de Medina, Fermin Sanchez2023-01-252023-01-252016-08-10de Medina FS. Similar but Not the Same? Inflamm Bowel Dis. 2016 Sep;22(9):E31-E32.http://hdl.handle.net/10668/10372In the clinical review article entitled “Biosimilars in Crohn's disease and ulcerative colitis” by Dr. Wolf, which I read with great interest, the author briefly presents the basics of biosimilar development and the application of biosimilars to inflammatory bowel diseases. I was surprised however to find some imprecisions which I consider to deserve comment as they may cast unwarranted doubts on biosimilars. In particular, Dr. Wolf states that “biosimilars are not deemed therapeutically equivalent, as are generic chemical medicines,” and that “they are presumed to work equally well but may not,” stressing the “similar but not identical” principle. Indeed, biosimilars are not identical to the reference biological; the EMA defines them as versions of the reference drugs. However, it is important to remember that in the biological drug field there is hardly an “identicality” principle, as all biologicals, reference drugs included, undergo changes overtime, particularly when the process of production has to be modified, a frequent occurrence.1 To validate the lack of clinical relevance of any possible changes, a comparability exercise is performed, whereby a series of tests, typically in vitro only, are run to validate that changes are of no consequence.enColitis, UlcerativeClinical Relevancemethyl salicylateBiosimilar PharmaceuticalsWolvesInflammatory Bowel DiseasesCrohn DiseaseAnimalsresearch article27542139Restricted AccessAnimalesBiosimilares farmacéuticosEnfermedad de CrohnEnfermedades inflamatorias del intestinoLobos10.1097/MIB.00000000000008771536-4844https://academic.oup.com/ibdjournal/article-pdf/22/9/E31/23404381/ibd0e31a.pdf