Depelestat is a small-protein neutrophil elastase (NE) inhibitor. The elastase at the neutrophil surface was fully inhibited by depelestat and formed soluble complexes. The elastase in cystic fibrosis sputum supernatants was inhibited by stoichiometric amounts of depelestat, allowing titration of the protease. But the percentage of inhibition in whole sputum homogenates varied from 50 to 100%. Depelestat could reduce neutrophil trans-epithelial migration and reduce activity released from neutrophils and NE-induced cytokine expression in airway epithelial cells. NE inhibition could be useful in managing neutrophilic airway inflammation in cystic fibrosis.

Tyloxapol is a nonionic liquid polymer of the alkyl aryl polyether alcohol type that is used as a surfactant to aid liquefaction and removal of mucopurulent (containing mucus and pus) bronchopulmonary secretions. Tyloxapol is also used as a detergent, dispersing agent, encapsulating agent and a hydroxy radical scavenger. Tyloxapol has been used as a mucolytic agent for over 50 years and has proven to be well tolerated during this time. Tyloxapol influences the respiratory system by the following four different action mechanisms: secretolytic action, reduction of surface tension, dissolution of coatings and down-regulation of inflammation. Several studies have shown that small quantities of Tyloxapol applied as an aerosol liquefy sputum. The viscosity of sputum is reduced by 10% to 20% according to rotational viscosimetry measurements. Tyloxapol also penetrates the mucous wall and dissolves viscous and dried secretions, thus enabling increased ciliary activity in the respiratory tract. Although the mechanism of Tyloxapol has been well described, and there is a long-standing basis for its clinical usefulness, there are almost no randomized, double-blind, placebo-controlled trials available that demonstrate the superiority of Tyloxapol vs. saline. Side-effects in the form of hypersensitivity reactions have only occurred very rarely.

Fusidic acid is a anti-bacterial agent, initially isolated from Fusidium coccineum by Godtfredsen et al (Leo Pharma) in 1960. It is discussed that fusidic acid exerts its anti-microbial effect by inhibiting bacterial elongation factor G, thus suppressing the protein synthesis. Fusidic acid is widely used in Europe under the names Fucidin H(fusidic acid / hydrocortisone acetate), Fucidin (fusidic acid / sodium fusidate) and Fucicort (fusidic acid / betamethasone valerate) for the treatment of primary/secondary skin infections and inflammatory dermatoses.