Good question, had to look that up for you.
I think it depends on the school you apply to and other factors but I did find an answer on the AAPA dot org website where the following is pasted in from:
Application to PA school is highly competitive.
Look into PA programs you want to apply to as early as your freshman year in college.
You’ll typically need to complete at least two years of college coursework in basic and behavioral sciences before applying to a PA program, which is very similar to premedical studies.
You asked a very important and interesting question! here are some attempts to answer that question:
Please keep me posted. I would like to follow your progress!