The impending expiry of the patent on a number of leading biologic drugs has led to a surge in the development of 'biosimilar' or 'follow-on' products. However, in contrast to generic small-molecule medicines, biosimilars are not identical to their reference products. The differences and complexities surrounding both the molecular structure and the manufacturing process for biologics and biosimilars have resulted in a lack of clarity regarding the terms used in different parts of the world to define various aspects of development and utilization such as regulatory approval, pharmacovigilance, interchangeability and treatment-naivety. This makes quantitative evaluation of biosimilars a great challenge to both the scientific community and regulatory agencies. This manuscript attempts to clarify the terms used and address an important knowledge gap which is currently resulting in an increasing rush to position biosimilars for certain indications and patients in the absence of agreed upon definitions.
Keywords: Biologics; Biosimilars; Interchangeability; Pharmacovigilance.