An orally bioavailable, selective and reversible inhibitor of human neutrophil elastase (NE), with potential anti-inflammatory activity. Upon administration, alvelestat binds to and inhibits the activity of human NE. This inhibits NE-mediated inflammatory responses, which may prevent lung inflammation and injury, and may improve lung function associated with NE-induced respiratory diseases. NE, a serine protease released by neutrophils during inflammation, is upregulated in a number of respiratory diseases.