Hemoglobin-based antidotes for the treatment of carbon monoxide poisoning

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Project Summary/Abstract Carbon monoxide (CO) poisoning remains a major cause of death and disability, affecting 50,000 persons a year in the U.S. alone. Victims removed from fires or rescued after exposure to car or home generator exhaust only have two options: 100% oxygen or transfer via ambulance or medical evacuation helicopter to a specialized facility with emergency hyperbaric oxygen chamber. As there are approximately only 300 hyperbaric oxygen centers available for CO poisoned patients, inherent delays in access to and initiation of therapy greatly limit efficacy. In fact, even with hyberbaric oxygen therapy, 1-2% of patients die and >25% of surviving patients exhibit long-term neurocognitive impairments. There is no point-of-care antidote for CO poisoning currently available. In the present proposal, Globin Solutions, Inc. will seek to complete preclinical development of a novel antidotal therapy for CO poisoning based on the use of high CO affinity derivatives of human hemoglobin, including stripped hemoglobin (S-Hb) and NEM-modified hemoglobin (NEM-Hb). On-going work funded by the NIH at the University of Pittsburgh demonstrates that extremely high affinity heme-based molecules can sequester CO from red blood cells and tissue mitochondria to reverse the systemic hypoxia of CO poisoning. We discovered a near-irreversible CO-binding affinity of mutationally engineered human neuroglobin (Ngb). This molecule includes four point mutations (Ngb-H64Q-CCC) allowing for high concentration and intravenous infusion. Ngb-H64Q-CCC binds CO ≈ 500 times more strongly than Hb. Infusions of Ngb-H64Q-CCC in CO- poisoned mice enhanced CO removal from red blood cells in vivo from 25-minutes to 25-seconds, reversed hypotension, increased survival from less than 10% to over 85%, and were followed by rapid renal elimination of CO-bound Ngb-H64Q-CCC. These findings provide proof of concept, that heme-based scavenger molecules with very high CO binding affinity can be developed as potential antidotes for CO poisoning. In further work, high CO affinity derivatives of human hemoglobin, including stripped hemoglobin (S-Hb) and NEM-modified hemoglobin (NEM-Hb) could be used for the treatment of CO poisoning. These molecules can be produced from expired blood units at a low cost. Here we propose experiments to determine efficacy and safety of S-Hb and NEM-Hb in the treatment of CO poisoning in our mouse models. The best performing molecule will be further developed into a full IND enabling preclinical program: determine pharmacokinetics and safety profiles in mouse and non-human primates; certified Good Manufacturing Procedure production at scale; and validating quality and reproducibility assays. Globin Solutions, Inc. will leverage a recent Series A funding round to cost-share the project expenses proposed in this grant for an IND application to the US FDA and to enable first in human trials. Overall, these proposed studies are in keeping with the mission of the NHLBI and NIH to advance highly impactful, significant, and novel studies that have great potential to improve the public health. Support for these proposed studies has the potential to change our current paradigm for the management of CO poisoning patients.