This study is a randomized, double-blind, placebo-controlled study that will evaluate the safety and efficacy of dasiglucagon in children between the ages of 7 days and 12 months who have congenital hyperinsulinism. Dasiglucagon will be given as a subcutaneous infusion while patients are admitted to the hospital. Other treatments for hyperinsulinism may be changed as allowed while maintaining safe blood sugar levels. For the second part of the study, patients may be able to go home on the medication.

Our team at the Congenital Hyperinsulinism Center at CHOP is working on a research study to determine whether an experimental gene therapy product, DTX401, is safe and effective in people with glycogen storage disease type Ia (GSDIa). The FDA has not approved this drug for the treatment of GSDIa but has approved us to use this drug as part of this clinical trial. The purpose of this research study is to see if DTX401 can help people with GSDIa have normal blood sugar levels and fewer episodes of hypoglycemia. DTX041 works by delivering copies of the G6PC gene to your liver through a one-time infusion. Participation in this study will last for 2 years and will involve 30 study visits. It is possible that treatment with the study drug infusion may improve your blood sugar levels. Travel costs will be covered by the study and you will receive compensation for participating.

This clinical trial is for patients with congenital hyperinsulinism (HI) who are experiencing low blood sugar on their current treatment. The purpose of this study is to find out if the study drug, named RZ358, helps improve blood sugar levels compared to current HI treatments. RZ358 is an experimental drug which the FDA has approved for use in this clinical trial, but it has not approved the study drug to be given outside of clinical research testing. The study drug is a specialized protein (called a monoclonal antibody) meant to decrease the effect insulin has on lowering blood sugar.

Participation will last for up to 33 weeks or up to 3 years overall for subjects who would like to join the open-label extension phase. This includes a 5-week Screening Period, a Treatment Period that lasts 24 weeks, and then either an 8-week Follow-up Period or a 2-year Extension Period where participants can continue to receive the study drug. Individuals do not need to participate in the 2-year extension part of the study to take part in the treatment and monitoring period. During the treatment period, participants will be given the study drug or a placebo. A placebo is an inactive substance used to compare how well the study drug works. Only study drug and not placebo is given during the extension period.

Participants in this trial will:

• Receive the study drug or a placebo 7 times during the treatment period
• Receive the study drug for up to 2 years in the optional extension period
• Have electrocardiograms (ECGs)
• Have ultrasounds of their liver
• Wear a continuous glucose monitor (CGM) and take fingerstick glucose checks
• Have research blood tests
• Complete study diaries and surveys

The main risks of this study are from the study drug. These include infusion reactions (redness, tenderness, irritation at the infusion site), headaches, dizziness, hypoglycemia (low blood sugar), upper respiratory infections (colds), and excess body hair growth. Participants may benefit if the study drug proves to be more effective than current HI medications.