted to virtual screening. Nine selected molecules were synthesized and biologically evaluated, disclosing among them four compounds able to reduce the activity of both enzymes in the mid- and low- micromolar range of activities. These results are of interest for further expanding the chemical diversity around the 2,4-thiazolidinedione central core, facilitating the identification of novel anti-inflammatory agents endowed with a promising and safer pharmacological profile.

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.

Discovery and synthesis of the first selective BAG domain modulator of BAG3 as an attractive candidate for the development of a new class of chemotherapeutics.

BAG3 protein has emerged as a key regulator of important cellular processes and its expression is increased in some tumor types; however, despite its potential value for future chemotherapeutics, no selective BAG3 modulators have been yet reported. Here we report the 2,4-thiazolidinedione derivative 28 as the first BAG3 protein modulator.

Identification by Inverse Virtual Screening of magnolol-based scaffold as new tankyrase-2 inhibitors.

The natural product magnolol (1) and a selection of its bioinspired derivatives 2-5, were investigated by Inverse Virtual Screening in order to identify putative biological targets from a panel of 308 proteins involved in cancer processes. By this in silico analysis we selected tankyrase-2 (TNKS2), casein kinase 2 (CK2) and bromodomain 9 (Brd9) as potential targets for experimental evaluations. The Surface Plasmon Resonance assay revealed that 3-5 present a good affinity for tankyrase-2, and, in particular, 3 showed an antiproliferative activity on A549 cells higher than the well-known tankyrase-2 inhibitor XAV939 used as reference compound.

Discovery of new molecular entities able to strongly interfere with Hsp90 C-terminal domain.

Heat shock protein 90 (Hsp90) is an ATP dependent molecular chaperone deeply involved in the complex network of cellular signaling governing some key functions, such as cell proliferation and survival, invasion and angiogenesis. Over the past years the N-terminal protein domain has been fully investigated as attractive strategy against cancer, but despite the many efforts lavished in the field, none of the N-terminal binders (termed "classical inhibitors"), currently in clinical trials, have yet successfully reached the market, because of the detrimental heat shock response (HSR) that showed to induce; thus, recently, the selective inhibition of Hsp90 C-terminal domain has powerfully emerged as a more promising alternative strategy for anti-cancer therapy, not eliciting this cell rescue cascade. However, the structural complexity of the target protein and, mostly, the lack of a co-crystal structure of C-terminal domain-ligand, essential to drive the identification of new hits, represent the largest hurdles in the development of new selective C-terminal inhibitors. Continuing our investigations on the identification of new anticancer drug candidates, by using an orthogonal screening approach, here we describe two new potent C-terminal inhibitors able to induce cancer cell death and a considerable down-regulation of Hsp90 client oncoproteins, without triggering the undesired heat shock response.

Discovery of new potent molecular entities able to inhibit mPGES-1.

mPGES-1, a glutathione-dependent membrane protein is involved in the last step of PGE2 production and has been well recognized as a strategic target for the development of anti-inflammatory and anti-cancer agents. It has been proven to selectively control the PGE2 levels induced by inflammatory stimuli, with neither affecting PGE2 constitutively produced, nor homeostatic prostanoids, so that its modulation can represent a better strategy to control PGE2 related disorders, compared to the use of the classical anti-inflammatory drugs, endowed with severe side effects. Despite the intensive research on the identification of potent mPGES-1 inhibitors as attractive candidates for drug development, none of the disclosed molecules, except for LY3023705, which recently entered clinical trials, are available for clinical use, therefore the discovery of new effective mPGES-1 inhibitors with increased drug-like properties are urgently needed. Continuing our work aimed at identifying new chemical platforms able to interact with this enzyme, here we describe the discovery of potent mPGES-1 modulators, featuring a 1-fluoro-2,4-dinitro-biphenyl-based scaffold, by processing and docking a small collection of synthetically accessible molecules, built around two main fragments, disclosed in our in silico screening. The top scoring hits obtained have been synthesized and tested, and five of the predicted compounds showed to potently inhibit mPGES-1 enzyme, without affecting COX enzymes activities.

