Gene Therapy in the Womb Is Inching Closer to Reality

IN A FUTURE when gene therapy can tweak a person’s genome precisely enough to cure them of severe disease, treating earlier will often be better—and the womb is as early as it gets. Last week, at the annual meeting of the American Society of Gene & Cell Therapy in Los Angeles, a handful of researchers presented their progress on in utero gene therapy, showing that research in lab animals offers some hope for human treatments, but still faces significant hurdles.

Doctors can already detect abnormalities in the DNA of a developing human fetus. Conditions like sickle cell anemia and spinal muscular atrophy arise with genetic signatures—sometimes as simple as a single gene mutation—that appear in prenatal screens. New gene therapies can treat adults and even kids with these conditions, but they have some drawbacks: They can cost millions of dollars for a one-time dose, and many are currently only available to clinical trial participants. Most of all, by the time a person receives them, they may have already spent months, if not many years, living with a serious illness. 

Physicians and...