In June 2026, a Columbia-led team reported a striking advance in early human embryos: base editing. Unlike older CRISPR approaches that create double-strand DNA breaks, base editing tries to swap a single DNA “letter” more precisely. In a bioRxiv preprint posted on June 1, the researchers edited the PCSK9 and HBG targets with high efficiency and, crucially, did not see the large deletions or chromosomal abnormalities that conventional CRISPR editing has often caused in human embryos. When the editor was delivered as a protein, some embryos developed to the blastocyst stage; when it was delivered as RNA, development stopped early. (sciety.org)

That sounds like a medical breakthrough, but the story is far from simple. Coverage of the preprint noted remaining problems, including guide-dependent off-target edits and mosaic embryos, in which not all cells carry the same change. Nature also reported a deeper fear: if embryo editing becomes more accurate, commercial pressure could grow quickly. A tool designed to prevent severe inherited disease might gradually be marketed for enhancement, feeding the old nightmare of the “designer baby.” (cen.acs.org)

The contrast with current medicine is important. On December 8, 2023, the U.S. FDA approved Casgevy, the first FDA-approved therapy to use CRISPR/Cas9, for certain patients with sickle cell disease. But Casgevy edits a patient’s own blood stem cells outside the body. Embryo editing is different because it would alter the germline, meaning the change could be passed to future generations. That is why many scientists see embryo editing as not only a medical question, but also a social one. (fda.gov)

For now, major institutions remain cautious. The ISSCR says editing the nuclear genome of human embryos for reproduction is premature and should not be permitted at this time. A 2020 international commission organized by the U.S. National Academies, the National Academy of Medicine, and the U.K. Royal Society similarly said no pregnancy should begin with a genome-edited embryo until precise changes can be made reliably and without unwanted effects; if such use is ever allowed, it should begin only with serious single-gene diseases and only in rare cases with no good alternatives. WHO has also said that proceeding now with clinical germline genome editing would be irresponsible. The science offers real hope, but it also forces society to answer a difficult question before the technology outruns ethics. (isscr.org)