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What Are Biosimilars?

First Biosimilar Is Not Yet on the Market


Updated June 12, 2013

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

You may have heard the term "biosimilars" for the first time a couple of years ago. Likely, you are seeing the term crop up with more frequency now as the U.S. Food and Drug Administration (FDA), along with scientists and doctors, work out how biosimilars will be reviewed and licensed.

What Are Biosimilars?

By current definition, a biosimilar is a biological product that is "highly similar" to a U.S.-licensed biological product, without regard to minor differences in clinically inactive components. There must also be no clinically significant difference, in terms of safety, purity, and potency, between the "biosimilar" and the original, already-approved biological product.

What Constitutes a Biological Product?

Biological products are products that are made using human or animal materials. According to the FDA, biological products can include vaccines, blood, blood components, allergenics, somatic cells, gene therapy, tissues, and proteins. Biological products differ from small-molecule prescription drugs, which are synthesized using chemical processes. Biological products are more complex and are either derived from natural sources or produced using biotechnology.

The first biologic drug for the treatment of rheumatoid arthritis was approved by the FDA in 1998. That drug was Enbrel (etanercept), which was classified as a TNF (tumor necrosis factor) blocker. Tumor necrosis factor is a cytokine which is involved in the inflammatory process. More than a dozen years later, we can say with confidence that the approval of Enbrel dramatically changed how rheumatoid arthritis and other inflammatory types of arthritis are treated today. Since Enbrel, several more TNF blockers have been approved and marketed as well as biologics that target B-cells, T-cells, and IL-6.

The Process of Licensing Biosimilars

Most biological products are licensed under the Public Health Service Act, unlike small-molecule prescription drugs, which fall under the Food, Drug and Cosmetic Act. The Patient Protection and Affordable Care Act of 2010 amended the Public Health Service Act in order to shorten the path for licensing biosimilars. Up until now, there has been no approval of a biosimilar product. Standards are currently being worked on that will ensure the safety and effectiveness of biosimilars. The process is complicated but the regulating agencies must work out the kinks, since several companies are already developing biosimilars. At this time, it is not known which biosimilar will apply for approval first, or when they will apply.

Are Biosimilars Like Generics?

Biosimilars and generics are not synonymous. "Generic" refers to small-molecule drugs that are deemed bioequivalent to an already existing small-molecule drug, as dictated by the Food, Drug and Cosmetic Act.

If a product is deemd "biosimilar," the product will be interchangeable with the already-approved biological product and expected to produce the same clinical result.


Information for Consumers (Biosimilars). U.S. Food and Drug Administration. 11/03/2011. http://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandApproved/ApprovalApplications/TherapeuticBiologicApplications/Biosimilars/ucm241718.htm

Biosimilars. U.S. FDA. 3/1/2012. http://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandApproved/ApprovalApplications/TherapeuticBiologicApplications/Biosimilars/default.htm

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