Synthesis and biological evaluation of novel (thio)semicarbazone-based benzimidazoles as antiviral agents against human respiratory viruses

Respiratory RNA viruses are responsible for recurrent acute respiratory illnesses that stillrepresent a major medical need. Previously we developed a large variety of benzimidazole derivativesable to inhibit these viruses. Herein, two series of (thio)semicarbazone- and hydrazone-basedbenzimidazoles have been explored, by derivatizing 5-acetyl benzimidazoles previously reported by us,thereby evaluating the influence of the modification on the antiviral activity. Compounds6,8,16and17,bearing the 5-(thio)semicarbazone and 5-hydrazone functionalities in combination with the 2-benzylring on the benzimidazole core structure, acted as dual inhibitors of influenza A virus and humancoronavirus. For respiratory syncytial virus (RSV), activity is limited to the 5-thiosemicarbazone(25) and 5-hydrazone (22) compounds carrying the 2-[(benzotriazol-1/2-yl)methyl]benzimidazolescaffold. These molecules proved to be the most effective antiviral agents, able to reach the potencyprofile of the licensed drug ribavirin. The molecular docking analysis explained the SAR of thesecompounds around their binding mode to the target RSV F protein, revealing the key contacts forfurther assessment. The herein-investigated benzimidazole-based derivatives may represent valuablehit compounds, deserving subsequent structural improvements towards more efficient antiviralagents for the treatment of pathologies caused by these human respiratory viruses

Synthesis and Antiviral Evaluation of Bisnoradamantane Sulfites and Related Compounds

The reaction of a series of 1,2-diols with thionyl chloride led to bisnoradamantane sulfites in very good yields. The reaction has also been applied to related polycyclic scaffolds. The compounds have been tested for antiviral activity but none of them showed to be active. Several attempts to generate and trap SO from these polycyclic sulfites have been unsuccessful

Anti-influenza virus activity of benzo[d]thiazoles that target heat shock protein 90

Seasonal or pandemic influenza virus infections are a worldwide health problem requiring antiviral therapy. Since virus resistance to the established neuraminidase inhibitors and novel polymerase inhibitors is growing, new drug targets are needed. Heat shock protein 90 (Hsp90) is associated with several aspects of the influenza virus life cycle, and is considered a relevant host cell target. We report here on a series of benzo[d]thiazole and 4,5,6,7-tetrahydrobenzo [d]thiazole derivatives with robust and selective activities against influenza A (H1N1, H3N2) and influenza B viruses. Two compounds, 1 and 4, have low micromolar EC50 values and show high binding affinities for Hsp90, which suggests that inhibition of Hsp90 is the mechanism underlying their antiviral effects. These compounds represent suitable scaffolds for designing novel Hsp90 inhibitors with favourable activities against influenza virus.Peer reviewe

Metal-Chelating 2‑Hydroxyphenyl Amide Pharmacophore for Inhibition of Influenza Virus Endonuclease

The influenza virus PA endonuclease is an attractive target for development of novel anti-influenza virus therapeutics. Reported PA inhibitors chelate the divalent metal ion(s) in the enzyme’s catalytic site, which is located in the Nterminal part of PA (PA-Nter). In this work, a series of 2- hydroxybenzamide-based compounds have been synthesized and biologically evaluated in order to identify the essential pharmacophoric motif, which could be involved in functional sequestration of the metal ions (probably Mg2+) in the catalytic site of PA. By using HL1, H2L2, and HL3 as model ligands with Mg2+ ions, we isolated and fully characterized a series of complexes and tested them for inhibitory activity toward PA-Nter endonuclease. H2L2 and the corresponding Mg2+ complex showed an interesting inhibition of the endonuclease activity. The crystal structures of the uncomplexed HL1 and H2L2 and of the isolated magnesium complex [Mg(L3)2(MeOH)2]·2MeOH were solved by X-ray diffraction analysis. Furthermore, the speciation models for HL1, H2L2, and HL3 with Mg2+ were obtained, and the formation constants of the complexes were measured. Preliminary docking calculations were conducted to investigate the interactions of the title compounds with essential amino acids in the PANter active site. These findings supported the “two-metal” coordination of divalent ions by a donor triad atoms chemotype as a powerful strategy to develop more potent PA endonuclease inhibitors

Chelation motifs affecting metal-dependent viral enzymes: N′-acylhydrazone ligands as dual target inhibitors of HIV-1 Integrase and Reverse Transcriptase Ribonuclease H domain

Human immunodeficiency virus type 1 (HIV-1) infection, still represent a serious global health emergency. The chronic toxicity derived from the current anti-retroviral therapy limits the prolonged use of several antiretroviral agents, continuously requiring the discovery of new antiviral agents with innovative strategies of action. In particular, the development of single molecules targeting two proteins (dual inhibitors) is one of the current main goals in drug discovery. In this contest, metal-chelating molecules have been extensively explored as potential inhibitors of viral metal-dependent enzymes, resulting in some important classes of antiviral agents. Inhibition of HIV Integrase (IN) is, in this sense, paradigmatic. HIV-1 IN and Reverse Transcriptase-associated Ribonuclease H (RNase H) active sites show structural homologies, with the presence of two Mg(II) cofactors, hence it seems possible to inhibit both enzymes by means of chelating ligands with analogous structural features. Here we present a series of N′-acylhydrazone ligands with groups able to chelate the Mg(II) hard Lewis acid ions in the active sites of both the enzymes, resulting in dual inhibitors with micromolar and even nanomolar activities. The most interesting identified N′-acylhydrazone analog, compound 18, shows dual RNase H-IN inhibition and it is also able to inhibit viral replication in cell-based antiviral assays in the low micromolar range. Computational modeling studies were also conducted to explore the binding attitudes of some model ligands within the active site of both the enzymes

