Considering the dosing requirements of the two main organs involved in DGUOK deficiency (the liver and brain), it is clear that achieving efficacious targeting of both organs using a single neonatal IV dose of this AAV9 construct will be challenging, since 8 × 1014 vg/kg was unable to transduce the brain sufficiently and higher doses seem to be toxic. The gene discussed is DGUOK; the disease is hyperinsulinemic hypoglycemia, familial, 4.