C25-modified rifamycin derivatives with improved activity against .

Infections caused by are difficult to treat due to its intrinsic resistance to most antibiotics. Formation of biofilms and the capacity of to survive inside host phagocytes further complicate eradication. Herein, we explored whether addition of a carbamate-linked group at the C25 position of rifamycin SV blocks enzymatic inactivation by Arr, an ADP-ribosyltransferase conferring resistance to rifampicin (RMP). Unlike RMP, 5j, a benzyl piperidine rifamycin derivative with a morpholino substituted C3 position and a naphthoquinone core, is not modified by purified Arr. Additionally, we show that the Arr D82 residue is essential for catalytic activity. Thermal profiling of Arr in the presence of 5j, RMP, or rifabutin shows that 5j does not bind to Arr. We found that the activity of 5j is comparable to amikacin against planktonic cultures and pellicles. Critically, 5j also exerts potent antimicrobial activity against in human macrophages and shows synergistic activity with amikacin and azithromycin.