By Jon Holmlund
The Thursday, Dec 13 edition of the Wall Street Journal carries this headline: “Doubts Arise Over Gene-Editing Claim.” The work behind the recent report that the world’s first two gene-edited babies had been born has been publicly discussed, but the details have not yet been published for full scientific review. Apparently scientists in the gene-editing field are reviewing the public presentation and finding it lacking:
- Some, but not all, of the cells in the children may have been edited. One would expect changes in all of the cells, and this should be necessary for the overall stated medical goal (protection from HIV infection) to have a chance of having been met.
The edited babies may have variants of the edited gene that have not been fully studied and could have unforeseen health consequences.
The technique used to confirm the gene changes may not be sensitive enough to detect whether other, unintended and potentially undesirable gene changes had been made.
And perhaps most notably, the studies done in mice to demonstrate the feasibility of the technique, before editing the embryos that grew into the full-term babies, involve a different change in the target gene in mice than the change sought in the children. In other words, the animal studies appear not to be representative of the human situation.
This is a common problem for development of new treatments for cancer and other diseases. Tests are initially done in animals—usually mice—to determine whether the putative new treatment appears to be working. The animal models used never entirely reflect the human disease. Some come closer than others. But the way of handling that uncertainty is to define and limit the risks to people who subsequently have the new treatment tested on them in clinical trials.
In the case of the gene-edited babies, there’s really no way to limit the potential risks, at least not yet, if ever. Ultimately, one has to strike out and make changes that could backfire for the recipient humans, or be propagated into their descendants with unpredictable effects.
Accordingly, without good animal models, and appropriately extensive testing in them, then, as professor Sean Ryder of the University of Massachusetts Medical School is quoted as saying, “the babies are the experiment.” Ultimately, heritable gene editing may just require a leap of biomedical faith.
We should just say, “no, we shall not.”