Baby with rare genetic disease receives personalised gene therapy in world first
18 May 2025, 20:26
Nine-and-a-half-month-old baby boy is "growing and thriving" after receiving gene editing treatment in a world's first.
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Scientists took months to develop gene therapy for baby KJ Muldoon to treat his rare genetic disease.
KJ from Clifton Heights, Pennsylvania, was born with a rare metabolic condition, called carbamoyl phosphate synthetase 1 (CPS1) deficiency, resulting in the boy spending the first months of his life in hospital on a restrictive diet.
Infants who suffer from CPS1 lack an enzyme needed to help remove ammonia from the body, which can build up in their blood and become toxic.
"We prayed, we talked to people, we gathered information, and we eventually decided that this was the way we were going to go," said KJ's father Kyle Muldoon.
Gene therapy is a treatment designed to cure disease at the source.
The team behind KJ's treatment found the genetic mutation causing his disease, and used the treatment to flip a "letter" in the genetic code.
He has been able to eat normally and can now recover from illnesses like colds - which could strain his body and exacerbate symptoms.
He had the first dose of his treatment in February, followed by doses in March and April.
"We're still very much in the early stages of understanding what this medication may have done for KJ," said study author Dr Rebecca Ahrens-Nicklas, a gene therapy expert at the Children's Hospital of Philadelphia (CHOP), via Sky News.
"But every day, he's showing us signs that he's growing and thriving."
His mother Nicole Muldoon added, considering how ill KJ had been: "Any time we see even the smallest milestone that he's meeting - like a little wave or rolling over - that's a big moment for us."
The team leading the treatment was made up of experts from CHOP and the University of Pennsylvania. They published their working the New England Journal of Medicine.
The scientists used CRISPR, the gene editing tool that won the Nobel Prize in 2020.
"This is the first step towards the use of gene editing therapies to treat a wide variety of rare genetic disorders for which there are currently no definitive medical treatments," said Dr Kiran Musunuru, a University of Pennsylvania gene-editing expert who co-authored the study.
