Severe combined immunodeficiency due to ADA enzyme deficiency is a rare disease that, if left untreated, can be fatal in the first two years of life. Now, a scientific team presents the results of an experimental gene therapy tested on 62 children: it was 95% effective.
The treatment, developed by U.S. and British researchers, was successful in restoring and maintaining immune system function in 59 of 62 children. The conclusions of the trial are published in the New England Journal of Medicine and are, according to the authors, promising.
Gene therapy works in children with rare disease
🔴 Gene therapy saves the lives of 59 children with a rare and fatal disease
Lo cuenta @JRuizMz https://t.co/5nwUNdyNpb
– Cadena SER (@La_SER) October 15, 2025
“The durability of immune function, the consistency over time and the continued safety profile are incredibly encouraging,” summarizes Donald Kohn of the University of California, an institution involved along with the College of London and Great Ormond Street Hospital.
Severe combined immunodeficiency due to adenosine deaminase deficiency (ADA) is caused by mutations in the ADA gene, which creates an enzyme essential for immune function.
For “bubble children” who suffer from it, everyday activities such as going to school or playing with their friends can lead to dangerous, life-threatening infections.
Current standard treatments – bone marrow transplantation from a matched donor or weekly enzyme injections – have limitations and potential long-term risks, and gene therapy offers a new approach, explains a statement from the Californian university.
How does it work?
Doctors remove the child’s blood stem cells, which create all types of blood and immune cells, and use a modified lentivirus (as a vector) to introduce a healthy copy of the ADA gene.
Once reinjected into the patient, the corrected stem cells begin to produce healthy immune cells capable of fighting infections.
The development of these cells begins shortly after reinjection of the genetically modified stem cells, but it takes six to 12 months for the immune system to reconstitute itself to normal levels.
The paper published Wednesday, Oct. 15, details the outcomes of minors treated in the U.S. and U.K. with the gene therapy between 2012 and 2019.
According to the authors, who also include Katelyn Masiuk and Claire Booth, the study represents the largest and longest follow-up of such a gene therapy to date – some were observed for more than 7 years.
In the 59 patients successfully treated, immune function has been stable beyond the initial recovery period, with no treatment-limiting complications reported.
Most of the adverse effects were mild to moderate and were Buzzy related to routine preparatory procedures rather than to the gene therapy itself.
Treatment was successful in all but three cases; those children were able to return to current standard therapies.
Two received bone marrow transplants and one was receiving ADA enzyme injections while preparing for a transplant at the time of data closure.
More than half of the treated children received a frozen preparation of corrected stem cells and obtained similar results to those treated with non-frozen stem cells.
The cryopreservation method has important implications for making the therapy more accessible worldwide.
“The freezing method allows children with this disease to have their stem cells collected locally, processed at a manufacturing plant elsewhere and shipped back to a nearby hospital,” Masiuk summarizes.
What is the future?
The researchers are working to seek approval from the U.S. Food and Drug Administration (FDA). The goal is to have it approved within two to three years, Kohn says.
For this scientist, “the clinical data strongly support the approval; now we have to demonstrate that we can manufacture the treatment under commercial pharmaceutical standards”.
The research was funded by, among others, the U.S. National Institutes of Health, the California Institute for Regenerative Medicine, Orchard Therapeutics and the Biomedical Research Centre at Great Ormond Street Hospital in the United Kingdom.
Filed under: Gene therapy works in rare disease
With information from EFE
