Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Chemistry

Major Professor

James w. Leahy, Ph.D.

Committee Member

Edward Turos, Ph.D.

Committee Member

Jianfeng Cai, Ph.D.

Committee Member

Nicholas J. Lawrence, Ph.D.

Committee Member

Yu Chen, Ph.D.

Keywords

Infectious diseases, Leishmania donovani, promastigotes, amastigotes, parasite, Chaperone proteins, Alzheimer’s disease, slingshot homology-1, Cofilin, protein phosphatases

Abstract

Infectious and neurodegenerative diseases continue to be a major concern worldwide. In spite of the great advances in drug therapy for treating various infectious and neurodegenerative diseases, there is still an urgent need for new and improved drugs due to increasing drug resistance among pathogens, emergence of new pathogens, ease of transmission of infections, ineffective available treatments, toxicity associated with current standard of care, aging populations and the lack of better alternative treatment options.

The first part of this manuscript (chapters 1 - 5) describes the synthesis of novel agents active against Leishmania donovani. According to the World Health Organization (WHO), a significant number of deaths worldwide can be attributed to infectious diseases – particularly neglected tropical diseases (NTDs), one of which is leishmaniasis - a complex and clinically diverse disease transmitted through the bite of an infected female phlebotomine sand-fly. The pathogen that causes leishmaniasis develops through a complex life cycle via different morphological changes. Its clinical presentations range from the less severe (cutaneous) to lethal/fatal (visceral) forms depending upon the level of systemic involvement, infecting species and the endemic environment. Treatments (and vaccines) must be species-specific to be particularly effective since sensitivity to commonly used drugs is largely species-specific. Heat shock protein 90 (Hsp 90) has been shown to promote the differentiation of the protozoan parasite that causes leishmaniasis from the promastigote stage to the amastigote pathogenic stages. To this end a series of compounds were prepared based on known Hsp 90 inhibitors, SNX2112 and XL888. The synthetic approach allows the probing of a hydrophobic pocket and rapid access to a collection of anti-leishmanial compounds. The most active compound, was found to be more than twice as active as the climivally used drug, miltefosine, in an infected J774 macrophage at IC50 = 0.65 µM.

The second part of this manuscript (chapters 6 - 9) describes the synthesis novel anti-Alzheimer’s agents. Alzheimer’s disease is a progressive neurodegenerative disease believed to be caused by tau hyperphosphorylation and plaque aggregation in the brain. It is known to affect about 44 million people worldwide and it is marked as the 6th leading cause of death in the United States. Slingshot homology-1 (SSH1) proteins, important protein phosphatases, are promising targets for the discovery of a new generation of small molecule inhibitors as treatment for Alzheimer’s disease, since SSH1 is known to contribute to both tau hyperphosphorylation and plaque aggregation in the brain. Through structure and activity relationships (SAR) studies, two (2) series of compounds were synthesized, thiazoles and pyridones, bearing a carboxylic acid or phosphonic acid functionality as inhibitors of SSH1 enzymes. In the preliminary screening efforts against SSH1 phosphatase activity, the thiazole series were found to be more potent at inhibiting the phosphatase activity than the pyridone series. Among the active thiazole series, eight (8) analogs exhibited significant inhibitory activity over the initial hit compound, observed via phosphatase inhibition curves (using a pNPP phosphatase assay). Further investigations into the molecular target (SSH1) are currently underway.

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