Project Summary. The filamentous fungi, or moulds, present a particularly daunting clinical challenge with
high treatment failure rates and intrinsic and/or emerging multi-drug resistance. Currently, only 3 classes of
antifungal drugs are utilized to treat the majority of human fungal infections. We aim to address this significant
and growing human health problem by developing a nonspirocyclic piperidine series (NSP) series of small
molecules with potent antifungal activity that can overcome mould specific antifungal drug resistance in the
complex infection microenvironment. The NSP series was discovered using a high-throughput small molecule
antifungal screen under low oxygen conditions and in the presence or absence of fluconazole with the most
common mould human pathogen Aspergillus fumigatus. From this novel screen, we identified MBX-7591, a
NSP family small molecule with drug-like properties that displayed potent antifungal activity that is potentiated
under low oxygen conditions. MBX-7591 also potentiates the antifungal activity of fluconazole and other
triazoles against A. fumigatus, which is intrinsically fluconazole resistant. The combination of MBX-7591 and
voriconazole is highly active against azole resistant A. fumigatus isolates. Additional studies revealed that
MBX-7591 has potent antifungal activity against multiple drug resistant mould species including agents of
mucormycoses Rhizopus arrhizus and Mucor circinelloides. Pilot murine invasive pulmonary aspergillosis
model studies reveal a promising safety profile and in vivo efficacy. Based on these exciting results, our
premise is that MBX-7591 analogs represent a promising new generation of safe and in vivo efficacious small
molecules to combat the growing emergence of drug resistant human fungal infections. In aim 1, we will utilize
SAR-driven chemical optimization of the NSP series to synthesize 300 analogs with key drug-like properties
such as solubility. In aim 2, we will evaluate and prioritize NSP analogs in SAR-driving in vitro assays for
potency, selectivity, and ADME properties with the goal of identifying 5-10 analogs with potent MICs against A.
fumigatus, R. arrhizus, and M. circinelloides. In aim 3, we will utilize genetic, biochemical, and chemical biology
approaches to define the molecular target of MBX-7591 and key analogs. In aim 4, we will identify a lead NSP
compound and backup based on tolerability, pharmacokinetic parameters, and efficacy in murine models of
invasive mould infections. Taken together, our proposed studies will further develop an exciting novel small
molecule with infection microenvironment activity against a spectrum of clinically challenging pathogenic
moulds.
