In 2025, KJ Muldoon’s life has been defined by his “firsts.” Earlier this year, he became the first patient in the world to receive a personalized CRISPR gene editing therapy to treat his rare disease. Earlier this year, KJ received three doses of the groundbreaking treatment at Children’s Hospital of Philadelphia (CHOP) to treat a rare metabolic disease known as severe carbamoyl phosphate synthetase 1 (CPS1) deficiency. KJ spent the first ten months of his life in the hospital and was officially discharged in June after he continued to grow and thrive.
It’s because of that treatment that KJ can experience many of the “first” moments families look forward to. Since being discharged, he celebrated his first birthday at home with his family in August. Recently, he began taking his first steps, and he has reached many other key developmental milestones along the way. He’s also getting ready to celebrate his first Christmas at home, something that had to happen in his hospital room a year ago. While KJ continues to celebrate many “first” milestones, Rebecca Ahrens-Nicklas, MD, PhD, director of the Gene Therapy for Inherited Metabolic Disorders Frontier Program (GTIMD) at CHOP and an assistant professor of Pediatrics in the Perelman School of Medicine at the University of Pennsylvania, continues to collaborate with Kiran Musunuru, MD, PhD, the Barry J. Gertz Professor for Translational Research in Penn’s Perelman School of Medicine, on a path forward for other children with rare diseases to experience the same milestones as KJ.
Researchers are continuing to explore the causes and potential treatments for other difficult-to-treat metabolic disorders. The Gene Therapy for Inherited Metabolic Disorders (GTIMD) Program at CHOP was created to discover new ways of treating inborn errors of metabolism, a group of disorders (or diseases) that affect metabolic pathways in the body. Ahrens-Nicklas and Musunuru are actively exploring diseases including urea cycle disorders, organic acidemias, and fatty acid oxidation disorders in their laboratories. KJ’s case is also prompting important discussions on how to move forward with new models for approving personalized therapies for rare diseases. A recent editorial in the New England Journal of Medicine cited KJ’s case and the lessons learned from it to serve the rare disease community.
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In 2025, KJ Muldoon’s life has been defined by his “firsts.” Earlier this year, he became the first patient in the world to receive a personalized CRISPR gene editing therapy to treat his rare disease. Earlier this year, KJ received three doses of the groundbreaking treatment at Children’s Hospital of Philadelphia (CHOP) to treat a rare metabolic disease known as severe carbamoyl phosphate synthetase 1 (CPS1) deficiency. KJ spent the first ten months of his life in the hospital and was officially discharged in June after he continued to grow and thrive.
It’s because of that treatment that KJ can experience many of the “first” moments families look forward to. Since being discharged, he celebrated his first birthday at home with his family in August. Recently, he began taking his first steps, and he has reached many other key developmental milestones along the way. He’s also getting ready to celebrate his first Christmas at home, something that had to happen in his hospital room a year ago. While KJ continues to celebrate many “first” milestones, Rebecca Ahrens-Nicklas, MD, PhD, director of the Gene Therapy for Inherited Metabolic Disorders Frontier Program (GTIMD) at CHOP and an assistant professor of Pediatrics in the Perelman School of Medicine at the University of Pennsylvania, continues to collaborate with Kiran Musunuru, MD, PhD, the Barry J. Gertz Professor for Translational Research in Penn’s Perelman School of Medicine, on a path forward for other children with rare diseases to experience the same milestones as KJ.
Researchers are continuing to explore the causes and potential treatments for other difficult-to-treat metabolic disorders. The Gene Therapy for Inherited Metabolic Disorders (GTIMD) Program at CHOP was created to discover new ways of treating inborn errors of metabolism, a group of disorders (or diseases) that affect metabolic pathways in the body. Ahrens-Nicklas and Musunuru are actively exploring diseases including urea cycle disorders, organic acidemias, and fatty acid oxidation disorders in their laboratories. KJ’s case is also prompting important discussions on how to move forward with new models for approving personalized therapies for rare diseases. A recent editorial in the New England Journal of Medicine cited KJ’s case and the lessons learned from it to serve the rare disease community.
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Ben Leach
Gene Therapy for Inherited Metabolic Disorders Program