The differences in efficiency and safety (in vivo profile) cannot be detected in in vitro testing, as it is impossible to isolate and fully characterize these compounds. Nor are there defined models for proper evaluation.[1] Furthermore, it is unknown what to look for and what causes the differences, due to a lack of understanding of the exact composition. This calls for additional characterization in biological systems including clinical head-to-head analysis to define the extent of similarity and the place in therapy as therapeutic alternatives or interchangeable/substitutable medicinal products.