Spiropyrimidinetrione DNA Gyrase Inhibitors with Potent and Selective Antituberculosis Activity

New antibiotics with either a novel mode of action or novel mode of inhibition are urgently needed to overcome the threat of drug-resistant tuberculosis (TB). The present study profiles new spiropyrimidinetriones (SPTs), DNA gyrase inhibitors having activity against drug-resistant Mycobacterium tuberculosis (Mtb), the causative agent of TB. While the clinical candidate zoliflodacin has progressed to phase 3 trials for the treatment of gonorrhea, compounds herein demonstrated higher inhibitory potency against Mtb DNA gyrase (e.g., compound 42 with IC₅₀ = 2.0) and lower Mtb minimum inhibitor concentrations (0.49 μM for 42). Notably, 42 and analogues showed selective Mtb activity relative to representative Gram-positive and Gram-negative bacteria. DNA gyrase inhibition was shown to involve stabilization of double-cleaved DNA, while on-target activity was supported by hypersensitivity against a gyrA hypomorph. Finally, a docking model for SPTs with Mtb DNA gyrase was developed, and a structural hypothesis was built for structure–activity relationship expansion.