"A priority review can be granted at any time, including prior to Phase 1. That’s why the FDA states clinical evidence is not necessary, and it’s case by case." (Is there a way to do that other than case-by-case"?)
As logical as that sounds it still seems inconsistent with a few other FDA statements/documents:
"When to submit request With original BLA, NDA, or efficacy supplement"
"Priority review can be for all reviews including those between trials. It’s not just for a NDA or end-of-phase 3 review." "Features Shorter clock for review of marketing application (6 months compared with the 10-month standard review)"