Somewhat hypothetical, but: how difficult is it to reverse-engineer a drug's exact composition with only the final product (the pill/vaccine/etc. itself)? If it's difficult enough to be economically infeasible, then patent protection here could be replaced by simply keeping the drug a secret.
Of course, that kills the generics market, and I suspect it's not such a difficult problem to RE a drug, but... just curious.
They have to disclose the contents to be licensed for medical purposes.
My wife did a stint as a student with AstraZeneca (global pharma corp) they were making "new" drugs. One thing they do is take an existing drug and try swapping out different parts for functionally equivalent parts and run tests to see if the drug is effective enough to warrant proper trials and check to see if it circumvents the opposition patents.
Of course, that kills the generics market, and I suspect it's not such a difficult problem to RE a drug, but... just curious.