Posted on June 20, 2019 at 11:59 PM
This blog has carried several comments about the prospect of
heritable human gene editing. While
nearly no one currently supports bringing such babies to birth—and condemns
those who would rush ahead to do so—it appears a distinct minority think that
we the human race should, if we could, agree never to do such a thing. The most cautious perspective is to advocate
a moratorium. Others in favor of
proceeding argue that, in essence, with the technologic genie (my term, not necessarily
theirs) out of the box, a moratorium, much less a ban, is futile; the
“rogues” will press ahead, casting off restraint.
Advocates of research in this area have argued that a clear,
careful, regulated pathway is needed to guide the work through necessary laboratory
experiments that should be done first, before making a woman pregnant with a
gene-edited embryo, in an attempt to be sure that the process is safe and highly
likely to yield the intended result.
Even a moratorium would be, by definition, temporary, leaving the
question, “when we will know to remove the moratorium?” to be
article in Nature, accessible without a paid subscription, asks
“When will the world be ready” for gene-edited babies. It walks through scientists’ understanding of
what the technical issues are. It is
longer than a blog post, so I can only list key points here. It is worth a reading by anyone interested,
and it is written in sufficiently non-technical language that it’s accessible
to the general, non-scientist public.
Key concerns are:
- How would we be sure that genes that were NOT
intended to be edited, in fact were not?
- How would we be sure that genes that ARE
intended to be edited are edited correctly?
These two matters have been addressed to some degree, or
could be, in animals, but that would be faster and easier than in human egg cells
or human embryos, and the results in animals may be different from what is
found in the embryos. (A further
question is how many embryos, observed for how long, would need to be studied
to support confidence.)
- Even if the intended gene edit is made, is it
clear that doing so is safe and does not induce other health risks?
This blog recently reported the UK study that suggested that
changes in the gene edited in the twin girls born in China last year might
eventually reduce life span. A criterion
promulgated in 2017 by the National Academies of Sciences, Engineering, and
Medicine was that the edited gene should be common in the population and carry
no known risk (including, presumably, no increased risk) of disease. Such knowledge is lacking for human
populations, and what is believed known about the association of genes with
risk of future disease has often been developed in Western populations, and may
not apply to, for example, Africans.
- At least some embryos would include some edited
and some non-edited cells. It would not
easily be possible, if possible at all, to tell how many of which were present,
or needed to be for the editing to work and not cause risks to the embryo’s
development into a baby and beyond. And
what answers were obtained would require manipulating healthy embryos after in
vitro fertilization. The outcomes could
not be predicted from first principles.
- What should a clinical trial look like? How many edited children would have to be born,
and their health (and, most likely, the health of their progeny) observed for
how long to get provisional answers before practicing the technique more
widely? Or, would the work proceed as
IVF did—with dissemination in the general public, and no regulated research?
A US and UK committee is planned to address these questions,
with the intent of proposing guidelines in 2020. This will be important to follow, but with no
chance to affect. Most of us will just
be watching, which leads to the last concern:
- Is the world ready?
If that means, is there an international, or even
a national, consensus, then the answer is clearly “no.” That almost certainly remains “no”
if one asks whether there is a future prospect for consensus. It’s hard to envision something other than
different groups and nations holding different judgments, and, most likely,
remaining in some degree of irresolvable conflict.
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