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Kyle: He was a beautiful little boy, you know.
Nicole: Little preemie.
Kyle: He was born on Thursday. One of the doctors came to us and said, your son is very sick, but the best place in the world for your child to be when he is very sick is at Children's Hospital of Philadelphia.
Nicole: Do you Google CPS1 deficiency and it's either fatality rate or liver transplant.
Rebecca Ahrens Nicklas, MD, PhD: In these really severe metabolic diseases of infancy, we know that we have to act quickly if we're gonna make a difference in the lives of these babies.
Kiran Musunuru, MD, PhD: The clock is ticking. The sooner we, can figure out a solution as to how to fix that genetic issue, the sooner we would be able to potentially make a therapy.
Rebecca Ahrens Nicklas, MD, PhD: KJ received the first infusion of his therapy on February 25th, 2025.
Kiran Musunuru, MD, PhD: This is the first time a patient has received a personalized gene editing therapy.
Rebecca Ahrens Nicklas, MD, PhD: What we saw in the first 10 days, we really could give him a lot more protein.
Kiran Musunuru, MD, PhD: Which ordinarily would be a problem and should cause the ammonia, the glutamine to go up and they didn't go up.
Rebecca Ahrens Nicklas, MD, PhD: He's had quite a nice little growth spurt and so the fact that we've been able to give him more of that protein that he needs, I like to think has really helped him grow some nice chubby cheeks.
I have so many patients with huge unmet need, but I really hope that 10 years from, now targeted personalized therapies are available for most of my patients. That would be the dream.
Nicole: We're working in the labs. We're traveling to DC to meet with government officials. We're working with scientists from around the world. We're doing whatever it takes to make sure more children have this life-changing option.
Personalized Medicine
KJ was born with a rare urea cycle disorder. Doctors at CHOP and the University of Pennsylvania swiftly worked to create a one-of-a-kind gene editing therapy customized to treat his specific gene variant. His breakthrough story captured hearts around the world.
A devastating diagnosis
At 2 days old, KJ was getting sicker by the hour. After a battery of rapid genomic tests, CHOP diagnosed him with CPS1 deficiency, a rare disorder that would be fatal without treatment.
A quest for answers
While KJ’s medical team handled his day-to-day care, scientists from CHOP and Penn explored how to use gene editing to create customized treatments for diseases like CPS1 deficiency.
Unlocking a potential solution
As KJ was placed on the transplant list, doctors asked his family to participate in a research study. They hoped to tailor-make a drug for KJ in time to save his life.
A historic medical breakthrough
On Feb. 25, 2025, when KJ was 7 months old, he became the first patient in the world to receive a personalized gene editing drug. Within days, KJ showed improvement.
The result we hoped for
On June 3, 2025 – after more than 300 days in the hospital – 10-month-old KJ finally went home. Since then, he has thrived. He continues to be monitored at CHOP.
Relentless pursuit of the next frontier
The successful design and clinical use of a personalized gene editor demonstrate a potential new pathway for treating rare diseases – offering hope to millions of families worldwide.
Make more breakthroughs possible
When you give to CHOP, you fuel breakthrough discoveries, propel new treatments, and transform the lives of patients in our care and around the world.