It doesn't take anywhere near a billion dollars to test a new medicine, and if there were a good reason for singling it out as worthy of serious investigation, drug companies would probably already be on it.
The only good reason a drug company has to investigate a drug treatment is if they can make substantial money on it, which they generally can't with off patent drugs and natural compounds already in use.
In fact, when they have patent medicines for the same malady, they have every interest in seeing that off patent medicines are banned.
If a natural compound is already in use and works, drug companies have an interest in testing derivatives which can be made more effective or lower in side effects, and which can be patented. Aspirin and all forms of opiates are well known examples of drugs originating in this way.
"Drug companies can't patent natural compounds, so they don't bother to research them" is a commonly used excuse by alternative medicine industries, but in fact drug companies frequently do test natural compounds. It can be done cheaply with a small sample size, because...
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