Graduation Date

Spring 5-7-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Pharmaceutical Sciences

First Advisor

Martin Conda-Sheridan, Ph.D.

Abstract

Chlamydia trachomatis is the most prominent cause of sexually transmitted bacterial infections worldwide, with around 128 million reported cases annually. This pathogen can cause severe urogenital and ocular consequences, resulting in infertility and trachoma. In its unique developmental cycle, Chlamydia fluctuates between two distinct forms, elementary bodies (EBs) and reticulate bodies (RBs). We hypothesized that caseinolytic protease P (ClpP), a conserved protease among bacterial species, drives the Chlamydia developmental cycle. Earlier work by the Ouellette group demonstrated that Chlamydia relies on its ClpP2 paralogue (ctClpP2) to differentiate between its developmental forms. Dysregulation of ctClpP2 had a significant impact on Chlamydia survival and growth. A pyridine-derived compound (1.18) which is a reported E. coli ClpP activator, halted Chlamydia growth at 50 ug/mL through ctClpP2 activation. The promising activity of 1.18 as an anti-chlamydial agent encouraged us to use it as starting point to develop new anti-chlamydial agents.

The current dissertation emphasizes using classical medicinal chemistry approaches to design, synthesize, and evaluate novel anti-chlamydial compounds based on 1.18. The anti-chlamydial investigation of the synthesized library provided 1-(4-(4-chlorobenzyl)piperazin-1-yl)-2-methyl-2-((5-(trifluoromethyl)pyridin-2-yl)sulfonyl)propan-1-one (2.18h) with comparable activity and selectivity against Chlamydia. Moreover, the new molecules did not kill other tested bacteria (ESKAPE pathogens) up to 64 ug/mL, indicating selectivity for Chlamydia. To further explore the SAR of this scaffold, we compared the chemical structure of 1.18 with 2.18h and correlated it with their anti-chlamydial activity. The aryl group on the right side was replaced with different heterocycles, and a longer middle linker was introduced. These modifications improved the biological activity of the new compounds compared to 1.18 and 2.18h. Compound 3.7e with 3-((4-chlorophenyl)thio)propyl moiety showed the most comparable activity among the newly synthesized molecules. We also noticed a synergistic effect with a combined use of 3.7e and Azithromycin, and high efficacy in a 3D epithelial model. Finally, we utilized some physical tools to explore the dynamicity of our target (ctClpP2) and investigate its assembly into the homotetradecameric structure, which is suspected to perform the proteolysis process.

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