University of Pennsylvania and Children’s Hospital of Philadelphia reported meaningful clinical benefits from an mRNA-based CRISPR base-editing therapy delivered to “Baby KJ,” an infant with CPS1 deficiency. The case is described as expanded-access care rather than a formal trial, with lead investigators Kiran Musunuru and Rebecca Ahrens-Nicklas emphasizing that it was not positioned as curative evidence. The report notes that KJ achieved the ability to eat a normal protein-filled diet, with doctors aiming to potentially delay liver transplant until the child is older. Musunuru also urged a careful regulatory and scientific frame as other groups pursue base-editing programs. The episode matters because it reinforces what clinicians can do now with genome editing delivery—while also shaping how regulators and companies compare “clinical care” demonstrations to trial endpoints.