A First-in-Class\nPyrazole-isoxazole Enhanced Antifungal\nActivity of Voriconazole: Synergy Studies in an Azole-Resistant <i>Candida albicans</i> Strain, Computational Investigation and\nin Vivo Validation in a <i>Galleria mellonell

The widespread and irrational use of azole antifungal\nagents has\nled to an increase of azole-resistant <i>Candida albicans</i> strains with an urgent need for combination drug therapy, enhancing\nthe treatment efficacy. Here, we report the discovery of a first-in-class\npyrazole-isoxazole, namely, <b>5b</b>, that showed remarkable\ngrowth inhibition against the <i>C</i>. <i>albicans</i> ATCC 10231 strain in combination with voriconazole, acting as a\ndownregulator of ERG 11 (<i>Cyp51</i>) gene expression with\na significant reduction of the yeast-to-hypha morphological transition.\nFurthermore, <i>C</i>. <i>albicans</i> CYP51 enzyme\nassay and in-depth molecular docking studies unveiled the unique ability\nof the combination of <b>5b</b> and voriconazole to completely\nfill the CYP51 binding sites. <i>In vivo</i> studies using\na <i>Galleria mellonella</i> model confirmed the previously <i>in vitro</i> observed synergistic effect of <b>5b</b> with\nvoriconazole. Also considering its biocompatibility in a cellular\nmodel of human keratinocytes, these results indicate that <b>5b</b> represents a promising compound for a further optimization campaign.