Gene Therapy Shows Benefit in Children With X-Linked SCID

However, risk of leukemia linked to this treatment for severe combined immunodeficiency

WEDNESDAY, July 21 (HealthDay News) -- In patients lacking an HLA-identical donor for stem-cell transplantation, gene therapy may be effective in treating X-linked severe combined immunodeficiency (SCID-X1), though the treatment carries a risk of acute leukemia, according to research published in the July 22 issue of the New England Journal of Medicine.

Salima Hacein-Bey-Abina, Ph.D., of the Necker-Enfants Malades Hospital in Paris, and colleagues discuss the outcomes of nine patients with SCID-X1 who didn't have an HLA-identical donor. At a median age of 7 months, patients underwent infusion of autologous bone marrow-derived CD34+ cells transduced with γ chain-containing retroviral vector.

The researchers found that eight patients were still alive after a median nine years of follow-up. The therapy initially succeeded in correcting immune dysfunction in eight of the patients. Four patients subsequently developed acute leukemia, and one died. Transduced T cells were observed for up to 10.7 years following gene therapy. Seven patients had sustained immune reconstitution, including all three leukemia survivors. The persistence of naive T cells pointed to sustained thymopoiesis, and was seen in three patients after chemotherapy.

"Overall, the present study confirms the expectation that ex vivo gene therapy for SCID-X1 can result in long-term correction of the SCID phenotype. However, the risk of the development of a malignant condition related to treatment, which involved the use of a retroviral vector containing a competent enhancer of long terminal repeats, cannot be ignored," the authors write.

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