Two patients in a gene therapy trial for haemophilia, a blood-clotting disorder, have shown a marked improvement in their condition. The US team, from Stanford University School of Medicine and the Children's Hospital of Philadelphia, admit they were surprised by the results, which are published in this month's Nature Genetics.
The patients were affected by haemophilia B, a bleeding disorder caused by a lack of a blood clotting protein called factor IX. Currently, the only treatment for haemophilia B is regular injections of factor IX, to prevent life-threatening internal bleeding. During the gene therapy trial, the researchers used a virus to introduce a working factor IX gene into the patients' bodies. The researchers said they were only testing the safety of the virus, and never expected their approach to affect their patients' haemophilia. But following the treatment, two patients have been able to greatly reduce their factor IX injections. 'One patient had a 50 per cent reduction in the need to administer factor IX and the other had an 80 per cent reduction' said Dr Mark Kay of Stanford University.
The patients who showed the improvements still only produce less than one per cent of the normal amount of factor IX. 'It's just barely detectable' said Dr Kay. 'But it is enough to help control their bleeding.' He also said that he hoped the study would help people realise that gene therapy is not all based on the methods used in the Gelsinger case - a reference to the controversial clinical trial in which 18-year-old Jesse Gelsinger died last September.