Gene therapy for "children in a bubble"
Maxim Rousseau, Polit.roo
In the UK, the National Health Service announced that it will pay for gene therapy for a congenital disease that causes a child to lack immunity. The Strimvelis method, developed by GlaxoSmithKline, will be the first type of gene therapy to receive government funding in the UK. Although the price of such treatment is more than 500 thousand pounds, experts have recognized it as more effective and, ultimately, more financially justified compared to therapy with regular medication.
The treatment method is designed to combat adenosine deaminase deficiency (ADA deficiency, ADA-SCID). It occurs in about one newborn in a hundred thousand. Due to a mutation in the twentieth chromosome in patients, the enzyme adenosine deaminase, which is involved in the synthesis of purines, is not produced in the body. For this reason, the work of natural immunity is disrupted, and a person becomes vulnerable to any infection. Only half of children with this genetic disorder survive to six months.
Immediately after the birth of such a child, it is necessary to place it in a plastic cuvette, inside which a sterile environment is created. In the future, children are forced to grow up only in protected rooms, and when going outside, wear special protective suits, so this disease is sometimes called "bubble baby syndrome". Partially alleviate the condition of patients can be enzyme replacement therapy – constant intake of drugs that replace the missing enzyme. In some cases, bone marrow transplantation can help patients.
The first successful use of gene therapy in history was associated with the treatment of ADA deficiency. This happened back in 1990, when in Bethesda (Maryland, USA) William Anderson, using a modified virus, supplied a four-year-old girl Ashanti De Silva with a working copy of the gene. The treatment was successful, according to 2007 reports, Ashanti De Silva was still healthy, albeit subject to regular medication.
In the 2000s, a number of more successful cases of the use of genetic therapy for ADA deficiency, as well as for some other types of congenital immunodeficiency, followed. Scientists from the Milan clinic San Raphaele, as well as GlaxoSmithKline and MolMed companies created the Strimvelis method, which was suitable for a wide clinical practice. Work on it has been carried out since 2002. 75% of children who participated in clinical trials of Strimvelis did not need further enzyme replacement therapy.
The method consists in obtaining hematopoietic stem cells from the patient, from which only cells expressing the CD34 membrane protein are taken for further use. These cells are cultured with cytokines and growth factors, and then the adenosine deaminase gene is injected into them with the help of a virus. Then the cells are returned to the patient's body. They take root in the bone marrow, divide and create mature cells with a normal adenosine deaminase gene. So far, all the required manipulations can only be performed in the Milan San Rafael Hospital.
14-15 people in the EU countries and 12 people in the USA need such treatment every year. The price of the course is high – 594 thousand euros, but compared to regular injections of enzyme replacement therapy, it is cheaper, since such injections will cost at least $ 4.25 million over ten years of life. Gene therapy is performed only once and should then act for the entire life of the patient. In April 2016, the committee of the European Medicines Agency recommended approving the use of Strimvelis for children with adenosine deaminase deficiency who do not have a suitable bone marrow donor.
Now, in the UK, the treatment of ADA deficiency with the help of gene therapy will be paid for by the National Health Service. Last Friday, the National Institute for Health and Clinical Excellence (NICE) published a draft guideline stating that Strimvelis has better patient survival rates compared to replacement therapy and conventional stem cell transplantation. The authors of the document claim that such treatment will give children more chances to live a normal life, go to school and communicate with friends without fear of a life-threatening infection.
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