Repurposing clofazimine as an antibiotic to treat cholera: Identification of cellular and structural targets.

Vibrio cholerae has shaped the face of human civilization through at least seven pandemic waves. The current wave shows multidrug resistance, has produced enormous human and economic losses, as well as humanitarian crises, and has the potential to collapse the healthcare system of entire countries. Antibiotic resistance in this and other pathogens is an urgent threat that remains unaddressed due to the significant costs to develop new antibiotics. In this work, we have tested several FDA-approved phenazines and phenothiazines, and have identified that clofazimine (Lamprene) shows strong antibiotic effects against V. cholerae cells in culture and in an in vitro infection model, at concentrations well below the clinically-used doses in humans. Our results show that in an animal model, clofazimine is as effective as ampicillin in the treatment of cholerae. In addition, clofazimine shows strong antivirulence properties, almost completely inhibiting cholera toxin production. The characterization of V. cholerae metabolism allowed us to identify that clofazimine's main target in this pathogen is the respiratory complex NQR, an essential enzyme that plays a crucial role in energy metabolism, virulence factor production and multidrug resistance, which is widely distributed among pathogenic bacteria. Biochemical and computational analyses show that the structural target of clofazimine is the catalytically-active ubiquinone-binding site, which is a unique structural motif, not found in any human protein, making it an ideal pharmacologic target. These results show that clofazimine can be repurposed to treat cholera, and open opportunities to develop a novel class of antibiotics that target NQR.