Scientists Edited Human Embryos in the Lab, and It Was a Disaster

A team of scientists has used the gene-editing technique CRISPR to create genetically modified human embryos in a London lab, and the results of the experiment do not bode well for the prospect of gene-edited babies.

Biologist Kathy Niakan and her team at the Francis Crick Institute wanted to better understand the role of a particular gene in the earliest stages of human development. So, using CRISPR, they deleted that gene in human embryos that had been donated for research. When they analyzed the edited embryos and compared them to ones that hadn’t been edited, they found something troubling: Around half of the edited embryos contained major unintended edits.

“There’s no sugarcoating this,” says Fyodor Urnov, a gene-editing expert and professor of molecular and cell biology at the University of California, Berkeley. “This is a restraining order for all genome editors to stay the living daylights away from embryo editing.”

While the embryos were not grown past 14 days and were destroyed after the editing experiment, the results provide a warning for future attempts to establish pregnancies with genetically modified...