ADA and severe combined immunodeficiency: The majority of current clinical trials aim at the treatment of adenosine deaminase-deficient severe combined immunodeficiency (ADA-SCID; (Blaese et al., 1995; Aiuti et al., 2002; Gaspar and Thrasher, 2005); X-linked severe immunodeficiency (SCID-X1 (Cavazzana-Calvo et al., 2000; Howe et al., 2008; Hacein-Bey-Abina et al., 2014; Cavazzana et al., 2016); or Wiskott-Aldrich syndrome (WAS (Boztug et al., 2010; Braun et al., 2014; Hacein-Bey Abina et al., 2015; Ferrua et al., 2019)).