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Understanding biosimilar drugs: what are their key characteristics and how do they differ from generic drugs?

February 22, 2021
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Biological drugs (pharmaceutical drugs that are based on biological molecules such as proteins) are a fast-growing class of therapeutic products used in areas of treatment such as oncology, diabetes, or autoimmune diseases, among others. Consequently, biosimilars claim their share in this emerging pharma market, offering additional treatment options in lower costs.  

What are biosimilar drugs?

Biosimilar drugs, sometimes also referred to as biogenerics, are highly similar copies of biological medicines that have reached the end of their patent protection. They have the same properties with their reference product in terms of safety, purity, and potency (safety and effectiveness) [1].

Which are the key differences between generic and biosimilar drugs?

Biosimilar drugs are often confused with generic drugs. Both are available and allowed for sale after the exclusive patents of the original drug expire but there are fundamental differences between them, regarding their structure, development, and authorization.

The main difference between biosimilar and generic drugs is that generic drugs are identical copies of the reference drug, while biosimilars, due to their molecular size and complexity, are highly similar to it.

Another key difference is that generics are duplicates of synthetic drugs, while biosimilars are alternatives for drugs obtained from biological sources [2].

Due to their molecular size, structure, and the complexity of their development, biosimilars incur higher research & development and manufacturing costs and require a more complicated process of approval than generic drugs.

Biosimilars' regulations and approval procedure

As stated above, the fact that biosimilars are not exact copies of their reference biologic drugs makes their approval and release to the market a complicated process. Due to their complexity, the existing regulatory pathway for the generic medicines cannot be applied.

The basic concept of the biosimilars’ approval procedure is based on demonstrating biosimilarity to the reference product and for this reason specialized testing is required to ensure their quality, safety and efficacy.

WHO provides written guidelines on the evaluation of biological and biosimilar medicines to be incorporated into national requirements in order to establish international standards for national regulatory authorities and a harmonized regulatory framework for products available on international markets [3].



1. Biosimilar and Interchangeable Products: What Is the Difference Between a Biosimilar and an Interchangeable Product? U.S. Food and Drug Association. https://www.fda.gov/drugs/biosimilars/biosimilar-and-interchangeable-products. Aug. 20, 2020.

2. What's the difference? Biosimilar and generic drugs. Cancer Treatment Centers of America. https://www.cancercenter.com/community/blog/2018/12/whats-the-difference-biosimilar-and-generic-drugsDec. 26, 2018.

3. Kang H-N., Knezevic I., (2018). Regulatory evaluation of biosimilars throughout their product life-cycle. Bulletin of the World Health Organization. DOI: http://dx.doi.org/10.2471/BLT.17.206284