Novel Colchicine-Site Binders with a Cyclohexanedione Scaffold Identified through a Ligand-Based Virtual Screening Approach

Vascular disrupting agents (VDAs) constitute an innovative anticancer therapy that targets the tumor endothelium, leading to tumor necrosis. Our approach for the identification of new VDAs has relied on a ligand 3-D shape similarity virtual screening (VS) approach using the ROCS program as the VS tool and as query colchicine and TN-16, which both bind the α,β-tubulin dimer. One of the hits identified, using TN-16 as query, has been explored by the synthesis of its structural analogues, leading to 2-(1-((2-methoxyphenyl)­amino)­ethylidene)-5-phenylcyclohexane-1,3-dione (compound <b>16c</b>) with an IC₅₀ = 0.09 ± 0.01 μM in HMEC-1 and BAEC, being 100-fold more potent than the initial hit. Compound <b>16c</b> caused cell cycle arrest in the G2/M phase and interacted with the colchicine-binding site in tubulin, as confirmed by a competition assay with <i><i>N,N</i></i>′<b>-</b>ethylenebis­(iodoacetamide) and by fluorescence spectroscopy. Moreover, <b>16c</b> destroyed an established endothelial tubular network at 1 μM and inhibited the migration and invasion of human breast carcinoma cells at 0.4 μM. In conclusion, our approach has led to a new chemotype of promising antiproliferative compounds with antimitotic and potential VDA properties

Identification of [1,2,3]Triazolo[4,5‑<i>d</i>]pyrimidin-7(6<i>H</i>)‑ones as Novel Inhibitors of Chikungunya Virus Replication

Chikungunya virus (CHIKV) is a re-emerging Alphavirus that is transmitted to humans by Aedes mosquitoes. Currently, there are still no drugs or vaccines available for the treatment or prevention of this disease. Although traditionally restricted to Africa and Asia, the adaptation of the virus to Aedes albopictus, a mosquito species with an almost worldwide distribution, has contributed to the geographical spread of this virus in the past decade. Here, we report on a new family of compounds named [1,2,3]­triazolo­[4,5-<i>d</i>]­pyrimidin-7­(6<i>H</i>)-ones that inhibit CHIKV replication in the low micromolar range with no toxicity to the host (Vero) cells. The most potent compound in this series has an EC₅₀ value below 1 μM with no cytotoxicity detected up to 668 μM, therefore affording a selectivity index greater than 600. Interestingly, the compounds have little or no antiviral activity on the replication of other members of the Togaviridae family. The exploration and study of this class of selective inhibitors of CHIKV replication will contribute to deeper insights into the CHIKV life cycle and may be a first step toward the development of a clinical drug candidate

Inhibition of the Replication of Different Strains of Chikungunya Virus by 3‑Aryl-[1,2,3]triazolo[4,5‑<i>d</i>]pyrimidin-7(6<i>H</i>)‑ones

The re-emergence of chikungunya virus (CHIKV) is a serious global health threat. CHIKV is an alphavirus that is transmitted to humans by <i>Aedes</i> mosquitoes; therefore, their wide distribution significantly contributes to the globalization of the disease. Unfortunately, no effective antiviral drugs are available. We have identified a series of 3-aryl-[1,2,3]­triazolo­[4,5-<i>d</i>]­pyrimidin-7­(6<i>H</i>)-ones as selective inhibitors of CHIKV replication. New series of compounds have now been synthesized with the aim to improve their physicochemical properties and to potentiate the inhibitory activity against different CHIKV strains. Among these newly synthesized compounds modified at position 3 of the aryl ring, tetrahydropyranyl and <i>N</i>-<i>t</i>-butylpiperidine carboxamide derivatives have shown to elicit potent antiviral activity against different clinically relevant CHIKV isolates with 50% effective concentration (EC₅₀) values ranging from 0.30 to 4.5 μM in Vero cells, as well as anti-CHIKV activity in human skin fibroblasts (EC₅₀ = 0.1 μM), a clinically relevant cell system for CHIKV infection

Pyrrolopyrimidine vs Imidazole-Phenyl-Thiazole Scaffolds in Nonpeptidic Dimerization Inhibitors of Leishmania infantum Trypanothione Reductase

Disruption of protein–protein interactions of essential oligomeric enzymes by small molecules represents a significant challenge. We recently reported some linear and cyclic peptides derived from an α-helical region present in the homodimeric interface of Leishmania infantum trypanothione reductase (Li-TryR) that showed potent effects on both dimerization and redox activity of this essential enzyme. Here, we describe our first steps toward the design of nonpeptidic small-molecule Li-TryR dimerization disruptors using a proteomimetic approach. The pyrrolopyrimidine and the 5-6-5 imidazole-phenyl-thiazole α-helix-mimetic scaffolds were suitably decorated with substituents that could mimic three key residues (K, Q, and I) of the linear peptide prototype (PKII­QSV­GIS-Nle-­K-Nle). Extensive optimization of previously described synthetic methodologies was required. A library of 15 compounds bearing different hydrophobic alkyl and aromatic substituents was synthesized. The imidazole-phenyl-thiazole-based analogues outperformed the pyrrolopyrimidine-based derivatives in both inhibiting the enzyme and killing extracellular and intracellular parasites in cell culture. The most active imidazole-phenyl-thiazole compounds 3e and 3f inhibit Li-TryR and prevent growth of the parasites at low micromolar concentrations similar to those required by the peptide prototype. The intrinsic fluorescence of these compounds inside the parasites visually demonstrates their good permeability in comparison with previous peptide-based Li-TryR dimerization disruptors