Human Gene Editing Summit Organizers Say Proceed With Caution

Megan Brooks

December 03, 2015

It would be "irresponsible" to move ahead with any clinical use of germline editing unless and until relevant safety and efficacy issues are resolved, the Organizing Committee for the International Summit on Human Gene Editing said in a statement released today after 3 days of intense discussion on the topic.

These issues will only be resolved with a greater understanding and balancing of risks, potential benefits, and alternatives, and broad societal consensus about the appropriateness of the proposed application, said the committee, chaired by David Baltimore, PhD, president emeritus and professor of biology, California Institute of Technology, Pasadena.

Gene editing might be used, in principle, to make genetic alterations in gametes or embryos, which will be carried by all the cells of a resulting child and will be passed on to subsequent generations as part of the human gene pool. Examples that have been proposed range from avoiding severe inherited diseases to enhancing human capabilities.

However, the committee emphasized that clinical use of germline editing poses a number of key issues, including the risk for inaccurate editing (such as off-target mutations) and incomplete editing of the cells of early-stage embryos (mosaicism); the difficulty of predicting harmful effects that genetic changes may have under the wide range of circumstances experienced by the human population, including interactions with other genetic variants and with the environment; the need to consider implications for both the individual and the future generations who will carry the genetic alterations; the fact that, once introduced into the human population, genetic alterations would be difficult to remove and would not remain within any single community or country; the possibility that permanent genetic 'enhancements' to subsets of the population could exacerbate social inequities or be used coercively; and the moral and ethical considerations in purposefully altering human evolution using this technology.

The committee advised that clinical use of gene editing should proceed only with appropriate regulatory oversight. "At present, these criteria have not been met for any proposed clinical use: the safety issues have not yet been adequately explored; the cases of most compelling benefit are limited; and many nations have legislative or regulatory bans on germline modification. However, as scientific knowledge advances and societal views evolve, the clinical use of germline editing should be revisited on a regular basis," the committee concluded.

In addition, the committee reached the following conclusions regarding nongermline uses of genome editing:

  • Preclinical Research: Intensive basic and preclinical research is needed and should proceed, within appropriate legal and ethical rules and oversight, on technologies for editing DNA sequences in human cells, on the potential benefits and harms of proposed clinical uses, and on understanding the biology of human embryos and germline cells. "If, in the process of research, early human embryos or germline cells undergo gene editing, the modified cells should not be used to establish a pregnancy," the committee said.

  • Clinical Use (Somatic): Many "promising and valuable" clinical applications of gene editing aim to alter genetic sequences only in somatic cells whose genomes are not passed on to the next generation. Examples include editing genes for sickle cell anemia in blood cells or for improving the ability of immune cells to target cancer. "There is a need to understand the risks, such as inaccurate editing, and the potential benefits of each proposed genetic modification. Because proposed clinical uses are intended to affect only the individual who receives them, they can be appropriately and rigorously evaluated within existing and evolving regulatory frameworks for gene therapy, and regulators can weigh risks and potential benefits in approving clinical trials and therapies," the committee said.

  • Need for an Ongoing Forum: "While each nation ultimately has the authority to regulate activities under its jurisdiction, the human genome is shared among all nations. The international community should strive to establish norms concerning acceptable uses of human germline editing and to harmonize regulations, in order to discourage unacceptable activities while advancing human health and welfare."

The committee called on the national academies that cohosted the summit — the US National Academy of Sciences and US National Academy of Medicine, the Royal Society, and the Chinese Academy of Sciences — to spearhead creation of an ongoing international forum to discuss potential clinical uses of gene editing, help inform decisions by national policymakers and others, formulate recommendations and guidelines, and promote coordination among nations.

The committee said the forum should be inclusive among nations and engage a range of perspectives and expertise, including from biomedical scientists, social scientists, ethicists, healthcare providers, patients and their families, people with disabilities, policymakers, regulators, research funders, faith leaders, public interest advocates, industry representatives, and members of the general public.

In a separate statement, the presidents of the four national academies that cohosted the summit thank the leaders of the summit for their "thoughtful concluding statement and welcome their call for us to continue to lead a global discussion on issues related to human gene editing."

"Together with academies around the world, and in coordination with other international scientific and medical institutions, we stand ready to establish a continuing forum for assessment of the many scientific, medical, and ethical questions surrounding the pursuit of human gene-editing applications. The forum will mobilize the global expertise necessary to help society develop norms for acceptable uses of human gene-editing technology. This is an important moment in human history and we have a responsibility to provide all sections of society with an informed basis for making decisions about this technology, especially for uses that would affect generations to come," the statement reads.


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