Paper-based electrochemical device for early detection of integrin αvß6 expressing tumors.

Despite progress in the prevention and diagnosis of cancer, current technologies for tumor detection present several limitations including invasiveness, toxicity, inaccuracy, lengthy testing duration and high cost. Therefore, innovative diagnostic techniques that integrate knowledge from biology, oncology, medicinal and analytical chemistry are now quickly emerging in the attempt to address these issues. Following this approach, here we developed a paper-based electrochemical device for detecting cancer-derived Small Extracellular Vesicles (S-EVs) in fluids. S-EVs were obtained from cancer cell lines known to express, at a different level, the αvß6 integrin receptor, a well-established hallmark of numerous epithelial cancer types. The resulting biosensor turned out to recognize αvß6-containing S-EVs down to a limit of 0.7*103 S-EVs/mL with a linear range up to 105 S-EVs /mL, and a relative standard deviation of 11%, thus it may represent a novel opportunity for αvß6 expressing cancers detection.

Discovery of 2,3-Diaminoindole Derivatives as a Novel Class of NOD Antagonists.

NOD1 and NOD2 are members of the pattern recognition receptors involved in the innate immune response. Overactivation of NOD1 is implicated in inflammatory disorders, multiple sclerosis, and cancer cell metastases. NOD1 antagonists would represent valuable pharmacological tools to gain further insight into protein roles, potentially leading to new therapeutic strategies. We herein report the expansion of the chemical space of NOD1 antagonists via a multicomponent synthetic approach affording a novel chemotype, namely, 2,3-diaminoindoles. These efforts resulted in compound 37, endowed with low micromolar affinity toward NOD1. Importantly, a proof-of-evidence of direct binding to NOD1 of Noditinib-1 and derivative 37 is provided here for the first time. Additionally, the combination of computational studies and NMR-based displacement assays enabled the characterization of the binding modality of 37 to NOD1, thus providing key unprecedented knowledge for the design of potent and selective NOD1 antagonists.

Development and Nanoparticle-Mediated Delivery of Novel MDM2/MDM4 Heterodimer Peptide Inhibitors to Enhance 5-Fluorouracil Nucleolar Stress in Colorectal Cancer Cells.

Colorectal cancer (CRC) often involves wild-type p53 inactivation by MDM2 and MDM4 overexpression, promoting tumor progression and resistance to 5-fluoruracil (5-FU). Disrupting the MDM2/4 heterodimer can proficiently reactivate p53, sensitizing cancer cells to 5-FU. Herein, we developed 16 peptides based on Pep3 (1), the only known peptide acting through this mechanism. The new peptides, notably 3 and 9, showed lower IC50 values than 1. When incorporated into tumor-targeted biodegradable nanoparticles, these exhibited cytotoxicity against three different CRC cell lines. Notably, NPs/9 caused a significant increase in p53 levels associated with a strong increment of its main downstream target p21 inducing apoptosis. Also, the combined treatment of 9 with 5-FU caused the activation of nucleolar stress and a synergic apoptotic effect. Hence, the co-delivery of MDM2/4 heterodimer disruptors with 5-FU through nanoparticles might be a promising strategy to overcome drug resistance in CRC.

A combined approach of structure-based virtual screening and NMR to interrupt the PD-1/PD-L1 axis: Biphenyl-benzimidazole containing compounds as novel PD-L1 inhibitors.

Immunotherapy has emerged as a game-changing approach for cancer treatment. Although monoclonal antibodies (mAbs) targeting the programmed cell death protein 1/programmed cell death protein 1 ligand 1 (PD-1/PD-L1) axis have entered the market revolutionizing the treatment landscape of many cancer types, small molecules, although presenting several advantages including the possibility of oral administration and/or reduced costs, struggled to enter in clinical trials, suffering of water insolubility and/or inadequate potency compared with mAbs. Thus, the search for novel scaffolds for both the design of effective small molecules and possible synergistic strategies is an ongoing field of interest. In an attempt to find novel chemotypes, a virtual screening approach was employed, resulting in the identification of new chemical entities with a certain binding capability, the most versatile of which was the benzimidazole-containing compound 10. Through rational design, a small library of its derivatives was synthesized and evaluated. The homogeneous time-resolved fluorescence (HTRF) assay revealed that compound 17 shows the most potent inhibitory activity (IC50 ) in the submicromolar range and notably, differently from the major part of PD-L1 inhibitors, exhibits satisfactory water solubility properties. These findings highlight the potential of benzimidazole-based compounds as novel promising candidates for PD-L1 inhibition.

