June 15, 2016

National Academy of Sciences Report on Controversial Gene Drive Technology Endorses Further Research, Controlled Field Trials

The National Academies of Sciences, Engineering, and Medicine (NAS) has issued a report on gene drive technology, Gene Drive Research in Non-Human Organisms: Recommendations for Responsible Conduct. A gene drive is a method by which specific genetic mutations (or alleles) are preferentially inherited, and over time, the effect is to eliminate other competing alleles. This has population-wide consequences for an organism, and can permanently alter (or reduce) the genetic diversity of a species. The phenomenon of a gene drive occurs in nature, and has been observed in many organisms
In nature, certain genes ‘drive’ themselves through populations by increasing the odds that they will be inherited.
Now, however, advances in gene-editing technology have facilitated the development of deliberately engineered gene drives. From the report summary:
A wide variety of gene drives occur in nature. Researchers have been studying these natural mechanisms throughout the 20th century but, until the advent of CRISPR/Casfor gene editing, have not been able to develop a gene drive. Since early 2015, laboratory scientists have published four proofs-of-concept showing that a CRISPR/Cas9-based gene drive could spread a targeted gene through nearly 100% of a population of yeast, fruit flies, or mosquitos.
In other words, use of gene drive technology can impose a specific genetic allele (variant) on a population and eliminate all other forms of the gene. Effectively, the population is now homozygous for the preferred variant. That is both the attraction and the concern regarding the use of this technique. Genetic traits could be eliminated, and at its most extreme, whole populations could be "driven" out of existence. It is simple to imagine particular uses of the technology that would eliminate undesirable traits in a target population, such as the ability of mosquitos to spread malaria, or very currently, the ability of the Aedes aegypti mosquito to transmit the Zika virus. The report summarizes possible applications and the requirement for a deliberative approach to use of the technique:
Gene-drive modified organisms hold promise for addressing difficult-to-solve challenges, such as the eradication of insect-borne infectious diseases and the conservation of threatened and endangered species. However, proof-of-concept in a few laboratory studies to date is not sufficient to support a decision to release gene-drive modified organisms into the environment. The potential for gene drives to cause irreversible effects on organisms and ecosystems calls for a robust method to assess risks. A phased approach to testing, engagement of stakeholders and publics, and clarified regulatory over-sight can facilitate a precautionary, step-by-step approach to research on gene drives without hindering the development of new knowledge.
The report did not recommend a moratorium on research, despite noting the potential for adverse consequences. Instead, it endorsed continued research on the technology with some limited field evaluations:
Although there is insufficient evidence available at this time to support the release of gene-drive modified organisms into the environment, the likely benefits of gene drives for basic and applied research are significant and justify proceeding with laboratory research and highly-controlled field trials.
The current regulatory landscape for gene drive applications is summarized:
In the United States, regulation of gene-drive modified organisms will most likely fall under the Coordinated Framework for the Regulation of Biotechnology, which includes the U.S. Food and Drug Administration, the U.S. Department of Agriculture, and the U.S. Environmental Protection Agency. However, the diversity of potential gene-drive modified organisms and contexts in which they might be used reveals a number of regulatory overlaps and gaps. The U.S. government will need to clarify the assignment of regulatory responsibilities for field releases of gene-drive modified organisms, including the roles of relevant agencies.
At the present time, the patchwork structure for biotechnology regulation is currently under formal review by the Obama administration (see earlier post for more background). In general, as the new products of genetic engineering have been developed over the years, they encounter oversight from any one (or more) of three agencies: the FDA, EPA, or USDA. As the regulatory framework is redesigned, we could expect that various applications of gene drive technology will face an approval process customized to the particular goal and purpose of the technology. The report states:
It is important to note that a one-size-fits-all approach to governance is not likely to be appropriate. Each phase of research activity—from developing a research plan to post-release surveillance—raises different levels of concern depending on the organism being modified and the type of gene drive being developed.
The NAS report has received criticism from opponents of field testing, who noted that precise control of such experiments is not possible, and wider, possiblly uncontrolled spread of altered organisms could occur. Other criticisms suggest that the scope of the report is too limited, and does not adequately address possible dual-use concerns (malevolent uses of the technology). The report has some conceptual overlap with efforts of the World Health Organization (WHO) has previously released a guidance framework for how to introduce genetically engineered mosquitoes that are reproductively disabled, thus reducing the population of a malaria vector. In summary, the NAS panel has cautiously endorsed further gene drive research in the U.S., and contemplates eventual field trials of engineered organisms.

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