It seems to me that in an adult, it may already be too late. How would you remove the existing protein?
On the other hand whatever job PrP was doing will also cease getting done, and its downstream pathways will be disrupted. So there are likely consequences.
Now if you could totally shut down PrP synthesis for like a week, then turn it back on, that might work. In theory this is possible using a tet-expression system [1], but I've never worked with a tet system that wasn't leaky. The only sure way would be to KO PrP genes from all cells, then CRISPR it back in a week later. Oh, and I'm talking about cells in a culture dish; this strategy would never work in an adult human.
[1] https://www.jax.org/news-and-insights/2015/april/introductio...
All of them? I admit that I'm not a biologist, so that's new to me, but this would seem to put our bodies under immense stress if we had to replace half of all our proteins every day. If the average human body has 10 kg of proteins, this would mean the necessity of synthesizing 5 kg per day to prevent your death. Or is this specifically about PrP? If it's true that it doesn't last long, then perhaps stopping its synthesis would be a viable option.
Does the misfolded PrP have a different half-life?