SBIR-STTR Award

Fungal infections continue to be a major cause of morbidity and mortality among HIV-infected patients. Many of the emerging fungal pathogens that are resistant to the three classes of antifungal agents for AID-s-related infections are becoming more common and are associated with higher rates of mortality. Combating drug resistant fungal pathogens should be a top priority. The inhibition of Hsp90 has emerged as a bona fide antifungal target for a number of very important reasons. These include that if increases the efficacy of existing antifungal medications, blocks the emergence of drug resistance, works against a broad spectrum of fungal pathogens, increases survival rates, and pays an important role in attenuating fungal virulence. The development of a Hsp90 fungal inhibitor has been hampered by the fact that fungal and mammalian Hsp90 share structural homology and function. As a result, known Hsp90 inhibitors, such as geldanamycin, induce the heat shock response, an overexpression of Hsp90, Hsp70, and other co-chaperones. This response is both anti-apoptotic and prosurvival, thereby potentially limiting the inhibitors effectiveness as antifungal agents. The challenge is to find inhibitors of Hsp90 that are selective for fungal Hsp90. We have discovered two fungal compounds that are 10X selective inhibitors of Candida Hsp90 relative to mammalian Hsp90. No compounds with this activity have ever been reported. These compounds were screened for using LifePharms'natural product library of 26,000 samples of basidiomycetes and ascomycetes (mushrooms), including nearly every species found in continental United States. The goals of this grant proposal are the following: 1.) to isolate each active compound 2.) to identify and dereplicated lead compounds 3.) to determine the effect of our compounds on stress markers (Hsp90 and Hsp70) in both mammalian and fungal cells 4.) to determine whether our inhibitors interact directly with the ATP binding site on the fungal and mammalian Hsp90 molecule 5.) to determine the in vitro activity and potency of our compounds against panels of clinically important fungal species and 6.) to screen an additional 5,000 extracts for additional fungal-specific Hsp90 inhibitors. The work for goal 5 will be performed by University of Texas Health Science Center at San Antonio.

Public Health Relevance:
Fungal infections continue to be a major cause of morbidity and mortality among HIV-infected patients. Antifungal compounds have been discovered from natural products. In collaboration with the Antifungal Susceptibility Testing Laboratory and Division of Infectious Diseases at the University of Texas Health Science Center at San Antonio, we have identified natural products that restore fluconazole toxicity to previously resistant Candida strains.

Despite medical advances fungal infections still exact a heavy burden on the HIV/AIDs population. AIDs-related fungal infections account for 50% of all AIDs-related deaths. In the developed world, AIDS-related fungal infections are most frequently associated with Candida albicans, but Aspergillus fumigatus and Cryptococcus neoformans are also common. Unfortunately, the number of treatments for invasive fungal infections has remained relatively stagnant. Also, the three most widely-used classes of antifungals collectively inhibit only a few molecular targets. As a consequence of their widespread use, an increasing numbers of invasive fungi are resistant to multiple antifungals. A promising new strategy to enhance the efficacy of antifungals and block the evolution of drug resistance is to inhibit the molecular chaperone heat shock protein 90 (Hsp90). .Hsp90, an essential molecular chaperone, regulates the stability of its client proteins, many of which are involved in stress responses. Fungi depend on these stress responses to cope with cell membrane and cell wall damage induced by antifungal drugs. Inhibiting Hsp90 would dismantle cellular stress response circuitry and thus, abrogate drug resistance and dramatically enhance the efficacy of antifungal medications. Previous research has demonstrated that an Hsp90 inhibitor abolished drug resistance in azole-resistant and echinocandin-resistant strains. Hsp90 inhibition also impairs the acquisition of resistance. When Hsp90 is depleted or inhibited in the yeast model organism Saccharomyces cerevisiae or in C. albicans, the evolution of resistance to azoles is impaired. While several Hsp90 inhibitors are in development for cancer treatment, these inhibitors work on both fungal and human Hsp90, thereby making them toxic as antifungals. Our compound, LP13371, could be an important advancement in treating fungal infections. To our knowledge, LP13371 is the first characterized small molecule that selectively inhibits fungal Hsp90. It works in combination with known antifungals against a broad range of pathogenic fungi. It is a novel, patentable, easily analoged, and small molecular weight compound that demonstrates a promising safety profile. Our overarching research plan is to advance LP13371 and/or its analogs as a pre-clinical candidate. We will synthesize LP13371, perform complete ADME experiments to determine its likely pharmacokinetic properties, measure its ability to retard fungal biofilm, and determine the efficacy and safety of LP13371in five in vivo mouse models. We will develop resistant strains of C. albicans to help define LP13371 s mechanism of action. Even though LP13371 has impressive activity and specificity in our assays, we will also synthesize analogs of LP13371 because they may have better in vivo properties. We will investigate these analogues in a manner similar to the above-mentioned process for LP13371. To accomplish these goals, we have assembled an excellent team, including Timo Ovaska, Professor of Chemistry at Connecticut College, Mahmoud A. Ghannoum, Director of The Center for Medical Mycology at Case Western Reserve University, and Leah Cowen, Assistant Professor at the University of Toronto.

