A drug manufacturer wants to provide a generic version of a trade-name drug that eliminates all symptoms of an illness. Its laboratory studies show that the pill contains no dangerous chemicals, reduces symptoms of the illness, and has been produced consistently. Also, no deaths have occurred in the trial period. Why would this drug fail FDA approval as a therapeutic equivalent drug?

There are some reasons why a generic version of a trade-name drug could fail FDA approval as a therapeutic equivalent drug but what is described in the question suggests that the active ingredient of this generic version is different from that of the "original" trade-name drug. The reason is because, all the properties of the drug mentioned should have been compared to that of the original trade-name drug to prove bioequivalence - as the therapeutic effects of this drug should be in comparison to the original trade-name drug and not just be of it's own as suggested (for example, the drug should reduce symptoms of the illness with the same strength the trade-name does and not just as written that it reduces the symptoms of the illness) in the tone used in the question.