Neutrophil elastase is stored within cytoplasmic azurophilic granules in the neutrophil and released upon stimulation by pathogens where it acts either as free protein or is associated with neutrophil extracellular traps (NETs). Together with other proteases released from activated neutrophils, neutrophil elastase plays a critical role in degrading invading pathogens and thus provides the earliest line of defense in the immune system. Neutrophil elastase inhibitor is an N-benzoylindazole derivative that selectively targets the binding domain of neutrophil elastase (IC50 = 7 nM). It has been shown to inhibit additional serine proteases, thrombin and urokinase, only at higher, micromolar concentrations (IC50s = 1.9 and 6.6 μM, respectively).