Inhibitory effect of 2,3,5,6-tetrafluoro-4-[4-(Aryl)-1H-1,2,3-triazol-1-yl]benzenesulfonamide derivatives on HIV reverse transcriptase associated rnase H activities

The HIV-1 ribonuclease H (RNase H) function of the reverse transcriptase (RT) enzyme catalyzes the selective hydrolysis of the RNA strand of the RNA:DNA heteroduplex replication intermediate, and represents a suitable target for drug development. A particularly attractive approach is constituted by the interference with the RNase H metal-dependent catalytic activity, which resides in the active site located at the C-terminus p66 subunit of RT. Herein, we report results of an in-house screening campaign that allowed us to identify 4-[4-(aryl)-1H-1,2,3-triazol-1-yl]benzenesulfonamides, prepared by the “click chemistry” approach, as novel potential HIV-1 RNase H inhibitors. Three compounds (9d, 10c, and 10d) demonstrated a selective inhibitory activity against the HIV-1 RNase H enzyme at micromolar concentrations. Drug-likeness, predicted by the calculation of a panel of physicochemical and ADME properties, putative binding modes for the active compounds, assessed by computational molecular docking, as well as a mechanistic hypothesis for this novel chemotype are reported

N-benzyl 4,4-disubstituted piperidines as a potent class of influenza H1N1 virus inhibitors showing a novel mechanism of hemagglutinin fusion peptide interaction

The influenza virus hemagglutinin (HA) is an attractive target for antiviral therapy due to its essential role in mediating virus entry into the host cell. We here report the identification of a class of N-benzyl- 4,4,-disubstituted piperidines as influenza A virus fusion inhibitors with specific activity against the H1N1 subtype. Using the highly efficient one-step Ugi four-component reaction, diverse library of piperidine-based analogues was synthesized and evaluated to explore the structure-activity relation- ships (SAR). Mechanistic studies, including resistance selection with the most active compound (2) demonstrated that it acts as an inhibitor of the low pH-induced HA-mediated membrane fusion process. Computational studies identified an as yet unrecognized fusion inhibitor binding site, which is located at the bottom of the HA2 stem in close proximity to the fusion peptide. A direct p-stacking interaction between the N-benzylpiperidine moiety of 2 and F9HA2 of the fusion peptide, reinforced with an addi- tional p-stacking interaction with Y119HA2, and a salt bridge of the protonated piperidine nitrogen with E120HA2, were identified as important interactions to mediate ligand binding. This site rationalized the observed SAR and provided a structural explanation for the H1N1-specific activity of our inhibitors. Furthermore, the HA1-S326V mutation resulting in resistance to 2 is close to the proposed new binding pocket. Our findings point to the N-benzyl-4,4,-disubstituted piperidines as an interesting class of influenza virus inhibitors, representing the first example of fusion peptide binders with great potential for anti-influenza drug development

Antimalarial activity of prodrugs of N-branched acyclic nucleoside phosphonate inhibitors of 6-oxopurine phosphoribosyltransferases

Acyclic nucleoside phosphonates (ANPs) that contain a 6-oxopurine base are good inhibitors of the human and Plasmodium falciparum 6-oxopurine phosphoribosyltransferases (PRTs), key enzymes of the purine salvage pathway. Chemical modifications, based on the crystal structures of several inhibitors in complex with the human PRTase, led to the design of a new class of inhibitors - the aza-ANPs. Because of the negative charges of the phosphonic acid moiety, their ability to cross cell membranes is, however, limited. Thus, phosphoramidate prodrugs of the aza-ANPs were prepared to improve permeability. These prodrugs arrest parasitemia with IC values in the micromolar range against Plasmodium falciparum-infected erythrocyte cultures (both chloroquine-sensitive and chloroquine-resistant Pf strains). The prodrugs exhibit low cytotoxicity in several human cell lines. Thus, they fulfill two essential criteria to qualify them as promising antimalarial drug leads

A few atoms make the difference: Synthetic, CD, NMR and computational studies on antiviral and antibacterial activities of glycopeptide antibiotic aglycon derivatives

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New polycyclic dual inhibitors of the wild type and the V27A mutant M2 channel of the influenza A virus with unexpected binding mode

Two new polycyclic scaffolds were synthesized and evaluated as anti-influenza A compounds. The 5-azapentacyclo[6.4.0.02,10.03,7.09,11]dodecane derivatives were only active against the wild-type M2 channel in the low-micromolar range. However, some of the 14-azaheptacyclo[8.6.1.02,5.03,11.04,9.06,17.012,16]heptadecane derivatives were dual inhibitors of the wild-type and the V27A mutant M2 channels. The antiviral activity of these molecules was confirmed by cell culture assays. Their binding mode was analysed through molecular dynamics simulations, which showed the existence of distinct binding modes in the wild type M2 channel and its V27A variant