An infant diagnosed with a rare disease in Pennsylvania has responded well to an advanced gene-editing therapy. Born with a rare and often fatal condition called CPS1 deficiency, the child is among the first to be treated with a personalized therapy that targets a specific error in his genetic code. The disease affects about one in a million newborns and prevents the body from removing ammonia, which can become toxic. Without treatment, it is often deadly in infancy. In February 2025, researchers at the Children’s Hospital of Philadelphia and Penn Medicine successfully administered the treatment. It was designed in just six months using “base editing,” a cutting-edge version of CRISPR technology that alters a single DNA base without cutting the DNA strand. This innovative method lowers the chance of unintended genetic effects and opens the door to treating similar rare disorders.

The treatment was delivered through lipid nanoparticles—tiny fat-based particles that target liver cells. Since receiving multiple infusions, the baby has reached several health milestones, including improved appetite and recovery from minor illnesses. Experts stated that this advancement demonstrates the feasibility, efficiency, and precision of customized gene editing. Although it is still early to predict long-term outcomes, the case has established a precedent for treating rare conditions that often lack available therapies. Researchers emphasized that the cost of this custom therapy is comparable to traditional options like liver transplants. As scientists refine this technology, future treatments may become more accessible and economically sustainable, potentially helping millions living with rare genetic disorders worldwide.