Base-edited baby
Baby KJ was the first to receive a bespoke gene-editing treatment. Personalized drugs for others could be approved within the next few years.
Kyle “KJ” Muldoon Jr. was born with a rare genetic disorder that left his body unable to remove toxic ammonia from his blood. He was lethargic and at risk of developing neurological disorders. The condition can be fatal.
KJ joined a waiting list for a liver transplant. Then Rebecca Ahrens-Nicklas and Kiran Musunuru at the University of Pennsylvania offered his parents an alternative. The pair were developing potential gene-editing therapies for diseases like KJ’s. His parents signed him up.
The team set to work developing a tailored treatment using base editing—a form of CRISPR that can correct genetic “misspellings” by changing single bases, the basic units of DNA. They tested it in human cells, mice, and monkeys, and KJ received an initial low dose when he was seven months old. He later received two higher doses. Today, KJ is doing well. At an event in October, his happy parents described how he was meeting all his developmental milestones.
Others have received gene-editing therapies intended to treat conditions including sickle cell disease and a predisposition to high cholesterol. But KJ was the first to receive a personalized treatment—one that was designed just for him and will probably never be used again.
The expense was similar to that of a liver transplant, which costs around $1 million, says Musunuru, but he thinks that will come down to a few hundred thousand dollars per treatment within the next few years.
KJ’s doctors will monitor him for years, and they can’t yet say how effective this gene-editing approach is. But they plan to launch a clinical trial to test such personalized treatments in children with similar disorders caused by “misspelled” genes that can be targeted with base editing.
They’re hopeful that approval by the US Food and Drug Administration will soon follow. Musunuru says the FDA has agreed on a trial protocol that could involve as few as five patients with at least three genetic variants. In November, FDA administrators described in the New England Journal of Medicine how the agency might approve personalized therapies like KJ’s using a new pathway.
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