Teaser: This review summarizes the critical quality attributes of biosimilarity, also introducing the glycosimilarity index as an additional parameter to prove similarity between innovator and biosimilar products.
Highlights The critical quality attributes of biosimilarity are reviewed Regulatory and statistical considerations are summarized. Importance of glycosylation analysis during biosimilar production is detailed. Analytical methods to track N-glycosylation patterns are reviewed. Glycosimilarity index is introduced.The recent expiration of several protein therapeutics opened the door for biosimilar development. Biosimilars are biologic medical products that are similar but not identical copies of already-authorized protein therapeutics. Critical quality attributes (CQA), such as post-translational modifications of recombinant biotherapeutics, are important for the clinical efficacy and safety of both the innovative biologics and their biosimilar counterparts. Here, we summarize biosimilarity CQAs, considering the regulatory guidelines and the statistical aspects (e.g., biosimilarity index) and then discuss glycosylation as one of the important attributes of biosimilarity. Finally, we introduced the 'Glycosimilarity Index', which is based on the averaged biosimilarity criterion.