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The worldwide expansion of chikungunya virus (CHIKV) into tropical and subtropical areas in the last 15 years has posed a currently unmet need for vaccines and therapeutics. The E2-E1 envelope glycoprotein complex binds receptors on the host cell and promotes membrane fusion during CHIKV entry, thus constituting an attractive target for the development of antiviral drugs. In order to identify CHIKV antivirals acting through inhibition of the envelope glycoprotein complex function, our first approach was to search for amenable druggable sites within the E2-E1 heterodimer. We identified a pocket located in the interface between E2 and E1 around the fusion loop. Then, via a structure-based virtual screening approach and in vitro assay of antiviral activity, we identified compound 7 as a specific inhibitor of CHIKV. Through a lead optimization process, we obtained compound 11 that demonstrated increased antiviral activity and low cytotoxicity (EC 50 1.6 μM, CC 50 56.0 μM). Molecular dynamics simulations were carried out and described a possible interaction pattern of compound 11 and the E1-E2 dimer that could be useful for further optimization. As expected from target site selection, compound 11 inhibited virus internalization during CHIKV entry. In addition, virus populations resistant to compound 11 included mutation E2-P173S, which mapped to the proposed binding pocket, and second site mutation E1-Y24H. Construction of recombinant viruses showed that these mutations conferred antiviral resistance in the parental background. Finally, compound 11 presents acceptable solubility values and is chemically and enzymatically stable in different media. Altogether, these findings uncover a suitable pocket for the design of CHIKV entry inhibitors with promising antiviral activity and pharmacological profiles.

Dengue fever is a mosquito-borne viral disease that has become a major public health concern worldwide. This disease presents with a wide range of clinical manifestations, from a mild cold-like illness to the more serious hemorrhagic dengue fever and dengue shock syndrome. Currently, neither an approved drug nor an effective vaccine for the treatment are available to fight the disease. The envelope protein (E) is a major component of the virion surface. This protein plays a key role during the viral entry process, constituting an attractive target for the development of antiviral drugs. The crystal structure of the E protein reveals the existence of a hydrophobic pocket occupied by the detergent n-octyl-β-d-glucoside (β-OG). This pocket lies at the hinge region between domains I and II and is important for the low pH-triggered conformational rearrangement required for the fusion of the virion with the host's cell. Aiming at the design of novel molecules which bind to E and act as virus entry inhibitors, we undertook a de novo design approach by "growing" molecules inside the hydrophobic site (β-OG). From more than 240000 small-molecules generated, the 2,4 pyrimidine scaffold was selected as the best candidate, from which one synthesized compound displayed micromolar activity. Molecular dynamics-based optimization was performed on this hit, and thirty derivatives were designed in silico, synthesized and evaluated on their capacity to inhibit dengue virus entry into the host cell. Four compounds were found to be potent antiviral compounds in the low-micromolar range. The assessment of drug-like physicochemical and in vitro pharmacokinetic properties revealed that compounds 3e and 3h presented acceptable solubility values and were stable in mouse plasma, simulated gastric fluid, simulated intestinal fluid, and phosphate buffered saline solution., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Antiviral targeting of virus envelope proteins is an effective strategy for therapeutic intervention of viral infections. Here, we took a computer-guided approach with the aim of identifying new antivirals against the envelope protein E2 of bovine viral diarrhea virus (BVDV). BVDV is an enveloped virus with an RNA genome responsible for major economic losses of the cattle industry worldwide. Based on the crystal structure of the envelope protein E2, we defined a binding site at the interface of the two most distal domains from the virus membrane and pursued a hierarchical docking-based virtual screening search to identify small-molecule ligands of E2. Phenyl thiophene carboxamide derivative 12 (PTC12) emerged as a specific inhibitor of BVDV replication from in vitro antiviral activity screening of candidate molecules, displaying an IC 50 of 0.30 μM against the reference NADL strain of the virus. Using reverse genetics we constructed a recombinant BVDV expressing GFP that served as a sensitive reporter for the study of the mechanism of action of antiviral compounds. Time of drug addition assays showed that PTC12 inhibited an early step of infection. The mechanism of action was further dissected to find that the compound specifically acted at the internalization step of virus entry. Interestingly, we demonstrated that similar to PTC12, the benzimidazole derivative 03 (BI03) selected in the virtual screen also inhibited internalization of BVDV. Furthermore, docking analysis of PTC12 and BI03 into the binding site revealed common interactions with amino acid residues in E2 suggesting that both compounds could share the same molecular target. In conclusion, starting from a targeted design strategy of antivirals against E2 we identified PTC12 as a potent inhibitor of BVDV entry. The compound can be valuable in the design of antiviral strategies in combination with already well-characterized polymerase inhibitors of BVDV., (Copyright © 2017 Elsevier B.V. All rights reserved.)

X-ray crystal structures at 2.9 Å resolution are reported for two complexes of catechol diethers with HIV-1 reverse transcriptase. The results help elucidate the structural origins of the extreme antiviral activity of the compounds. The possibility of halogen bonding between the inhibitors and Pro95 is addressed. Structural analysis reveals key interactions with conserved residues P95 and W229 of importance for design of inhibitors with high potency and favorable resistance profiles.

A new series of bis-aminomethylnaphthalenes were synthesized in satisfactory overall yield, through a simple synthetic strategy using reductive amination. The DNA binding properties of these compounds have been examined and compared to those of reference drugs using an UV spectroscopy method. The compounds were evaluated for their in vitro anticancer activity and some of them were studied in vivo. Compound 15 exhibited remarkable antitumor activity and represents a novel template for anticancer chemotherapy and can serve as a new lead compound.