Design,Synthesis And Biological Evaluation Of Novel Scaffold Small Molecule Anti-influenza Lead Compounds

Influenza(Flu)is a febrile respiratory infectious disease,which is caused by influenza viruses.There are more than 5 million serious flu patients each year worldwide,among them,290~650 thousand death.Influenza outbreak not only threatens human health,but also plays destructive impact on golobal economy and ecosystem.Influenza viruses are enveloped RNA virus,which belong to the Orthomyxoviridae family.According to nucleoprotein and matrix protein,influenza viruses can be mainly classified as three types: Flu A,Flu B and Flu C strains.Because of higher antigenic mutation,influenza A virus is becoming a more serious threat to human health.Highly pathogenic avian influenza(HPAI)H5N1 virus is one subtype of influenza A virus possessing higher mortality(60%)compared with other flu A strains,which cause serious threats to ecological equilibrium and human health.To date,there are only six anti-influenza drugs approved by FDA,which can be classified as three classes: two M2 proton channel inhibitors(amantadine and rimantadine),three neuraminidase inhibitors(zanamivir,oseltamivir and peramivir)and one RNA dependent RNA polymerase inhibitor(xofluza).Furthermore,neuraminidase inhibitor laninamivir and the first RNA dependent RNA polymerase inhibitor of influenza virus favipiravir was approved in Japan.Recent years,the rapid emergency of drug resistant H5N1 or other flu A strains for both M2 and NA inhibitors makes it imperative to develop novel scaffolds or new targets anti-influenza drugs.On the basis of our previous antiviral research work,we firstly identified a series of furan-carboxamide derivatives as H5N1 inhibitors.Finally,we found furan-carboxamide derivative III-7a exhibited excellent inhibitory efficiency against H5N1 virus with EC50 value of 1.25 μM,which is comparable with reference drug amantadine by systematic SAR investigation.Preliminary mechanistic studies indicated that this series compounds inhibited the virus replication at early stages.Similar to M2 inhibitor amantadine,it was likely that compound III-7a blocked channel function to prevent the uncoating of the viral RNPs.After systematic structure-activity relationship(SAR)investigation and analysis of molecular modeling,we found furan moiety and sulfur atom played significant roles in the anti-influenza acitivity.Furthermore,the most potent furan-carboxamide analogue III-7a couldn’t efficiently fill the M2 protein cavity due to long linker length.Hence,in order to develop series one novel heteroaromatic-based benzenesulfonamide compounds as anti-influenza A/H5N1 inhibitors,an attempt was made to modify the structural features of furan-carboxamide derivatives by shortening the linker length and transforming the heteroaromatic core structure.Among them,the EC50 value of most potent heteroaromaticbased benzenesulfonamide compound IV-6k was 0.47 μM,which increased about 2.6-fold compared with furan-carboxamide compound III-7a.Moreover,based on computer-aided drug design(CADD)molecular simulation and classical medicinal chemistry design concept,we also designed second series arylsulfonamide compounds by introducing cyano side chain at the nitrogen atom of sulfonamide moiety to better fill the M2 protein cavity.Fortunately,we found this series compounds showed more potent anti-H5N1 activity when introducing the cyano side chain.And the most potent compound V-3h exhibited excellent potency against H5N1 virus with EC50 value of 0.006 μM,SI(EC50/CC50)of 33543.On the basis of our previous research work on EV71 inhibitors,we found benzoyl hydrazide derivatives showed excellent inhibition efficiency against wild type H5N1 virus.Among them,compound VI-5a,VI-5d,VI-5e and VI-5p exhibited two-digit nanomolar inhibitory potency,with EC50 value of 0.034 μM,0.037 μM,0.031 μM and 0.046 μM respectively.Moreover,western blotting experiment demonstrated that this series diarylhydrazides derivatives exhibited excellent inhibition potency against wild type H5N1 virus and amantadine-resistant H1N1 virus.Preliminary mechanism investigation indicated that it was likely that these diarylhydrazides derivatives inhibited viral replication by interacting with influenza A virus RNA dependent RNA polymerase.In conclusion,in this thesis,we have developed several series of novel scaffold small molecule anti-H5N1 inhibitors and evaluated their anti-influenza activity and preliminary mechanism in vitro.In order to develop high efficient and low toxic antiviral inhibitors for the prophylaxis and treatment of influenza and solve the problem of drug resistance for both M2 inhibitors and NA inhibitors,further mechanism investigation and in vivo studies of cyano side chain based benzenesulfonamide derivatives as M2 proton channel inhibitors and benzoyl hydrazide derivatives as RNA dependent RNA polymerase(Rd Rp)inhibitors are still going on in our laboratory.