Summary

Research in pulmonary drug delivery has focused mainly on new particle or device technologies to improve the aerosol generation and pulmonary deposition of inhaled drugs. Although substantial progress has been made in this respect, no significant advances have been made that would lead pulmonary drug delivery beyond the treatment of some respiratory diseases. One main reason for this stagnation is the still very scarce knowledge about the fate of inhaled drug or carrier particles after deposition in the lungs. Improvement of the aerosol component alone is no longer sufficient for therapeutic success of inhalation drugs; a paradigm shift is needed, with an increased focus on the pulmonary barriers to drug delivery. In this Review, we discuss some pathophysiological disorders that could benefit from better control of the processes after aerosol deposition, and pharmaceutical approaches to achieve improved absorption across the alveolar epithelium, prolonged pulmonary clearance, and targeted delivery to specific cells or tissues.

Since the introduction of the first metered dose inhalers to the market in 1956,88 pulmonary drug delivery has made substantial progress, even leading to the first introduction of an inhalation form of insulin (Exubera) to the market. However, since the withdrawal of Exubera from the market in 2007, the field of advanced pulmonary drug delivery, other than delivery of anti-asthma and bronchodilating drugs, has stagnated. Until now the main focus of research and development efforts has been on generation of better aerosols by engineering more sophisticated particles or devices. However, optimised aerosol deposition is a necessary, but not sufficient component of pulmonary drug delivery. To overcome the biopharmaceutical challenges associated with absorption across the alveolar epithelium, control of particle clearance and targeting of specific regions or cells within the lungs requires a thorough understanding of the processes occurring at the cellular and non-cellular elements of the air—blood—barrier after aerosol drug deposition.

To achieve these goals, advanced in-vitro models, preferentially based on human cells and tissues, will be important. Furthermore, nanotechnology might contribute to the development of aerosol drug carriers, and might be necessary for the success of pulmonary drug delivery in the future.

Source: Lancet