2017-02-14 12:37:09
Human Gene Editing Receives Science Panel’s Support

An influential science advisory group formed by the National Academy of Sciences and the National Academy of Medicine on Tuesday lent its support to a once-unthinkable proposition: clinical efforts to engineer humans with inheritable genetic traits.

In a report laden with caveats and notes of caution, the group endorsed the alteration of human eggs, sperm and embryos — but only to prevent babies from being born with genes known to cause serious diseases and disability, only when no “reasonable alternative” exists, and only when a plan is in place to track the effects of the procedure through multiple generations.

Human genetic engineering for any reason has long been seen as an ethical minefield. Many scientists fear that the techniques used to prevent genetic diseases might also be used to enhance intelligence or create humans physically suited to particular tasks, like soldiers.

Just over a year ago, an international group of scientists declared that it would be “irresponsible to proceed” with making heritable changes to the human genome until the risks could be better assessed and until there was “broad societal consensus about the appropriateness” of any proposed change.

Because any genetic changes in human eggs, sperm and embryos, also called the germ line, can be passed on to future generations, the recommendation crosses a line that “many have viewed as ethically inviolable,” the report acknowledges.

But in the last year, the report’s authors said, the techniques required to perform this sort of gene editing have passed crucial milestones that have forced ethical considerations to the fore.

“Previously, it was easy for people to say, ‘This isn’t possible, so we don’t have to think about it much,’” said Richard Hynes, a cancer researcher at the Massachusetts Institute of Technology, who was one of the leaders of the committee that wrote the new report.

“Now we can see a path whereby we might be able to do it, so we have to think about how to make sure it’s used only for the right things and not for the wrong things,” he said.

A more pragmatic concern driving the committee was the likelihood that the technology would be adopted elsewhere, in countries like China, where some pioneering research on editing human embryos — without the intent to gestate them — has already taken place.

“If we have an absolute prohibition in the United States with this technology advancing, it’s not like it won’t happen,” said R. Alta Charo, a bioethicist at the University of Wisconsin, Madison, and the committee’s other leader. “We see an advantage of setting out a stringent regulation that guards against the uses that people are most fearing and signals to the rest of the world what it should look like when it’s done right.”

But opponents of human germ line editing say that’s not a good enough reason for taking a crucial step toward what they fear will be the inevitable use of technology to engineer traits like strength, beauty and intelligence, perhaps eventually creating a dystopian social divide between those who can afford such enhancements and those who cannot.

“This opens the door to advertisements from fertility clinics of giving your child the best start in life with a gene-editing packet,” said Marcy Darnovsky, executive director of the Center for Genetics and Society, a public interest group based in Berkeley, Calif. “And whether these are real advantages or perceived advantages, they would accrue disproportionately to people who are already advantaged.”

The guidelines, Ms. Darnovsky noted, also set the United States apart from many European countries that have signed a treaty to refrain from human germ line editing.

The advent of a powerful gene-editing tool called Crispr-Cas9 that allows researchers to snip, insert and delete genetic material with precision has led to plans for the experimental treatment of adult patients with cancer, blindness and other conditions as early as this year. Such alterations, which do not infiltrate the entire genome, are not inherited. And the academies’ committee called for prohibiting anything bordering on “enhancement” in that sphere as well, including “off-label” applications. Under the guidelines, a genetic edit aimed at strengthening the muscles of patients with Duchenne muscular dystrophy, for instance, could not be used to make healthy people stronger, the report’s authors said.

While Crispr is generally precise, it can have off-target effects, cutting DNA at places where it is not meant to.

But no one should expect to order up a designer baby anytime soon. It will most likely be several years before gene-editing techniques tested in mice can be shown to work in human sperm or eggs. And for the moment, the Food and Drug Administration is prohibited from using federal money to review research on inheritable embryo modification.

Given the strict limitations recommended by the group, those who would qualify are likely to be a surpassingly small group: individuals who carry two copies of the genetic mutation that causes Huntington’s disease, for instance, and have no other way of having a genetically related child unaffected by the disease.

“But the fact that it’s a small number of people doesn’t mean their concerns are any less real,” Dr. Charo said. “You have to really confront the people who could benefit from it and tell them why you won’t let them use it.”