Molecular View on the iRGD Peptide Binding Mechanism: Implications for Integrin Activity and Selectivity Profiles.

Receptor-selective peptides are widely used as smart carriers for specific tumor-targeted delivery. A remarkable example is the cyclic nonapeptide iRGD (CRGDKPGDC, 1) that couples intrinsic cytotoxic effects with striking tumor-homing properties. These peculiar features are based on a rather complex multistep mechanism of action, where the primary event is the recognition of RGD integrins. Despite the high number of preclinical studies and the recent success of a phase I trial for the treatment of pancreatic ductal adenocarcinoma (PDAC), there is little information available about the iRGD three-dimensional (3D) structure and integrin binding properties. Here, we re-evaluate the peptide's affinity for cancer-related integrins including not only the previously known targets αvß3 and αvß5 but also the αvß6 isoform, which is known to drive cell growth, migration, and invasion in many malignancies including PDAC. Furthermore, we use parallel tempering in the well-tempered ensemble (PT-WTE) metadynamics simulations to characterize the in-solution conformation of iRGD and extensive molecular dynamics calculations to fully investigate its binding mechanism to integrin partners. Finally, we provide clues for fine-tuning the peptide's potency and selectivity profile, which, in turn, may further improve its tumor-homing properties.

Exploring the 1,3-benzoxazine chemotype for cannabinoid receptor 2 as a promising anti-cancer therapeutic.

The discovery of selective agonists of cannabinoid receptor 2 (CB2) is strongly pursued to successfully tuning endocannabinoid signaling for therapeutic purposes. However, the design of selective CB2 agonists is still challenging because of the high homology with the cannabinoid receptor 1 (CB1) and for the yet unclear molecular basis of the agonist/antagonist switch. Here, the 1,3-benzoxazine scaffold is presented as a versatile chemotype for the design of CB2 agonists from which 25 derivatives were synthesized. Among these, compound 7b5 (CB2 EC50 = 110 nM, CB1 EC50 > 10 µM) demonstrated to impair proliferation of triple negative breast cancer BT549 cells and to attenuate the release of pro-inflammatory cytokines in a CB2-dependent manner. Furthermore, 7b5 abrogated the activation of extracellular signal-regulated kinase (ERK) 1/2, a key pro-inflammatory and oncogenic enzyme. Finally, molecular dynamics studies suggested a new rationale for the in vitro measured selectivity and for the observed agonist behavior.

Theoretical and experimental studies on the interaction of biphenyl ligands with human and murine PD-L1: Up-to-date clues for drug design.

Today it is widely recognized that the PD-1/PD-L1 axis plays a fundamental role in escaping the immune system in cancers, so that anti-PD-1/PD-L1 antibodies have been evaluated for their antitumor properties in more than 1000 clinical trials. As a result, some of them have entered the market revolutionizing the treatment landscape of specific cancer types. Nonetheless, a new era based on the development of small molecules as anti PD-L1 drugs has begun. There are, however, some limitations to advancing these compounds into clinical stages including the possible difficulty in counteracting the PD-1/PD-L1 interaction in vivo, the discrepancy between the in vitro IC50 (HTFR assay) and cellular EC50 (immune checkpoint blockade co-culture assay), and the differences in ligands' affinity between human and murine PD-L1, which can affect their preclinical evaluation. Here, an extensive theoretical study, assisted by MicroScale Thermophoresis binding assays and NMR experiments, was performed to provide an atomistic picture of the binding event of three representative biphenyl-based compounds in both human and murine PD-L1. Structural determinants of the species' specificity were unraveled, providing unprecedented details useful for the design of next generation anti-PD-L1 molecules.

Broad-spectrum coronavirus 3C-like protease peptidomimetic inhibitors effectively block SARS-CoV-2 replication in cells: Design, synthesis, biological evaluation, and X-ray structure determination.

Despite the approval of vaccines, monoclonal antibodies and restrictions during the pandemic, the demand for new efficacious and safe antivirals is compelling to boost the therapeutic arsenal against the COVID-19. The viral 3-chymotrypsin-like protease (3CLpro) is an essential enzyme for replication with high homology in the active site across CoVs and variants showing an almost unique specificity for Leu-Gln as P2-P1 residues, allowing the development of broad-spectrum inhibitors. The design, synthesis, biological activity, and cocrystal structural information of newly conceived peptidomimetic covalent reversible inhibitors are herein described. The inhibitors display an aldehyde warhead, a Gln mimetic at P1 and modified P2-P3 residues. Particularly, functionalized proline residues were inserted at P2 to stabilize the ß-turn like bioactive conformation, modulating the affinity. The most potent compounds displayed low/sub-nM potency against the 3CLpro of SARS-CoV-2 and MERS-CoV and inhibited viral replication of three human CoVs, i.e. SARS-CoV-2, MERS-CoV, and HCoV 229 in different cell lines. Particularly, derivative 12 exhibited nM-low µM antiviral activity depending on the virus, and the highest selectivity index. Some compounds were co-crystallized with SARS-CoV-2 3CLpro validating our design. Altogether, these results foster future work toward broad-spectrum 3CLpro inhibitors to challenge CoVs related pandemics.

