By exploring three heterocycle spacers (oxadiazole, 1,2,3-triazole, and isoxazole) on the ring-fused thiazolo-2-pyridone scaffold I [R = 3-MeOC6H4, 1-naphthyl, 4-pyridyl, etc.;], II [Ar = 3-CF3C6H4, 4-t-BuC6H4, 1-naphthyl, 2-naphthyl], III [R = Ph, 3,5-di-F-C6H3, 1-naphthyl, etc.;], and IV [Ar = 3-CF3C6H4, 1-naphthyl], identified two novel isoxazoles, III [R = 4-t-BuC6H4, 2-naphthyl].Compounds III [R = 4-t-BuC6H4, 2-naphthyl]. inhibited Mtb respiration and biofilm formation more potently with a broader therapeutic window, were better potentiators of INH-mediated inhibition of an INH-resistant Mtb mutant, and more effectively inhibited intracellular Mtb replication than C10.The III [R = 4-t-BuC6H4] enantiomer showed further enhanced activity compared to its enantiomer and the III [R = 4-t-BuC6H4] racemic mixtureOur potent second-generation C10 III and IV analogs offer promise for therapeutic development against drug-resistant Mtb.