Indeed, it has been used for all our San Raffaele-Telethon Institute for Gene Therapy (SR-TIGET) trials for ADA-SCID, WAS and MLD [1, 4, 5, 7], as well as in other gene therapy clinical trials for primary immune deficiencies [2, 3, 6, 14, 15]. The gene discussed is ADA; the disease is Immunodeficiency.