The remarkable timeline of a custom gene-editing therapy to save a newborn
Ars Technica 2025-05-16
News broke yesterday that researchers in Philadelphia appear to have successfully treated a 6-month-old baby boy, called KJ, with a personalized CRISPR gene-editing therapy. The treatment corrects an ultra-rare mutation in KJ that breaks a liver enzyme. That enzyme is required to convert ammonia, a byproduct of metabolism, to urea, a waste product released in urine. Without treatment, ammonia would build up to dangerous levels in KJ—and he would have a 50 percent chance of dying in infancy.
While the gene-editing treatment isn't a complete cure, and long-term success is still uncertain, KJ's condition has improved and stabilized. And the treatment's positive results appear to be a first for personalizing gene editing.
Now, who doesn't love a good story about a seemingly miraculous medical treatment saving a cute, chubby-cheeked baby? But, this story delivers more than an adorable bundle of joy; the big triumph is the striking timeline of the treatment's development—and the fact that it provides a template for how to treat other babies with ultra-rare mutations.