RNA drugs are an emerging class of therapeutics that address diseases at the genomic and/or transcriptomic level. However, their widespread clinical translation is hampered by many extra-and intracellular barriers. Most importantly, RNAs are negatively charged macromolecules that cannot cross biological membranes, making delivery into diseased target cells challenging. To guide RNA molecules across these barriers, they are generally encapsulated into lipid nanoparticles (LNPs).
The lung is an attractive target organ for RNA delivery. Non-invasive pulmonary instillation of RNA requires lower RNA doses and can substantially reduce the risk of systemic side effects. Of note, pulmonary administration allows direct access to target cells, e.g. epithelial cells and alveolar macrophages. The prevalence of respiratory pathologies is surging and for many an unmet therapeutic need exists, underscoring the need for novel therapies. A variety of interesting therapeutic targets are identified for RNA-mediated therapeutic intervention in lung-related diseases. However, in spite of many advantages of RNA inhalation therapy, to date no innovative LNP-based RNA formulations are available for application in the lung. Moreover, given the transient nature of RNA drugs and the need for repeated administration, questions arise regarding the use of current LNP formulations for chronic treatment, highlighting the need for more biocompatible RNA formulations that merge efficient cellular delivery with acceptable toxicity.
Successful proof-of-concept was obtained that cytosolic delivery of RNA into lung-related target cells can be promoted by exploiting lung surfactant protein B as a naturally occurring RNA delivery enhancer. In the RESPIRNA project, I aim to repurpose this natural surfactant protein for intracellular RNA delivery, (1) through identification of SP-B mimicking peptides that can be chemically synthesized and can equally promote RNA delivery, (2) by exploring SP-B’s cellular mode-of-action towards improved cytosolic delivery of RNA, using state-of-the-art fluorescence microscopy and membrane perturbation assays, (3) by designing multifunctional and multicomponent SP-B (peptide) lipid nanoparticles (LNPs) via microfluidic mixing technology and (4) by applying these nanocarriers for RNA delivery in the lung, using models of eosinophilic asthma and cystic fibrosis.
