Bioequivalence, Therapeutic Equivalence and Generic Drugs (Editorial‪)‬

Between 1995 and 2002 I served as an external expert to the Belgian Medicines Evaluation Board and during those 8 years I assessed most, if not all, dossiers in which one or more bioequivalence studies were described as part of the application for marketing authorization of a medicinal product. During that period I evaluated more than 400 bioequivalence studies submitted for marketing authorization of generic drug products in Belgium via the National Procedure or via the Mutual Recognition Procedure of the EMEA (European Medicines Agency). I therefore read with much interest the articles on generic drugs by Dupont and Heller and Heller and Dupont which appear in this issue of Acta Clinica Belgica (1,2). Clinical experts generally agree that a bioequivalence study is the most appropriate approach for demonstrating therapeutic equivalence between two drug products and the value of bioequivalence as a surrogate for therapeutic equivalence is not questioned (3,4). Consequently, bioequivalence studies have been for many years an essential part of registration dossiers not only for generic drug products but also for innovator drug products (4,5). For example, registration of the majority of orally administered innovator drug products is based on one or more bioequivalence studies for the simple reason that in most cases the formulation that will be marketed is not the same as the formulation that was used in the clinical efficacy/ safety studies during the clinical phases of drug development (5). A bioequivalence study, a so-called "bridging study", is in those cases necessary to demonstrate therapeutic equivalence between the "clinical" and the final "market image" formulation of the innovator drug product. Thus for the majority of new drugs administered orally, clinical studies were not carried out on the final "market image" formulation, just as is the case for generic drugs.