I imagine the costs of trials, and who paid them, are well documented. In the event of a dispute about which company discovered which drug, could a company not point to its investment in research or funding of a specific trial as evidence of its discovery, rather than trying to spam system with provisional patent applications? (By the way, there's no such thing as a "provisional patent" http://en.wikipedia.org/wiki/Provisional_patent#cite_note-1)