More successes for gene therapy treatment

Four children who received gene therapy for a severe inherited immune disorder are now all at home living normal lives, UK scientists report. The boys, who were affected by severe combined immunodeficiency (SCID), received the pioneering treatment at Great Ormond Street Hospital in London. In a commentary accompanying the study, which is published in the Lancet, French gene therapy researchers Marina Cavazzana-Calvo and Alain Fischer say that 17 SCID patients have now been successfully treated in this way.

Children affected by SCID have a faulty gene that means they have no working immune system, so their bodies cannot fight infections. This life-threatening condition is sometimes called 'bubble boy' disease, as unless they can be successfully treated with a matched bone marrow transplant, patients must spend their lives in a sterile environment. To carry out gene therapy treatment, doctors must first harvest bone marrow from the patients, from which they isolate blood stem cells. They then infect these cells with a retrovirus (a virus that inserts its genetic material into the host cell's DNA) carrying a working gene, before returning the modified cells back to the patients.

A team lead by Fischer, at the Necker Hospital in Paris, announced the first successful use of gene therapy to treat SCID in 2000. Then, in 2002, toddler Rhys Evans became the first UK patient to benefit from the new approach. However, the field suffered a serious setback later that year, when it emerged that two of the French patients developed leukaemia as a result of the treatment. Although both responded well to treatment for the leukaemia, governments in many countries temporarily suspended similar gene therapy trials, while the exact cause of the cancer was determined.

No more patients in either the UK or French trials have developed leukaemia. In their Lancet commentary, Fischer and Cavazzana-Calvo discuss all of the SCID clinical research done so far, and conclude that '17 of these 18 patients had their immunodeficiencies corrected with clear and sustained clinical benefits'. They added that 'the data show that the results of this gene therapy strategy are reproducible'. Great Ormond Street team member Bobby Gaspar told BBC News Online that the results could pave the way for developing gene therapy treatments for other inherited immunodeficiencies, as well as blood disorders such as sickle cell anaemia.