Engineered levothyroxine dry powder for inhalation to treat idiopathic pulmonary fibrosis

Interest in drug repurposing has increased significantly in recent decades owing to its potential to accelerate the development of new medicinal products, provide new therapeutic options for patients, and generate business opportunities for pharmaceutical companies. Idiopathic pulmonary fibrosis (IPF) is defined as a chronic disease that causes an irreversible loss of lung function and premature death. Recent studies have highlighted the key role of mitochondria in lung homeostasis and the ability of thyroid hormones to promote mitochondrial activity, suggesting their potential involvment in IPF pathogenesis. In this work, we translate the findings derived from the above-mentioned researches into a dry powder drug delivery system intended to target epithelial lung cells with levothyroxine. To this end we developed nano-embedded respirable microparticles by spray drying a nanosuspension composed of levothyroxine and a hydrophilic polymer. The powder was characterized in terms of physico-chemical, toxicological and aerodynamic performance, as well as for its ability to be internalized by A549 cells and modulate their metabolic activity. The nano-embedded microparticulate drug delivery system proved to be potentially able not only to reach the deep lung but also to promote levothyroxine internalisation and mitochondria activation.