Response on bioequivalence for biotherapeutic drugs

We have had the opportunity to read your letter related to our review article: "Biotherapeutic drugs: use of botulinum toxins in the era of biosimilars". We would like to express our agreement with your comments on the relevance of the subject in our environment, as well as with your reflections on the interchangeability of drugs and the need to clarify the concepts on the subject very well.In particular, you refer to the confusion that can be generated by the phrase in our conclusion: "biological drugs are not interchangeable with each other, even if they demonstrate bioequivalence". With interest we read how many of our colleagues were confused with the last part of the sentence because it is contradictory, since as you classically mention "bioequivalence studies are carried out to demonstrate that the generic drug is equivalent and interchangeable with the original drug".