On Thursday (September 3), the International Commission on the Clinical Use of Human Germline Genome Editing released a report that reviews the available research and determines gene editing’s ethical use on human embryos. The 225-page document offers a roadmap to the testing and regulations necessary to develop the technology and ultimately concludes that the technology is not yet reliable enough to use on humans. Any country that permits its scientists to do so in the future should limit the activity to severe single-gene diseases.

The commission, composed of dozens of scientists worldwide, was formed after Chinese geneticist He Jiankui claimed in 2018 to have used CRISPR-Cas9 on a set of twins and a third baby to make them HIV-resistant. While the validity of the editing has yet to be determined, He’s claims have been met with international condemnation and a three-year prison sentence for illegally...

Somatic gene editing introduces altered DNA into some of the body’s cells post-development as a means to treat genetic conditions. Germline editing manipulates DNA in the earliest stages of embryonic development, affects all tissue types, and permits the organism to then pass down those alterations to their offspring. Instead of treating the disease, germline editing would theoretically be able to eliminate it not only from the organism but from its lineage completely, making it attractive in the context of heritable genetic diseases.

Although manipulating genomes via CRISPR has become commonplace in genetic labs around the world, the commission states that, currently, “the outcomes of genome editing in human zygotes cannot be adequately controlled” and could bear unintended consequences. 

“It underscores what really I think most researchers who think about this are aware of: There must not be any use of germline editing for clinical purposes at this time,” Jennifer Doudna, a geneticist at the University of California, Berkeley, who was not a member of the commission, tells STAT. “And the reason is the technology is just too early-stage and we don’t understand well enough how it works in human embryos.”

Once it is possible to safely make these changes, the commission advises, countries could adopt policies allowing this technology only for the cases when a single gene is responsible for the disorder, such as sickle cell anemia, cystic fibrosis, or Tay-Sachs.

“We think the bar should be high, and appropriately so,” Richard Lifton, cochair of the panel, tells The Guardian. “If you are going to be creating human beings, you want to know that you can reliably make the edits you’re intending. If you can’t do it reliably, without introducing unintended effects, you shouldn’t be going [forward].”

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