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Gene therapy offers a potential cure to children born without an immune system

11 May 2021

A team of researchers at Great Ormond Street Hospital (GOSH), and University of California, Los Angeles (UCLA) have developed a gene therapy that successfully treated 48 out of 50 children with a form of severe combined immunodeficiency that leaves them without an immune system.

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What is ADA- SCID?

Severe combined immunodeficiency due to adenosine deaminase deficiency, also known as ADA-SCID, is a rare, life-threatening disease that prevents children from living a normal life. It is caused by mutations in the gene that creates the enzyme adenosine deaminase, which is essential to a functioning immune system.

Children with ADA-SCID have no immune system and, if left untreated, the condition can be fatal within the first two years of life. Day-to-day activities like going to school or playing with friends can lead to a dangerous infection. Recently, new-born screening for SCID has been implemented in some countries to help diagnose the condition early in life.

Results of the study

In a new study published in the New England Journal of Medicine, co-lead authors Professor Donald Kohn (UCLA) and Dr Claire Booth (GOSH and UCL Great Ormond Street Institute of Child Health) reported the two- to three-year outcomes of 50 children who were treated in clinical trials with an experimental stem cell gene therapy for ADA-SCID between 2012 and 2017.

The standard treatment for ADA-SCID involves once or twice weekly injections of the ADA enzyme until a matched bone marrow donor – usually a close family member – can be found. If a matched bone marrow donor is not available, patients require lifelong ADA injections along with preventative medicines. These treatments are expensive and therefore out of reach for patients in many countries.

If approved, gene therapy would be a welcome new treatment option for ADA-SCID as it is a one-time procedure that has the potential to provide life-long results.

Two to three years after the treatment, all of the 50 children treated with the new gene therapy at Great Ormond Street Hospital, UCLA Mattel Children’s Hospital and the National Institutes of Health (NIH) are alive and well. Of these, 48 are no longer showing symptoms of ADA-SCID, although they will have lifelong monitoring. In the two cases in which treatment wasn’t successful, both children were able to return to current standard treatments, with one eventually receiving a bone marrow transplant.No serious side effects have so far been reported, with generally mild or moderate complications experienced from the necessary preparation for the gene therapy.

Image

Zayed Centre for Research into Rare Disease in Children by Stanton Willians. Photography: Hufton + Crow

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