High affinity, potent inhibitor of human leukocyte elastase (HLE) (IC50 = 3.9 nM). Displays species-selectivity (Ki values are 0.017, 1.70, 3.01, 58 and > 100 nM for human, mouse, rat, rabbit and porcine elastase respectively). Inhibits HLE-induced lung hemorrhage in mice (ID50 = 2.8 mg/kg) and reduces infarct size in an in vivo acute model of coronary ischemia-reperfusion injury. Orally active. Purity 98%. MW (observed): 556.63