A nine-and-a-half-month-old baby, KJ Muldoon, diagnosed with severe carbamoyl phosphate synthetase 1 (CPS1) deficiency, is thriving after receiving a bespoke gene therapy developed in just seven months, marking a world-first in treating his specific condition. Following treatment, KJ has improved his diet, recovered from illnesses, and requires fewer medications, with his parents witnessing significant developmental milestones. Researchers from the Children’s Hospital of Philadelphia and the University of Pennsylvania hope this breakthrough paves the way for similar treatments for other rare genetic disorders.