Fungal infections constitute a major threat to an ever expanding spectrum of immune- and medically-compromised patients. The opportunistic pathogenic fungi Candida, Aspergillus and Cryptococcus spp. areamong the most common etiologic agents of mycoses; but infections caused by other yeasts and moulds are onthe rise as advances in modern medicine prolong lives resulting in increasingly susceptible and vulnerablepatients. However, fungi have recently been referred to as the ?hidden killers/the neglected epidemic? due to alack of concomitant public awareness in fungal disease. The limited arsenal of antifungal agents contributes tothe unacceptably high morbidity and mortality rates associated with fungal infections. Fungi are eukaryotes, andthere is a paucity of selective targets that can be exploited for antifungal drug development. As a consequence,the antifungal arsenal is exceedingly short, mostly limited to three classes: polyenes, azoles and echinocandins.However, high toxicity and the emergence of resistance are limited factors for their clinical usage. To makematters even worse, some of the most troublesome emerging fungal pathogens fall completely outside of thespectrum of activity of these current antifungals. Moreover, the antifungal pipeline in most pharmaceuticalcompanies is essentially dry. To conquer this formidable challenge the current proposal uses a highly efficientapproach consisting of screening a repurposing library to identify compounds with novel antifungal activityfollowed by advancing the development of the leading hit compounds by assessing their activity in murine modelsof fungal infections, with an overall focus on resistant infections. The main objectives for the R21 Phase are: i)to conduct a large-scale screening of Calibr?s ReFRAME chemical library to identify high value compounds withnovel antifungal activity against Candida albicans biofilms and against multidrug resistant Candida auris, anemerging pathogen and increasing nosocomial threat, and ii) to confirm the antifungal activity and determine theantifungal spectrum of action of hits from primary screening. Upon achieving the set transitional milestones forselection of a limited number of promising leads, the specific aims for the R33 Phase will be: i) to characterizethe in vivo activity of the leading compounds in a number of clinically-relevant animal models of fungal infectionthat are fully established within the laboratories, and ii) to further characterize the in vitro antifungal activity ofthe leading compounds by testing them against an expanded number of clinical isolates of fungal species ofinterest, as well as testing their in vitro activity in combination with current existing antifungals. Altogether thestrong translational impetus associated with the proposed studies, together with the complementary expertise ofthe assembled team of investigators covering from basic to clinical aspects of Medically Mycology, shouldmaximize the chances for success and allow for accelerated development of new antifungal drugs, for whichthere is an urgent and dire need.