A Study of the Pharmacokinetics and Deposition of Inhaled Salbutamol in Patients With Idiopathic Pulmonary Fibrosis (TOPICAL-IPF)

Idiopathic pulmonary fibrosis is a relentlessly progressive disease that is responsible for the deaths of over 5000 people in the UK each year. At present, despite a dramatic increase in clinical trials in the last decade, there are no licensed treatments for IPF. The pathogenesis of the condition remains incompletely understood, nonetheless there is good evidence to suggests that the condition arises as the consequence of an aberrant wound healing response in genetically susceptible individuals. Basic science research into IPF has identified a wide range of potential treatment targets. However, in many cases developing compounds to act against these targets, because of their role in normal wound healing, is limited by the possibility of major systemic side effects.

The lung is highly amenable to topical therapy in the form of inhaled drug preparations and this route is utilised in the treatment of the majority of respiratory disease. The inhaled route offers a number of important potential advantages for administration of therapy to patients with IPF. Firstly, by limiting systemic exposure to drugs, the inhaled route offers the potential for achieving higher lung doses of drugs that might otherwise cause systemic toxicity. Secondly, inhaled treatment may more effectively reach the areas of abnormality in IPF, namely the hyperplastic epithelium and the underlying fibroblastic foci. Thirdly, the inhaled route offers an alternative to parenteral administration of compounds that are poorly absorbed through the gastro-intestinal tract e.g. monoclonal antibodies. It should be noted however, that the fibrosis in IPF develops peripherally involving the alveolar interstitium and the terminal bronchioles. Furthermore, the disease causes architectural destruction and distortion of the lung that is liable to alter the normal laminar flow of air (and inhaled particles) through the bronchial tree. It is therefore, by no means certain that it is possible to deliver inhaled therapies directly to regions of fibrosis in IPF.

The feasibility of delivering inhaled drugs in IPF has not been previously studied. This research by assessing the effect of particle size on inhaled particle deposition and by relating to this the pharmacokinetic profile of salbutamol aims to validate the potential of the inhaled route in IPF. This study is an important precursor to the development of specific topical therapies for patients with IPF.