In a landmark first, doctors developed a customized gene-editing drug in just seven months to treat an infant, Kyle ´KJ´ Muldoon Jr., who suffers from a rare and deadly metabolic disorder. The gene-editing treatment, detailed in the New England Journal of Medicine, marks the inaugural instance of gene editing tailored to correct a genetic mutation unique to a single patient. KJ’s diagnosis revealed a particularly unusual gene misspelling in the CPS1 gene, which halted production of a crucial metabolic enzyme and led to life-threatening ammonia buildup.
The team, led by experts at the University of Pennsylvania and Children’s Hospital of Philadelphia, utilized an advanced form of CRISPR technology known as base editing. Unlike traditional CRISPR approaches that often delete defective genes, base editing allows precise rewriting of a single DNA letter, restoring gene function. The process required rapid collaboration among more than 45 scientists and doctors, along with assistance from biotechnology firms, to design, test, and secure emergency authorization for the therapy. KJ received three escalating doses with encouraging early signs, as he continues to grow and develop with apparent improvement in his condition, though researchers caution that long-term efficacy remains to be determined as invasive confirmation like a liver biopsy poses risks.
This case highlights the unprecedented accuracy of new gene-editing tools but also underscores a profound challenge: most genetic diseases are so rare that it is financially unfeasible for companies to develop personalized treatments for every individual. Experts point to the need for new models to fund, scale, and standardize these bespoke therapies, as the current cost and regulatory hurdles are substantial. The successful application of a one-off gene-editing drug signals a possible future where individual DNA errors are quickly identified and corrected, at least for certain organs like the liver, and potentially beyond as the science advances. However, bridging the gap between technological possibility and real-world availability remains an urgent issue for the field.
