When patients are introduced to biosimilars, as with any new therapy, they are likely to have questions as to what they are and why they are important. In this context, it may be useful to discuss how biologics are made and compare biosimilars with generic small-molecule medicines. Although biosimilars are not generics, they can potentially have similar economic benefits and increase patient access to effective but costly medications.

What are biosimilars? Unlike small-molecule pharmaceuticals, which are chemically synthesized, biologic medicines are produced by genetically engineered cells, such as bacteria, yeast, or mammalian cells. Because small-molecule drugs are synthesized chemically, different manufacturers can produce identical drugs, referred to as generics. Since biologics are produced by living organisms, and no living cell is the same, it is impossible to independently develop a molecule that is identical to an existing biologic. When a manufacturer develops a product to achieve the same clinical result as an existing biologic, the new biologic product is called a biosimilar. Unlike generic medicines, biosimilars are highly similar but not equivalent to their reference biologic.