Candida species are among the most important human fungal diseases, with approx. 40% death rate and a total of 1.5 million deaths per year. Echinocandins and azoles are effective first-line therapies, but antifungal resistance is a growing problem. Small compounds that target chromatin signaling pathways have recently entered clinical trials for cancer therapy and other non-infectious diseases. The chromatin-associated proteins, bromodomain and extra-terminal (BET), control gene transcription and chromatin structure (Cochran 2019). BET proteins identify chromatin through their two bromodomains, BD1 and BD2, which are small helical domains that recognize acetylated lysine residues present on N-terminal tails of histones. Because of the large pocket, BET bromodomains are easily druggable and several inhibitors targeting human BET bromodomains have been discovered (Cochran, 2019). In the realm of fungal infection, however, the bromodomain targets are largely unexplored. It was recently reported that fungal BET bromodomains are viable anti-fungal targets that could be inhibited without antagonizing human BET function (Mietton 2017, Wei 2023). We hypothesize that small molecules selectively targeting fungal bromodomains represent a potential new class of Candida antifungal drug.

Candida BET proteins will be expressed and purified in large amounts, and isotropically labeled when needed. Multiple compound libraries will be screened against them using NMR spectroscopy. We will explore fragments, FDA-approved drugs, and natural compounds. Computer-assisted drug design approaches to further explore the chemical space will also be employed, capitalizing on the large data set available for human BETs. Molecular hits will be cross-validated with orthogonal methods, such as SPR. Fragment evolution and hit-to-lead optimization will be guided by NMR experiments, such as epitope mapping and structure-activity relationship by NMR. Structure elucidation of the most potent molecules bound to the target protein receptor will be derived in-house by NMR spectroscopy. With the collaborators we can readily start to explore the chemical space of a reduced set of molecules, which were recently reported as promising starting points for developing a pan Candida anti-fungal (Wei 2023). Growth inhibition assays will be performed for the top 20 hits and compounds of interest will be selected for exploratory formulation studies.