The Inhibition of DNA Viruses by the Amphibian Antimicrobial Peptide Temporin G: A Virological Study Addressing HSV-1 and JPCyV.

Herpes simplex virus type-1 (HSV-1) and John Cunningham polyomavirus (JCPyV) are widely distributed DNA viruses causing mainly asymptomatic infection, but also mild to very severe diseases, especially when these viruses reach the brain. Some drugs have been developed to inhibit HSV-1 replication in host cells, but their prolonged use may induce resistance phenomena. In contrast, to date, there is no cure for JCPyV. The search for alternative drugs that can reduce viral infections without undermining the host cell is moving toward antimicrobial peptides (AMPs) of natural occurrence. These include amphibian AMPs belonging to the temporin family. Herein, we focus on temporin G (TG), showing that it strongly affects HSV-1 replication by acting either during the earliest stages of its life cycle or directly on the virion. Computational studies have revealed the ability of TG to interact with HSV-1 glycoprotein B. We also found that TG reduced JCPyV infection, probably affecting both the earliest phases of its life cycle and the viral particle, likely through an interaction with the viral capsid protein VP1. Overall, our results are promising for the development of short naturally occurring peptides as antiviral agents used to counteract diseases related to HSV-1 and JCPyV.

Targeting SARS-CoV-2 Proteases and Polymerase for COVID-19 Treatment: State of the Art and Future Opportunities.

The newly emerged coronavirus, called SARS-CoV-2, is the causing pathogen of pandemic COVID-19. The identification of drugs to treat COVID-19 and other coronavirus diseases is an urgent global need, thus different strategies targeting either virus or host cell are still under investigation. Direct-acting agents, targeting protease and polymerase functionalities, represent a milestone in antiviral therapy. The 3C-like (or Main) protease (3CLpro) and the nsp12 RNA-dependent RNA-polymerase (RdRp) are the best characterized SARS-CoV-2 targets and show the highest degree of conservation across coronaviruses fostering the identification of broad-spectrum inhibitors. Coronaviruses also possess a papain-like protease, another essential enzyme, still poorly characterized and not equally conserved, limiting the identification of broad-spectrum agents. Herein, we provide an exhaustive comparative analysis of SARS-CoV-2 proteases and RdRp with respect to other coronavirus homologues. Moreover, we highlight the most promising inhibitors of these proteins reported so far, including the possible strategies for their further development.

Halting the Spread of Herpes Simplex Virus-1: The Discovery of an Effective Dual αvß6/αvß8 Integrin Ligand.

Over recent years, αvß6 and αvß8 Arg-Gly-Asp (RGD) integrins have risen to prominence as interchangeable co-receptors for the cellular entry of herpes simplex virus-1 (HSV-1). In fact, the employment of subtype-specific integrin-neutralizing antibodies or gene-silencing siRNAs has emerged as a valuable strategy for impairing HSV infectivity. Here, we shift the focus to a more affordable pharmaceutical approach based on small RGD-containing cyclic pentapeptides. Starting from our recently developed αvß6-preferential peptide [RGD-Chg-E]-CONH2 (1), a small library of N-methylated derivatives (2-6) was indeed synthesized in the attempt to increase its affinity toward αvß8. Among the novel compounds, [RGD-Chg-(NMe)E]-CONH2 (6) turned out to be a potent αvß6/αvß8 binder and a promising inhibitor of HSV entry through an integrin-dependent mechanism. Furthermore, the renewed selectivity profile of 6 was fully rationalized by a NMR/molecular modeling combined approach, providing novel valuable hints for the design of RGD integrin ligands with the desired specificity profile.

The organometallic ferrocene exhibits amplified anti-tumor activity by targeted delivery via highly selective ligands to αvß3, αvß6, or α5ß1 integrins.

