A Baby with a Rare Disease Receives the World’s First Personalized CRISPR Gene Therapy

A young boy afflicted with a serious genetic disorder is set to be the first recipient of personalized CRISPR gene editing treatments, offering a glimpse into the potential future of medicine.

This groundbreaking event marks the first instance of an individual receiving a gene editing therapy tailored to correct unique mutations contributing to their illness. Rebecca Ahrens-Nicklas explained during a press briefing held at Children’s Hospital in Philadelphia, Pennsylvania, “He is showing early signs of progress,” though she noted that it’s premature to determine the complete effectiveness of the treatment.

Researchers released information promptly, aiming to motivate others, as stated by team member Kiran Musnur at the University of Pennsylvania. “We sincerely hope that demonstrating the feasibility of personalized gene editing therapy for one patient within a few months will encourage additional efforts in this area,” he remarked.

“When I refer to this as the future of medicine, I believe I’m stating a fact,” he emphasized. “This is a crucial step towards employing gene editing therapies to address a range of rare genetic disorders that currently lack viable treatment options.”

KJ inherited mutations on both alleles of a liver enzyme gene known as CPS1. The absence of this enzyme leads to ammonia accumulating in the bloodstream, posing a risk of brain damage during the breakdown of dietary proteins. According to Ahrens-Nicklas, over half of children born with CPS1 deficiency do not survive.

She and Musnur are developing therapies targeting this condition by focusing on the liver, allowing them to rapidly formulate a basic editing therapy that modifies one of KJ’s two CPS1 gene copies.

The team engaged with US regulatory bodies early in the process. “They recognized the exceptional nature of this situation,” Musnur stated. “KJ was critically ill and time was of the essence. Following our official submission to the FDA [Food and Drug Administration] when KJ was six months old, we received approval within just a week.”

KJ underwent initial low-dose treatment at six months in February 2025, followed by higher doses in March and April. He is now able to consume more protein than before, albeit while still taking other medications for his condition.

Ideally, children should receive treatment earlier to mitigate long-term damages linked to conditions like CPS1 deficiency. As reported by New Scientist, Musnur has ambitions to enable gene editing in humans prior to birth one day.

In contrast, other gene editing therapies are designed for broader applications, aiming to work for many individuals irrespective of the specific mutations causing their condition. For instance, the first approved gene editing treatment for sickle cell disease functions by enhancing fetal hemoglobin production, rather than altering the mutations in adult hemoglobin responsible for the disorder. Despite being a “one-size-fits-all” solution, it comes at a price of £1,651,000 per treatment in the UK, as noted by Each treatment course costs £1,651,000.

Custom treatments can be significantly more costly. Musnur mentioned that he cannot provide exact figures for KJ’s treatment due to the extensive pro bono work by the involved companies. However, he is optimistic about a decline in costs. “As we enhance our methods, we can anticipate economies of scale, leading to a substantial reduction in prices,” he stated.

One barrier to the development of personalized gene editing therapies has been the regulatory perspective, which previously treated therapies targeting different mutations within the same gene as separate entities. This necessitated restarting the approval process for each mutation individually. However, there’s a growing movement towards a platform approach, allowing broader approvals for treatments targeting various mutations.

“Platform-based methods, like CRISPR gene editing, offer scalable solutions for even the rarest diseases, as exemplified by KJ’s case,” stated Nick Mead from Genetic Alliance UK, a charity that advocates for individuals with rare conditions. “This development finally renders treatment a plausible possibility for countless families.”