Gene Editing Saves Infant’s Life

In a remarkable milestone for genetic medicine, a desperately ill infant has not only survived but begun to thrive thanks to a pioneering, tailor-made gene editing therapy. The case, published this week in the New England Journal of Medicine, could mark the beginning of a new era where ultra-personalized gene therapies tackle rare and previously untreatable genetic diseases.

The baby, KJ Muldoon (Pictured – Photo: Chloe Dawson/CHOP) from Pennsylvania, was born with a rare metabolic disorder called CPS1 deficiency, a condition so severe that half of the infants diagnosed with it don’t survive. The disease impairs the body’s ability to remove toxic ammonia from the blood, typically leaving liver transplants as the only long-term option. Faced with grim odds, KJ’s parents chose an experimental therapy that had never before been tried in a human with his condition.

In just six months, a research team from Children’s Hospital of Philadelphia (CHOP) and Penn Medicine engineered a bespoke gene editing treatment using CRISPR technology — but with a next-generation twist. Instead of cutting DNA strands, the scientists deployed a technique called base editing, which precisely swaps out a faulty genetic “letter” for the correct one, dramatically reducing the risk of unintended mutations elsewhere in the genome.

In February, KJ received his first infusion of the gene therapy via tiny fatty droplets known as lipid nanoparticles, designed to deliver the editing tools directly to liver cells. The procedure, groundbreaking in itself, passed almost uneventfully for the infant, who reportedly slept through it.

Around 350 Million People Worldwide Live with Rare Diseases

Since then, follow-up doses and careful monitoring have shown extraordinary promise. KJ, now 9½ months old, is eating better, recovering from illnesses more easily, and taking fewer medications. For his parents, even simple milestones — like a wave or a roll — are cause for celebration.

“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 co-author of the study and a University of Pennsylvania gene editing specialist.

While still early days, the implications are massive. Around 350 million people worldwide live with rare diseases, most of which are genetic. Historically, gene therapies have targeted more prevalent conditions to justify development costs, leaving those with ultra-rare disorders with limited or no options. The successful creation and application of a custom treatment like KJ’s — reportedly at a cost comparable to a standard liver transplant — hints that these economics may be shifting.

Experts believe advances in CRISPR base editing and lipid nanoparticle delivery will drive down costs and accelerate timelines, setting the stage for similar therapies targeting other rare conditions.

“This really sets the pace and the benchmark for such approaches,” noted Senthil Bhoopalan, a gene therapy researcher at St. Jude Children’s Research Hospital.