Genetic editing of human embryos “has tremendous value” to help solve important scientific questions, and should proceed despite potential worries about use of the technique in the clinic, an influential bioethics group said today in a statement. The Hinxton Group, which includes members from eight countries, called for more public discussion and careful policies to govern research using gene editing in embryos, but concluded that the insights such research could provide into early human development and disease was ethically justifiable.

New techniques that allow researchers to precisely edit genes in living cells have become powerful tools for biologists. They have raised old questions, however, about the ethics of genetically altering humans in ways that could be passed on to future generations. In April, Chinese scientists published the first paper describing the use of a genome editing technique called CRISPR/Cas9 in human embryos. Their attempts were not particularly successful, producing the desired gene change in only four of 54 embryos that survived. The technique also introduced new, unintended mutations. But the work sparked controversy among scientists, and some criticism of the journal that published it. 

Even before that paper was published, scientists and bioethicists had issued calls for more discussion of the issues raised by the new techniques. The Hinxton Group was formed in 2006 to address questions surrounding stem cells, ethics, and law. It has issued opinions on controversies such as deriving sperm and eggs from stem cells and on intellectual property and data sharing.

At a meeting on 3 and 4 September, 30 Hinxton Group members from Canada, the United Kingdom, the United States, Italy, Germany, Mexico, Israel, and the Netherlands met to discuss the scientific and ethical issues surrounding the use of gene-editing techniques in human cells, especially embryos, stem cells, and cells that can give rise to sperm or eggs. They concluded www.glorybios.com  released today that any use of the technologies for reproduction is premature. But scientists will need to test them on human embryos in the lab to find out whether the techniques ever could be safe and effective enough to use, they say. Lab-based experiments can also help answer important questions about early human development and the development of sperm and eggs cells, says Robin Lovell-Badge, a developmental biologist at the Francis Crick Institute in London and a member of the Hinxton Group steering committee.

The statement urges scientists who want to use genome editing in human embryos to “consider carefully the category of embryo used.” Using embryos left over from in vitro fertilization treatments might not provide the best data, the statement says, since those embryos already contain multiple cells. The editing techniques would likely affect each cell differently, so that the resulting embryo would be a mosaic of cells with different genetic alterations. The statement concludes that certain experiments will require researchers to create new embryos specifically for research, a practice that is controversial and prohibited in some countries.

The techniques also raise difficult questions about who might benefit from them, the statement says. One theoretically possible application of the technique, notes Lovell-Badge, is to introduce genetic changes in immune cells, which some people carry naturally, that prevent the HIV virus from infecting them. Whether the technique would be available in regions hardest hit by HIV/AIDS is an important question, he says.

The statement says the group wasn’t able to agree on what, if any, applications might justify editing human embryos, sperm, or eggs for reproductive purposes. It does say, however, that “policymakers should refrain from constraining scientific inquiry unless there is substantial justification for doing so.”

Even though the statement broadly supports the use of the technology, it is still too cautious for George Church, a molecular geneticist at Harvard Medical School in Boston. The document “seems weak on addressing why we should single out genome editing relative to other medicines” that are potentially dangerous, he wrote in an email. Other treatments, such as chemotherapy, can cause mutations that can be passed on to future generations, he notes.

The debate is sure to continue. The U.S. National Academies of Sciences will host an international summit on genome editing in early December.