SUMMARY We propose to develop a novel miRNA-based therapeutic to treat acute lung injury in a bacterial pneumonia model. Bacterial pneumonia is a leading cause of serious and lethal infections in children and the elderly worldwide. Even with antibiotic intervention, many patients still rapidly progress to acute respiratory distress syndrome (ARDS) requiring hospitalization, intensive care, and mechanical ventilation. Mortality rate in ARDS patients is high, with many survivors still facing a long road to recovery from various long-term complications of lung dysfunction. Recovery from ARDS is critically dependent on regeneration of the damaged airway epithelial cells, and failure to repair epithelial damage impairs lung function and leaves airways vulnerable to recurrent infection and airway inflammation. There are currently no FDA approved therapies to stimulate regrowth of lung tissue to repair lung injury, which would provide great benefits to pneumonia/ARDS patients. In our preliminary studies using a mouse model of pneumonia caused by Streptococcus pneumoniae (Sp), we observed acute lung injury with substantial destruction of airway epithelial cells (AECs) and extensive damage to the distal airway of the parenchyma, similar to pathology described in human patients with ARDS. We discovered that Sp-infection induces lung expression in the lung of a specific family of miRNA that plays a critical role in the generation of respiratory epithelia during embryogenesis. To test the role of this miRNA in repairing lung injury, we treated Sp-infected mice with liposomes loaded with “miRNA-mimic”, a double- stranded RNA molecule intended to mimic and augment the function of endogenous miRNA in vivo. We found that administration of miRNA-mimic to Sp-infected mice promoted airway epithelial regeneration, resulting in improved lung function, enhanced host recovery and survival. To translate these findings into clinical application, we propose to further improve this technology with targeted delivery of miRNA-mimic to inflamed lungs, to increase efficacy, minimize off-target effects, and reduce potential drug toxicity. To this end, we will develop alveolar-targeted liposomes (ATLs) loaded with miRNA-mimic and assess lung accumulation and therapeutic efficacy after intravenous administration compared to the non-targeted counterparts. We will also evaluate pharmacokinetics/bio-distribution/pharmacodynamics and safety profiles in Sp-infected mice and ex vivo human lung. The results of this phase I STTR project will set the stage for future studies to develop a first- in-class drug of regenerative medicine for treating pneumonia/ARDS.

Narrative Acute respiratory distress syndrome (ARDS) is a rapidly progressing lung disease with a very high mortality rate. Many patients who recover from ARDS will still experience various long-term complications of lung dysfunction, such as shortness of breath. The single most frequent cause of ARDS is pulmonary infections including bacterial here are relatively few treatments available for ARDS, with supportive care via mechanical ventilation as the mainstay of management. In this study, we will develop a novel miRNA-based therapeutic that will stimulate regeneration of lung cells and enhance repair of lung injury for treatment of ARDS induced by pneumonia. and viral pneumonia. ARDS has been the most serious complication in COVID-19 patients. Currently, t