Biological drugs are produced in living organisms including both animal cells and microorganisms such as bacteria or yeast, and are purified through a complex manufacturing process, unlike small-molecule drugs which are typically manufactured by chemical synthesis. In general, biological drugs exhibit greater structural and molecular complexity than chemical entities subjecting them to inherent variability. Therefore extensive and thorough physicochemical and biological characterization is required to demonstrate that this variability is tightly controlled and remains within predefined limits approved by health authorities.
A biosimilar is a type of biological drug that has been formally approved by the competent health authorities after demonstrating that it is highly similar to the already approved original or innovator biological drug, also referred to as the reference product. Extensive analytical testing of structure and function together with targeted non-clinical and clinical studies are demanded by the authorities in order to demonstrate that the biosimilar does not present clinically meaningful differences in terms of quality, safety and efficacy to the originator reference product.
Health authorities including the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA) and Health Canada have their own definitions of biosimilars and also guidelines with regards to the requirements for demonstrating the similar nature of two biological products. However, they concur that biosimilars must be highly similar to the reference product in order to receive marketing authorization.