The Concept of Biosimilars: From Characterization to Evolution-A Narrative Review

Biologic agents are currently the fastest emerging segment of drug expenditure. Unlike chemically synthesized smallmolecule drugs, biologics are more complex, medicinal products produced by a living organism. They have become part of the standard of care in the treatment of a large variety of diseases, such as growth disorders, autoimmune diseases, cancer, cardiovascular illnesses, hemophilia, and rare genetic conditions, to name a few. Biosimilars, which are copies of biologics that are highly similar, were introduced in the market with an aim to offer efficacy that is not clinically different from the originator or reference product, at lower prices. We aim to clarify the concept of biosimilar, from definitions, history, market entry, challenges faced, and future evolution. For that purpose, we performed a literature search on the sites of the medicines regulatory agencies and PubMed from 1990 to 2014 with the keywords "biosimilars," "market," and "regulatory." In 2006, the first biosimilar, somatropin [rDNA origin], was marketed and led the way for biosimilar drug manufacturing. As a result, manufacturers have entered a diversified competition, facing challenges in manufacturing these complex agents, such as immunogenicity and efficiency. Biosimilars are set to evolve differently in various markets, namely the U.S., Japan, the European Union, and the "pharmerging" economies.