Genetic therapies slow to produce breakthrough treatments

For example, in one trial, children who were born without a working immune system had been injected with working copies of a gene that helps the immune system grow. Though most of the children developed functional immune systems, as many as thirty percent later died or developed leukemia-like conditions.

• Fifteen years ago, scientists heralded gene therapy as a medical revolution that would quickly bring cures for crippling and deadly diseases.
• "Everybody realizes that using a gene as a drug is a good idea," says Ronald Crystal, chairman of genetic medicine at Cornell University's Weill Medical College.
• Experts say the story of the treatment of 10 sick children at a Paris hospital, which made news in March, illustrates the technology's promise as well as its challenges.
• The boys were born with a rare and lethal genetic disorder that left them without working immune systems.
• Although bone marrow transplants can cure the disease, many children are unable to find matched donors, says Donald Kohn, a professor of pediatrics at Keck School of Medicine at the University of Southern California.
• Instead of treating the symptoms, French doctors hoped to correct the source of the illness by providing the boys with working copies of a gene that helps the immune system develop.
• "They're out with their playmates rolling around in the dirt," says Theodore Friedmann, a professor of pediatrics and biomedical ethics at the University of California San Diego School of Medicine.
• Many new medical treatments --- from heart transplants to cancer drugs --- took decades to perfect, doctors say.
• Scientific companies are shifting efforts away from rare disorders and toward more common maladies such as cancer, blindness and Parkinson's disease because of the larger potential markets, says Mark Kay, a researcher at Stanford University and president-elect of the gene therapy society.
• Only 10% of gene therapy trials in the USA now involve single-gene disorders, says Sonia Skarlatos, gene therapy coordinator for the National Heart, Lung, and Blood Institute.