PROJECT SUMMARY: Acute Respiratory Distress Syndrome (ARDS) is a devastating syndrome that afflicts more than 300,000 patients in United States alone and has an unacceptably high mortality rate of 35-40%. Currently there are no therapies that address the loss of lung vascular barrier integrity, vascular leakage and alveolar flooding that are critical features of ARDS pathobiology. The PI was the first to demonstrate that sphingosine 1-phosphate (S1P), a multifunctional lipid mediator, is an effective therapy for reducing vascular leakage in inflammatory lung injury via ligation of S1P receptor 1 (S1P1), a G-protein-coupled S1P receptor highly expressed in lung vascular endothelial cells (ECs). We demonstrated that S1P1 receptor ligation by S1P or a long-acting phosphonated S1P analogue, TySIPonate, rapidly stimulates a signaling cascade that reorganizes the lung EC cytoskeleton, enhances junctional integrity and decreases lung vascular permeability. Intravenous administration of S1P or TySIPonate reduces murine and canine lung vascular hyper-permeability evoked by ventilator-induced lung injury (VILI), bacterial endotoxin (LPS), ischemia/reperfusion, radiation, or traumatic brain death with marked improvement alveolar edema formation. In addition, this STTR team of investigators have demonstrated that lung vascular permeability in ARDS is directly related to excessive generation of reactive oxygen species (ROS). ROS are key contributors to lung inflammation and injury with a key role for the ROS-generating enzyme, NADPH oxidase (Nox4), a critical mediator of inflammatory lung injury in preclinical models of VILI and ARDS. The goal of this STTR Phase I application is to formulate the ?ReStore Liposome?, an ACE antibody-conjugated liposome that encargoes the combination of TySIPonate and a novel Nox4 small molecule inhibitor (Nox4-smi) (Specific Aim #1). Specific Aim #2 will evaluate in vitro effects of the ReStore Liposome on vascular permeability and ROS generation and Specific Aim #3 will evaluate in vivo effects of the ReStore Liposome in murine preclinical models of ARDS/VILI models of lung injury as a prelude to use as a therapeutic intervention to reduce the morbidity and mortality of ARDS in humans. As there is an acute unmet need for novel therapies against ARDS, the academic (University of Arizona)-private biotech partnership (Restore Therapeutics, LLC) will leverage unparalleled expertise in drug delivery, inflammatory lung injury and ROS biochemistry to reduce both lung vascular permeability and ROS burden to effectively attenuate preclinical and human ARDS pathobiology.