Discovery of thiosemicarbazone derivatives as effective New Delhi metallo-β-lactamase-1 (NDM-1) inhibitors against NDM-1 producing clinical isolates

New Delhi metallo-β-lactamase-1 (NDM-1) is capable of hydrolyzing nearly all β-lactam antibiotics, posing an emerging threat to public health. There are currently less effective treatment options for treating NDM-1 positive “superbug”, and no promising NDM-1 inhibitors were used in clinical practice. In this study, structure–activity relationship based on thiosemicarbazone derivatives was systematically characterized and their potential activities combined with meropenem (MEM) were evaluated. Compounds 19bg and 19bh exhibited excellent activity against 10 NDM-positive isolate clinical isolates in reversing MEM resistance. Further studies demonstrated compounds 19bg and 19bh were uncompetitive NDM-1 inhibitors with Ki = 0.63 and 0.44 μmol/L, respectively. Molecular docking speculated that compounds 19bg and 19bh were most likely to bind in the allosteric pocket which would affect the catalytic effect of NDM-1 on the substrate meropenem. Toxicity evaluation experiment showed that no hemolysis activities even at concentrations of 1000 mg/mL against red blood cells. In vivo experimental results showed combination of MEM and compound 19bh was markedly effective in treating infections caused by NDM-1 positive strain and prolonging the survival time of sepsis mice. Our finding showed that compound 19bh might be a promising lead in developing new inhibitor to treat NDM-1 producing superbug.

Discovery of novel diarylamides as orally active diuretics targeting urea transporters

Urea transporters (UT) play a vital role in the mechanism of urine concentration and are recognized as novel targets for the development of salt-sparing diuretics. Thus, UT inhibitors are promising for development as novel diuretics. In the present study, a novel UT inhibitor with a diarylamide scaffold was discovered by high-throughput screening. Optimization of the inhibitor led to the identification of a promising preclinical candidate, N-[4-(acetylamino)phenyl]-5-nitrofuran-2-carboxamide (1H), with excellent in vitro UT inhibitory activity at the submicromolar level. The half maximal inhibitory concentrations of 1H against UT-B in mouse, rat, and human erythrocyte were 1.60, 0.64, and 0.13 μmol/L, respectively. Further investigation suggested that 8 μmol/L 1H more powerfully inhibited UT-A1 at a rate of 86.8% than UT-B at a rate of 73.9% in MDCK cell models. Most interestingly, we found for the first time that oral administration of 1H at a dose of 100 mg/kg showed superior diuretic effect in vivo without causing electrolyte imbalance in rats. Additionally, 1H did not exhibit apparent toxicity in vivo and in vitro, and possessed favorable pharmacokinetic characteristics. 1H shows promise as a novel diuretic to treat hyponatremia accompanied with volume expansion and may cause few side effects.