Ferrua F, et al. - Researchers present the findings from an interim analysis to describe safety as well as the efficacy of lentiviral vector-derived gene therapy in pediatric patients with severe Wiskott-Aldrich syndrome. One intravenous infusion of autologous CD34+ cells genetically modified with a lentiviral vector encoding for human WAS cDNA was received by the patients following treatment with rituximab and a reduced-intensity conditioning regimen of busulfan and fludarabine. Before gene therapy vs after gene therapy, an increase in the fraction of Wiskott-Aldrich syndrome protein (WASP)-positive lymphocytes was noted, from a median of 3.9% (range 1.8–35.6) to 66.7% (55.7–98.6) at 12 months following therapy. Also, an increase in WASP-positive platelets was evident, from 19.1% (range 4.1–31.0) before gene therapy to 76.6% (53.1–98.4) following gene therapy. Overall, the utility of gene therapy was evident in the treatment of this patient population, especially in those who did not have a suitable hemopoietic stem/progenitor cell donor available.