IN A SLICK VIDEO RELEASED ON Nov. 25, Chinese scientist He Jiankui dropped a scientific doozy on the world. He claimed, and further explained in an interview with a journalist, that his work had produced the world’s first human babies whose genomes had been edited using the technique called CRISPR. The twin girls, born a few weeks ago, harbor genetic changes that are supposed to make them resistant to HIV infection. And they may not be alone;He said another woman is pregnant with a potential third baby with CRISPR altered genes and that he has edited more than a dozen additional embryos that remain frozen.
Those embryos will stay that way for the near future, awaiting the outcome of an investigation by Chinese authorities on the legality and ethics of He’s study, which is currently on hold.And that investigation is just part of the major backlash He faces. Because he published on YouTube rather than in a scientific journal, his claims haven’t been properly validated. Both the university where He is on the faculty (and has been on leave since February) and the hospital where the births occurred denied even knowing his controversial study was taking place. Even more important, nearly all leading genetics experts believe CRISPR—a tool developed in 2012 through which a DNA-protein complex can seek out and remove specific DNA sequences—is not yet safe for use in humans. International scientific groups specifically prohibit the use of CRISPR to alter DNA in human embryos that would be implanted for birth,which is exactly what He did.Appearing at a major genetics conference in Hong Kong in the days after his announcement, He faced skepticism, and worse, from scandalized colleagues who called his experiment “irresponsible” and “reckless.”Harvard Medical School dean Dr. George Daley said He crossed a scientific and ethical line, and warned that scientists who “go rogue” jeopardize legitimate CRISPR research efforts to find new treatments for life-threatening diseases.
WHAT CONCERNS EXPERTS is that as precise as CRISPR is, it can still make mistakes. Its edits can be incomplete or, like an overzealous autocorrect feature, can cause unintended changes in random parts of the genome. That’s particularly worrisome when it comes to cells that, once tweaked, pass those changes on to the next generation: eggs, sperm and embryos like the ones He worked on. Researchers in the U.S. and the U.K. have edited human embryo DNA for research purposes only—in other words, those embryos were not transferred to become pregnancies—and most experts currently support research into CRISPR’s uses only in cells that don’t get passed on. “I’m in favor of a moratorium on implantation of edited embryos until we have come up with a thoughtful set of safety requirements first,” says one of CRISPR’s co-discoverers, Feng Zhang, of the Broad Institute of MIT and Harvard.
The U.S.’s National Academy of Sciences concluded last year that CRISPR could someday be used on human embryos—but only under strict oversight and only to treat diseases that can’t otherwise be addressed. Neither condition was met in He’s study. He recruited couples in which the father was HIV-positive. In their IVF-produced embryos, he then altered a gene to hamper HIV’s ability to infect cells. But the fathers were on anti-HIV drugs, so it was unlikely they’d pass on the virus anyway, and there’s evidence that the gene alteration He used can make people more susceptible to West Nile virus as well as possibly the flu. The upside of editing—if it worked—was minimal compared with the potential risk. “If there is no benefit, then they have no business doing this,” says Dr. Kiran Musunuru, a genetics expert at the University of Pennsylvania. He says he plans to follow the twins until they are 18 years old. Apart from his scientific questions, those years will raise far more profound ones for society, as the first people born with genomes edited not by chance but by science grow into adulthood. Navigating those unknowns is a burden the twins will carry for the rest of their lives, along with their controversial history-making DNA.