Gene therapy approved to treat ‘Bubble Babies’

Gerolf Nikolay

By Pakinee Pooprasert

A genetic therapy has been approved by the European Medicines Agency to treat a disorder that leaves children with a severely deficient immune system, causing any infection could be fatal. This means that all patients in Europe can potentially access the treatment, enabling them to build lifelong immune systems with the help of transplanted genes.

Gene therapy is where DNA is inserted into a patient to correct for faulty genes that cause genetic disorders.This is a massive advance for this type of treatment. Susan Walsh, director of PID UK, a charity representing parents and children with inherited immunodeficiency diseases, described it as “an amazing moment and an absolute landmark for gene therapy,” adding that “an advance in one area improves prospects for other conditions.”

Such a treatment will be highly implicated in those suffering from severe immunodeficiency disorders that are affected by faulty genes, such as children with severe combined immunodeficiency (SCID). Children with SCID don’t have a working immune system, which can make routine infections fatal. Thus, babies with SCID must be isolated, dubbed “bubble baby” disease. In this disorder, patients have defective copies of the gene that makes adenosine deaminase (ADA), an enzyme extremely important to the immune system – without it, toxic debris builds up in white blood cells, killing them before maturation.

Bone marrow transplants can help treat this disease. Some children might be lucky enough to find a bone marrow donor, but tragically many die while waiting for one.

An alternative treatment to bone marrow transplant is called Strimvelis. This treatment has been developed by the teams at San Raffaelel Telethon Institute for Gene Therapy in Milan, Italy and GSK, the giant pharmaceutical company, and aims to permanently alter DNA within a patient’s cells. This involves extracting bone marrow stem cells that regenerate the immune systems and infecting them with a harmless virus that uploads a correct copy of the gene for ADA. These altered cells are then injected back into the patient and are able to generate a healthy immune system. Moreover, since the gene inserted is assimilated completely into the genome, this means that the effects are long-lasting, even, permanent.

A trial consisting of 22 patients, a mix of boys and girls at an average age of 18 months showed 100 per cent survival and that “the first patient is now 13 years post-treatment, and the median over all the patients is seven years survival so far” said Sven Kili, head of gene therapy development at GSK.

While this is just the first time this technique has gained approval, for more than 20 years, children with ADA SCID have been treated with a similar procedure on a trial basis at Great Ormond Street Hospital in London and the Necker Hospital in Paris.

Additionally, doctors at the Milan institute have also used this technique to treat 20 children with a fatal, nerve-destroying inherited disease called metachromatic leukodystrophy, and in the future, hope to try it on an inherited condition, beta thalassemia, or even more common conditions such as rheumatoid arthritis.

Bobby Gaspar of Great Ormond Street summed up the whole avenue accurately, saying “we’ve seen the huge impact gene therapy can have on children’s lives and that the approval of a licensed gene therapy medicine for SCID is a very positive step and shows that gene therapy can become a standardised medicine.”

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