An interesting approach.

As I remember, PCSK9 is an enzyme that breaks down the parts of the liver that remove LDL and VLDL particles from the blood.

There are some drugs now that block PCSK9. They're quite effective, but aren't in widespread usage because they're much more expensive than the 'standard of care', statins., which instead interfere with lipid production.

Speaking of particles, it's the number of particles, particularly VLDL, that pose a threat to artery epithelial cells, according to Dr. Thomas Dayspring, a 'lipid educator'. (google 'dr lipid' for links if you're interested in how the lipid system works).

CRISPR is a breakthrough technology. I've recently seen that it can also be used to change methylation (AKA epigenetics). Any idea if that's what they're doing here? I find making epigenetic changes to humans significantly less terrifying than directly to DNA (but, hey, that's me)

Oh, and it is possible to have too few lipids. They are a provider of phospholipids, which are essential for cell membranes.

And finally, there's been progressively less and less evidence that HDL is protective against CVD, so it's not clear that boosting that will do anything particularly positive. Niacin, for instance, boosts HDL, but doesn't change mortality.