A collaborative gene‑therapy program led by UCLA, University College London and Great Ormond Street Hospital reported durable restoration of immune function in children with adenosine deaminase severe combined immunodeficiency (ADA‑SCID). The experimental therapy achieved long‑term immune reconstitution in treated patients, offering an alternative to enzyme replacement and hematopoietic stem cell transplant. The multiinstitutional study documented sustained clinical benefit and immune recovery, with investigators reporting safety and durability outcomes that support continued development. The program advances the gene‑therapy field for ultra‑rare monogenic immune disorders and exemplifies international translational collaboration. The results may influence clinical practice for ADA‑SCID and support additional regulatory and commercial development pathways for one‑time genetic cures in pediatric rare‑disease populations.