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Possible cure for 'bubble boy disease' nearing EU approval

The treatment, Strimvelis, inserts a gene into patients' stem cells, motivating the proper development of the immune system -- effectively curing the disease.

By
Stephen Feller
Symptoms of ADA-SCID, which prevents the immune system from operating properly, can be seen as early as six months old, and many children with the disease do not survive past two years old because they are more susceptible to infection. Photo by DONOT6_STUDIO/Shutterstock
Symptoms of ADA-SCID, which prevents the immune system from operating properly, can be seen as early as six months old, and many children with the disease do not survive past two years old because they are more susceptible to infection. Photo by DONOT6_STUDIO/Shutterstock

WASHINGTON, April 1 (UPI) -- A European Medicines Agency committee today gave the thumbs up to a potential cure for "bubble boy disease," an ultra rare genetic condition preventing the development a child's immune system.

The treatment, Strimvelis, involves removing a patient's stem cells, reprogramming the genetic defect causing adenosine-deaminase-deficient severe combined immunodeficiency, or ADA-SCID, and would be a step up from the 50-50 success rate of standard treatment for it.

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ADA-SCID is an immune disorder caused by a faulty gene preventing the production of adenosine deaminase, without which the body can't break down deoxyadenosine, a toxic substance. Deoxyadenosine builds up, destroying lymphocytes and impairing the body's abiltiy to fight infection.

In addition to leading to developmental and growth problems, hearing loss, and liver and kidney problems, ADA-SCID often results in children's deaths within about two years because of their susceptibility to infection.

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Currently, the best option is a bone marrow transplant, but just one of four infants with the disease has a well-matched family member, Bobby Gaspar, a professor of pediatrics and immunology at Great Ormond Street Hospital, told the Wall Street Journal. For those who have a good match, researchers say the chance of survival and immune recovery is good, but for those without a match, transplanted T-cells often attack the body causing other adverse events.

"If approved, Strimvelis will become the first corrective ex-vivo gene therapy for children to achieve regulatory approval anywhere in the world," Martin Andrews, head of the rare disease unit at GlaxoSmithKline, which is working with Italian researchers to develop it for use, said in a press release.

The treatment, which is currently available only in Milan, where it was developed, involves removing stem cells from the patient's bone marrow and a vector is used to insert a normal copy of the ADA gene into them. The cells are then injected back into the patient, who is also treated with low-dose chemotherapy to improve acceptance of the cells.

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Among 12 children treated with Strimvelis in a trial, there is a 100 percent survival rate and 92 percent intervention-free survival over the course of three years. With its green light for overall approval by the EMA, the committee recommended a requirement for all patients who receive Strimvelis to be entered into a registry so the long-term effects can be monitored, according to a press release.

"We welcome this opinion from the CHMP which is an important step towards making Strimvelis available to the children living with this incredibly rare and fatal condition," said Patrick Vallance, president of research and development at GlaxoSmithKline. "Going forward, we hope to apply this gene therapy platform technology across other diseases, enabling many more patients to benefit from this innovative treatment approach."

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