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Five Russian couples who are deaf want to try the CRISPR gene-editing technique so they can have a biological child who can hear, biologist Denis Rebrikov has told �鶹��ý. He plans to apply to the relevant Russian authorities for permission in “a couple of weeks”.

The case for using CRISPR for this purpose is stronger than for trying to make children HIV-resistant, as attempted previously, but the risks still outweigh the benefits, say other researchers.

“Rebrikov is definitely determined to do some germline gene editing, and I think we should take him very seriously,” says CRISPR expert Gaetan Burgio at the Australian National University. “But it’s too early, it’s too risky.”

Both would-be parents in each couple have a recessive form of deafness, meaning that all their children would normally inherit the same condition. While the vast majority of genetic diseases can be prevented by screening IVF embryos before implantation, with no need for gene-editing, this is not an option for these couples.

Several have suggested that – if it can be done safely – editing the genes of babies might be justified in this kind of situation.

Risky procedure

That is exactly why Rebrikov, at Russia’s largest fertility clinic, the Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology in Moscow, has sought out these very unusual couples.

“It is clear and understandable to ordinary people,” he says. “Each new baby for this pair would be deaf without gene mutation editing.”

In November, a biophysicist in China announced that he had secretly created the first-ever gene edited babies using CRISPR. He Jiankui tried – but probably failed – to induce mutations that protect against HIV by gene-editing IVF embryos from couples in which the man is HIV-positive.

His work has been condemned for many reasons, but one of the biggest is that there is no need to resort to such a risky experimental procedure to prevent these men infecting their children with HIV.

In June, Nature reported that – but this time for couples where the mother is HIV-positive. Unlike He, Rebrikov is openly discussing his plans in advance.

Again, though, experts have pointed out that there is no need for risky gene editing in this case.

Recessive deafness gene

Now Rebrikov has told �鶹��ý that he also wants to prevent children inheriting a form of deafness caused by mutations in the GJB2 gene. In western Siberia, in position 35 of . Having one copy has no effect, but those who inherit this mutation from both parents never develop the ability to hear.

Rebrikov has found five couples in which both would-be parents are deaf because of this mutation and don’t want their children to be deaf too.

So he plans to use CRISPR to correct this mutation in IVF embryos from these couples. All these embryos will have the mutation in both copies of the GJB2 gene – correcting one copy using a method known as homology-directed repair will prevent deafness.

“Technically, it is achievable,” says Burgio.

In November, saying that this kind of germline genome editing could be acceptable if the risks were addressed and if certain criteria are met. Those criteria include “a compelling medical need” and “an absence of reasonable alternatives”.

Preserving deaf culture

The five couples don’t have any other choice if they want to have their own biological children who can hear. But not everyone will agree that there is a compelling need, because deafness isn’t a life-threatening disorder. In fact, some people who are deaf don’t consider it to be a disability and want their children to inherit the condition in order to preserve unique deaf cultures.

And the risks of CRISPR certainly haven’t been addressed. There is no proven way to ensure that gene-edited children won’t have unintended mutations, or to ensure that every cell in the children’s bodies will have the corrected gene.

“We continue to believe that proceeding with any clinical use of germline editing remains irresponsible at this time,” the November statement says.

“The first human trials should start with embryos or infants with nothing to lose, with fatal conditions,” says bioethicist Julian Savulescu of the University of Oxford. “You should not be starting with an embryo which stands to lead a pretty normal life.”

So why isn’t Rebrikov trying to prevent more serious genetic disorders? The answer is that people with serious recessive disorders almost never find themselves in the same situation as the five couples. For instance, people with cystic fibrosis usually die young and are actively discouraged from meeting to avoid swapping the bacteria that infect their lungs.

Savulescu thinks the first gene-editing trials should involve couples whose children could inherit fatal conditions such as Tay-Sachs, but who refuse to opt for screening IVF embryos because they are opposed to destroying embryos on religious grounds.

If germline gene-editing is one day shown to be safe, Savulescu thinks there would then be a moral imperative to use it to prevent conditions such as deafness.