A Novel Pre-Clinical Strategy to Deliver Antimicrobial Doses of Inhaled Nitric Oxide

Background: Effective treatment of respiratory infections continues to be a major challenge. In high doses (³160 ppm), inhaled Nitric Oxide (iNO) has been shown to act as a broad-spectrum antimicrobial agent in preliminary studies. However, the safety of prolonged in vivo implementation of high-dose iNO therapy has not been studied. Herein we aim to explore the feasibility and safety of delivering continuous high-dose iNO over an extended period of time using an in vivo animal model. Methods: Yorkshire pigs were randomized to one of the following two groups: group 1, standard ventilation; and group 2, standard ventilation + continuous iNO 160 ppm + methylene blue (MB) as intravenous bolus, whenever required, to maintain metHb <6%. Both groups were ventilated continuously for 6 hours, then the animals were weaned from sedation, mechanical ventilation and followed for 3 days. During treatment, and on the third post-operative day, physiologic assessments were performed to monitor lung function and other significative markers were assessed for potential pulmonary or systemic injury. Findings: No significant change in lung function, or inflammatory markers were observed during the study period. Both gas exchange function, lung tissue cytokine analysis and histology was similar between treated and control animals. During treatment, levels of metHb were maintained <6% by administration of MB, and NO2 remained <5 ppm. Additionally, considering extrapulmonary effects, no significant changes were observed in biochemistry markers. Interpretation: Our findings showed that high-dose iNO delivered continuously over 6 hours with adjuvant MB is clinically feasible and safe. These findings support the development of investigations of continuous high-dose iNO treatment of respiratory tract infections, including SARS-CoV-2. Funding: The Toronto General Hospital Foundation supported this work. Declaration of Interest MC and SK are founders of Traferox Inc. MC and SK are consultants for Lung Bioengineering. All the other authors have no conflict of interest to report. Ethical Approval: Animal care and experimental protocol were approved by the Toronto General Hospital Research Institute Animal Care Committee. All animals received humane care in compliance with the Principles of Laboratory Animal Care formulated by the National Society for Medical Research and the Guidelines for the Care and Use of Laboratory Animals prepared by the Institute of Laboratory Animal Resources. This project was performed and reported according to the ARRIVE guidelines 2.0.