Development of Thieno[2,3-b]pyridin-6(7H)-one derivatives against drug-resistant Mycobacterium tuberculosis

In this study, two series of thieno[2,3-b]pyridin-6(7H)-one derivatives were rationally designed via substituent swapping and scaffold flipping strategies. Structure-activity relationship (SAR) analysis identified four compounds exhibiting potent in vitro against autoluminescent Mycobacterium tuberculosis H37Ra (Mtb UAlRa), with minimum inhibitory concentrations <0.5 μg/mL, which was superior to or comparable to the first-line drug rifampin. The representative derivative 3a exhibited: Potent efficacy against clinical drug-resistant Mtb isolates and intracellular UAlRa in macrophages; A narrow antibacterial spectrum; And favorable microsomal stability, supporting further pharmacological development. Drug resistance mechanism investigations, integrating whole-genome sequencing of Mtb mutants resistant to compound 3a with in vitro inhibition assays involving wild-type Mtb overexpressing IdsA2 (Rv2173) or PEPCK (Rv2011), demonstrated that resistance to these derivatives is mediated by IdsA2-dependent isoprenoid biosynthesis and PEPCK-governed gluconeogenesis. These findings establish thieno[2,3-b]pyridin-6(7H)-ones as promising hit compounds for developing novel antitubercular agents.