Design, synthesis, and biological evaluation of 1,2,4-triazole derivatives as potent antitubercular agents

Inhibition of mycobacterial membrane protein large 3 (MmpL3) thereby affecting the mycolic acid biosynthetic pathway has been proven to be an effective strategy for developing antitubercular drugs. Based on the X-ray crystal structure of MmpL3 inhibitor complexes, a series of novel 1,2,4-triazole derivatives were designed, synthesized and evaluated antitubercular activity against Mtb strain H37Rv. Comprehensive structure–activity relationship exploration resulted in the identification of compounds 21 and 28, which possess potent antitubercular activity against Mtb strain H37Rv [minimum inhibitory concentration (MIC) = 0.03–0.13 μg/mL] and the clinical isolates of multidrug resistance (MDR) and extensive drug resistance (XDR) tuberculosis (MIC = 0.06–1.0 μg/mL). Moreover, compounds 21 and 28 showed neglectable cytotoxicity (IC₅₀ ≥ 32 μg/mL) to the mammalian Vero cells and favorable physicochemical and pharmacokinetic properties according to the in silico absorption, distribution, metabolism and excretion (ADME) prediction. Finally, the potential target of representative 1,2,4-triazole 28 was identified to be MmpL3 using a microscale thermophoresis (MST) assay.