![]() trials, led by principal investigator Donald Kohn, M.D., of UCLA, enrolled 30 participants with ADA-SCID ranging in age from 4 months to 4 years at UCLA Mattel Children’s Hospital and the NIH Clinical Center in Bethesda, Maryland. The results come from three separate Phase 1/2 clinical trials, two conducted in the United States and one in the United Kingdom. ![]() Some people who have received gamma retroviral gene therapies have later developed leukemia, which scientists suspect is due to the vector causing activation of genes that control cell growth. The lentiviral vector is designed to avoid this outcome and to enhance the effectiveness of gene delivery into cells. Previous gene-therapy approaches for ADA-SCID have relied on a different type of virus called a gamma retrovirus. The experimental gene therapy, developed by researchers from the University of California, Los Angeles (UCLA) and Great Ormond Street Hospital (GOSH) in London, uses a modified lentivirus to deliver the ADA gene to cells. The genetically corrected stem cells then are infused back into the patient, who has received a low dose of the chemotherapy medication busulfan to help the cells establish themselves in the bone marrow and begin producing new immune cells. Next, a harmless virus is used as a “vector,” or carrier, to deliver the normal ADA gene to these cells in the laboratory. First, stem cells are collected from the patient’s bone marrow or peripheral blood. This gene therapy involves inserting a normal copy of the ADA gene into the patient’s own blood-forming stem cells. The new research evaluated an experimental lentiviral gene therapy designed to be safer and more effective than previously tested gene-therapy strategies for ADA-SCID. Additionally, stem cell transplants carry risks such as graft-versus-host disease and side effects from chemotherapy medications given to help the donor stem cells establish themselves in the patient’s bone marrow. Transplants of blood-forming stem cells, ideally from a genetically matched sibling donor, can provide a more lasting solution. People with ADA-SCID can be treated with enzyme replacement therapy, but this treatment does not fully reconstitute immune function and must be taken for life, usually once or twice weekly. “Importantly, gene therapy is a one-time procedure that offers patients the hope of developing a completely functional immune system and the chance to live a full, healthy life.” Fauci, M.D., director of NIH’s National Institute of Allergy and Infectious Diseases (NIAID). “These findings suggest that this experimental gene therapy could serve as a potential treatment option for infants and older children with ADA-SCID,” said Anthony S. If untreated, the disease is fatal, usually within the first two years of life. ![]() This impairment leaves children with the condition highly susceptible to severe infections. ![]() The findings were published today in the New England Journal of Medicine.ĪDA-SCID, which is estimated to occur in approximately 1 in 200,000 to 1,000,000 newborns worldwide, is caused by mutations in the ADA gene that impair the activity of the adenosine deaminase enzyme needed for healthy immune system function. The researchers found that 48 of 50 children who received the gene therapy retained their replenished immune system function two to three years later and did not require additional treatments for their condition, known as severe combined immunodeficiency due to adenosine deaminase deficiency, or ADA-SCID. Darryl Leja, NHGRIĪn investigational gene therapy can safely restore the immune systems of infants and children who have a rare, life-threatening inherited immunodeficiency disorder, according to research supported in part by the National Institutes of Health. A DNA double helix rests on a print-out illustration of the DNA letters A, T, C and G. ![]()
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