Overview

• Baby KJ, born with a rare enzyme deficiency causing ammonia buildup, received three doses of a customized gene therapy between February and April 2025.
• The treatment, using base editing to correct a single pathogenic nucleotide without cutting DNA, has shown no serious side effects so far.
• KJ is now thriving with improved protein tolerance and reduced medication needs, according to the Children’s Hospital of Philadelphia.
• Researchers have developed a rapid pipeline to design patient-specific therapies within days of diagnosis, but clinical routine use is still years away.
• The findings were presented in the New England Journal of Medicine and at the American Society of Gene & Cell Therapy annual meeting.