Lodelaben (SC-39026) is a human neutrophil elastase inhibitor. Its inhibition of elastase is reversible and noncompetitive at low concentrations. Inhibition is "mixed" at higher inhibitor concentrations. SC-39026 is inactive against hog pancreatic elastase, bovine alpha-chymotrypsin and Pseudomonas aeruginosa elastase, but does inhibit human neutrophil cathepsin G. Lodelaben was developed as antiarthritic agent and tested as adjunct to emphysema therapy. Monocrotaline-injected rats given SC-39026 had significantly lower mean pulmonary artery pressure than those given vehicle, and this correlated with a significant reduction in the number of abnormally muscularized arteries at alveolar wall level. SC-39026 did not significantly reduce monocrotaline-induced medial hypertrophy of muscular arteries, endothelial injury, and associated subendothelial edema. Lodelaben reduces endotoxin-induced lung dysfunction in awake sheep.