Discovery Of Lead Compounds Targeting Influenza Hemagglutinin And Neuraminidase

Influenza is an acute respiratory infectious disease caused by the influenza virus and frequently breaks out in spring and autumn.Many influenza characteristics,such as strong contagion,widespread,short incubation period and various complications,causes 200,000-500,000 deaths every year and pose a more significant threat to high-risk groups like children and aged people.Recently,the mutation of influenza viruses,causing an increase of zoonotic diseases,exacerbated the current anti-influenza situation and brought great panic to society.On the one hand,M2 ion channel inhibitors and neuraminidase inhibitors have achieved great significance in influenza viruses drug discovery.On the other hand,the emergence of drug-resistant virus strains and the ineffectiveness of many drugs in their treatment indicated that the development of novel inhibitors with safe,highly effective and anti-drug resistance has become an immediate assessment.The influenza virus’s life cycle includes adsorption,endocytosis,fusion,replication,translation,assembly,budding,and release.Neuraminidase(NA)and hemagglutinin(HA),which are key functional glycoproteins on the surface of influenza viruses,play an essential role in the virus’s entire life cycle.With the vigorous development of structural biology,various NA and HA’s crystal structures have been resolved.Many inhibitors targeting these two proteins have also been reported,which prompted us to continue drug research on HA and NA targets in the present thesis work.Design,synthesis and bioactivity evaluation of influenza virus HA inhibitors.Based on Arbidol and hemagglutinin’s crystal structure,we try to improve the pharmacological activity and water solubility of Arbidol.Therefore,molecular hybridization and bioisosteric replacement strategies were used to modify the C-4,C-5,and C-6 positions of the indole ring and introduce diversified acidic groups into the C-2 side chain which can interact with Arg54 of HA to increase HA inhibit activity and improve water solubility.From this scheme,31 novel molecules were obtained,and all were evaluated for anti-influenza virus activity(H1N1 and H3N2).HA interaction studies were also conducted for a few synthesized compounds.From the tested series,compound A-1 displayed the prominent activity against the H3N2 influenza virus with an EC50 value of 9.86 μM and KD value of 1.7 μM(equivalent to Arbidol),the rest of the compounds were found to be less potent.In addition,the solubility of A-1 was 14.20-16.43 μg/mL which was more prominent than Abidol,suggesting that A-1 could be considered for further research.Molecular docking studies indicated A-1 formed a hydrogen bond with the target Arg54 and produced additional interaction on the surrounding amino acid residues.However,the original hydrogen bond with Lys307 and Gln311 was missing,which may be the main reason why the compound was not effective compared to Arbidol.In conclusion,these synthesized series of compounds provide a reference for the design of subsequent hemagglutinin inhibitors.Design,synthesis and bioactivity evaluation of influenza virus NA inhibitors.Herein,based on the NA catalytic centre of influenza virus and the adjacent 150-cavity,we design a novel series of zanamivir derivatives.The modification strategy of molecular hybridization was utilized based on the catalytic centre and the 150-cavity’s structural characteristics,and the ligand aptitude requirements.Zanamivir as the lead compound for structural optimization,9 dual-site binding NAIs were designed and synthesized to improve zanamivir’s oral bioavailability and develop novel compounds with high specificity,bioactivity and improved drug resistance profile.According to the bioactivity results,most compounds showed inhibitory activity and compound B-9 displayed the potent activity against H5N1 and H5N6 with the EC50 value of 0.25 μM and 1.69 μM,respectively.From the NAI evaluation,it was noticed that most of the compounds from this series displayed decreased activity results compared to zanamivir.Nevertheless,this part’s research was still a meaningful exploration for discovering zanamivir derivatives with more potent activity and favorable drug resistance profile.In conclusion,the second chapter of this thesis focuses on the scientific problems of low pharmacological activity and poor water solubility of Arbidol.Based on molecular hybridization and bioelectronics isometric strategies,31 novel compounds were designed and synthesized.Compound A-1 was identified as the most potent molecule,which is equipotent to the positive compound Arbidol,providing essential information for developing a new generation of HA inhibitors.The third chapter of this thesis aims to find NA inhibitors with high specificity,high activity,improved drug resistance profile and high oral bioavailability.Considering zanamivir as the lead compound,using ligand structure-based modification strategies and molecular hybridization strategies,we synthesized a series of 9 target compounds.NAI inhibitory activity and structure-activity relationship analysis provided valuable insights to the subsequent structural optimization of these zanamivir based analogues.