High levels of reactive oxygen species (ROS) in tumors have been shown to exert anti-tumor activity, leading to the concept of ROS induction as therapeutic strategy. The organometallic compound ferrocene (Fc) generates ROS through a reversible one-electron oxidation. Incorporation of Fc into a tumor-targeting, bioactive molecule can enhance its therapeutic activity and enable tumor specific delivery. Therefore, we conjugated Fc to five synthetic, Arg-Gly-Asp (RGD)-based integrin binding ligands to enable targeting of the cell adhesion and signaling receptor integrin subtypes αvß3, α5ß1, or αvß6, which are overexpressed in various, distinct tumors. We designed and synthesized a library of integrin-ligand-ferrocene (ILF) derivatives and showed that ILF conjugates maintained the high integrin affinity and selectivity of their parent ligands. A thorough biological characterization allowed us to identify the two most promising ligands, an αvß3 (L2b) and an αvß6 (L3b) targeting ILF, which displayed selective integrin-dependent cell uptake and pronounced ferrocene-mediated anti-tumor effects in vitro, along with increased ROS production and DNA damage. Hence, ILFs are promising candidates for the selective, tumor-targeted delivery of ferrocene to maximize its anti-cancer efficacy and minimize systemic toxicity, thereby improving the therapeutic window of ferrocene compared to currently used non-selective anti-cancer drugs.

Disulfide Bond Replacement with 1,4- and 1,5-Disubstituted [1,2,3]-Triazole on C-X-C Chemokine Receptor Type 4 (CXCR4) Peptide Ligands: Small Changes that Make Big Differences.

Here we investigated the structural and biological effects ensuing from the disulfide bond replacement of a potent and selective C-X-C chemokine receptor type 4 (CXCR4) peptide antagonist, with 1,4- and 1,5- disubstituted 1,2,3-triazole moieties. Both strategies produced candidates that showed high affinity and selectivity against CXCR4. Notably, when assessed for their ability to modulate the CXCL12-mediated cell migration, the 1,4-triazole variant conserved the antagonistic effect in the low-mid nanomolar range, while the 1,5-triazole one displayed the ability to activate the migration, becoming the first in class low-molecular-weight CXCR4 peptide agonist. By combining NMR and computational studies, we provided a valuable model that highlighted differences in the interactions of the two peptidomimetics with the receptor that could account for their different functional profile. Finally, we envisage that our findings could be translated to different GPCR-interacting peptides for the pursuit of novel chemical probes that could assist in dissecting the complex puzzle of this fundamental class of transmembrane receptors.

Bioinformatics and Biosimulations as Toolbox for Peptides and Peptidomimetics Design: Where Are We?

Peptides and peptidomimetics are strongly re-emerging as amenable candidates in the development of therapeutic strategies against a plethora of pathologies. In particular, these molecules are extremely suitable to treat diseases in which a major role is played by protein-protein interactions (PPIs). Unlike small organic compounds, peptides display both a high degree of specificity avoiding secondary off-targets effects and a relatively low degree of toxicity. Further advantages are provided by the possibility to easily conjugate peptides to functionalized nanoparticles, so improving their delivery and cellular uptake. In many cases, such molecules need to assume a specific three-dimensional conformation that resembles the bioactive one of the endogenous ligand. To this end, chemical modifications are introduced in the polypeptide chain to constrain it in a well-defined conformation, and to improve the drug-like properties. In this context, a successful strategy for peptide/peptidomimetics design and optimization is to combine different computational approaches ranging from structural bioinformatics to atomistic simulations. Here, we review the computational tools for peptide design, highlighting their main features and differences, and discuss selected protocols, among the large number of methods available, used to assess and improve the stability of the functional folding of the peptides. Finally, we introduce the simulation techniques employed to predict the binding affinity of the designed peptides for their targets.

GPBAR1 Activation by C6-Substituted Hyodeoxycholane Analogues Protect against Colitis.

GPBAR1 agonists have been identified as potential leads for the treatment of diseases related to colon inflammation such as Crohn's and ulcerative colitis. In this paper, we report the discovery of a small library of hyodeoxycholane analogues, decorated at C-6 with different substituents, as potent and selective GPBAR1 agonists. In vitro pharmacological assays showed that compound 6 selectively activates GPBAR1 (EC50 = 0.3 µM) and reduces the production of pro-inflammatory cytokines (IL-1ß, IL-6, and TNF-α) in THP1 cells. The binding mode of compound 6 in GPBAR1 was elucidated by docking calculations. Moreover, compound 6 protects against TNBS-induced colitis in Gpbar1+/+ rodent model, representing an intriguing lead for the treatment of these inflammatory disorders.

Targeting the KRAS oncogene: Synthesis, physicochemical and biological evaluation of novel G-Quadruplex DNA binders.

