Inclusion Criteria:  Documented GSD1a with confirmation by genetic testing Documented history of ≥1 hypoglycemic event with blood glucose <60 milligrams/deciliter (mg/dL) (<3.3 millimoles/liter [mmol/L]) and symptoms of hypoglycemia in the absence of acute illness, with at least one such event in the 4 weeks before signing the Informed Consent.  Exclusion Criteria:  Liver transplant, including hepatocyte cell therapy/transplant Received gene therapy for GSD1a Presence of liver adenoma >5 centimeters (cm) in size Presence of liver adenoma with growth of >2 cm or >5 newly diagnosed liver adenoma, in the previous 2 years.  Note: Additional inclusion/exclusion criteria may apply, per protocol.