Drug delivery for traditional and emerging airway models

Respiratory diseases such as asthma and COPD have no cures and few new treatments. These diseases have an immutable mortality rate and impact millions of individuals worldwide. Respiratory drug development is time-consuming and costly, owing to the inability of existing models to replicate the complexity of human disease (static cell cultures and animal models). The problem is intensified through the way in which drugs are delivered to these models, which is not always representative of the human microenvironment, where different drug delivery methods (impaction, sedimentation and diffusion) target different regions of the lungs. This review describes current models of the human airways together with the range of different aerosol drug delivery methods (commercially available and in development) alongside emerging Organ on Chip technologies.