Columbia University Vagelos College of Physicians and Surgeons

Base edits made before the first cell division persisted in every daughter cell of human embryos

Dieter Egli's Columbia team edited single letters in PCSK9, HBG1 and HBG2 and followed the embryos for six to seven days. Large chromosomal deletions and extra changes near the target still appeared, and he says clinical use is not currently safe.