Fragment to small molecule hit discovery targeting Mycobacterium tuberculosis FtsZ

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Tuberculosis (TB) is a major cause of morbidity and mortality in developing and developed countries. 10.6 million people developed the disease and 1.6 million people died from TB in 2021. Approximately 450,000 reported cases are classified as multidrug-resistant tuberculosis (MDR-TB), with a subset of patients developing extensively-drug-resistant tuberculosis (XDR-TB).About a quarter of the world's population have latent TB, with ~10-15% going on to develop and spread the infection. Patient access to current treatments, and compliance with the lengthy dosing regimens is a global challenge. MDR-TB is more difficult to treat, and options for the emerging XDR-TB are even more limited. There is an urgent unmet medical need to develop novel anti-TB agents to successfully combat emerging resistance. Recent progress has been achieved by the repurposing and redosing of known anti-TB drugs, but there are no new drug classes in clinical trials that act by novel mechanisms of action.The protein "Filamenting temperature-sensitive mutant Z" (FtsZ) is highly conserved among all types of bacteria, including Mycobacterium species that cause TB. It is an essential cell division protein with both GTPase and polymerisation activities. FtsZ subunits polymerise into protofilaments to form a dynamic ring-like structure called the Z-ring that functions as a scaffold for the assembly of the divisome, a multiprotein complex that causes contraction of the Z-ring, finally resulting in septum formation and cell division. Abnormalities in FtsZ block the Z-ring functions, leading to an elongated, filamentous phenotype, inhibition of cell division and subsequent cell death. Although FtsZ inhibitors have been identified, most are derived from natural products and there is a general lack of structural information, with many of the inhibitors classified as "false positives".We have purified M. tuberculosis (MTb) FtsZ in large amounts for biochemical, biophysical and structural studies. In collaboration with the Monash NMR screening facility, we identified 38 fragment hits against FtsZ. We established biophysical (DSF, MST) and biochemical (GTPase, right-angle scattering) assays to characterise its GTPase activity and polymerisation/depolymerisation dynamics. Uniquely, we have determined the crystal structure of FtsZ in complex with fragment hits and established their mechanism of action. We have evaluated the fragment binding sites with respect to fragment growth and merging and we are ready to initiate SAR-by-catalogue and custom-made optimisation of the hits to develop more potent analogues.In this project we aim to develop and characterise potent inhibitors of MTb FtsZ as a new class of antibiotic for the treatment of tuberculosis infections. We anticipate that such compounds will be a welcome addition to the treatment options available for TB and its drug-resistant variants. This collaborative drug discovery project addresses a clear unmet medical need. Successful completion of this project will underpin a broader collaborative drug discovery program including other UCL partners.