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Fragment-Based Drug Discovery of Inhibitors of Phosphopantetheine Adenylyltransferase from Gram-Negative Bacteria

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journal contribution
posted on 02.03.2018 by Robert J. Moreau, Colin K. Skepper, Brent A. Appleton, Anke Blechschmidt, Carl J. Balibar, Bret M. Benton, Joseph E. Drumm, Brian Y. Feng, Mei Geng, Cindy Li, Mika K. Lindvall, Andreas Lingel, Yipin Lu, Mulugeta Mamo, Wosenu Mergo, Valery Polyakov, Thomas M. Smith, Kenneth Takeoka, Kyoko Uehara, Lisha Wang, Jun-Rong Wei, Andrew H. Weiss, Lili Xie, Wenjian Xu, Qiong Zhang, Javier de Vicente
The discovery and development of new antibiotics capable of curing infections due to multidrug-resistant and pandrug-resistant Gram-negative bacteria are a major challenge with fundamental importance to our global healthcare system. Part of our broad program at Novartis to address this urgent, unmet need includes the search for new agents that inhibit novel bacterial targets. Here we report the discovery and hit-to-lead optimization of new inhibitors of phosphopantetheine adenylyltransferase (PPAT) from Gram-negative bacteria. Utilizing a fragment-based screening approach, we discovered a number of unique scaffolds capable of interacting with the pantetheine site of E. coli PPAT and inhibiting enzymatic activity, including triazolopyrimidinone 6. Structure-based optimization resulted in the identification of two lead compounds as selective, small molecule inhibitors of bacterial PPAT: triazolopyrimidinone 53 and azabenzimidazole 54 efficiently inhibited E. coli and P. aeruginosa PPAT and displayed modest cellular potency against the efflux-deficient E. coli ΔtolC mutant strain.