In the 1970s, a rare immune disease was made famous in the movie The Boy in the Plastic Bubble, based on a true story. The child in the film, born with a defective immune system, lives inside a sterile incubator to avoid dying from an infection.
Forty years later, patients with X-linked severe combined immunodeficiency (SCID) still face tough odds. Without treatment, they rarely live past age 2. Bone marrow transplants can cure them, but only about a third have matched donors. Most patients require lifelong immune replacement therapy to survive.
New clinical trial results suggest gene therapy may offer a promising option for some X-linked SCID patients. This treatment may even lead to a cure. Patients in the study received a unique gene therapy developed at St. Jude Children’s Research Hospital and the National Institute of Allergy and Infectious Diseases (NIAID).
Patients were given a healthy copy of the faulty gene that causes X-linked SCID. Earlier bone marrow transplants had failed to cure the patients, who were 7 to 23 years old.
Two years after gene therapy, the first two patients showed a high level of normal immune function. They stopped taking immune replacement therapy for the first time in their lives, and were found to have unprecedented levels of corrected blood and immune cells. Six to nine months after therapy, the three other patients also showed promising changes in their immune systems. That suggests they may see similar results.
Patients in previous SCID gene therapy trials showed less immune correction and were not able to stop replacement therapy. The new trial differed from those previous studies in two major ways:
- A new type of vector, or gene delivery system, was used to introduce the healthy gene into patients’ cells. This vector was designed and manufactured at St. Jude.
- Patients received low doses of a chemotherapy drug called busulfan to increase the number and types of immune cells arising from the therapy. This strategy had not been previously used in gene therapy for X-linked SCID.
St. Jude is now leading a clinical trial using the same gene therapy approach for infants with X-linked SCID.
“Based on the benefits for older patients treated at the NIH Clinical Center and reported in this study, we hope this novel gene therapy will help improve immune functioning and transform the lives of younger patients with this devastating disease,” said Brian Sorrentino, MD, of St. Jude Hematology.
The results were published in the journal Science Translational Medicine.