[Biosimilars in the European Union: current situation and challenges].

Biosimilars are medicinal products that are highly similar to approved biopharmaceuticals. Biosimilars enable patient access to biological therapies that would otherwise be restricted or delayed due to cost reasons. After the successful introduction of low-molecular biosimilars in 2006, highly complex monoclonal antibodies have also been available since 2013 as biosimilars for treating autoimmune diseases and oncologic indications. In principle, the biosimilar concept can be applied to all well-characterized biologicals; in the future, blood clotting factors or drugs containing nucleic acids, such as DNA or RNA gene therapy or mRNA vaccines, will also be an option for biosimilar development.In some instances, biosimilarity can be demonstrated by physicochemical and functional similarity, and additional comparative clinical efficacy and safety studies have been considered no longer necessary for several product categories in recent years. Switching a patient from a reference drug to a biosimilar or from one biosimilar to another (interchangeability) has so far been considered harmless. Since February 2020, there has been a provisional decision in Germany that patients should be switched according to an economic prescription method. Further scientific findings on the interchangeability of biosimilars and experiences with the supply practices of biosimilars should be collected and evaluated.In this article, the current situation regarding marketing authorizations of biosimilars in the European Union is reviewed. The role of clinical trials for biosimilars is presented, and challenges of biosimilar development and views on interchangeability are discussed.