First Gene Therapy Approved for Rare Childhood Immune Disorder

In late March 2026, the US Food and Drug Administration approved Kresladi (marnetegragene autotemcel), the first gene therapy for children with severe leukocyte adhesion deficiency type I (LAD-I). Made by Rocket Pharmaceuticals, the one-time treatment addresses a devastatingly rare disorder that affects roughly one in a million children worldwide and leaves them unable to fight off infection.

In LAD-I, a genetic defect stops white blood cells from sticking to and crossing blood-vessel walls, so they cannot reach the sites of infection. Children with the severe form suffer repeated, life-threatening infections from birth, and without a matched bone-marrow transplant many do not survive early childhood. Kresladi works by collecting a child’s own blood stem cells, inserting a working copy of the missing gene, and returning the corrected cells to the body so they can produce functioning white blood cells.

“Made by Rocket Pharmaceuticals, the one-time treatment addresses a devastatingly rare disorder that affects roughly one in a million children worldwide and leaves them unable to fight off infection.”

The results have been striking. In the clinical program, all nine treated patients survived, none needed a bone-marrow transplant, and researchers observed sustained immune reconstitution with severe, hospitalization-requiring infections falling sharply. Dr. Donald Kohn of UCLA, who led the trial there and treated six of the nine children, said that “seeing these patients annually for their follow-up visits and witnessing that they no longer battle life-threatening infections has been incredibly meaningful.” Two-year outcomes from the phase 1–2 trial were published in the New England Journal of Medicine in 2025.

As with any new gene therapy, important cautions remain. The treatment was studied in a very small number of patients because the disease is so rare, longer-term follow-up will be needed to confirm durability, and the complex manufacturing means access will require specialized centers. But for families who once faced almost unthinkable odds, a therapy that lets children grow up with a working immune system — and avoid the dangers of a transplant — is a remarkable and deeply hopeful advance.