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Baby who was world's 1st-ever CRISPR gene editing therapy patient released from hospital

The world's first patient to be treated with personalized gene editing therapy is finally headed home after over 300 days in the hospital.

Nine-month-old KJ Muldoon recently underwent  by a team at Children's Hospital of Philadelphia and Penn Medicine in a historical medical breakthrough. 

The landmark study published in The New England Journal of Medicine showcases the power of customized gene editing therapy to treat patients with rare metabolic disease. 

Muldoon was the first patient to be treated with a gene editing technology customized for his rare disease.

On Tuesday, nurses and doctors held a "clap out" at CHOP, with staffers lining the hallway as baby KJ was led out.

Baby KJ Muldoon, 1st to be treated with personalized gene therapy, released from hospital 00:45

Prior treatement, KJ was dealing with ammonia building up in his system.

"In patients who have urea cycle disorders, they can't break down protein, and unfortunately, what happens is , and ammonia can be toxic to the brain and cause permanent neurologic damage," Dr. Rebecca Ahrens-Nicklas, of CHOP, said.

Quick action was needed for KJ, and his parents, Nicole and Kyle Muldoon, had to process a lot fast.

"Our child is sick," Kyle Muldoon, of Delaware County, said. "We either have to get a liver transplant or give him this medicine that's never been given to anybody before, right? I mean, what an impossible decision to make."

With the team at CHOP and Penn, they decided to try the gene therapy called CRISPR animation DNA, which edits out the original, defective DNA and replaces it with the altered, repaired sequence.

"CRISPR, a gene editor, enters the nucleus of the cell. And in this case, we programmed it to go to the site of the genetic variant that is actually causing the disease in KJ," University of Pennsylvania Dr. Kiran Musunuru said. 

KJ Muldoon received the first infusion in February and has follow-up doses in March and April – and it worked.

"This could revolutionize the way we treat rare disorders for patients who have limited or no other options," Ahrens-Nicklas said.

Doctors said KJ's condition has improved significantly.

"I just knew he was ready, like he was ready to fight," Kyle Muldoon said. 

"He's proven to us time and time again how stubborn and spunky he really is," Nicole Muldoon said.

The CRISPR gene editing therapy has been used for other diseases like sickle cell, but this is the first time it's been customized for one patient.

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