Mamcarz E, et al. - Because allogeneic hematopoietic stem-cell transplantation for X-linked severe combined immunodeficiency (SCID-X1) often fails to reconstitute immunity related to T cells, B cells, and natural killer (NK) cells when matched sibling donors are unavailable unless high-dose chemotherapy is given, researchers conducted a dual-center, phase 1–2 lentiviral vector safety and effectiveness study to transfer IL2RG complementary DNA to bone marrow stem cells following low-exposure, targeted busulfan conditioning in eight newly diagnosed infants with SCID-X1. According to findings, in infants with newly diagnosed SCID-X1, lentiviral vector gene therapy in combination with low-exposure, targeted busulfan conditioning had low-grade acute toxic effects, resulting in multilineage transduced cells engraftment, reconstitution of functional T cells and B cells, and normalization of NK-cell counts over a 16-month median follow-up.