One Baby, One Mutation, One Remarkable Step Forward in Gene Editing
Personalized Gene Editing Treatment for CPS1
Imagine being told that your newborn has a rare genetic disorder that prevents his body from safely processing one of the basic products created when protein is broken down. Now imagine learning that scientists may be able to design a treatment specifically for his genetic mutation.
That situation became a reality for an infant named KJ, who was diagnosed with severe carbamoyl phosphate synthetase 1 deficiency, commonly called CPS1 deficiency. In 2025, Musunuru and colleagues reported something that had never been accomplished before: a personalized CRISPR gene editing treatment designed around an individual patient.
How Was This Study Done?
Researchers first identified the specific variants in KJ’s CPS1 gene. They then designed a personalized base editing therapy intended to correct one of those variants in his liver cells. Base editing is related to CRISPR technology, but instead of making a traditional cut through both strands of DNA, it can change a specific DNA letter. This approach allowed the researchers to target the genetic error with remarkable precision (Musunuru et al., 2025).
The treatment instructions were packaged inside lipid nanoparticles. The goal was to deliver the therapy to the liver, where the CPS1 enzyme normally helps the body process ammonia. Before treating KJ, the research team conducted extensive laboratory testing. KJ received two infusions at approximately seven and eight months of age.
What Did They Find?
The early results were encouraging. After treatment, KJ was able to tolerate more dietary protein, and physicians reduced his nitrogen scavenging medication to approximately half of the original dose. Importantly, no serious adverse events were reported during the initial observation period (Musunuru et al., 2025).
One particularly meaningful observation occurred when KJ experienced viral infections. Illness can place additional metabolic stress on patients with urea cycle disorders. Despite these illnesses, KJ continued to tolerate increased protein intake and reduced medication. However, longer observation is necessary to determine lasting safety and effectiveness.
Put It All in Context
What makes this study so important is not simply that CRISPR was used. What is different is the level of personalization. Researchers moved from identifying the mutation to creating and administering a customized therapy within months (Musunuru et al., 2025).
The study does not mean that scientists can now routinely create a personalized genetic treatment for every patient. Still, this research represents an important shift in how we think about treatment. Instead of asking only whether one therapy can treat thousands of patients, biomedical science may increasingly ask whether technology can safely create highly individualized treatments.
About the Author
Rae Wood is a graduate student studying Clinical Research Management with an interest in biomedical research and the translation of scientific discoveries into meaningful improvements in patient care. Her interests include clinical research, neurology, genetics, and emerging therapies that may improve outcomes for patients and families.