Date Available

10-25-2019

Year of Publication

2018

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Pharmacy

Department/School/Program

Pharmaceutical Sciences

First Advisor

Dr. Sylvie Garneau-Tsodikova

Abstract

Tuberculosis (TB) and fungal infections are two of the most lethal infectious diseases worldwide due to the emergence of drug-resistant Mycobacterium tuberculosis (Mtb) and fungal strains that can resist the most potent antimicrobial drugs currently employed. Due to the rise of these drug resistant strains, effective treatment options for these two infections are limited. This dissertation aims at exploring novel drug scaffolds to help combat drug resistance in TB and fungal infections.

TB caused by the pathogenic Mtb is, alongside with human immunodeficiency virus acquired immunodeficiency virus (HIV), the deadliest infectious disease worldwide with approximately 2-3 billion people infected yearly. The situation has become increasingly intensified due to the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mtb strains.Aminoglycoside (AG) antibiotics such as amikacin and kanamycin A (KAN) are heavily relied upon for the treatment of MDR- and XDR-Mtb strains. However, the success rate for the treatment of these MDR- and XDR-TB cases is decreasing as a result of increased KAN resistance. It was reported by the Centers for Disease Control and Prevention (CDC) that upregulation of the enhanced intracellular survival (eis) gene was the cause of resistance to KAN in a large portion of Mtb clinical isolates. Our lab previously demonstrated that Eis is an AG acetyltransferase that can inactivate AGs via chemoenzymatic modification of the AG scaffolds. As Eis has been shown to acetylate a wide variety of AG scaffolds, the development of novel AGs that can completely escape the action of Eis remains highly challenging. Therefore, we suggested an alternative therapeutic approach involving inhibiting Eis enzyme and still employing the current FDA-approved KAN. As exemplified by the clinically successful combination of penicillin and b-lactamase inhibitors, we hypothesized that an Eis inhibitor may be used as adjuvant therapy in combination with KAN to treat MDR- and XDR-tuberculosis. Using high-throughput screening, we were able to identify several small-molecule scaffolds capable of inhibiting Eis. We performed structure activity relationship (SAR) studies using purified Eis enzyme and optimized lead compounds. Additionally, we also showed that co-administration of Eis lead inhibitors with KAN led to recovery of KAN activity against a KAN-resistant Mtb cell line that overexpressed Ei

Invasive fungal infections are on the rise due to an increased population of critically ill patients as a result of HIV infections, chemotherapies, and organ transplantations. Unlike antibiotics that are greatly diverse in categories and mechanisms of action, our current antifungal drug repertoire is greatly limited and insufficient in addressing the problem of drug-resistant fungal infections. Thus, there is a growing need for novel antimycotics that are safe and effective. We report a number of lead compounds with potent antifungal activitiy. The MIC values of these compounds were as low as 0.02 mg/mL against the fungal strains tested. Our compounds are derived from the ebselen core structure, which has been shown to be safe in multicenter clinical trials. Notably, fungal cells treated with our compounds showed the accumulation of ROS, which may further contribute to the growth inhibitory effect against fungi. This study provides new lead compounds for the development of antimycotic agents.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2018.396

Funding Information

University of Kentucky College of Pharmacy (UKCOP) start-up fund (SGT), the UKCOP 2017-2018 Pharmaceutical Sciences Excellence in Achievement Fellowship, and the National Institutes of Health (NIH) grant AI090048 (SGT).

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