EU Regulators Favor 'Bubble Boy' Gene Therapy (Strimvelis)


April 04, 2016

Editor’s note: The European Commission approved the gene therapy Strimvelis (GlaxoSmithKline) on May 27, 2016, to treat children with the very rare disease Severe Combined Immunodeficiency due to Adenosine Deaminase deficiency (ADA-SCID), according to a company news release.

The European Medicines Agency (EMA) announced April 1 that it has recommended approval of a gene therapy called Strimvelis (GlaxoSmithKline) for children with a very rare form of severe combined immunodeficiency (SCID).

SCID renders patients unable to stave off everyday bacterial, viral, or fungal infections. It sometimes is called "bubble boy disease," based on the nickname of David Vetter, who was born with SCID in 1971. The subject of extensive news coverage, Vetter was forced to live in a plastic, germ-free chamber until his death in 1984.

Vetter had a form of SCID linked to a defective X chromosome that hinders the development and function of infection-fighting lymphocytes. Strimvelis treats another form of SCID caused by a faulty gene that stops the production of the enzyme adenosine deaminase. Children with adenosine deaminase deficiency (ADA) cannot break down a toxic substance called deoxyadenosine, which destroys lymphocytes. In addition to crippling the immune system, ADA-SCID can result in a failure to grow and develop normally, hearing loss, and liver and kidney problems. Patients born with this condition, of whom there are roughly 350 worldwide, usually die within 2 years.

David Vetter, who died in 1984 shortly after a bone marrow transplant to treat SCID.

Children with ADA-SCID who receive hematopoietic, or blood-forming, stem cells from the bone marrow of a healthy person, ideally a genetically matched sibling, have a good chance of survival, according to the EMA. Strimvelis is indicated for patients with ADA-SCID who lack a suitable transplant donor.

This gene therapy treatment involves taking the patient's own hematopoietic stem cells and inserting a normal gene that codes for adenosine deaminase. Then the cells are injected back into the patient so that he or she can produce lymphocytes going forward.

An autologous transplant skirts the problem of host rejection or the need for immunosuppressive therapy, which increases the risk for infection.

In a clinical trial studying Strimvelis, all 12 patients with ADA-SCID who received the gene therapy are still alive, with their average follow-up period at 7 years. Fever, higher hepatic enzyme levels, and autoimmune reactions such as neutropenia were among the most common adverse events observed.

The recommendation to approve Strimvelis came from the EMA's Committee for Medicinal Products for Human Use. The European Commission, the European Union's executive branch, will make the final decision on whether the therapy should be marketed across the European Union.

More information on 'the announcement is available on the EMA website.


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