PROJECT SUMMARY/ABSTRACT The goal of the proposed project is to evaluate the potential of the gasotransmitter carbon monoxide (CO) as an agent to prevent Vaso-Occlusive Crises (VOCs) in Sickle Cell Disease (SCD) using a novel oral formulation of CO (HBI-002). Numerous studies, both in vitro and in vivo, demonstrate that CO has cytoprotective properties through anti-oxidant, anti-inflammatory and anti-apoptotic processes. Our SBIR Phase 1 supported research has produced efficacy data similar to that reported in four studies using four different transgenic sickle cell mouse models that the heme oxygenase-1/CO pathway is key in SCD, demonstrating that low doses of CO are a novel approach to limiting vascular stasis and down-regulating inflammatory processes. These studies provide compelling support for a potential beneficial role for CO in limiting the morbidity of SCD. The safety and tolerability of CO has been demonstrated in eight successfully completed Phase 1 and Phase 2 studies, including two Phase 1b studies in SCD patients, using a variety of forms of CO administration. Moreover, there are ten ongoing clinical studies with CO, using various forms of CO administration. The absence of toxicity of CO at low levels of carboxy-hemoglobin (COHb) has been well defined in the literature, providing supportive safety data for the targeted COHb levels being considered for SCD patients with HBI-002. HBI-002, a liquid formulation of CO, is being developed for the prevention of VOCs in SCD. The administration of a defined dose of CO delivered by oral administration of HBI-002 enables the further development of CO as a therapeutic while obviating the problems associated with previously studied inhaled or intravenously administered carrier-metal CO, including environmental safety, dosing and compliance with chronic administration (inhaled CO) and carrier molecule toxicity, stability, and bioavailability (carrier-metal bound CO). Pharmacokinetic and pharmacodynamic studies in rodents with orally administered HBI-002 have demonstrated proof-of-concept feasibility, tolerability, and bioavailability. The next step in development is to evaluate the mechanistic, preclinical toxicologic, and clinical safety, tolerability, pharmacokinetic, and pharmacodynamic profile of HBI-002 for further development in sickle cell disease.