Design,Synthesis And Biological Activity Of Novel Antifungal Lead Compounds

Recently,the incidence and mortality of invasive fungal infections in clinic is increasing rapidly due to serious drug resistance and the limitations of current antifungal agents.Thus,discovery of new targets and lead compounds with novel mechanism of action have become an important area of antifungal drug research.Presently,there are three major strategies for novel antifungal drug discovery and development:?1?optimization and improvement of existing antifungal agents;?2?validation of new antifungal targets and design of effective inhibitors;?3?phenotypic screening of antifungal lead compounds.Based on the latter two strategies,herein three kinds of lead compounds with excellent antifungal activity were investigated.1.Design,synthesis and evaluation of antifungal Pdr1-KIX inhibitors.Based on the lead compound iKIX1,a inhibitor of Pdr1-Gal11A KIX protein-protein interaction,a series of derivatives were designed by analyzing the hydrogen bonding patterns of iKIX1 and KIX proteins.Through the in vitro antifungal activity assay,the direct inhibitory activity of iKIX1 on wild-type Candida glabrata was confirmed.Moreover,the structure-activity relationship of three series of derivatives was summarized and the thiourea structure was found to be the key motif for its antifungal activity.Besides,the structure-activity relationship of the side chain is relatively narrow,bacause the substitution of the benzene ring can greatly affect the antifungal activity.Among them,the compounds 5q and 12a had good antifungal activity and showed a broad spectrum of antifungal activity compared to the lead compound iKIX1.In addition,the inhibitory activity of compound 5q and 12a against Candida glabrata and Cryptococcus neoformans was comparable to the positive drug fluconazole.Preliminary in vivo antifungal efficacy studies showed that compound 5q and 12a could increase the survival of C.elegans infected with C.albicans.2.Novel pyrazole thioamides derivatives as antifungal lead compounds:discovery,optimization and biological evaluation.New pyrazole thioamide antifungal lead compound was identified by antifungal screening of the synthetic intermediates of iKIX1 derivatives.Interestingly,pyrazole thioamide derivatives had excellent in vitro antifungal activity with a broad spectrum.Among them,compounds 7a,6d and 11a were selected to test the antifungal activity against Cryptococcus neoformans.It was found that compound 7a was a promsing lead compound.First,compound 7a could effectively inhibit the growth of Cryptococcus neoformans(MIC₅₀=0.0625?g/mL),which was more potent than fluconazole.Second,compound 7a significantly inhibited fungal biofilm formation and hydrophobicity,which are important virulence factors of C.neoformans,and revealed the potential to solve the problem of fungal resistance.More importantly,compound 7a also showed in vivo antifungal potency in murine and C.elegans model of C.neoformans.3.Antifungal potency and mechanism of novel carboline compounds.In our previous study,highly active carboline derivatives JYJ-19 and JYJ-20 were identified by a series of in vivo and in vitro antifungal assays.Herein their antifungal potency and mechanism were further investigated.The time-growth curve tests showed that compounds JYJ-19 and JYJ-20 inhibited the proliferation of fungal cells in a concentration-dependent manner,and could significantly prevent C.neoformans adhesion and biofilm formation.Compounds JYJ-19 and JYJ-20 also showed anti-virulence activities,such as the inhibition of melanin,urease and fungal cell surface hydrophobicity.Compound JYJ-19 exhibited more potent in vivo antifungal efficacy than JYJ-20 due to the fact that JYJ-19 had better liver microsomal enzyme stability.Further antifungal mechanism studies indicated that JYJ-19 could upregulate the expression of Cdc25C?or its upstream protein?,which was a CDK1 phosphatase,and then up-regulated the CDK1 and activated CDK1-CyclinB pathway,thus blocking the cell cycle in G2,causing fungal cell apoptosis.As a new class of antifungal leads,carboline compounds showed potent anti-Cryptococcus activity and are expected to act by targeting new targets,which provided a basis for the development of novel anti-Cryptococcus agents.