I can tell you that this program basically almost requires you to be a second-year PhD before you begin. Successful applicants must also have an exemplary record -- sometimes from high school on -- in a life sciences major, and usually have multiple top-level publications, numerous years of experience, nearly perfect scores across the board. I know that there is a "back channel" into PiN, but I don't quite understand how it works, so I don't want to post about it publicly. Profs and doctoral students in the program will basically tell you, so it's an "open secret".