5-Carboxamide-Substituted Barbituric Acids: Promising Scaffolds for Drug Development against Mycobacterium tuberculosis.

The continued spread of drug-resistant Mycobacterium tuberculosis (Mtb) necessitates the development of new chemotypes with novel modes of action. Here, we report 5-carboxamide-substituted barbituric acid as a promising scaffold for developing new drugs against Mtb. Fenoxacrim, the initial hit compound identified through phenotypic screening, demonstrated potent activity against Mtb. It is active against drug-susceptible and multidrug-resistant clinical Mtb isolates as well as against intracellular Mtb in infected THP-1 derived macrophages. Fenoxacrim demonstrates high selectivity (>73-fold) for the pathogen over several tested mammalian cell lines. Other than Mtb, fenoxacrim exhibits strong bactericidal activity against several Gram-positive pathogens, including methicillin-resistantStaphylococcus aureus (MRSA), with in vitro potency comparable to, or exceeding several clinically used antibiotics. Medicinal chemistry optimization efforts yielded new fenoxacrim analogues with improved Mtb specificity, enhanced potency, and reduced cytotoxicity. Mode-of-action studies suggest that fenoxacrim inhibits undecaprenyl pyrophosphate synthase (UPPS) and dissipates the bacterial membrane potential. Together, these findings highlight the potential of 5-carboxamidebarbituric acid derivatives as a foundation for developing new antibacterial agents with novel modes of action for the treatment of tuberculosis and other drug-resistant bacterial infections.