Public Health Relevance Statement:


Public Health Relevance:
Fungal infections continue to be a major cause of morbidity and mortality among HIV infected patients. There have been an increased number of varied and resistant fungal pathogens that are difficult to treat. Also, there are very few fungal specific targets that are appropriate for drug discovery. . A promising new strategy to enhance the efficacy of antifungals and block the evolution of drug resistance is to inhibit the molecular chaperone heat shock protein 90 (Hsp90). Hsp90, an essential molecular chaperone, regulates the stability of its client proteins, many of which are involved in stress responses. Fungi depend on these stress responses to cope with cell membrane and cell wall damage induced by antifungal drugs. Our compound could be an important advancement in treating fungal infections. To our knowledge, it is the first characterized small molecule that selectively inhibit fungal Hsp90. It works in combination with known antifungals against a broad range of pathogenic fungi. We intend to use this SBIRII to develop this compound and its analogs as a novel treatment for fungal infections.

Project Terms:
absorption; Accounting; Acquired Immunodeficiency Syndrome; Address; Alkanes; alkyl group; Amphotericin B; analog; Animal Model; Animals; Antifungal Agents; Antifungal Therapy; Aspergillus; Aspergillus fumigatus; Azole resistance; biological adaptation to stress; Biological Assay; cancer therapy; Candida; Candida albicans; carboxyl group; Caspofungin; Cell Line; Cell membrane; Cell Wall; Cellular Stress Response; Cessation of life; Chemistry; Client; college; Connecticut; coping; Cryptococcus; Cryptococcus neoformans; Development; Development Plans; drug discovery; Drug Kinetics; Drug resistance; echinocandin resistance; Effectiveness; Evolution; Excretory function; Fluconazole; Fluconazole resistance; Foundations; fungus; Goals; Heat-Shock Proteins 90; HIV; HSP 90 inhibition; Human; Immunocompromised Host; In Vitro; in vitro activity; in vitro testing; in vivo; in vivo Model; Infection; inhibitor/antagonist; invertebrate host; Lead; Mammalian Cell; Measures; Medical; Medical center; Metabolism; Methods; Microbial Biofilms; Modeling; Modification; Molecular Chaperones; Molecular Target; Molecular Weight; Morbidity - disease rate; Mortality Vital Statistics; mouse model; mutant; Mycoses; novel; pathogen; Patients; Pharmaceutical Preparations; Pneumocystis; Pneumocystis Infections; Population; pre-clinical; Procedures; Process; professor; Property; Proteins; public health relevance; Research; research study; Resistance; Resistance development; resistant strain; Saccharomyces cerevisiae; Safety; small molecule; Specificity; Structure; Testing; The science of Mycology; Toxic effect; Toxicology; Universities; Work; Yeast Model System