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Sometimes rare diseases allow for scientists to pioneer bold new ideas. That's been the case with a condition that affects fewer than a hundred babies a year in the U.S. Those babies are born without a functioning immune system, and the quest to cure them has led to advances in a technique called gene therapy. NPR's Richard Harris reports.
RICHARD HARRIS, BYLINE: The disease is called severe combined immunodeficiency, or SCID. Matt Porteus, a Stanford pediatrician, says you might be familiar with it.
MATT PORTEUS: It was made famous, I guess, in the mid-'70s when the bubble boy was described in a documentary. And I think he capture the imagination of a lot of people.
HARRIS: David Vetter spent most of his short life in a plastic bubble to protect him from infection. He died at the age of 12. Things have come a long way since then. All babies born in the United States are now screened for this condition, and standard treatment - a bone marrow transplant - succeeds more than 90 percent of the time when it's done promptly. Yet SCID remains a source of great interest to researchers.
PORTEUS: This is one of those diseases in which there's probably more doctors and scientists studying the disease than patients who have the disease.
HARRIS: In the 1990s, European scientists actually cured it in some patients using gene therapy. This technique involves removing defective blood cells from a patient, inserting a new gene with the help of a virus and then putting the cells back into the body. Those cells then build up the patient's immune systems. Dr. Donald Kohn at UCLA says at first it looked really good.
DONALD KOHN: And initially, I think of the 20 patients, they all had immune recovery. But over time, five of them went on to develop a leukemia.
HARRIS: Scientists scrambled to figure out how to inject new genes into cells without triggering that blood cancer, and they're cautiously optimistic they've succeeded. Since then, there have been gradual improvements in the technique. The latest advance, involving eight infants, shows that a short dose of chemotherapy helped the new cells take root. The infants ended up with apparently healthy immune systems.
EWELINA MAMCARZ: I am thrilled to see these outstanding results.
HARRIS: Ewelina Mamcarz at St. Jude's Children's Research Hospital in Memphis is first author of a paper reporting these findings in the New England Journal of Medicine.
MAMCARZ: To be able to see these babies in my clinic now as toddlers is really very rewarding. They live normal lives. They're not any different from my daughters.
HARRIS: Today, most children with SCID who get a bone marrow transplant also need ongoing treatment, including lifetime injections of antibodies. Jennifer Puck, a pediatrician at UC-San Francisco and a study collaborator, says infants who got the newest gene therapy don't need that medication.
JENNIFER PUCK: And they're growing normally. They're getting colds like everybody else. And they get over infections, so I would say that that is a cure.
HARRIS: Of course, she adds that they will be watched carefully for signs of leukemia and to see if the effects of the therapy are wearing off. In her mind, the key is finding these children early through newborn screening before they start to get life-threatening infections. That had typically been the case.
PUCK: And now we're seeing happy, bouncy little newborns who just look perfectly normal.
HARRIS: This is not only good news for those rare families. The disease provides a good opportunity for all those scientists to develop even newer gene therapy techniques. For example, instead of inserting a healthy gene, Matt Porteus at Stanford has used a powerful gene-editing technique called CRISPR to correct the genetic error in SCID blood cells. It works with human cells in a dish.
PORTEUS: And this really sets the stage then for testing the approach in a clinical trial hopefully in the next 12 to 18 months.
HARRIS: All this makes the leukemia setback from the 1990s feel like a fading memory. Kohn at UCLA said for more than a decade, it seemed that the field was a dead end but no more.
KOHN: It's just nice to see another success for gene therapy.
HARRIS: Richard Harris, NPR News.
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