The oncogene KRAS is involved in the pathogenesis of many tumors such as pancreatic, lung and colorectal cancers, thereby representing a relevant target for the treatment of these diseases. The KRAS P1 promoter contains a nuclease hypersensitive, guanine-rich sequence able to fold into a G-quadruplex motif (G4). The stabilization of this G4 structure by small molecules is emerging as a feasible approach to downregulate KRAS expression. Here, a set of novel stabilizing molecules was identified through a virtual screening campaign on the NMR structure of the 22-mer KRAS G4. The most promising hits were then submitted to structure-activity relationships studies which allowed improving their binding affinity and selectivity over double helix DNA and different G4 topologies. The best derivative (19) underwent fluorescence titration experiments and further computational studies to disclose its binding mechanism to KRAS G4. Finally, biological assays showed that this compound is capable to reduce the viability of colorectal cancer cells in which mutated KRAS acts as a driver oncogene. Thus, 19 might represent the prototype of a new class of drugs for the treatment of tumors that, expressing mutated forms of KRAS, are refractory to current therapeutic regimens.

Discovery of dihydroxyindole-2-carboxylic acid derivatives as dual allosteric HIV-1 Integrase and Reverse Transcriptase associated Ribonuclease H inhibitors.

The management of Human Immunodeficiency Virus type 1 (HIV-1) infection requires life-long treatment that is associated with chronic toxicity and possible selection of drug-resistant strains. A new opportunity for drug intervention is offered by antivirals that act as allosteric inhibitors targeting two viral functions (dual inhibitors). In this work, we investigated the effects of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) derivatives on both HIV-1 Integrase (IN) and Reverse Transcriptase associated Ribonuclease H (RNase H) activities. Among the tested compounds, the dihydroxyindole-carboxamide 5 was able to inhibit in the low micromolar range (1-18 µM) multiple functions of IN, including functional IN-IN interactions, IN-LEDGF/p75 binding and IN catalytic activity. Docking and site-directed mutagenesis studies have suggested that compound 5 binds to a previously described HIV-1 IN allosteric pocket. These observations indicate that 5 is structurally and mechanistically distinct from the published allosteric HIV-1 IN inhibitors. Moreover, compound 5 also inhibited HIV-1 RNase H function, classifying this molecule as a dual HIV-1 IN and RNase H inhibitor able to impair the HIV-1 virus replication in cell culture. Overall, we identified a new scaffold as a suitable platform for the development of novel dual HIV-1 inhibitors.

Structural Insight into the Binding Mode of FXR and GPBAR1 Modulators.

In this chapter we provide an exhaustive overview of the binding modes of bile acid (BA) and non-BA ligands to the nuclear farnesoid X receptor (FXR) and the G-protein bile acid receptor 1 (GPBAR1). These two receptors play a key role in many diseases related to lipid and glucose disorders, thus representing promising pharmacological targets. We pay particular attention to the chemical and structural features of the ligand-receptor interaction, providing guidelines to achieve ligands endowed with selective or dual activity towards the receptor and paving the way to future drug design studies.

Novel Isoxazole Derivatives with Potent FXR Agonistic Activity Prevent Acetaminophen-Induced Liver Injury.

Acetaminophen misuse is a leading cause of acute liver failure and liver transplantation for which therapy is poorly effective. FXR ligands have shown effective in reducing liver injury in several experimental and clinical settings. In this Letter, we have elaborated on the structure of GW4064, the first nonsteroidal agonist for FXR, to identify novel isoxazoles endowed with FXR agonistic activity and improved ADME properties. The pharmacological characterization and molecular docking studies for the structure-activity rationalization allowed the identification of several FXR agonists with nanomolar potency in transactivation and SRC-1 recruitment assays. This characterization resulted in the identification of a potent FXR agonist, compound 20 that was orally active, and rescued mice from acute liver failure caused by acetaminophen overdose in a FXR-dependent manner.

Investigation around the Oxadiazole Core in the Discovery of a New Chemotype of Potent and Selective FXR Antagonists.

Recent findings have shown that Farnesoid X Receptor (FXR) antagonists might be useful in the treatment of cholestasis and related metabolic disorders. In this paper, we report the discovery of a new chemotype of FXR antagonists featured by a 3,5-disubstituted oxadiazole core. In total, 35 new derivatives were designed and synthesized, and notably, compounds 3f and 13, containing a piperidine ring, displayed the best antagonistic activity against FXR with promising cellular potency (IC50 = 0.58 ± 0.27 and 0.127 ± 0.02 µM, respectively). The excellent pharmacokinetic properties make compound 3f the most promising lead identified in this study.