For the first time, a CRISPR-based drug treats a child's unique genetic mutation

A milestone in genetic medicine

In a world-first achievement, scientists from the Children's Hospital of Philadelphia (CHOP) and the University of Pennsylvania have developed and administered a CRISPR-based gene therapy tailored to a baby suffering from a life-threatening and rare disorder: carbamoyl phosphate synthetase 1 (CPS1) deficiency.

This genetic condition prevents the body from eliminating ammonia, a waste product, causing toxic buildup. Without effective treatment, the only option would have been a liver transplant.

A rapid, customized approach

Researchers acted swiftly: within six months, they designed a gene-editing therapy specifically for the baby, KJ Muldoon. The therapy used CRISPR to correct his unique mutation directly in the liver, bypassing the need for invasive organ transplantation.

The experimental treatment was administered in early 2025, with three doses delivered through lipid nanoparticles targeting liver cells.

Encouraging early results

Post-treatment, KJ showed significant improvement: better weight gain, reduced reliance on medication, and greater resilience to infections. While long-term outcomes are still being monitored, the signs point to a successful correction of the disease-causing mutation.

A new horizon for personalized gene therapy

This case demonstrates how CRISPR technology can be used not just for common conditions, but for ultra-rare mutations unique to individual patients. It opens the door to the possibility of “n=1” therapies—treatments customized for a single person.

As technology evolves, experts hope to reduce costs and streamline development processes, allowing more families to benefit from tailored genetic medicine.

Ethical and economic challenges

Personalized treatments come with ethical and logistical questions. How do we ensure equity in access? Can these therapies be scaled? Despite these concerns, the success of KJ's case proves that such efforts are not only feasible, but potentially transformative for rare disease care.

Main source: The Wall Street Journal

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