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bioRxiv · 10.1101/2025.07.31.667927

Selectivity of the time-dependent M. tuberculosis LeuRS inhibitor ganfeborole is driven by target vulnerability

Wang, M.·He, Y.·Cohen, S. A.·Strohm, A. R.·Shetye, G.·Franzblau, S. G.·Walker, S. G.·Alley, D.·Tonge, P. J.
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Abstract

Ganfeborole (GSK3036656) inhibits the Mycobacterium tuberculosis leucyl-tRNA-synthetase (mtLeuRS) and is in phase 2a clinical trials for the treatment of tuberculosis. Here we show that ganfeborole is a time-dependent inhibitor of mtLeuRS (IC50 1 nM) and generates a post-antibiotic effect of 77 h at 50xMIC (MIC 0.058 M) with M. tuberculosis H37Rv (Mtb), indicating that mtLeuRS is a highly vulnerable drug target and supporting the excellent in vivo efficacy of the drug. Ganfeborole is also a potent time-dependent inhibitor of Escherichia coli LeuRS (ecLeuRS, IC50 2 nM), however no antibacterial activity is observed towards E. coli up to 1 mM ganfeborole despite the observation that less potent ganfeborole analogs have antibacterial activity. To rationalize this observation, we propose that ganfeborole forms a complex with AMP that binds to the ecLeuRS editing site but does not impact aminoacylation. In support, addition of 12.5 M norvaline generates a ganfeborole MIC of 0.4 M since ecLeuRS is unable to hydrolyze norvaline-tRNALeu. Additionally, mutations that reduce the affinity and residence time of ganfeborole-AMP on ecLeuRS result in antibacterial activity. We propose that the activity of ganfeborole towards Mtb is because mtLeuRS is a highly vulnerable target so that only low levels of enzyme need to be inhibited by the ganfeborole-tRNALeu complex in contrast to ecLeuRS, which we previously demonstrated is a low vulnerability target.

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Wang, M., He, Y., Cohen, S. A., Strohm, A. R., Shetye, G., Franzblau, S. G., Walker, S. G., Alley, D., Tonge, P. J.. 2025-08-03. Selectivity of the time-dependent M. tuberculosis LeuRS inhibitor ganfeborole is driven by target vulnerability. https://doi.org/10.1101/2025.07.31.667927

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