Pyrazinamide (PZA) is a cornerstone of first-line antitubercular drug therapy and is unique in its ability to kill nongrowing populations of Mycobacterium tuberculosis through disruption of coenzyme A synthesis. Unlike other drugs, PZA action is conditional and requires potentiation by host-relevant environmental stressors, such as low pH and nutrient limitation. Despite its pivotal role in tuberculosis therapy, the mechanistic basis for PZA potentiation remains unknown and the durability of this crucial drug is challenged by the emergent spread of drug resistance. To advance our understanding of PZA action and facilitate discovery efforts, we characterized the activity of a more potent PZA analog, morphazinamide (MZA). Here, we demonstrate that like PZA, MZA acts in part through impairment of coenzyme A synthesis. Unexpectedly, we find that, in contrast to PZA, MZA does not require potentiation due to aldehyde-mediated disruption of thiol metabolism and maintains bactericidal activity against PZA-resistant strains. Our findings reveal a novel dual action mechanism of MZA that synergistically disrupts coenzyme A synthesis resulting in a faster rate of killing and a higher barrier to resistance relative to PZA. Together, these observations resolve the mechanistic basis for potentiation of a key first-line antitubercular drug and provide new insights for discovery of improved therapeutic approaches for tuberculosis.
Keywords: Biological Sciences; Coenzyme A; Drug Discovery; Microbiology; Pyrazinamide; Thiol Stress; Tuberculosis.