SUMMARY/ABSTRACT In severe persistent hyperinsulinism (HI), repeated hypoglycemic episodes can ultimately lead to permanent seizure disorders, learning disabilities, cerebral palsy, blindness and even death. Clinical studies have demonstrated the effectiveness of both short-term and long-term treatment with glucagon for severe forms of HI and continuous subcutaneous administration of glucagon has been recommended both because of the potential improvement in patient outcome and high costs of surgical intervention followed by long-term annual care costs. However, the instability of native glucagon renders it inappropriate for chronic use in HI, and care-giver concerns about pump and infusion-tube blockage for stable glucagon analogs creates both administration problems and potential complications. In our redirected Phase II grant, we successfully discovered long-acting solution stable glucagon analogs suitable for treating HI, which would eliminate these concerns. In this Phase IIb project, we aim to further validate these lead analogs in HI mouse models, perform large scale (gram level) GLP production of the lead candidates to support the necessary toxicology, immunogenicity and formulation studies for an IND application. We also intend to pursue Orphan Drug Designation (ODD) and Rare Pediatric Disease Designation (RPDD) prior to IND submission.