Soft steroids

Improved topical selectivity for airways and lung may be achieved if inhale d corticosteroids (ICS) were inactivated during their systemic distribution (and not just in the liver as with current ICS). Several projects have bee n evaluated based upon steroids inactivated by esterases. Compounds hydroly zed by ubiquitous, nonselective esterases have failed (fluocortin butyleste r, itrocinonide), probably due to too rapid inactivation in the target tiss ue. A new approach has been attempted based upon paraoxonase-catalyzed brea kdown selectivity in plasma. This may better answer the question, whether s oft steroids can reach the same efficacy as current ICS in the absence of s ystemic activity.