LeuRS-IN-1 is a highly potent and orally active inhibitor of the leucyl-tRNA synthetase enzyme derived from Mycobacterium tuberculosis (M.tb LeuRS). It exhibits significant inhibitory activity against M.tb LeuRS with IC 50 and Kd values of 0.06 μM and 0.075 μM, respectively. Additionally, LeuRS-IN-1 effectively inhibits human cytoplasmic LeuRS with an IC 50 value of 38.8 μM and suppresses protein synthesis in HepG2 cells with an EC 50 value of 19.6 μM.

LeuRS (Human cytoplasmic):38.8 μM (IC50), LeuRS (M. tuberculosis):0.06 μM (IC50), LeuRS (M. tuberculosis):0.075 μM (Kd), Protein synthesis (HepG2 cells):19.6 μM (EC50)

LeuRS-IN-1 (compound 13) demonstrates antimicrobial efficacy against M.tb H37Rv bacteria with a minimum inhibitory concentration (MIC) of 0.02 μg/mL[1], and also exhibits cytotoxic activity in HepG2 cells after 48 hours, achieving a half-maximal effective concentration (EC50) of 65.8 μM[2].

LeuRS-IN-1 administered at a dosage of 100 mg/kg orally each day for 14 days has been shown to decrease lung [colony-forming unit (CFU)] values in mice with acute tuberculosis (TB), demonstrating its therapeutic potential[1]. In a chronic TB mouse model, a lower dose of LeuRS-IN-1, 33 mg/kg administered orally five times a week for four weeks, effectively reduced both lung and spleen CFU values, indicating its effectiveness in prolonged TB infection[1]. Pharmacokinetic studies in mice reveal that intravenously injected LeuRS-IN-1 at 30 mg/kg achieves a maximum concentration (Cmax) of 13.6 μg/ml within 5 minutes, with a clearance rate (CL) of 582 ml/h/kg, a steady-state volume of distribution (Vss) of 3,142 ml/kg, a mean residence time (MRT) of 5.4 hours, and an area under the curve (AUC) from 0 to infinity of 51.6 h·μg/ml. The alpha half-life (α-t1/2) is noted as 0.10 hours (representing 2% of the AUC), and the beta half-life (β-t1/2) as 3.83 hours (98% of the AUC). When administered orally at the same dosage, LeuRS-IN-1’s Cmax is 6.4 μg/ml at a Tmax of 0.25 hours, with an AUC from 0 to 24 hours of 47.5 h·μg/ml, a terminal half-life of 3.1 hours, and a bioavailability of 9.2%. The protein binding percentage in mice is 23%. In specific murine models, the compound has been tested with conclusive results showing reduced CFU values, marking a significant step towards addressing TB infections.