A novel N-heterocycles substituted oseltamivir derivatives as potent inhibitors of influenza virus neuraminidase: discovery, synthesis and biological evaluation.

Our previous studies have shown that the introduction of structurally diverse benzyl side chains at the C5-NH2 position of oseltamivir to occupy 150-cavity contributes to the binding affinity with neuraminidase and anti-influenza activity. To obtain broad-spectrum neuraminidase inhibitors, we designed and synthesised a series of novel oseltamivir derivatives bearing different N-heterocycles substituents that have been proved to induce opening of the 150-loop of group-2 neuraminidases. Among them, compound 6k bearing 4-((r)-2-methylpyrrolidin-1-yl) benzyl group exhibited antiviral activities similar to or weaker than those of oseltamivir carboxylate against H1N1, H3N2, H5N1, H5N6 and H5N1-H274Y mutant neuraminidases. More encouragingly, 6k displayed nearly 3-fold activity enhancement against H3N2 virus over oseltamivir carboxylate and 2-fold activity enhancement over zanamivir. Molecular docking studies provided insights into the explanation of its broad-spectrum potency against wild-type neuraminidases. Overall, as a promising lead compound, 6k deserves further optimisation by fully considering the ligand induced flexibility of the 150-loop.

Recent advances of phenotypic screening strategies in the application of anti-influenza virus drug discovery.

Seasonal and pandemic influenza virus infections not only pose a serious threat to human health but also cause tremendous economic losses and social burdens. However, due to the inherent high variability of influenza virus RNA genomes, the existing anti-influenza virus drugs have been frequently faced with the clinical issue of emerging drug-resistant mutants. Therefore, there is an urgent need to develop efficient and broad-spectrum antiviral agents against wild-type and drug-resistant mutant strains. Phenotypic screening has been widely employed as a reliable strategy to evaluate antiviral efficacy of novel agents independent of their modes of action, either directly targeting viral proteins or regulating cellular factors involved in the virus life cycle. Here, from the point of view of medicinal chemistry, we review the research progress of phenotypic screening strategies by focusing direct acting antivirals against influenza virus. It could provide scientific insights into discovery of a distinctive class of therapeutic candidates that ensure high efficiency but low cytotoxicity, and address issues from circulation of drug-resistant influenza viruses in the future.

Discovery of N-substituted oseltamivir derivatives as novel neuraminidase inhibitors with improved drug resistance profiles and favorable drug-like properties.

To yield potent neuraminidase inhibitors with improved drug resistance and favorable drug-like properties, two series of novel oseltamivir derivatives targeting the 150-cavity of neuraminidase were designed, synthesized, and biologically evaluated. Among the synthesized compounds, the most potent compound 43b bearing 3-floro-4-cyclopentenylphenzyl moiety exhibited weaker or slightly improved inhibitory activity against wild-type neuraminidases (NAs) of H1N1, H5N1, and H5N8 compared to oseltamivir carboxylate (OSC). Encouragingly, 43b displayed 62.70- and 5.03-fold more potent activity than OSC against mutant NAs of H5N1-H274Y and H1N1-H274Y, respectively. In cellular antiviral assays, 43b exerted equivalent or more potent activities against H1N1, H5N1, and H5N8 compared to OSC with no significant cytotoxicity up to 200 µM. Notably, 43b displayed potent antiviral efficacy in the embryonated egg model, in which achieved a protective effect against H5N1 and H5N8 similar to OSC. Molecular docking studies were implemented to reveal the binding mode of 43b in the binding pocket. Moreover, 43b possessed improved physicochemical properties and ADMET properties compared to OSC by in silico prediction. Taken together, 43b appeared to be a promising lead compound for further investigation.