Principal Investigator (PI)
The Foundation is providing £298,805 in support.
Joel McMillan
Emanuel Pinto
Malkeet Kumar
GSK has developed both extra-cellular assays for Shigella and also intracellular assays, both in Caco2 cells and macrophages (THP1 cells). These assays will be used to assay compounds for whole cell activity. In addition, GSK has the possibility to run most promising hits in a panel of enteric bacteria (E.g. Salmonella, E. coli, Campylobacter) including drug-sensitive and MDR organisms. For key compounds, screening against a panel fo Gram-negative and Gram-positive bacteria. GSK has already identified LpxC inhibitors with activity against Shigella, and they can provide this expertise. The in-kind contributions from GSK will also be involve in the characterization of promising hits (in vitro profiling). In the medium term, further evaluations of these types will guide a medicinal chemistry effort for hit-to-lead development.
Shigellosis is a major cause of diarrhea in Low and Middle Income Countries and is responsible for hundreds of thousands of deaths each year. Drug resistance is a major problem and there is a need for new drugs with novel modes of action to tackle this terrible disease. Furthermore, the complex array of Shigella species and serotypes may make vaccine development challenging. The aim of this project is to develop novel inhibitors of LpxC as potential agents for the treatment of shigellosis. A recent screen carried out in GSK against whole cell bacteria has validated this as a drug target in Shigella. LpxC is a zinc metalloprotein responsible for de-acetylation of an advanced precursor to Lipid A. A number of different organizations have worked on LpxC inhibitors; the majority of disclosed inhibitors of LpxC are based on hydroxamic acid analogues, which suffer from poor pharmacokinetics and toxicity issues. No hydroxamate based LpxC inhibitor has reached the clinic. Our aim is to use a structure-based approach to find non-hydroxamate-based inhibitors of Shigella LpxC. To achieve this, we will screen with a series of Zn binders, identified from the literature and protein data bank (pdb). We aim to explore a wide range of zinc binding groups. We wil also explore the possibility to use benzoxaboroles as new Zn binders (exploiting the ability of zinc to activate a water molecule to generate active Zn binders as reported in DDU recent publication: PNAS, 2018, vol. 115,no. 38, 9616–9621). As well as finding non-hydroxamate Zn binders, we also aim to exploit the relatively weakly explored UDP-binding region of the enzyme, which should allow us to develop novel scaffolds. We will screen using our fragment library. There is a lot of structural information from the literature and the pdb we could then utilize to guide optimization. Final goal for this proposal is to find a non-hydroxamate zinc binding motif for LpxC and to carry out a fragment-based optimization to find inhibitors that are active in a cellular model.