Scientists Edited Genes Inside a Living Person for First Time, Saved His Life

Summary

Here’s what you’ll learn in this story.The world’s first bespoke gene therapy saved the life of a newborn with a rare genetic disorder that cause the build-up of life-threatening ammonia in the body. In a race against time, scientists and doctors across the U.S. developed the first in vivo gene therapy, thanks to decades of medical research. After three doses, the newborn patient showed drastic improvement, and this new era of in vivo gene therapies could save the lives of millions more in the future.Life’s ability to successfully copy three billion distinct letters in the human genome is an absolute biological wonder—but sometimes, mistakes are made. Whether inherited or formed in utero, genetic disorders and other birth defects are common, and occur in one in every 33 babies in the U.S., according to the Centers of Disease Control and Prevention (CDC). For all of human history, a person born with such a disorder likely had to live with the condition, and depending on the defect, those lives could be brutally short. But in 2025, human history changed forever. In a groundbreaking announcement, detailed in a study published in the New England Journal of Medicine, scientists, doctors, and specialists from institutions around the U.S.—including the Children’s Hospital of Philadelphia, University of California-Berkeley, and Penn Medicine—successfully saved the life of a newborn patient named KJ, who had been born with a rare genetic disorder. To pull off this incredible medical feat, doctors employed the world’s first custom in vivo (i.e. inside a living organism, rather than in a petri dish) CRISPR gene therapy. This technique, developed over decades thanks to U.S.-funded medical research, could help alleviate painful lives for millions of people born every year with now-fixable genetic disorders. “Years and years of progress in gene editing and collaboration between researchers and clinicians made this moment possible, and while KJ is just one patient, we hope he is t...