Broad scientists and geneticists discuss issues raised by clinical germline genome editing

In a conversation with the Broad community, core institute members Feng Zhang and David Liu, institute member and clinical geneticist Heidi Rehm, and director of global policy initiatives Bina Venkataraman considered a range of scientific, medical, ethical, and societal concerns raised by reports that a researcher in China engineered the “world’s first genetically edited babies.”

Len Rubenstein Photography
Credit: Len Rubenstein Photography

(L-R) Feng Zhang, Heidi Rehm, David Liu, and Bina Venkataraman discuss a variety of issues raised by reports of germline genome editing in human embryos. Recorded 12/14/2018.


11/26/2018: Broad scientists Feng Zhang and David Liu also released statements regarding reports that a researcher in China has engineered the “world’s first genetically edited babies.”

Feng Zhang’s team pioneered the development of genome editing tools for use in eukaryotic cells from natural microbial CRISPR-Cas9 systems. Zhang is an investigator at the McGovern Institute for Brain Research at MIT, the James and Patricia Poitras Professor of Neuroscience at MIT, and an associate professor at MIT, with joint appointments in the departments of Brain and Cognitive Sciences and Biological Engineering. Zhang is also an investigator at the Howard Hughes Medical Institute.

Although I appreciate the global threat posed by HIV, at this stage, the risks of editing embryos to knock out CCR5 seem to outweigh the potential benefits, not to mention that knocking out of CCR5 will likely render a person much more susceptible for West Nile Virus. Just as important, there are already common and highly-effective methods to prevent transmission of HIV from a parent to an unborn child. 

Given the current early state of genome editing technology, I'm in favor of a moratorium on implantation of edited embryos, which seems to be the intention of the CCR5 trial, until we have come up with a thoughtful set of safety requirements first.

Not only do I see this as risky, but I am also deeply concerned about the lack of transparency surrounding this trial. All medical advances, gene editing or otherwise and particularly those that impact vulnerable populations, should be cautiously and thoughtfully tested, discussed openly with patients, physicians, scientists, and other community members, and implemented in an equitable way.

In addition, in 2015, the international research community said it would be irresponsible to proceed with any germline editing without "broad societal consensus about the appropriateness of the proposed application." (This was the consensus statement from the 2015 International Summit on Human Gene Editing.)

It is my hope that this year’s summit will serve as a forum for deeper conversations about the implications of this news and provide guidance on how we as a global society can best benefit from gene editing.


David Liu is the Richard Merkin Professor and Director of the Merkin Institute for Transformative Technologies in Healthcare at the Broad Institute, Vice Chair of the Faculty, and Director of the Chemical Biology and Therapeutic Sciences Program.

The recently reported use of CRISPR nuclease to edit CCR5 in human embryos, resulting in live births, represents a serious breach of ethics that I hope will serve as a wake-up call for the community. Foremost, that edited human babies were generated without the full engagement of independent scientific and ethics experts, relevant regulatory institutions, and governing bodies is appalling. In addition, the unmet medical need motivating the work is unclear at best. Compared to other known approaches to protect newborns from HIV infection, genome editing CCR5 in an uninfected human embryo offers questionable benefits and substantial risks, including increased risk of encephalopathy from West Nile virus.  

Credit: Eric Jacobs

Like many in the biomedical research community, I anticipate a future in which the application of genome editing technologies provide therapies or even cures for grievous genetic diseases for which no treatment is known. In somatic cells, which do not become part of future generations, these technologies can be used in a focused manner and with the consent of the patient. Embryo editing, in which changes are made to the genome of cells that may include the sperm and egg cells that become future generations, is a very different situation that raises additional critical scientific and ethical issues. There may be a future in which embryo editing is justified following a careful analysis of potential benefits, risks, and ethical issues, but the recently reported work does not meet these standards. Because of the potential of genome editing to provide a transformative benefit to patients, it is essential that we progress in a thoughtful and coordinated manner. Failure to do so risks both harming patients, and delaying or denying potential therapies to many that urgently need them.