Doctors in the US have become the first to treat a baby with a customised gene-editing therapy after diagnosing the child with a severe genetic disorder that kills about half of those affected in early infancy. Ian Sample explains to Madeleine Finlay how this new therapy works and how it paves the way for even more complex gene editing techniques. David Liu, a professor at the Broad Institute of MIT and Harvard and the inventor of these therapies, also describes the barriers that could prevent them reaching patients, and how he thinks they can be overcome
