Design and Evaluation of Pyridinyl Sulfonyl Piperazine LpxH Inhibitors with Potent Antibiotic Activity Against Enterobacterales

Enterobacterales, a large order of Gram-negative bacteria, including <i>Escherichia coli</i> and <i>Klebsiella pneumoniae</i>, are major causes of urinary tract and gastrointestinal infections, pneumonia, and other diseases in healthcare settings and communities. ESBL-producing Enterobacterales and carbapenem-resistant Enterobacterales can break down commonly used antibiotics, with some strains being resistant to all available antibiotics. This public health threat necessitates the development of novel antibiotics, ideally targeting new pathways in these bacteria. Gram-negative bacteria possess an outer membrane enriched with lipid A, a saccharolipid that serves as the membrane anchor of lipopolysaccharides and the active component of the bacterial endotoxin, causing septic shock. The biosynthesis of lipid A is crucial for the viability of Gram-negative bacteria, and as an essential enzyme in this process, LpxH has emerged as a promising target for developing novel antibiotics against multidrug-resistant Gram-negative pathogens. Here, we report the development of pyridinyl sulfonyl piperazine LpxH inhibitors. Among them, <i>ortho</i>-substituted pyridinyl compounds significantly boost LpxH inhibition and antibiotic activity over the original phenyl series. Structural and QM/MM analyses reveal that these improved activities are primarily due to the enhanced interaction between F141 of the LpxH insertion lid and the pyridinyl group. Incorporation of the <i>N</i>-methyl-<i>N</i>-phenyl-methanesulfonamide moiety into the pyridinyl sulfonyl piperazine backbone results in JH-LPH-106 and JH-LPH-107, both of which exhibit potent antibiotic activity against wild-type Enterobacterales such as <i>K. pneumoniae</i> and <i>E. coli</i>. JH-LPH-107 exhibits a low rate of spontaneous resistance and a high safety window <i>in vitro</i>, rendering it an excellent lead for further clinical development.