**Abstract**

The use of biological drugs has significantly increased over the past decades and has allowed for the treatment of many life-threatening and chronic diseases. The patent expiration of biological innovative medicines enables copies of these drugs called biosimilars. The availability of biosimilars enhances competition, with the potential to improve patient access to biological medications and contribute to the financial sustainability of the healthcare systems. Unlike equivalent drugs, biosimilars are not identical but similar to their innovator products because of the differences in the manufacturing process, which is a biological process. However, they are considered comparable to their originators in safety, quality characteristics, biological activity, and efficacy. The regulatory procedures used for generic drugs cannot be applied for biosimilars, so they are subjected to rigorous characterization as well as comparative clinical studies. Since they are highly complex molecules produced from living cells, even small change in the production process can have major implications on their safety and effectiveness profile, causing a potential risk of immune-based adverse reactions. For all these reasons, for biological drugs, a robust long-term pharmacovigilance system is necessary. It is desirable that in the future, there are further guidance and resolution of the ongoing discussions on biosimilar labeling, naming, pharmacovigilance and interchangeability/substitution, to ensure the appropriate use of these drugs in clinical practice.

**Keywords:** biologic, biosimilar, pharmacovigilance, regulation, interchangeability
