A joint UCL‑UCLA research initiative reported multi‑year follow‑up showing their gene therapy for ADA‑SCID restored immune function in roughly 95% of treated children with no serious long‑term safety signals, according to a New England Journal of Medicine report. The therapy, UCL/A‑ADA, replaces the defective ADA gene and produced durable immune reconstitution in the cohort. The study authors—Claire Booth, Donald Kohn and collaborators—noted sustained immune recovery without the morbidities associated with lifelong enzyme replacement or poorly matched transplants. The trial’s outcomes add momentum to curative, one‑time genetic interventions for severe pediatric immunodeficiencies. Regulators, payers and therapy developers will use the data to shape approval expectations, manufacturing scale plans, and reimbursement models for rare‑disease, bespoke gene therapies.