Human genome editing was always going to happen, eventually. And it was probably going to happen first in China, where there is far less stigma around the idea. The Chinese word for “eugenics”, yousheng, has entirely positive connotations; not smoking while pregnant, for example, is considered yousheng. The Chinese public has embraced preimplantation genetic diagnosis, screening embryos for health characteristics and aborting them if they have, for instance, deafness or Downs syndrome, to a far greater extent that the West has.
So it’s not a huge surprise that, apparently, twin girls have been born in China with a specific gene, CCR5, eliminated, using the technique CRISPR/Cas9. I say “apparently” because it’s all a bit murky: there are medical documents posted online, but they’re not peer reviewed, the scientist involved – He Jiankui of the Southern University of Science and Technology, in Shenzhen – has declined to speak to the press (although he has now addressed a conference in Hong Kong), and everyone has residual memories of that guy who claimed to have successfully performed a head transplant and that other one who reckoned he’d cloned humans. Plus, some of the organisations apparently involved say they don’t know anything about it. But it’s plausible. At least one geneticist I’ve spoken to thinks it’s real.
It may not be a surprise, but nor is it a good thing. In Britain, human genome editing is regulated by the Human Fertilisation and Embryology Authority (HFEA). It’s a good and far-sighted organisation, willing to allow the use of new technologies when they are shown to be safe and effective; Britain became, in 2016, the first country to allow mitochondrial donation, the so-called “three-parent baby” technique, to prevent devastating mitochondrial disease.
The HFEA allows human embryos to be edited. But they have to be destroyed after 14 days, and can’t be implanted. That’s not out of some misguided fear of playing God: if it could be shown that the procedure could reliably and safely prevent disease, I’m pretty sure that the HFEA would back it. But it can’t.
That is, in short, because as yet it’s not safe, or reliable. There are frequent “off-target effects” – basically, unwanted mutations introduced by the procedure – and “chimeras”, where some of the cells in the embryo are successfully edited, but others aren’t, so you end up with a patchwork embryo, half-full of cells which still have the gene you wanted to remove.
These problems mean that only about 20-30% of attempts to edit human genomes are successful, at least on trials of CRISPR for thalassaemia, which similarly involved knocking out a single gene. Those embryos, of course, were destroyed at the 14 day mark.
It may be that, soon, those odds improve. And then it could well be ethical to, cautiously, do the first human trials. The Oxford bioethicist Julian Savulescu says that those first trials should be in embryos with “otherwise lethal catastrophic genetic mutations who are certain to die”. Then the edits might save the lives of the babies, when they are born.
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