A baby born with a rare and dangerous genetic disease is growing and thriving after undergoing an experimental gene editing treatment made just for him. Researchers described the case in a new study, saying young KJ Muldoon is among the first to be successfully treated with a custom therapy that seeks to fix a tiny but critical error in his genetic code that kills half of affected infants, the AP reports. Although it may be a while before similar personalized treatments are available for others, doctors hope the technology can someday help the millions left behind even as genetic medicine has advanced because their conditions are so rare.
"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 University of Pennsylvania gene editing expert who co-authored the study published Thursday in the New England Journal of Medicine. KJ, of Clifton Heights, Pennsylvania, is one of 350 million people worldwide with rare diseases, most of which are genetic. He was diagnosed shortly after birth with severe CPS1 deficiency, estimated by some experts to affect around 1 in a million babies. Those infants lack an enzyme needed to help remove ammonia from the body, so it can build up in their blood and become toxic. A liver transplant is an option for some.
Knowing their son's odds, Kyle and Nicole Muldoon, both 34, worried they could lose him. "We were, like, you know, weighing all the options, asking all the questions for either the liver transplant, which is invasive, or something that's never been done before," Nicole Muldoon said. Within six months, the team at Children's Hospital of Philadelphia and Penn Medicine, along with their partners, created a therapy designed to correct KJ's faulty gene. They used CRISPR, the gene editing tool that won its inventors the Nobel Prize in 2020, per the AP. Instead of cutting the DNA strand like the first CRISPR approaches, doctors employed a technique that flips the mutated DNA "letter"—also known as a base—to the correct type. Known as "base editing," it reduces the risk of unintended genetic changes.
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It's exciting that the team created the therapy so quickly, said gene therapy researcher Senthil Bhoopalan at St. Jude Children's Research Hospital in Memphis, who wasn't involved in the study. "This really sets the pace and the benchmark for such approaches." In February, KJ got his first IV infusion with the gene editing therapy, delivered through tiny fatty droplets called lipid nanoparticles that are taken up by liver cells. While the room was abuzz with excitement that day, "he slept through the entire thing," recalled Dr. Rebecca Ahrens-Nicklas, a study author. After follow-up doses in March and April, KJ has been able to eat more normally and has recovered well from illnesses like colds, which can strain the body and exacerbate symptoms of CPS1. The 9 ½-month-old also takes less medication. Still, researchers caution that it's only been a few months. They'll need to monitor him for years.
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