NOVEL STRATEGY FOR COMBATING FUNGAL INFECTIONS BY TARGETING INOSITOL LIPID SIGNALING

About This Grant

Project Summary/Abstract Society is witnessing the alarming worldwide rise of fungal ‘superbugs’ that exhibit multi-drug resistance to the limited cohort of anti-fungal agents used by clinicians to treat invasive fungal infections. This pharmacological shield has dwindled to the extent that the Centers for Disease Control and Prevention has designated invasive fungal infections as a looming health crisis. These circumstances inject a sharp urgency to the development of new classes of anti-fungal drugs and identification of new fungal targets. The foundation of this proposal is two-fold: (i) the identification of a new and compelling target that regulates fungal phosphoinositide (PIP) signaling pathways required for viability and virulence; and (ii) the discovery of small molecule inhibitors (SMIs) that inhibit these pathways. Instead of targeting the highly conserved core enzymes of PIP signaling, these SMIs take advantage of Sec14 phosphatidylinositol transfer proteins (Sec14 PITPs) as portals through which fungal PIP signaling can be disrupted with exquisite selectivity. The focus of this application is the structure-based design, synthesis, and validation of new classes of broad spectrum anti-mycotics that target fungal Sec14 PITPs of Candida auris and Candida albicans. Aim 1 of the R21 phase describes a structure-guided fragment-based screen and synthesis of new SMIs that preserve key pharmacophoric features of the first generation SMIs and target the Candida Sec14 PITPs. Those newly designed SMIs will be advanced through a powerful in vitro/in vivo validation platform in Aim 2 using purified virulent fungal Sec14 PITPs and a ‘pathogenized’ yeast system to interrogate SMI potencies and target specificities. Although primary focus will be on targeting the Sec14 PITPs of Candida auris and Candida albicans, the broad-spectrum potential of the SMIs will also be explored by testing their efficacies in inhibiting the Sec14 PITPs of Candida glabrata, Aspergillus fumigatus, and Coccidioides posadasii (Valley Fever Fungus). The R33 phase will be undertaken if the key R21 milestones of producing potent and selective inhibitors of C. auris and/or C. albicans Sec14 PITPs that show no overt toxicities to mammalian cells are achieved. Aim 3 of the R33 phase will identify SMIs most effective in inhibiting: (i) Candida growth in axenic culture (minimal inhibitory concentration determinations), (ii) Candida PIP signaling, (iii) protein (virulence factor) trafficking, and (iv) Candida ex vivo biofilm formation and maintenance. The study will culminate in Aim 4 with determinations of the pharmacokinetic properties of the most promising SMIs that are advanced from Aim 3, and examination of their therapeutic efficacies in two independent preclinical models of disseminated candidiasis in mice. The ultimate goal is to introduce new broad spectrum anti-fungal leads, with exquisite Sec14 targeting specificities, as springboard to development of potent next-generation anti-mycotics suitable for clinical use.