Mustang Bio, St. Jude new gene therapy for ‘bubble boy’ disease XSCID

For babies born with the severe genetic condition known as “bubble boy” disease, a run-of-the-mill common cold can be deadly.

Born without crucial disease-fighting immune cells, they must be kept isolated from the outside world for their own protection. Months in the hospital and being treated for severe infections is the norm. Without treatment, most born with the disease die as infants.

A new experimental medicine is now being called a cure for the condition by researchers at St. Jude Children’s Research Hospital. Ten babies born with the genetic disease, X-linked severe combined immunodeficiency (XSCID), have been successfully treated, with no apparent side effects, the researchers said on Wednesday.

The kids are now making their own immune cells. Nearly all have been able to go home with their families and live normal lives, including attending day care, with one more recently treated child remaining at St. Jude for the time being.

“This is a first for patients with XSCID,” said Dr. Ewelina Mamcarz, of the St. Jude Department of Bone Marrow Transplantation and Cellular Therapy. Mamcarz is the first author on a paper about the results, which reports on the first eight children to get the treatment and is being published in the peer-reviewed New England Journal of Medicine.

A severe genetic disease that rose to fame in the 1970s may now have a cure

XSCID, which according to US government estimates probably affects at least 1 in 100,000 newborns, became famous in the 1970s because of a young boy with XSCID named David Vetter.

Vetter lived his entire life in a plastic bubble, to protect him from a deadly infection, becoming known as “the bubble boy.”

His story quickly captured the public’s sympathy and imagination, and even inspired a made-for-TV movie about Vetter starring John Travolta.

Those plastic chambers are now gone, but those with XSCID today still need to be kept in protective isolation, sheltering them from infection.

One current treatment option is a bone marrow transplant, but not everyone can find a matching donor, and the treatments don’t always work. The latter was the case for Vetter, who died at age 12 after an unsuccessful transplant.

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There has long been hope that gene therapy, a cutting-edge new area of medicine that tinkers with the body’s genetic material to treat disease, could help. But in early treatments some patients went on to develop leukemia, stymieing research efforts.

The new experimental treatment is called MB-107, and it’s being developed by the biotech Mustang Bio, which has a market value of roughly $80 million. The researchers worked to minimize the risk that patients would develop leukemia.

That has so far been successful, with no patients from the research trial developing the cancer.

The treatment begins with a patient’s stem cells, which are collected and treated outside the body with a hollowed-out virus, introducing a normally-functioning gene to the cells.

Patients then get chemotherapy, before being infused with their newly-altered cells. The entire process takes about 10 days from start to finish.

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The use of low doses of chemotherapy was an innovation borrowed from bone marrow transplants, where it is used to wipe out a patient’s existing immune system. In the new experimental gene therapy, it seemed to improve uptake of the treatment and minimize safety issues.

Researchers say this is effectively a cure for XSCID, but they don’t know yet how long it will last. They’ve tracked patients for two-and-a-half years at most so far.

In terms of “physiological, quality of life — this is a cure,” Dr. James Downing, president and CEO of St. Jude Children’s Research Hospital, said. “The question is, will it be durable and last 10, 20, 50 years for these children?”