Gene therapy developed and produced at St. Jude Children’s Research Hospital has cured infants born with X-linked severe combined immunodeficiency (SCID-X1), also known as “bubble boy” disease.1 The study results were published in the April 18th, 2019, issue of the New England Journal of Medicine.2

In collaboration with the hospital, researchers at the University of California, San Francisco Benioff Children’s Hospital as well as those from St. Jude conducted a safety and efficacy study of a lentiviral vector to transfer IL2RG DNA to bone marrow stem cells after receiving 1 to 2 daily doses of busulfan intravenously in 8 infants diagnosed with SCID-X1. 

Within 3 months of treatment, gene-corrected immune cells, including T cells and NK cells, were present in the blood of all but 1 patient, who underwent a second round of gene therapy. Significantly, antibody-producing B cells were found in the blood of all patients, which marks the first time these cells appeared in SCID-X1 infants treated with gene therapy.

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After the conclusion of the follow-up period (16.4 months), all patients were alive and well, with normal growth with respect to weight and height. No life-threatening infections have developed, including leukemia, which was a previous side effect for patients undergoing gene therapy.

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“These patients are toddlers now, who are responding to vaccinations and have immune systems to make all immune cells they need for protection from infections as they explore the world and live normal lives,” stated lead author Ewelina Mamcarz, MD, of the St. Jude Department of Bone Marrow Transplantation and Cellular Therapy. “This is a first for patients with SCID-X1.”


1. Mamcarz E, Zhou S, Lockey T, et al. Lentiviral gene therapy combined with low-dose busulfan in infants with SCID-X1. N Engl J Med. 2019;380(16):1525-1534.

2. St. Jude Children’s Research Hospital. St. Jude gene therapy cures babies with ‘bubble boy’ disease [news release]. April 17, 2019. Accessed May 7, 2019.