Proposal Summary/Abstract Acute respiratory distress syndrome (ARDS) is an acute inflammation of the lungs. It represents 10% of all intensive care unit (ICU) admissions in the United States. Despite decades of research and numerous large clinical trials, there are few treatments for ARDS. This lack of disease-specific therapies is primarily due to three main factors: First, ARDS patients are “fragile” due to frequent multi-system organ failure, and thus cannot tolerate drug side effects. Second, ARDS, is very heterogeneous in its underlying pathophysiology, and thus targeting a single pathway may not be sufficient. Third, the disease has a rapidly developing time course, meaning that it can activate pathways that actively change patient outcomes in the order of hours.To solve the above problems, the goal of this proposal is to develop and establish mRNA-loaded nanoparticles (mRNA- LNPs) that can be targeted to specific cell types and organs, whereupon they can express multiple therapeutic proteins as a platform technology for ARDS. Our lab has previously utilized three targeting moieties we use to deliver nanocarriers: monoclonal antibodies binding to PECAM (an endothelial cell surface protein), ICAM (another surface protein abundant on endothelial cells), and non-immune IgG (hereafter called “IgG”). We have further shown that nanocarriers covalently coated with anti-PECAM and -ICAM antibodies are directed to the lungs at levels 300-fold higher than “free drugs” (no carrier) addressing (problem #1), Further, mRNA-loaded nanoparticles can be loaded with mRNA that encodes for various proteins, targeting various pathways (problem #2). Additionally, mRNA-LNPs can express a variety of proteins for the length of time (~48 hours) associated with the high-risk period of acute critical illnesses (problem #3) above. It seemed that we developed a method to exclusively deliver therapeutics to the lung endothelium, as the standing theory was (without direct evidence) that lung uptake was due entirely to endothelial cells. However, in pilot experiments, my sponsor and I became aware that other cells reside in the pulmonary capillaries, marginated neutrophils. We found that while PECAM coated particles are primarily taken up by the endothelial cells, we interestingly, in a paradigm shift for the field of targted delivery to the lungs, found anti-ICAM targeted nanocarriers were taken up equally by endothelial cells and leukocytes. This leads to the two key objectives of this proposal: 1) we want to understand if with increases in leukocytes during ARDS, there will be a change in the cells that take up and express anti-CAM targeted mRNA-LNPs and 2) develop a novel class of therapeutics for ARDS. This will be done via 2 Specific Aims. Aim 1 will investigate the cell types that take up and express mRNA-LNPs both in human, with ex vivo human lungs, and mouse models of ARDS. Aim 2 will investigate the therapeutic potential of mRNA-LNPs by leveraging the Ang-Tie path...