Biological medicines are medicines whose active principle is represented by a substance produced or extracted from a biological system. Products such as hormones, enzymes, blood derived products, serums and vaccines, immunoglobulins, allergens, monoclonal antibodie belong to the category of biological medicinal products. Biological medicines include biotechnological medicines whose active substances are derived through procedures including recombinant DNA technologies, controlled expression of genes coding for biologically active proteins in prokaryotes and eukaryotes, hybridoma and monoclonal antibody methods.

The active substances of biological medicinal products differ in many respects from active principles synthesized by traditional chemical pharmaceutical methods: they consist of large and complex molecular structures, and present a different stability of the final product and impurity profile. Unlike chemical synthesis products, in addition, production processes of biological medicines are often characterised by the use of living systems with the possibility of significant structural variations in the final product (e.g. different glycosylation profiles), which can give rise to important immunogenic differences.

Given the intrinsic variability of molecules and the complexity of production techniques operating on living systems, the characterisation of biological medicines is particularly difficult and cannot be disregarded from the production process. The production process of these medicinal products is so highly distinctive that it can be said that "the product is the production process" (Karson KL., Nature Biotecnol, 2005).