New Gene Therapy Treatment Offers Possible Cure for SCID-X1

Researchers at St. Jude Children’s Research Hospital have cured infants with X-linked severe combined immunodeficiency (SCID-X1) using gene therapy involving a re-engineered virus. In the clinical trial, researchers used a modified version of HIV that can’t cause AIDS to deliver the correct gene into the DNA of eight newly diagnosed SCID-X1 infants’ blood stem cells, replacing those that do not function correctly. Two days prior to that, the infants received low-dose busulfan, an agent used in chemotherapy to help make space for donor stem cells to grow in the marrow. The majority of patients were able to leave the hospital within a month. And, all patients are developing normally so far, and none has incurred a life-threatening infection. In addition, none has developed leukemia, which was an outcome of previous gene therapy attempts for SCID-X1.

“While longer follow-up is needed to assess any late effects of treatment, these results suggest most patients treated with this gene therapy will develop a complete durable immune response without side effects,” said co-author Mort Cowan, a University of California at San Francisco professor of pediatrics.

The only other viable treatment for SCID-X1 is a bone marrow transplant, but patients must have a matched sibling donor, and fewer than 20 percent of patients usually do. Instead, they have to rely on blood stem cells from donors who are not family, a situation that is better than no treatment, but often leads to marked side effects