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Title: Design, synthesis and biological evaluation of novel, dual targeting inhibitors of bacterial DNA gyrase and topoisomerase IV
Author: Yule, Ian Andrew
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2012
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Full text unavailable from EThOS. Thesis embargoed until 01 Dec 2031
The inevitability of bacterial drug resistance to all marketed antibiotic drug classes warrants continual research into the development of novel chemotype antibacterial agents. Drug resistant `superbugs' such as methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococci (VRE) account for >70% of US hospital bound bacteremias. Such infections are associated with vastly increased rates of morbidity and mortality resulting in a heavy economic burden on health care authorities. The bacterial topoisomerase enzymes DNA gyrase and topoisomerase IV are highly conserved amongst almost all bacterial species on account of their unique and essential function in the conservation of chromosomal integrity during DNA replication and transcription. Furthermore, structural similarity between gyrase and topo IV, and distinction from human homologues, makes the selective dual-inhibition of these enzymes a realistic goal. In this thesis, three distinct approaches were utilized in the discovery of novel inhibitors of gyrase (GyrB) and topoisomerase IV (ParE) acting at the ATP binding domains of these enzymes. In the initial strategy, structural variants based on known inhibitors were modelled within the GyrB ATPase site in a bid to displace a highly conserved water molecule at the ligand-enzyme interface. Synthesis and biological screening of these variants proved that such changes were to the detriment of activity, although the work did yield a novel, convenient preparation of Nsubstituted thieno[2,3-d]pyrimidinones. In an alternative strategy, the de novo molecular design software SPROUT was used in concert with crystallographic data on the GyrB ATP binding site. Putative inhibitors were thus generated 'from scratch', the most attractive of which were further modelled using docking software (AUTODOCK), synthesised and screened for enzyme inhibitory and antimicrobial activity. A number of early series were derived which demonstrated modest (GyrB IC50 <100 μM) enzyme activity. The most promising of these, a series of pyridine-3-carboxamides, was optimized to offer potent (GyrB IC50 <100 nM) enzyme inhibitory activity, dual target specific antibacterial activity (MICs <0.5 μg / mL) and a low potential for resistance development. Finally, using the GLIDE docking software, virtual compound libraries were screened in silico against the ATP binding domain of GyrB. Though largely unsuccessful, the process did identify a moderate inhibitor (GyrB IC50 118 μM, MIC 32 μg / mL), in a cost and time effective manner relative to high-throughput screening.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available