A joint UCL–UCLA research program reported long‑term, disease‑modifying results for an ADA‑SCID gene therapy, with a multi‑year follow‑up showing roughly 95% success and no serious safety signals. The NEJM‑reported dataset indicates sustained immune reconstitution in treated children without the safety concerns that have dogged some earlier gene therapies. The work represents a major translational success for ex vivo hematopoietic gene therapy and validates decades of development for ADA‑SCID. Investigators and clinicians highlighted the therapy’s potential to replace enzyme replacement or bone marrow transplant for many patients. The milestone strengthens regulatory and commercial arguments for wider investment in rare‑disease gene cures and could accelerate adoption pathways for other bespoke hematopoietic editing programs if reproducibility and manufacturing scale can be addressed.