WHEN families leave the genetic institute at the San Raffaele Hospital in Milan, they are still anxious. Later, many will come to see the day their children received gene therapy as a blessed new start. Youngsters who had been sentenced to short lives, full of suffering caused by faulty DNA, get better and thrive. Cures for rare genetic diseases, both for children and adults, were once no more than a dream, but now they are set to become commercial reality.

Gene therapies take sections of correct DNA and insert them into cells, often using viruses. Once inside the cell, the new DNA produces the protein that was formerly missing and the fault is fixed. Last week America’s Food and Drug Administration (FDA) handed out “breakthrough” designations—intended to hasten the approval of important new treatments—to two gene therapies. One, made by Pfizer, a giant drugmaker, and Spark Therapeutics, a biotech company, is for haemophilia B, a rare bleeding disorder. The other, made by a specialist gene-therapies firm, AveXis, is for a severe neuromuscular disease. Money is pouring into the area: this week a gene-therapy biotech firm, Audentes, raised...Continue reading