This novel strategy could be implemented for ongoing clinical trials for immunodeficiencies like X-linked SCID (5–9), ADA SCID (45), Artemis SCID (10–13), X-linked chronic granulomatous disease (CGD) (15, 16, 46) or WAS (17–21, 47), as well as for other diseases with a similar gene therapy approaches like Pyruvate Kinase deficiency (48), Fanconi Anemia (49) or hemoglobinopathies (50–52). Here, ADA is linked to Fanconi anemia.