GT resulted in 100% survival, with few patients requiring intervention. No deaths have occurred in this patient population. Intervention-free survival was defined as survival without post-GT SCT or PEG-ADA use for a continuous period of ≥3 months. Three patients resumed PEG-ADA therapy following GT; 2 of those patients later received a matched-sibling SCT (previously unavailable before GT). Intervention-free survival represents a sensitivity analysis of the overall survival rate.