A new form of gene therapy has been developed to target a condition in boys with X-linked severe combined immunodeficiency syndrome (SCID-X1), also known as “bubble boy” disease. The new therapy appears to be safe and effective, according to researchers from Dana-Farber/Boston Children’s Cancer and Blood Disorders Center and other institutions who were involved in an international clinical trial.

This new therapy may help to avoid the development of leukemia that is seen in one-quarter of SCID-X1 patients.

This life-threatening condition is a genetic disorder that can be caused by a variety of genetic issues. Regardless of what genetic disorder precisely causes SCID-X1, the results are usually the same: the person’s immune system is unable to adequately produce T-cells and B-cells that fight off infection.

In this international study, nine boys with SCID-X1 were treated with the new targeted gene therapy. After 12 and 38 months following treatment, eight of the nine boys are still alive, and are showing no signs of SCID-X1-related illnesses. Out of the surviving eight boys, seven of them were able to generate immune system functioning as a result of the gene therapy.

Six of these seven boys that showed success in response to this new gene therapy had achieved a T-cell count over 300 cells per µL of blood.

David A. Williams, MD, lead investigator for the gene therapy trial’s U.S. sites, and corresponding senior author of the NEJM paper, was determined to devise a therapy that would be highly effective in treating SCID-X1, without the associated risk of patients developing leukemia.

“Our goal was to take the molecular data from the prior trial and use it to produce a vector that would remain effective and at the same time reduce the risk of leukemia. The efficacy data from our study is clear: The vector does work to correct the disease. And by a surrogate endpoint, we have improved the treatment’s safety, although it’s too early to say that we’ve completely eliminated the long-term risk of leukemia,” said David A. Williams, MD, corresponding senior author of the NEJM paper. 

The findings of the study are published in the New England Journal of Medicine.