New gene therapy trial for “bubble boy” disease gives a young boy in Chile a chance for a healthy life

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By: Irene Sege

Gabriel Solis is a typical 3-year-old. He likes puzzles and swimming and singing. He shakes off colds like other children. Gabriel, however, is not like other children. He was born without a functioning immune system. Gabriel’s healthy immune system came by way of an international gene therapy trial for “bubble boy” disease.

When Gabriel was 4½ months old, he came down with a fever and pneumonia that landed him in the intensive care unit of the local hospital in the family’s hometown of La Serena, Chile. A few days later, tethered to a ventilator, he was flown to Santa Maria Clinic in the capital of Santiago. “I was getting very worried,” says his mother, Carolina Riquelme. “The situation was getting worse and worse.”

The diagnosis: SCID-X1

In Santiago, Gabriel’s parents received the devastating diagnosis. Their only child had X-linked severe combined immunodeficiency (SCID-X1). His blood did not contain the T-cells that form the core of the body’s immune system. For the next five months, Gabriel lived in the hospital’s isolation unit. Left untreated, boys with SCID-X1 usually die of infection before their first birthday.

The preferred treatment was a stem cell transplant with a matched sibling donor, which Gabriel did not have. “We were in a state of shock,” Riquelme says.

A gene therapy trial at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center offered the family some hope. Researchers had created a modified virus designed to correct the genetic defect that causes SCID-X1 and avoid the leukemia that developed in one-quarter of patients in earlier gene therapy trials in Europe.

“Our goal was to produce a vector [or modified virus] that would remain effective and at the same time reduce the risk of leukemia,” explains David A. Williams, MD, the Dana-Farber/Boston Children’s leader who is principal investigator for the gene therapy trial’s United States sites.

In April 2012, the family traveled to Dana-Farber/Boston Children’s so Gabriel could participate in the trial.

Eight of nine boys recruited to the trial, including Gabriel, are alive between 12 and 38 months after treatment, with no SCID-X1-associated infections, the researchers reported recently in the New England Journal of Medicine. One boy died of an overwhelming infection he had at the time of treatment. Gene therapy generated functioning immune systems in seven of the eight surviving boys, and the eighth child successfully underwent a conventional stem cell transplant using mismatched umbilical cord blood.Bubble-boy-patient-healthy-after-gene-therapy-225x300

“Gabriel was critically ill on a ventilator at the time of diagnosis, and now he is thriving,” says Sung-Yun Pai, MD, his pediatric hematologist-oncologist at Dana-Farber/Boston Children’s.

Investigators will continue to monitor Gabriel and the other patients for treatment-related leukemia for 15 years.

“Gabriel is living a normal kid’s life,” his mother says. “We thank God and the doctors from Boston Children’s. We’re Catholic, and we believe God put the doctors and this therapy in our way.”