First Personalized CRISPR Gene Editing Therapy Patient Baby KJ Discharged

On Tuesday, 307 days after he was first admitted to Children’s Hospital of Philadelphia (CHOP), KJ Muldoon went home after being successfully treated with the first personalized CRISPR gene editing therapy . KJ, who has a serious and rare genetic condition called severe carbamoyl phosphate synthetase 1 (CPS1), received two doses of a base editor bound to a bespoke targeting guide sequence using lipid nanoparticles (LNPs) when he was 7 and 8 months old. Around two months after the second infusion, KJ was discharged with his parents, Nicole and Kyle, accompanied by a police escort.

KJ’s case was brought to the world’s attention on May 15, 2025, when Kiran Musunuru, MD, PhD, presented it in a plenary session at the American Society for Gene and Cell Therapy (ASGCT) in New Orleans. Th