Scientists are inventing treatments for devastating diseases. There’s just one problem.

Last spring, a biotechnology company announced the first use of a new gene-editing technology in humans to correct an errant gene that causes a serious immune disorder. In June, a baby born with a life-threatening metabolic disorder was allowed to leave hospital after a six-month sprint by scientists to create a tailor-made treatment for him. And increasingly, a generation of “bubble babies” born without immune defenses is approaching adolescence after receiving experimental gene therapy in early childhood.