Development of triaryl antimicrobials by scaffold hopping from an aminopropanol hit targeting bacterial RNA polymerase-NusG interactions.

Bacterial RNA polymerase (RNAP) requires the NusG factor to facilitate transcription, with the RNAP clamp-helix domain (CH) serving as the primary binding site for NusG and representing a promising target for antimicrobial intervention. In previous work, we unprecedentedly developed a pharmacophore model based on key clamp-helix residues (R270, R278, R281) at RNAP CH essential for NusG binding, which led to the identification of a hit compound exhibiting modest antimicrobial activity against Streptococcus pneumoniae. In this study, we designed a new class of triaryl inhibitors via scaffold hopping, substituting the linear structure of the hit compound with a benzene ring. Antimicrobial testing showed that several newly synthesised lead compounds achieved the minimum inhibitory concentration of 1 µg/mL against drug-resistant S. pneumoniae, superior to some marketed antibiotics. The following inhibitory and cell-based assays demonstrated the potential of these triaryl compounds as promising candidates for further development as novel antimicrobial agents.