They actually have to do multiple studies to prove both safety and efficacy. That company has to go through the FDA drug approval process to prove safety and efficacy of the drug. http://www.fda.gov/ForPatients/Approvals/Drugs/ucm405382.htm
In the case of the company that was named by the FDA in the warning letters (not going to say b/c it could be considered offtopic), they applied for "orphan drug" status for the treatment of a rare disease where adequate drugs for treatment have not been developed. A rare disease generally affects less than 200,000 people. Awhile ago, Congress passed the Orphan Drug Act which basically was created to push for the development of drugs for rare diseases. If a company is granted orphan drug status, and is first to gain approval for treatment for a rare disease, it gains "exclusive" rights and FDA may not approve another drug for treatment of that specific disease for 7 years.
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