A form of gene therapy that was once dismissed as far-fetched should start trials in patients within months. The aim is to destroy tumour cells in the brain by introducing a gene from the herpes simplex virus into them. This makes the cells susceptible to the anti-herpes drug ganciclovir, which kills them.

So far, most gene therapy trials have involved introducing into cells a healthy copy of a gene that is faulty or absent. The new approach is to change the nature of the cell with a foreign gene, so that the cell can then be targeted with a specific drug. Like some other forms of gene therapy, the technique uses a mouse retrovirus to carry the gene into cells.

Kenneth Culver, who led a team at the National Cancer Institute in Bethesda, Maryland, says people thought he was ‘crazy’ when he first suggested the idea. However, the group has …