Cyclic Peptoids as Mycotoxin Mimics: An Exploration of Their Structural and Biological Properties.

Cyclic peptoids have recently emerged as important examples of peptidomimetics for their interesting complexing properties and innate ability to permeate biological barriers. In the present contribution, experimental and theoretical data evidence the intricate conformational and stereochemical properties of five novel hexameric peptoids decorated with N-isopropyl, N-isobutyl, and N-benzyl substituents. Complexation studies by NMR, in the presence of sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), theoretical calculations, and single-crystal X-ray analyses indicate that the conformationally stable host/guest metal adducts display architectural ordering comparable to that of the enniatins and beauvericin mycotoxins. Similarly to the natural depsipeptides, the synthetic oligolactam analogues show a correlation between ion transport abilities in artificial liposomes and cytotoxic activity on human cancer cell lines. The reported results demonstrate that the versatile cyclic peptoid scaffold, for its remarkable conformational and complexing properties, can morphologically mimic related natural products and elicit powerful biological activities.

Structure-Based Design of Microsomal Prostaglandin E2 Synthase-1 (mPGES-1) Inhibitors using a Virtual Fragment Growing Optimization Scheme.

A small library of 2,3-dihydroxybenzamide- and N-(2,3-dihydroxyphenyl)-4-sulfonamide-based microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibitors was identified following a step-by-step optimization of small aromatic fragments selected to interact in focused regions in the active site of mPGES-1. During the virtual optimization process, the 2,3-dihydroxybenzamide moiety was first selected as a backbone of the proposed new chemical entities; the identified compounds were then synthesized and biologically evaluated, identifying derivatives with very promising inhibitory activities in the micromolar range. Subsequent structure-guided replacement of the 2,3-dihydroxybenzamide by the N-(2,3-dihydroxyphenyl)sulfonamide moiety led to the identification of N-(2,3-dihydroxyphenyl)-4-biphenylsulfonamide (6), the most potent small molecule of the series (IC50 =0.53 ± 0.04 µM). The simple synthetic procedure and the possibility of enhancing the potency of this class of inhibitors through additional structural modifications pave the way for further development of new molecules with mPGES-1-inhibitory activity, with potential application as anti-inflammatory and anticancer agents.

Targeting the Hsp90 C-terminal domain by the chemically accessible dihydropyrimidinone scaffold.

Hsp90 C-terminal ligands are potential new anti-cancer drugs alternative to the more studied N-terminal inhibitors. Here we report the identification of a new dihydropyrimidinone binding the C-terminus, which is not structurally related to other well-known natural and nature-inspired inhibitors of this second druggable Hsp90 site.

Exploration of the dihydropyrimidine scaffold for the development of new potential anti-inflammatory agents blocking prostaglandin E2 synthase-1 enzyme (mPGES-1).

Agents targeting microsomal prostaglandin E2 synthase-1 (mPGES-1) would inhibit only PGE2 production induced by inflammatory stimuli and thus could represent a valuable alternative to non-steroidal anti-inflammatory drugs (NSAIDs) as they should be free from the severe side effects of the classic anti-inflammatory drugs. Although several mPGES-1 inhibitors have been so far identified, none of them is currently in clinical trials, therefore the discovery of new molecular platforms, able to interfere with this interesting target, is urgently required. Here, we report the results of a focused collection of dyhidropyrimidin-2(1H)-one based molecules projected by Virtual Screening computational techniques. The key interactions with the receptor counterpart were introduced as a qualitative filter for the selection of the most promising compounds. The biological data obtained are consistent with the computer-aided suggestions and disclosed two interesting molecules showing in vitro mPGES-1 inhibitory activity in the low µM range.