A Chinese researcher’s claim he created the world’s first genetically engineered babies—causing a worldwide backlash—could taint the entire field of gene editing, ultimately stifling new treatments, the head of the NIH told Bloomberg Law.

“It’s clear that this was an egregious example of ignoring the ethical norms that had been developed by many scientists across the world,” and it potentially does damage to the entire promising field of gene editing, Francis S. Collins, director of the National Institutes of Health,...