Design, Synthesis, and Biological Evaluation of Tetrazol-2-yl-acetamides as Novel Antitubercular Agents.

A focused small-molecule library was screened against extracellular Mycobacterium tuberculosis (Mtb) across four distinct carbon sources that mimic different metabolic states of the pathogen. This screen identified a novel tetrazol-2-yl-acetamide compound, sALT629 (P1), with potent intramacrophage activity (EC50 = 1.5 μM). sALT629 showed broad-spectrum activities across all carbon sources, equipotent efficacy against drug-resistant Mtb, and activity against both slow-replicating and nonreplicating Mtb. Structure-activity relationship (SAR) studies optimized the potency and drug-like properties, leading to analogue P39 with improved intramacrophage activity (EC50 = 0.68 μM) and pharmacokinetics (PK) properties. In mice, P39 achieved a plasma exposure of 58,754 ng/mL and maintained plasma concentrations above EC50 for 16 h after a 20 mg/kg oral dose. Additionally, sALT629 showed good exposure and tolerability after repeated dosing for 4 days at 200 mg/kg once daily (QD) or 100 mg/kg twice daily (BID), indicating low toxicity liability and the potential for further development as an anti-tuberculosis (TB) drug candidate.