Analytical aspects of biosimilarity issues of protein drugs.

The term "biosimilar" is used to designate a follow-on biologic that meets extremely high standards for comparability or similarity to the originator biologic drug that is approved for use in the same indications. Use of biosimilar products has already decreased the cost of treatment in many regions of the world and now a regulatory pathway for approval of these products has been established both in US and in the EU. The analytical tests to demonstrate comparability and similarity of a biosimilar product to a reference drug with respect to protein content, activity, physiochemical integrity, stability, impurities and additives, as well as immunogenicity are discussed.