New asthma drugs: small molecule inhaled corticosteroids

Small-particle inhaled corticosteroid (ICS) metered-dose inhalers were recently developed to treat asthma as part of the CFC to HFA propellant switch mandated by the Montreal Protocol. Two such ICS, beclomethasone dipropionate (BDP) and ciclesonide (CIC), are available in the United States and are formulated in HFA solutions. A major advantage of small-particle ICS is that they have improved total lung deposition and consequently, effective asthma control is achieved at lower daily doses than the large-particle ICS. Another advantage of small-particle ICS is that they are able to reach the small airways and consequently, may result in increased efficacy. Indeed, recent studies have demonstrated the effect of small-particle ICS on asthmatic inflammation in the small airways. Another advantage of small-particle ICS is that they may have an improved safety profile. Small-particle inhalers generally deposit decreased amounts of drug in the oropharynx than their CFC counterparts possibly resulting in a lower incidence of oropharyngeal candidiasis. However, growth studies and most HPA studies do not support improved safety on the basis of particle size alone and some studies suggest even higher systemic bioavailability and safety risk with smaller particles, depending on the molecule and the formulation. Further efficacy and safety studies are clearly warranted to determine any potential advantages of small-particle ICS, particularly in long-term disease modification where large-particle ICS have failed, and in infants and pre-schoolers, in whom airway delivery is problematic with current formulations.