[jameskraus]

One reason may be that a general fix that produces good hemoglobin is much more efficient than attempting to fix the original problem. People can have a near-limitless number of mutations that lead to defective proteins, so creating fixes for all those "bugs" can be very expensive. A general fix that works around the "bug" is cheaper, consistant, and more scalable.

Another way to look at it: Would a per-patient fix be possible? Maybe. Is it worth debugging and fixing everyone's crappy DNA to do that? Probably not.

[dogma1138]

That’s true even if the mutation is the same it’s hard to actually fix it, while reactivating or over-expressing a gene that already exists and works is much easier.

For this specific case it’s also better because lesser coverage might still produce sufficient results since fetal hemoglobin out competes adult hemoglobin.

I think in general CRISPR would be patch over rather than a point fix.