What kind of testing could be done to make natural drugs more acceptable as therapeutics?

Prescription and over-the-counter drugs must go through years of expensive, large-scale clinical trials and rigorous FDA scrutiny to prove they work and are safe for specific diseases before they can be sold. This kind of testing of a supplement will not ever be done. Both the high cost of testing and the inability of the developer to protect (patent) the drug render this kind of development unaffordable. However, since many supplements already have a reasonable safety profile, the determination of the dose per response and safety for a supplement would not be that costly to determine. And once known, these products could open a wealth of therapeutic opportunity for treating human disease.