Way to cure blood-clotting disease found: Gene therapy

Medical researchers in Britain have successfully treated six patients suffering from the blood-clotting disease known as hemophilia B by injecting them with the correct form of a defective gene, a landmark achievement in the troubled field of gene therapy.




Hemophilia B, which was carried by Queen Victoria and affected most of the royal houses of Europe, is the first wellknown disease to appear treatable by gene therapy, a technique with a 20-year record of almost unbroken failure. "I think this is a terrific advance for the field," said Dr Ronald G Crystal, a gene therapist at Weill Cornell Medical College. "After all the hype in the early 1990s, I think the field is really coming back now."

Gene therapy has had minor successes in very rare diseases but suffered a major setback in 1999 with the death of a patient in a clinical trial at the University of Pennsylvania.

Another gene therapy trial treated an immune deficiency but caused cancer in some patients . The general concept of gene therapy - replacing the defective gene in any genetic disease with the intact version - has long been alluring. But carrying it out in practice, usually by loading the replacement gene onto a virus that introduces it into human cells, has been a struggle.

The immune system is all too effective at killing the viruses before the genes can take effect. The success with hemophilia B, reported online Saturday in The New England Journal of Medicine, embodies several minor improvements developed over many years by different groups of researchers.