Project Summary/Abstract The aging of the population in industrialized nations is increasing the number of ischemic strokes that present in the emergency rooms of hospitals. In the ischemic stroke neurons die rapidly (estimated at 1 million neurons per minute) prompting the need for rapid triage and treatment to open the blocked blood vessel. We have previously established that the exact rate at which neurons die and size of the infarction grows is highly variable among patients and depends strongly on the degree of leptomeningeal arterial collateralization. The goal of this proposal is to test a new biopharmaceutical agent (Sanguinate®) that is designed to boost the collateralization in ischemic stroke as well as deliver and release oxygen locally in tissue with low oxygen tension. We believe that this approach will reduce infarct volume in all strokes and reduce reperfusion injury in those successfully recanalized by during interventional procedures. Sanguinate® is an investigational bio-pharmaceutical blood substitute that facilitates the transfer of oxygen to oxygen-deprived cells and tissues. Sanguinate’s unique oxygen-delivery system has the potential to treat hypoxia/ischemia. Sanguinate® is purified bovine hemoglobin that has been pegylated and combined with carbon monoxide to suppress vasoconstriction and provide anti-inflammatory effects. The bovine hemoglobin then carries oxygen for targeted release to areas with a low partial pressure of oxygen (ischemic tissue). It has been shown to successfully address detrimental vasoconstrictive side effects associated with older generation artificial blood products, but the effect on tissue perfusion, infarct volumes, infarct growth and tissue hypoxia and have not been directly measured. The rationale for this work is that brain infarcts grow rapidly if a blood vessel feeding the brain is blocked and even with the most efficient triage and shortest door-to-needle time, millions of neurons will die. There is an unmet need for an easy, safe i.v. infusion that can stop to growth of an infract and unlike thrombolytic agents, be safely administered to all patients as soon as symptoms arise. We will establish the effectiveness of a new pharmaceutical that can be easily deployed in emergency rooms, ambulances and satellite hospitals prior to transfer to a stroke center comparing doses and time-to-treatment effect with serial imaging a biomarkers of brain damage and inflammation in a controlled model of ischemic stroke. Our findings will elucidate the mechanism of action of the agent and inform the design of future human clinical trials.