Safer gene therapy?

Gene therapy researchers in the US have unveiled a new technique that could cut down the risk of serious side effects associated with current methods. The team, based at Stanford University, California, say their new method delivers genes to specific locations within the chromosomes (bundles of genetic material) of the cells that need them.

They hope that this will prove a safer and more reliable technique than current methods, in which genes are delivered by viruses, and end up inserted at random positions along the chromosomes. The possible dangers of this approach became apparent earlier this month - doctors revealed that a French gene therapy patient has developed leukaemia-like symptoms, probably as a result of his treatment.

Team leader Dr Michele Calos says that the new method, published in this month's Nature Biotechnology, seems to offer more predictability and control over genes. The random insertion of genes by virus delivery systems can activate genes that trigger cancer, which is what is thought to have happened in the trial at the Necker Hospital, Paris. Random insertion can also mean that the therapeutic genes end up in inactive parts of the genetic material, so they are never switched on and used by the cell. The new technique uses a 'guiding protein' to direct the genes to specific positions on the chromosome, and appears to work well in experiments using mice. Calos hopes to begin human trials soon, using the technique to treat a serious childhood skin disease called recessive dystrophic epidermolysis bullosa.

US gene therapy trials for a rare immune disorder are to continue, announced the Food and Drug Administration (FDA) last week. The trials were halted following news of the French patient in a similar trial who developed leukaemia, but are to resume following the advice of an expert panel.