I know someone well who works in this space, personalized gene therapy as cancer treatment.
> until it finds the exact DNA letter that needs to be changed.
This pine is disingenuous (at best). There is no way of guaranteeing where the DNA is inserted. It is designed to only slot into a very specific portion of the DNA but they don't have a way to control that precisely, the accuracy is high but "exact DNA letter" is skipping over a few pretty important details.
To be clear I'm not saying it is ineffective or unsafe, only that the claim made is marketing speak and not actually true.
The approach they used which is base editing doesn’t actually insert or remove DNA, it actually uses an enzyme to convert one base to another, which is much safer as this doesn’t require a double strand break in DNA: https://blog.addgene.org/single-base-editing-with-crispr
That is interesting, I didn't catch the difference my first time through the article.
I do still question their claim of 100% precise results though. At least based on that high level description I can definitely see it being safer, but I question any scientific claim that is an absolute.
Specific to the editing vs insertion mechanism, I question how it doesn't run into similar constraints where the mechanics of targeting exact portions of the DNA can occasionally miss or impact the wrong segment of DNA entirely.
I haven't dug as deeply down the base pair conversion though, so I could absolutely be wrong!