When scientists at Columbia University announced they had used a newer technology to precisely edit the genes of human embryos last week, they set the academic community ablaze with debate. Is this good news or bad? How fast will this move? And more philosophically: Where does medicine end and eugenics begin?
The results of the new study, first reported by The New York Times, showed that a technique called base editing meticulously swapped out individual letters in an embryo’s genome, altering genes linked to fetal hemoglobin production, cholesterol levels and the risk of heart disease.
Though the work is still under peer review and has not yet been published in a scientific journal, experts from a vast array of disciplines are discussing whether the tool will bring us one step closer to curing inherited diseases or one step closer to designer babies — or both.
Optimistic clinicians saw the Columbia study as a major step in medicine, bolstering their hope that scientists could one day fix embryo mutations in a clinical setting. Dr. Ellen Goldstein, a reproductive endocrinologist and fertility specialist in Los Angeles, said that for some of her patients, the tool could mean a successful pregnancy with an embryo that would have otherwise been discarded.
“There are very specific problems that this technology could be applied to — conditions where we all agree there are devastating consequences,” she said, like Huntington’s disease, which causes nerve cells in the brain to break down, or Duchenne muscular dystrophy, in which skeletal and heart muscles waste away. As a doctor, “You wish you could just go in and start fixing embryos,” she said.
Tweaking embryos with an earlier form of gene editing, CRISPR, is considered far too risky. The tool functions like a pair of molecular scissors, hacking off long segments of DNA, sometimes in error. Researchers who tried it found their specimens with strange DNA rearrangements, large swaths missing and, in some cases, entire chromosomes destroyed.
Base editing is not nearly as clunky. The Columbia researchers were in many cases able to change single letters of the genome safely, as if they had a precision eraser and a red pencil to simply correct the spelling. For proponents of the new tool, the argument is: If we could safely prevent a child from inheriting a devastating genetic condition, isn’t it unethical not to?
“We have to be really careful not to have knee-jerk reactions to reject this kind of research,” Dr. Goldstein said, “as long as you’re doing it with proper understanding, and proper respect for the future implications and with correct oversight from biologists and ethicists.”
Many of those ethicists are the ones issuing caution. Dr. Lainie Friedman Ross, a pediatrician and bioethicist at the University of Rochester, was skeptical not just of the future implications of the technology, but of the present-day work.
“Let us be clear,” she said. “Human embryos become living human persons. The research is being done on future persons without their consent.”
The researcher who led the project, Dieter Egli, told The Times that a public conversation about the pros and cons of editing genes in embryos was necessary, but that “as a scientist, you can provide the data for discussion, but then essentially there you stop and let others take over.”
Dr. Ross vehemently disagreed. “This is morally irresponsible. There is no such thing as value-neutral science,” she said. “The team has already made an ethical decision to pursue this line of work.”
Geneticists, too, are tempering their excitement, arguing that the technology still has major limitations. The tweaks, though precise, only worked in a portion of the cells, which resulted in so-called mosaic embryos that contained a mix of edited and unedited cells. If one of the mosaic embryos had been implanted and led to a pregnancy, the health implications of the mix might not have become apparent for years after the child’s birth.
Another clinical complexity: Since modern I.V.F. usually extracts a small cluster of cells for genetic testing, the mosaic nature of an embryo could easily be missed. If the randomly selected pocket is healthy, it could offer parents false reassurance, masking the mutation elsewhere.
“We are very far away from having safe embryonic gene-editing methods where the benefits outweigh the risks,” said Rasmus Nielsen, a geneticist at the University of California, Berkeley.
Early embryo editing also comes with a sobering level of permanence. Unlike edits to standard body cells, any changes made to reproductive cells are passed down to future generations. That means edits — or errors — in a clinical setting wouldn’t end with that child, but would be passed down their family line, altering the gene pool forever.
“How would we as a society intervene if the intervention led to serious health or reproductive consequences? We have no strategy,” Dr. Ross said. “This can have dire consequences for our species.”
Despite the risks, many experts expect a substantial commercial push, not just to make this technology available, but also to encourage it. The chief clinical officer of Nucleus Genomics was an author on the new paper, and the company announced it was “proud to fund the next phase of research focused on further advancing this technology toward clinical use.”
At a booming moment in reproductive technology — and one at which Nucleus is among the companies at the center — some researchers worry that the initial concept of editing away diseases will quickly be repurposed into a Silicon Valley push to optimize the human genome, promising wealthy parents the chance to edit for elective traits like eye color and height.
Many of the eugenic traits that bioethicists worry about most, like intelligence, rely on hundreds or thousands of genes that interact with one another and a child’s environment. Thus, it’s highly unlikely that one-by-one base editing would be useful. But that doesn’t mean companies would not capitalize on parents’ hopes and fears.
“Given the lack of regulation around reproductive technologies,” said Daphne Oluwaseun Martschenko, a bioethicist at Stanford University, “it feels like only a matter of time.”
