In my (admittedly indirect) experience, there's always a specific medical issue being targeted, and usually a specific biochemical system (i.e. protein binding

In my (admittedly indirect) experience, there's always a specific medical issue being targeted, and usually a specific biochemical system (i.e. protein binding partner). Very occasionally, they end up with a drug for a condition completely different from what they were trying to treat, but that's the exception. (Viagra was one of these; I would have loved to have been a fly on the wall when they realized the implications of the side effect profile from the original trial.)