Design,Synthesis And Biological Activity Study Of Antifungal Lead Compounds

Invasive fungal infections（IFI）,with high morbidity and high mortality,are considered to be major public health problems on a scale similar to tuberculosis or malaria.Clinically,there are only four types of antifungal drugs for the treatment of IFI,currently.However,the existing antifungal drugs have problems such as large toxic and side effects,low bioavailability,and drug-drug interactions.It is worth noting that the problem of resistance to antifungal drugs is also becoming more and more serious,especially for the first-line clinical drugs azoles.Therefore,it is urgent to develop a new mechanism of action antifungal drugs to solve the problem of fungal resistance.Therefore,based on the action mechanism of azole drugs and HDAC inhibitors,designsed and synthesized a new class of antifungal lead compounds,and conducts in-depth research on the antifungal action mechanism of SAP2 inhibitors found in the previous research of the research group.Ⅰ.Design,Synthesis and Biological Activity of CYP51/HDAC Dual InhibitorBased on the action mechanism of azole drugs and HDAC inhibitors,a dual-target inhibitor of CYP51/HDAC has designed and synthesized containing azole drug pharmacophores and HDAC pharmacophores.The compound’s antifungal activity and mechanism of action were thoroughly evaluated.The results show that these compounds have moderate to excellent inhibitory effects on Candida albicans,Candida tropicalis,Cryptococcus neoformans,and Candida krusei(MIC₈₀=64⁰.125μg/mL).Among them,compounds A4 and A5 have inhibitory effects on a variety of drug-resistant fungal pathogens,and have significant inhibitory effects on the important virulence factors hyphae,biofilm and capsular polysaccharides of Candida and Cryptococcus.In particular,compound A5 can not only effectively reduce the fungal load in the kidney of systemic fungal infection mice caused by drug-resistant Candida tropicalis,but also significantly reduce its brain fungal load in cryptococcus meningitis（CM）mouse model.Mechanism studies show that compounds A4 and A5 can inhibit the synthesis of ergosterol,an important component of fungal cell membranes,and can effectively inhibit the activity of fungal HDAC enzymes.Ⅱ.Study on Biological Activity of Novel SAP2 InhibitorsSecreted aspartic protease 2（SAP2）is an important fungal virulence factor.The research team designed and synthesized a class of novel indole SAP2 inhibitors based on virtual screening and structural optimization.This subject evaluates the antifungal activity of these compounds in vitro and in vivo,and examines their inhibitory effects on fungal hyphae and biofilm.In order to further study its mechanism of action,the effects on the expression levels of fungal hyphae and biofilm-related genes were investigated by RT-PCR.The results showed that in vitro antifungal activity test,SAP2 inhibitors could not inhibit fungal proliferation,and had no synergistic antifungal effect with azoles.However,these compounds can significantly reduce the fungal load in mouse kidney in vivo experiments.In the hyphae and biofilm formation experiments,the compound can significantly inhibit the formation of fungal hyphae and biofilm at higher concentrations,and combination with azole drugs can significantly inhibit the formation of fungal hyphae and biofilm at lower concentrations.These compounds could down-regulate the expression of SAP2,ECE1,ALS3 and EFG1 genes.In summary,this project designed and synthesized a new class of CYP51/HDAC dual-target inhibitors,and obtain a compound with excellent antifungal activity in vitro and in vivo,and verify its mechanism of action.The novel indolinone SAP2inhibitors was evaluated in depth for their biological activity,which was synthesized by the research group in the early stage.This topic provides a new direction for the study of antifungal drugs with a new mechanism of action and lays a certain research foundation.