Viagra was an ineffective drug that now gets sold based on a side-effect noted during testing for it's initial purpose. Maybe that's technically "hard to discover" but it's not really what initially leaps to mind when I hear that phrase.
If a drug that does what Viagra does wasn't hard to discover, why wasn't it invented before? And why would they bother pursuing the ED applications in the first place if someone could copy the formulation the moment it was substantiated?
